pcm.c File Reference

PCM Interface. More...

Functions
const char *	snd_pcm_name (snd_pcm_t *pcm)
	get identifier of PCM handle
snd_pcm_type_t	snd_pcm_type (snd_pcm_t *pcm)
	get type of PCM handle
snd_pcm_stream_t	snd_pcm_stream (snd_pcm_t *pcm)
	get stream for a PCM handle
int	snd_pcm_close (snd_pcm_t *pcm)
	close PCM handle
int	snd_pcm_nonblock (snd_pcm_t *pcm, int nonblock)
	set nonblock mode
int	snd_pcm_info (snd_pcm_t *pcm, snd_pcm_info_t *info)
	Obtain general (static) information for PCM handle.
int	snd_pcm_hw_params_current (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
	Retreive current PCM hardware configuration chosen with snd_pcm_hw_params.
int	snd_pcm_hw_params (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
	Install one PCM hardware configuration chosen from a configuration space and snd_pcm_prepare it.
int	snd_pcm_hw_free (snd_pcm_t *pcm)
	Remove PCM hardware configuration and free associated resources.
int	snd_pcm_sw_params (snd_pcm_t *pcm, snd_pcm_sw_params_t *params)
	Install PCM software configuration defined by params.
int	snd_pcm_status (snd_pcm_t *pcm, snd_pcm_status_t *status)
	Obtain status (runtime) information for PCM handle.
snd_pcm_state_t	snd_pcm_state (snd_pcm_t *pcm)
	Return PCM state.
int	snd_pcm_hwsync (snd_pcm_t *pcm)
	(DEPRECATED) Synchronize stream position with hardware
int	snd_pcm_delay (snd_pcm_t *pcm, snd_pcm_sframes_t *delayp)
	Obtain delay for a running PCM handle.
int	snd_pcm_resume (snd_pcm_t *pcm)
	Resume from suspend, no samples are lost.
int	snd_pcm_htimestamp (snd_pcm_t *pcm, snd_pcm_uframes_t *avail, snd_htimestamp_t *tstamp)
	Obtain last position update hi-res timestamp.
int	snd_pcm_prepare (snd_pcm_t *pcm)
	Prepare PCM for use.
int	snd_pcm_reset (snd_pcm_t *pcm)
	Reset PCM position.
int	snd_pcm_start (snd_pcm_t *pcm)
	Start a PCM.
int	snd_pcm_drop (snd_pcm_t *pcm)
	Stop a PCM dropping pending frames.
int	snd_pcm_drain (snd_pcm_t *pcm)
	Stop a PCM preserving pending frames.
int	snd_pcm_pause (snd_pcm_t *pcm, int enable)
	Pause/resume PCM.
snd_pcm_sframes_t	snd_pcm_rewindable (snd_pcm_t *pcm)
	Get safe count of frames which can be rewinded.
snd_pcm_sframes_t	snd_pcm_rewind (snd_pcm_t *pcm, snd_pcm_uframes_t frames)
	Move application frame position backward.
snd_pcm_sframes_t	snd_pcm_forwardable (snd_pcm_t *pcm)
	Get safe count of frames which can be forwarded.
snd_pcm_sframes_t	snd_pcm_forward (snd_pcm_t *pcm, snd_pcm_uframes_t frames)
	Move application frame position forward.
snd_pcm_sframes_t	snd_pcm_writei (snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size)
	Write interleaved frames to a PCM.
snd_pcm_sframes_t	snd_pcm_writen (snd_pcm_t *pcm, void **bufs, snd_pcm_uframes_t size)
	Write non interleaved frames to a PCM.
snd_pcm_sframes_t	snd_pcm_readi (snd_pcm_t *pcm, void *buffer, snd_pcm_uframes_t size)
	Read interleaved frames from a PCM.
snd_pcm_sframes_t	snd_pcm_readn (snd_pcm_t *pcm, void **bufs, snd_pcm_uframes_t size)
	Read non interleaved frames to a PCM.
int	snd_pcm_link (snd_pcm_t *pcm1, snd_pcm_t *pcm2)
	Link two PCMs.
int	snd_pcm_unlink (snd_pcm_t *pcm)
	Remove a PCM from a linked group.
int	snd_pcm_poll_descriptors_count (snd_pcm_t *pcm)
	get count of poll descriptors for PCM handle
int	snd_pcm_poll_descriptors (snd_pcm_t *pcm, struct pollfd *pfds, unsigned int space)
	get poll descriptors
int	snd_pcm_poll_descriptors_revents (snd_pcm_t *pcm, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
	get returned events from poll descriptors
const char *	snd_pcm_stream_name (const snd_pcm_stream_t stream)
	get name of PCM stream type
const char *	snd_pcm_access_name (const snd_pcm_access_t acc)
	get name of PCM access type
const char *	snd_pcm_format_name (const snd_pcm_format_t format)
	get name of PCM sample format
const char *	snd_pcm_format_description (const snd_pcm_format_t format)
	get description of PCM sample format
snd_pcm_format_t	snd_pcm_format_value (const char *name)
	get PCM sample format from name
const char *	snd_pcm_subformat_name (const snd_pcm_subformat_t subformat)
	get name of PCM sample subformat
const char *	snd_pcm_subformat_description (const snd_pcm_subformat_t subformat)
	get description of PCM sample subformat
snd_pcm_subformat_t	snd_pcm_subformat_value (const char *name)
	get PCM sample subformat from name
const char *	snd_pcm_start_mode_name (snd_pcm_start_t mode)
	(DEPRECATED) get name of PCM start mode setting
const char *	snd_pcm_xrun_mode_name (snd_pcm_xrun_t mode)
	(DEPRECATED) get name of PCM xrun mode setting
const char *	snd_pcm_tstamp_mode_name (const snd_pcm_tstamp_t mode)
	get name of PCM tstamp mode setting
const char *	snd_pcm_tstamp_type_name (snd_pcm_tstamp_type_t type)
	get name of PCM tstamp type setting
const char *	snd_pcm_state_name (const snd_pcm_state_t state)
	get name of PCM state
const char *	snd_pcm_type_name (snd_pcm_type_t type)
	get name of PCM type
int	snd_pcm_dump_hw_setup (snd_pcm_t *pcm, snd_output_t *out)
	Dump current hardware setup for PCM.
int	snd_pcm_dump_sw_setup (snd_pcm_t *pcm, snd_output_t *out)
	Dump current software setup for PCM.
int	snd_pcm_dump_setup (snd_pcm_t *pcm, snd_output_t *out)
	Dump current setup (hardware and software) for PCM.
int	snd_pcm_status_dump (snd_pcm_status_t *status, snd_output_t *out)
	Dump status.
int	snd_pcm_dump (snd_pcm_t *pcm, snd_output_t *out)
	Dump PCM info.
snd_pcm_sframes_t	snd_pcm_bytes_to_frames (snd_pcm_t *pcm, ssize_t bytes)
	Convert bytes in frames for a PCM.
ssize_t	snd_pcm_frames_to_bytes (snd_pcm_t *pcm, snd_pcm_sframes_t frames)
	Convert frames in bytes for a PCM.
long	snd_pcm_bytes_to_samples (snd_pcm_t *pcm, ssize_t bytes)
	Convert bytes in samples for a PCM.
ssize_t	snd_pcm_samples_to_bytes (snd_pcm_t *pcm, long samples)
	Convert samples in bytes for a PCM.
int	snd_async_add_pcm_handler (snd_async_handler_t **handler, snd_pcm_t *pcm, snd_async_callback_t callback, void *private_data)
	Add an async handler for a PCM.
snd_pcm_t *	snd_async_handler_get_pcm (snd_async_handler_t *handler)
	Return PCM handle related to an async handler.
int	snd_pcm_open (snd_pcm_t **pcmp, const char *name, snd_pcm_stream_t stream, int mode)
	Opens a PCM.
int	snd_pcm_open_lconf (snd_pcm_t **pcmp, const char *name, snd_pcm_stream_t stream, int mode, snd_config_t *lconf)
	Opens a PCM using local configuration.
int	snd_pcm_open_fallback (snd_pcm_t **pcmp, snd_config_t *root, const char *name, const char *orig_name, snd_pcm_stream_t stream, int mode)
	Opens a fallback PCM.
int	snd_pcm_wait (snd_pcm_t *pcm, int timeout)
	Wait for a PCM to become ready.
snd_pcm_sframes_t	snd_pcm_avail_update (snd_pcm_t *pcm)
	Return number of frames ready to be read (capture) / written (playback)
snd_pcm_sframes_t	snd_pcm_avail (snd_pcm_t *pcm)
	Return number of frames ready to be read (capture) / written (playback)
int	snd_pcm_avail_delay (snd_pcm_t *pcm, snd_pcm_sframes_t *availp, snd_pcm_sframes_t *delayp)
	Combine snd_pcm_avail and snd_pcm_delay functions.
int	snd_pcm_area_silence (const snd_pcm_channel_area_t *dst_area, snd_pcm_uframes_t dst_offset, unsigned int samples, snd_pcm_format_t format)
	Silence an area.
int	snd_pcm_areas_silence (const snd_pcm_channel_area_t *dst_areas, snd_pcm_uframes_t dst_offset, unsigned int channels, snd_pcm_uframes_t frames, snd_pcm_format_t format)
	Silence one or more areas.
int	snd_pcm_area_copy (const snd_pcm_channel_area_t *dst_area, snd_pcm_uframes_t dst_offset, const snd_pcm_channel_area_t *src_area, snd_pcm_uframes_t src_offset, unsigned int samples, snd_pcm_format_t format)
	Copy an area.
int	snd_pcm_areas_copy (const snd_pcm_channel_area_t *dst_areas, snd_pcm_uframes_t dst_offset, const snd_pcm_channel_area_t *src_areas, snd_pcm_uframes_t src_offset, unsigned int channels, snd_pcm_uframes_t frames, snd_pcm_format_t format)
	Copy one or more areas.
int	snd_pcm_areas_copy_wrap (const snd_pcm_channel_area_t *dst_channels, snd_pcm_uframes_t dst_offset, const snd_pcm_uframes_t dst_size, const snd_pcm_channel_area_t *src_channels, snd_pcm_uframes_t src_offset, const snd_pcm_uframes_t src_size, const unsigned int channels, snd_pcm_uframes_t frames, const snd_pcm_format_t format)
	Copy one or more areas.
int	snd_pcm_hw_params_dump (snd_pcm_hw_params_t *params, snd_output_t *out)
	Dump a PCM hardware configuration space.
int	snd_pcm_hw_params_can_mmap_sample_resolution (const snd_pcm_hw_params_t *params)
	Check if hardware supports sample-resolution mmap for given configuration.
int	snd_pcm_hw_params_is_double (const snd_pcm_hw_params_t *params)
	Check if hardware does double buffering for start/stop for given configuration.
int	snd_pcm_hw_params_is_batch (const snd_pcm_hw_params_t *params)
	Check if hardware does double buffering for data transfers for given configuration.
int	snd_pcm_hw_params_is_block_transfer (const snd_pcm_hw_params_t *params)
	Check if hardware does block transfers for samples for given configuration.
int	snd_pcm_hw_params_is_monotonic (const snd_pcm_hw_params_t *params)
	Check if timestamps are monotonic for given configuration.
int	snd_pcm_hw_params_can_overrange (const snd_pcm_hw_params_t *params)
	Check if hardware supports overrange detection.
int	snd_pcm_hw_params_can_pause (const snd_pcm_hw_params_t *params)
	Check if hardware supports pause.
int	snd_pcm_hw_params_can_resume (const snd_pcm_hw_params_t *params)
	Check if hardware supports resume.
int	snd_pcm_hw_params_is_half_duplex (const snd_pcm_hw_params_t *params)
	Check if hardware does half-duplex only.
int	snd_pcm_hw_params_is_joint_duplex (const snd_pcm_hw_params_t *params)
	Check if hardware does joint-duplex (playback and capture are somewhat correlated)
int	snd_pcm_hw_params_can_sync_start (const snd_pcm_hw_params_t *params)
	Check if hardware supports synchronized start with sample resolution.
int	snd_pcm_hw_params_can_disable_period_wakeup (const snd_pcm_hw_params_t *params)
	Check if hardware can disable period wakeups.
int	snd_pcm_hw_params_is_perfect_drain (const snd_pcm_hw_params_t *params)
	Check if hardware is capable of perfect drain.
int	snd_pcm_hw_params_supports_audio_wallclock_ts (const snd_pcm_hw_params_t *params)
	Check if hardware supports audio wallclock timestamps.
int	snd_pcm_hw_params_supports_audio_ts_type (const snd_pcm_hw_params_t *params, int type)
	Check if hardware supports type of audio timestamps.
int	snd_pcm_hw_params_get_rate_numden (const snd_pcm_hw_params_t *params, unsigned int *rate_num, unsigned int *rate_den)
	Get rate exact info from a configuration space.
int	snd_pcm_hw_params_get_sbits (const snd_pcm_hw_params_t *params)
	Get sample resolution info from a configuration space.
int	snd_pcm_hw_params_get_fifo_size (const snd_pcm_hw_params_t *params)
	Get hardware FIFO size info from a configuration space.
const unsigned char *	snd_pcm_hw_params_get_sync (const snd_pcm_hw_params_t *params)
	Get hardware synchronization ID from a PCM info container.
int	snd_pcm_hw_params_any (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
	Fill params with a full configuration space for a PCM.
size_t	snd_pcm_access_mask_sizeof ()
	get size of #snd_pcm_access_mask_t
int	snd_pcm_access_mask_malloc (snd_pcm_access_mask_t **ptr)
	allocate an empty #snd_pcm_access_mask_t using standard malloc
void	snd_pcm_access_mask_free (snd_pcm_access_mask_t *obj)
	frees a previously allocated #snd_pcm_access_mask_t
void	snd_pcm_access_mask_copy (snd_pcm_access_mask_t *dst, const snd_pcm_access_mask_t *src)
	copy one #snd_pcm_access_mask_t to another
void	snd_pcm_access_mask_none (snd_pcm_access_mask_t *mask)
	reset all bits in a #snd_pcm_access_mask_t
void	snd_pcm_access_mask_any (snd_pcm_access_mask_t *mask)
	set all bits in a #snd_pcm_access_mask_t
int	snd_pcm_access_mask_test (const snd_pcm_access_mask_t *mask, snd_pcm_access_t val)
	test the presence of an access type in a #snd_pcm_access_mask_t
int	snd_pcm_access_mask_empty (const snd_pcm_access_mask_t *mask)
	test, if given a #snd_pcm_access_mask_t is empty
void	snd_pcm_access_mask_set (snd_pcm_access_mask_t *mask, snd_pcm_access_t val)
	make an access type present in a #snd_pcm_access_mask_t
void	snd_pcm_access_mask_reset (snd_pcm_access_mask_t *mask, snd_pcm_access_t val)
	make an access type missing from a #snd_pcm_access_mask_t
size_t	snd_pcm_format_mask_sizeof ()
	get size of #snd_pcm_format_mask_t
int	snd_pcm_format_mask_malloc (snd_pcm_format_mask_t **ptr)
	allocate an empty #snd_pcm_format_mask_t using standard malloc
void	snd_pcm_format_mask_free (snd_pcm_format_mask_t *obj)
	frees a previously allocated #snd_pcm_format_mask_t
void	snd_pcm_format_mask_copy (snd_pcm_format_mask_t *dst, const snd_pcm_format_mask_t *src)
	copy one #snd_pcm_format_mask_t to another
void	snd_pcm_format_mask_none (snd_pcm_format_mask_t *mask)
	reset all bits in a #snd_pcm_format_mask_t
void	snd_pcm_format_mask_any (snd_pcm_format_mask_t *mask)
	set all bits in a #snd_pcm_format_mask_t
int	snd_pcm_format_mask_test (const snd_pcm_format_mask_t *mask, snd_pcm_format_t val)
	test the presence of a format in a #snd_pcm_format_mask_t
int	snd_pcm_format_mask_empty (const snd_pcm_format_mask_t *mask)
	test, if given a #snd_pcm_format_mask_t is empty
void	snd_pcm_format_mask_set (snd_pcm_format_mask_t *mask, snd_pcm_format_t val)
	make a format present in a #snd_pcm_format_mask_t
void	snd_pcm_format_mask_reset (snd_pcm_format_mask_t *mask, snd_pcm_format_t val)
	make a format missing from a #snd_pcm_format_mask_t
size_t	snd_pcm_subformat_mask_sizeof ()
	get size of #snd_pcm_subformat_mask_t
int	snd_pcm_subformat_mask_malloc (snd_pcm_subformat_mask_t **ptr)
	allocate an empty #snd_pcm_subformat_mask_t using standard malloc
void	snd_pcm_subformat_mask_free (snd_pcm_subformat_mask_t *obj)
	frees a previously allocated #snd_pcm_subformat_mask_t
void	snd_pcm_subformat_mask_copy (snd_pcm_subformat_mask_t *dst, const snd_pcm_subformat_mask_t *src)
	copy one #snd_pcm_subformat_mask_t to another
void	snd_pcm_subformat_mask_none (snd_pcm_subformat_mask_t *mask)
	reset all bits in a #snd_pcm_subformat_mask_t
void	snd_pcm_subformat_mask_any (snd_pcm_subformat_mask_t *mask)
	set all bits in a #snd_pcm_subformat_mask_t
int	snd_pcm_subformat_mask_test (const snd_pcm_subformat_mask_t *mask, snd_pcm_subformat_t val)
	test the presence of a subformat in a #snd_pcm_subformat_mask_t
int	snd_pcm_subformat_mask_empty (const snd_pcm_subformat_mask_t *mask)
	test, if given a #snd_pcm_subformat_mask_t is empty
void	snd_pcm_subformat_mask_set (snd_pcm_subformat_mask_t *mask, snd_pcm_subformat_t val)
	make a subformat present in a #snd_pcm_subformat_mask_t
void	snd_pcm_subformat_mask_reset (snd_pcm_subformat_mask_t *mask, snd_pcm_subformat_t val)
	make a subformat missing from a #snd_pcm_subformat_mask_t
size_t	snd_pcm_hw_params_sizeof ()
	get size of #snd_pcm_hw_params_t
int	snd_pcm_hw_params_malloc (snd_pcm_hw_params_t **ptr)
	allocate an invalid #snd_pcm_hw_params_t using standard malloc
void	snd_pcm_hw_params_free (snd_pcm_hw_params_t *obj)
	frees a previously allocated #snd_pcm_hw_params_t
void	snd_pcm_hw_params_copy (snd_pcm_hw_params_t *dst, const snd_pcm_hw_params_t *src)
	copy one #snd_pcm_hw_params_t to another
int	snd_pcm_hw_params_get_access (const snd_pcm_hw_params_t *params, snd_pcm_access_t *access)
	Extract access type from a configuration space.
int	snd_pcm_hw_params_test_access (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_t access)
	Verify if an access type is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_access (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_t access)
	Restrict a configuration space to contain only one access type.
int	snd_pcm_hw_params_set_access_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_t *access)
	Restrict a configuration space to contain only its first access type.
int	snd_pcm_hw_params_set_access_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_t *access)
	Restrict a configuration space to contain only its last access type.
int	snd_pcm_hw_params_set_access_mask (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_mask_t *mask)
	Restrict a configuration space to contain only a set of access types.
int	snd_pcm_hw_params_get_access_mask (snd_pcm_hw_params_t *params, snd_pcm_access_mask_t *mask)
	Get access mask from a configuration space.
int	snd_pcm_hw_params_get_format (const snd_pcm_hw_params_t *params, snd_pcm_format_t *format)
	Extract format from a configuration space.
int	snd_pcm_hw_params_test_format (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_t format)
	Verify if a format is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_format (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_t format)
	Restrict a configuration space to contain only one format.
int	snd_pcm_hw_params_set_format_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_t *format)
	Restrict a configuration space to contain only its first format.
int	snd_pcm_hw_params_set_format_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_t *format)
	Restrict a configuration space to contain only its last format.
int	snd_pcm_hw_params_set_format_mask (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_mask_t *mask)
	Restrict a configuration space to contain only a set of formats.
void	snd_pcm_hw_params_get_format_mask (snd_pcm_hw_params_t *params, snd_pcm_format_mask_t *mask)
	Get format mask from a configuration space.
int	snd_pcm_hw_params_get_subformat (const snd_pcm_hw_params_t *params, snd_pcm_subformat_t *subformat)
	Extract subformat from a configuration space.
int	snd_pcm_hw_params_test_subformat (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_subformat_t subformat)
	Verify if a subformat is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_subformat (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_subformat_t subformat)
	Restrict a configuration space to contain only one subformat.
int	snd_pcm_hw_params_set_subformat_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_subformat_t *subformat)
	Restrict a configuration space to contain only its first subformat.
int	snd_pcm_hw_params_set_subformat_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_subformat_t *subformat)
	Restrict a configuration space to contain only its last subformat.
int	snd_pcm_hw_params_set_subformat_mask (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_subformat_mask_t *mask)
	Restrict a configuration space to contain only a set of subformats.
void	snd_pcm_hw_params_get_subformat_mask (snd_pcm_hw_params_t *params, snd_pcm_subformat_mask_t *mask)
	Get subformat mask from a configuration space.
int	snd_pcm_hw_params_get_channels (const snd_pcm_hw_params_t *params, unsigned int *val)
	Extract channels from a configuration space.
int	snd_pcm_hw_params_get_channels_min (const snd_pcm_hw_params_t *params, unsigned int *val)
	Extract minimum channels count from a configuration space.
int	snd_pcm_hw_params_get_channels_max (const snd_pcm_hw_params_t *params, unsigned int *val)
	Extract maximum channels count from a configuration space.
int	snd_pcm_hw_params_test_channels (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
	Verify if a channels count is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_channels (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
	Restrict a configuration space to contain only one channels count.
int	snd_pcm_hw_params_set_channels_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Restrict a configuration space with a minimum channels count.
int	snd_pcm_hw_params_set_channels_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Restrict a configuration space with a maximum channels count.
int	snd_pcm_hw_params_set_channels_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *min, unsigned int *max)
	Restrict a configuration space to have channels counts in a given range.
int	snd_pcm_hw_params_set_channels_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Restrict a configuration space to have channels count nearest to a target.
int	snd_pcm_hw_params_set_channels_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Restrict a configuration space to contain only its minimum channels count.
int	snd_pcm_hw_params_set_channels_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Restrict a configuration space to contain only its maximum channels count.
int	snd_pcm_hw_params_get_rate (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract rate from a configuration space.
int	snd_pcm_hw_params_get_rate_min (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract minimum rate from a configuration space.
int	snd_pcm_hw_params_get_rate_max (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract maximum rate from a configuration space.
int	snd_pcm_hw_params_test_rate (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Verify if a rate is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_rate (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Restrict a configuration space to contain only one rate.
int	snd_pcm_hw_params_set_rate_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a minimum rate.
int	snd_pcm_hw_params_set_rate_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a maximum rate.
int	snd_pcm_hw_params_set_rate_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *min, int *mindir, unsigned int *max, int *maxdir)
	Restrict a configuration space to have rates in a given range.
int	snd_pcm_hw_params_set_rate_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to have rate nearest to a target.
int	snd_pcm_hw_params_set_rate_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its minimum rate.
int	snd_pcm_hw_params_set_rate_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its maximum rate.
int	snd_pcm_hw_params_set_rate_resample (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
	Restrict a configuration space to contain only real hardware rates.
int	snd_pcm_hw_params_get_rate_resample (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Extract resample state from a configuration space.
int	snd_pcm_hw_params_set_export_buffer (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
	Restrict a configuration space to allow the buffer to be accessible from outside.
int	snd_pcm_hw_params_get_export_buffer (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Extract buffer accessibility from a configuration space.
int	snd_pcm_hw_params_set_period_wakeup (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
	Restrict a configuration space to settings without period wakeups.
int	snd_pcm_hw_params_get_period_wakeup (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Extract period wakeup flag from a configuration space.
int	snd_pcm_hw_params_set_drain_silence (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
	Restrict a configuration space to fill the end of playback stream with silence when drain() is invoked.
int	snd_pcm_hw_params_get_drain_silence (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
	Extract drain with the filling of silence samples from a configuration space.
int	snd_pcm_hw_params_get_period_time (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract period time from a configuration space.
int	snd_pcm_hw_params_get_period_time_min (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract minimum period time from a configuration space.
int	snd_pcm_hw_params_get_period_time_max (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract maximum period time from a configuration space.
int	snd_pcm_hw_params_test_period_time (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Verify if a period time is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_period_time (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Restrict a configuration space to contain only one period time.
int	snd_pcm_hw_params_set_period_time_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a minimum period time.
int	snd_pcm_hw_params_set_period_time_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a maximum period time.
int	snd_pcm_hw_params_set_period_time_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *min, int *mindir, unsigned int *max, int *maxdir)
	Restrict a configuration space to have period times in a given range.
int	snd_pcm_hw_params_set_period_time_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to have period time nearest to a target.
int	snd_pcm_hw_params_set_period_time_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its minimum period time.
int	snd_pcm_hw_params_set_period_time_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its maximum period time.
int	snd_pcm_hw_params_get_period_size (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Extract period size from a configuration space.
int	snd_pcm_hw_params_get_period_size_min (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Extract minimum period size from a configuration space.
int	snd_pcm_hw_params_get_period_size_max (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Extract maximum period size from a configuration space.
int	snd_pcm_hw_params_test_period_size (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t val, int dir)
	Verify if a period size is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_period_size (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t val, int dir)
	Restrict a configuration space to contain only one period size.
int	snd_pcm_hw_params_set_period_size_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Restrict a configuration space with a minimum period size.
int	snd_pcm_hw_params_set_period_size_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Restrict a configuration space with a maximum period size.
int	snd_pcm_hw_params_set_period_size_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *min, int *mindir, snd_pcm_uframes_t *max, int *maxdir)
	Restrict a configuration space to have period sizes in a given range.
int	snd_pcm_hw_params_set_period_size_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Restrict a configuration space to have period size nearest to a target.
int	snd_pcm_hw_params_set_period_size_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Restrict a configuration space to contain only its minimum period size.
int	snd_pcm_hw_params_set_period_size_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
	Restrict a configuration space to contain only its maximum period size.
int	snd_pcm_hw_params_set_period_size_integer (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
	Restrict a configuration space to contain only integer period sizes.
int	snd_pcm_hw_params_get_periods (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract periods from a configuration space.
int	snd_pcm_hw_params_get_periods_min (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract minimum periods count from a configuration space.
int	snd_pcm_hw_params_get_periods_max (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract maximum periods count from a configuration space.
int	snd_pcm_hw_params_test_periods (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Verify if a periods count is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_periods (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Restrict a configuration space to contain only one periods count.
int	snd_pcm_hw_params_set_periods_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a minimum periods count.
int	snd_pcm_hw_params_set_periods_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a maximum periods count.
int	snd_pcm_hw_params_set_periods_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *min, int *mindir, unsigned int *max, int *maxdir)
	Restrict a configuration space to have periods counts in a given range.
int	snd_pcm_hw_params_set_periods_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to have periods count nearest to a target.
int	snd_pcm_hw_params_set_periods_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its minimum periods count.
int	snd_pcm_hw_params_set_periods_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its maximum periods count.
int	snd_pcm_hw_params_set_periods_integer (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
	Restrict a configuration space to contain only integer periods counts.
int	snd_pcm_hw_params_get_buffer_time (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract buffer time from a configuration space.
int	snd_pcm_hw_params_get_buffer_time_min (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract minimum buffer time from a configuration space.
int	snd_pcm_hw_params_get_buffer_time_max (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Extract maximum buffer time from a configuration space.
int	snd_pcm_hw_params_test_buffer_time (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Verify if a buffer time is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_buffer_time (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	Restrict a configuration space to contain only one buffer time.
int	snd_pcm_hw_params_set_buffer_time_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a minimum buffer time.
int	snd_pcm_hw_params_set_buffer_time_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space with a maximum buffer time.
int	snd_pcm_hw_params_set_buffer_time_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *min, int *mindir, unsigned int *max, int *maxdir)
	Restrict a configuration space to have buffer times in a given range.
int	snd_pcm_hw_params_set_buffer_time_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to have buffer time nearest to a target.
int	snd_pcm_hw_params_set_buffer_time_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its minimum buffer time.
int	snd_pcm_hw_params_set_buffer_time_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	Restrict a configuration space to contain only its maximum buffered time.
int	snd_pcm_hw_params_get_buffer_size (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Extract buffer size from a configuration space.
int	snd_pcm_hw_params_get_buffer_size_min (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Extract minimum buffer size from a configuration space.
int	snd_pcm_hw_params_get_buffer_size_max (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Extract maximum buffer size from a configuration space.
int	snd_pcm_hw_params_test_buffer_size (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t val)
	Verify if a buffer size is available inside a configuration space for a PCM.
int	snd_pcm_hw_params_set_buffer_size (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t val)
	Restrict a configuration space to contain only one buffer size.
int	snd_pcm_hw_params_set_buffer_size_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Restrict a configuration space with a minimum buffer size.
int	snd_pcm_hw_params_set_buffer_size_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Restrict a configuration space with a maximum buffer size.
int	snd_pcm_hw_params_set_buffer_size_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *min, snd_pcm_uframes_t *max)
	Restrict a configuration space to have buffer sizes in a given range.
int	snd_pcm_hw_params_set_buffer_size_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Restrict a configuration space to have buffer size nearest to a target.
int	snd_pcm_hw_params_set_buffer_size_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Restrict a configuration space to contain only its minimum buffer size.
int	snd_pcm_hw_params_set_buffer_size_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Restrict a configuration space to contain only its maximum buffer size.
int	snd_pcm_hw_params_get_tick_time (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Extract tick time from a configuration space
int	snd_pcm_hw_params_get_tick_time_min (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Extract minimum tick time from a configuration space
int	snd_pcm_hw_params_get_tick_time_max (const snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Extract maximum tick time from a configuration space
int	snd_pcm_hw_params_test_tick_time (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	(DEPRECATED) Verify if a tick time is available inside a configuration space for a PCM
int	snd_pcm_hw_params_set_tick_time (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int dir)
	(DEPRECATED) Restrict a configuration space to contain only one tick time
int	snd_pcm_hw_params_set_tick_time_min (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Restrict a configuration space with a minimum tick time
int	snd_pcm_hw_params_set_tick_time_max (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Restrict a configuration space with a maximum tick time
int	snd_pcm_hw_params_set_tick_time_minmax (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *min, int *mindir, unsigned int *max, int *maxdir)
	(DEPRECATED) Restrict a configuration space to have tick times in a given range
int	snd_pcm_hw_params_set_tick_time_near (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Restrict a configuration space to have tick time nearest to a target
int	snd_pcm_hw_params_set_tick_time_first (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Restrict a configuration space to contain only its minimum tick time
int	snd_pcm_hw_params_set_tick_time_last (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir)
	(DEPRECATED) Restrict a configuration space to contain only its maximum tick time
int	snd_pcm_hw_params_get_min_align (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val)
	Get the minimum transfer align value in samples.
int	snd_pcm_sw_params_current (snd_pcm_t *pcm, snd_pcm_sw_params_t *params)
	Return current software configuration for a PCM.
int	snd_pcm_sw_params_dump (snd_pcm_sw_params_t *params, snd_output_t *out)
	Dump a software configuration.
size_t	snd_pcm_sw_params_sizeof ()
	get size of #snd_pcm_sw_params_t
int	snd_pcm_sw_params_malloc (snd_pcm_sw_params_t **ptr)
	allocate an invalid #snd_pcm_sw_params_t using standard malloc
void	snd_pcm_sw_params_free (snd_pcm_sw_params_t *obj)
	frees a previously allocated #snd_pcm_sw_params_t
void	snd_pcm_sw_params_copy (snd_pcm_sw_params_t *dst, const snd_pcm_sw_params_t *src)
	copy one #snd_pcm_sw_params_t to another
int	snd_pcm_sw_params_get_boundary (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	Get boundary for ring pointers from a software configuration container.
int	snd_pcm_sw_params_set_start_mode (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_start_t val)
	(DEPRECATED) Set start mode inside a software configuration container
snd_pcm_start_t	snd_pcm_sw_params_get_start_mode (const snd_pcm_sw_params_t *params)
	(DEPRECATED) Get start mode from a software configuration container
int	snd_pcm_sw_params_set_xrun_mode (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_xrun_t val)
	(DEPRECATED) Set xrun mode inside a software configuration container
snd_pcm_xrun_t	snd_pcm_sw_params_get_xrun_mode (const snd_pcm_sw_params_t *params)
	(DEPRECATED) Get xrun mode from a software configuration container
int	snd_pcm_sw_params_set_tstamp_mode (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_tstamp_t val)
	Set timestamp mode inside a software configuration container.
int	snd_pcm_sw_params_get_tstamp_mode (const snd_pcm_sw_params_t *params, snd_pcm_tstamp_t *val)
	Get timestamp mode from a software configuration container.
int	snd_pcm_sw_params_set_tstamp_type (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_tstamp_type_t val)
	Set timestamp type inside a software configuration container.
int	snd_pcm_sw_params_get_tstamp_type (const snd_pcm_sw_params_t *params, snd_pcm_tstamp_type_t *val)
	Get timestamp type from a software configuration container.
int	snd_pcm_sw_params_set_sleep_min (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, unsigned int val)
	(DEPRECATED) Set minimum number of ticks to sleep inside a software configuration container
int	snd_pcm_sw_params_get_sleep_min (const snd_pcm_sw_params_t *params, unsigned int *val)
	(DEPRECATED) Get minimum numbers of ticks to sleep from a software configuration container
int	snd_pcm_sw_params_set_avail_min (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
	Set avail min inside a software configuration container.
int	snd_pcm_sw_params_get_avail_min (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	Get avail min from a software configuration container.
int	snd_pcm_sw_params_set_period_event (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, int val)
	Set period event inside a software configuration container.
int	snd_pcm_sw_params_get_period_event (const snd_pcm_sw_params_t *params, int *val)
	Get period event from a software configuration container.
int	snd_pcm_sw_params_set_xfer_align (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
	(DEPRECATED) Set xfer align inside a software configuration container
int	snd_pcm_sw_params_get_xfer_align (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	(DEPRECATED) Get xfer align from a software configuration container
int	snd_pcm_sw_params_set_start_threshold (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
	Set start threshold inside a software configuration container.
int	snd_pcm_sw_params_get_start_threshold (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	Get start threshold from a software configuration container.
int	snd_pcm_sw_params_set_stop_threshold (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
	Set stop threshold inside a software configuration container.
int	snd_pcm_sw_params_get_stop_threshold (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	Get stop threshold from a software configuration container.
int	snd_pcm_sw_params_set_silence_threshold (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
	Set silence threshold inside a software configuration container.
int	snd_pcm_sw_params_get_silence_threshold (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	Get silence threshold from a software configuration container.
int	snd_pcm_sw_params_set_silence_size (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
	Set silence size inside a software configuration container.
int	snd_pcm_sw_params_get_silence_size (const snd_pcm_sw_params_t *params, snd_pcm_uframes_t *val)
	Get silence size from a software configuration container.
size_t	snd_pcm_status_sizeof ()
	get size of #snd_pcm_status_t
int	snd_pcm_status_malloc (snd_pcm_status_t **ptr)
	allocate an invalid #snd_pcm_status_t using standard malloc
void	snd_pcm_status_free (snd_pcm_status_t *obj)
	frees a previously allocated #snd_pcm_status_t
void	snd_pcm_status_copy (snd_pcm_status_t *dst, const snd_pcm_status_t *src)
	copy one #snd_pcm_status_t to another
snd_pcm_state_t	snd_pcm_status_get_state (const snd_pcm_status_t *obj)
	Get state from a PCM status container (see snd_pcm_state)
void	snd_pcm_status_get_trigger_tstamp (const snd_pcm_status_t *obj, snd_timestamp_t *ptr)
	Get trigger timestamp from a PCM status container.
void	snd_pcm_status_get_trigger_htstamp (const snd_pcm_status_t *obj, snd_htimestamp_t *ptr)
	Get trigger hi-res timestamp from a PCM status container.
void	snd_pcm_status_get_tstamp (const snd_pcm_status_t *obj, snd_timestamp_t *ptr)
	Get "now" timestamp from a PCM status container.
void	snd_pcm_status_get_htstamp (const snd_pcm_status_t *obj, snd_htimestamp_t *ptr)
	Get "now" hi-res timestamp from a PCM status container.
void	snd_pcm_status_get_audio_htstamp (const snd_pcm_status_t *obj, snd_htimestamp_t *ptr)
	Get "now" hi-res audio timestamp from a PCM status container.
void	snd_pcm_status_get_driver_htstamp (const snd_pcm_status_t *obj, snd_htimestamp_t *ptr)
	Get "now" hi-res driver timestamp from a PCM status container. Defines when the status was generated by driver, may differ from normal timestamp.
void	snd_pcm_status_get_audio_htstamp_report (const snd_pcm_status_t *obj, snd_pcm_audio_tstamp_report_t *audio_tstamp_report)
	Get audio_tstamp_report from a PCM status container.
void	snd_pcm_status_set_audio_htstamp_config (snd_pcm_status_t *obj, snd_pcm_audio_tstamp_config_t *audio_tstamp_config)
	set audio_tstamp_config from a PCM status container
snd_pcm_sframes_t	snd_pcm_status_get_delay (const snd_pcm_status_t *obj)
	Get delay from a PCM status container (see snd_pcm_delay)
snd_pcm_uframes_t	snd_pcm_status_get_avail (const snd_pcm_status_t *obj)
	Get number of frames available from a PCM status container (see snd_pcm_avail_update)
snd_pcm_uframes_t	snd_pcm_status_get_avail_max (const snd_pcm_status_t *obj)
	Get maximum number of frames available from a PCM status container after last snd_pcm_status call.
snd_pcm_uframes_t	snd_pcm_status_get_overrange (const snd_pcm_status_t *obj)
	Get count of ADC overrange detections since last call.
size_t	snd_pcm_info_sizeof ()
	get size of #snd_pcm_info_t
int	snd_pcm_info_malloc (snd_pcm_info_t **ptr)
	allocate an invalid #snd_pcm_info_t using standard malloc
void	snd_pcm_info_free (snd_pcm_info_t *obj)
	frees a previously allocated #snd_pcm_info_t
void	snd_pcm_info_copy (snd_pcm_info_t *dst, const snd_pcm_info_t *src)
	copy one #snd_pcm_info_t to another
unsigned int	snd_pcm_info_get_device (const snd_pcm_info_t *obj)
	Get device from a PCM info container.
unsigned int	snd_pcm_info_get_subdevice (const snd_pcm_info_t *obj)
	Get subdevice from a PCM info container.
snd_pcm_stream_t	snd_pcm_info_get_stream (const snd_pcm_info_t *obj)
	Get stream (direction) from a PCM info container.
int	snd_pcm_info_get_card (const snd_pcm_info_t *obj)
	Get card from a PCM info container.
const char *	snd_pcm_info_get_id (const snd_pcm_info_t *obj)
	Get id from a PCM info container.
const char *	snd_pcm_info_get_name (const snd_pcm_info_t *obj)
	Get name from a PCM info container.
const char *	snd_pcm_info_get_subdevice_name (const snd_pcm_info_t *obj)
	Get subdevice name from a PCM info container.
snd_pcm_class_t	snd_pcm_info_get_class (const snd_pcm_info_t *obj)
	Get class from a PCM info container.
snd_pcm_subclass_t	snd_pcm_info_get_subclass (const snd_pcm_info_t *obj)
	Get subclass from a PCM info container.
unsigned int	snd_pcm_info_get_subdevices_count (const snd_pcm_info_t *obj)
	Get subdevices count from a PCM info container.
unsigned int	snd_pcm_info_get_subdevices_avail (const snd_pcm_info_t *obj)
	Get available subdevices count from a PCM info container.
snd_pcm_sync_id_t	snd_pcm_info_get_sync (const snd_pcm_info_t *obj)
	(DEPRECATED) Get hardware synchronization ID from a PCM info container
void	snd_pcm_info_set_device (snd_pcm_info_t *obj, unsigned int val)
	Set wanted device inside a PCM info container (see snd_ctl_pcm_info)
void	snd_pcm_info_set_subdevice (snd_pcm_info_t *obj, unsigned int val)
	Set wanted subdevice inside a PCM info container (see snd_ctl_pcm_info)
void	snd_pcm_info_set_stream (snd_pcm_info_t *obj, snd_pcm_stream_t val)
	Set wanted stream inside a PCM info container (see snd_ctl_pcm_info)
int	snd_pcm_mmap_begin (snd_pcm_t *pcm, const snd_pcm_channel_area_t **areas, snd_pcm_uframes_t *offset, snd_pcm_uframes_t *frames)
	Application request to access a portion of direct (mmap) area.
snd_pcm_sframes_t	snd_pcm_mmap_commit (snd_pcm_t *pcm, snd_pcm_uframes_t offset, snd_pcm_uframes_t frames)
	Application has completed the access to area requested with snd_pcm_mmap_begin.
snd_pcm_chmap_query_t **	snd_pcm_query_chmaps (snd_pcm_t *pcm)
void	snd_pcm_free_chmaps (snd_pcm_chmap_query_t **maps)
snd_pcm_chmap_t *	snd_pcm_get_chmap (snd_pcm_t *pcm)
int	snd_pcm_set_chmap (snd_pcm_t *pcm, const snd_pcm_chmap_t *map)
const char *	snd_pcm_chmap_type_name (enum snd_pcm_chmap_type val)
const char *	snd_pcm_chmap_name (enum snd_pcm_chmap_position val)
const char *	snd_pcm_chmap_long_name (enum snd_pcm_chmap_position val)
int	snd_pcm_chmap_print (const snd_pcm_chmap_t *map, size_t maxlen, char *buf)
unsigned int	snd_pcm_chmap_from_string (const char *str)
snd_pcm_chmap_t *	snd_pcm_chmap_parse_string (const char *str)
int	snd_pcm_recover (snd_pcm_t *pcm, int err, int silent)
	Recover the stream state from an error or suspend.
int	snd_pcm_set_params (snd_pcm_t *pcm, snd_pcm_format_t format, snd_pcm_access_t access, unsigned int channels, unsigned int rate, int soft_resample, unsigned int latency)
	Set the hardware and software parameters in a simple way.
int	snd_pcm_get_params (snd_pcm_t *pcm, snd_pcm_uframes_t *buffer_size, snd_pcm_uframes_t *period_size)
	Get the transfer size parameters in a simple way.

Detailed Description

PCM Interface.

Author

Jaroslav Kysela perex.nosp@m.@per.nosp@m.ex.cz

Abramo Bagnara abram.nosp@m.o@al.nosp@m.sa-pr.nosp@m.ojec.nosp@m.t.org

Date

2000-2001

PCM Interface is designed to write or read digital audio frames. A frame is the data unit converted into/from sound in one time unit (1/rate seconds), by example if you set your playback PCM rate to 44100 you'll hear 44100 frames per second. The size in bytes of a frame may be obtained from bits needed to store a sample and channels count.

See the PCM (digital audio) interface page for more details.

Function Documentation

snd_async_add_pcm_handler()

int snd_async_add_pcm_handler	(	snd_async_handler_t **	handler,
		snd_pcm_t *	pcm,
		snd_async_callback_t	callback,
		void *	private_data )

Add an async handler for a PCM.

Parameters

handler	Returned handler handle
pcm	PCM handle
callback	Callback function
private_data	Callback private data

Returns

0 otherwise a negative error code on failure

The asynchronous callback is called when period boundary elapses.

Examples

/test/pcm.c.

snd_async_handler_get_pcm()

snd_pcm_t * snd_async_handler_get_pcm

(

snd_async_handler_t *

handler

)

Return PCM handle related to an async handler.

Parameters

handler

Async handler handle

Returns

PCM handle

Examples

/test/pcm.c.

snd_pcm_access_mask_any()

void snd_pcm_access_mask_any

(

snd_pcm_access_mask_t *

mask

)

set all bits in a #snd_pcm_access_mask_t

Parameters

mask	pointer to mask

snd_pcm_access_mask_copy()

void snd_pcm_access_mask_copy	(	snd_pcm_access_mask_t *	dst,
		const snd_pcm_access_mask_t *	src )

copy one #snd_pcm_access_mask_t to another

Parameters

dst	pointer to destination
src	pointer to source

snd_pcm_access_mask_empty()

int snd_pcm_access_mask_empty

(

const snd_pcm_access_mask_t *

mask

)

test, if given a #snd_pcm_access_mask_t is empty

Parameters

mask	pointer to mask

Return values

0	not empty
1	empty

snd_pcm_access_mask_free()

void snd_pcm_access_mask_free

(

snd_pcm_access_mask_t *

obj

)

frees a previously allocated #snd_pcm_access_mask_t

Parameters

obj	pointer to object to free

snd_pcm_access_mask_malloc()

int snd_pcm_access_mask_malloc

(

snd_pcm_access_mask_t **

ptr

)

allocate an empty #snd_pcm_access_mask_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_access_mask_none()

void snd_pcm_access_mask_none

(

snd_pcm_access_mask_t *

mask

)

reset all bits in a #snd_pcm_access_mask_t

Parameters

mask	pointer to mask

snd_pcm_access_mask_reset()

void snd_pcm_access_mask_reset	(	snd_pcm_access_mask_t *	mask,
		snd_pcm_access_t	val )

make an access type missing from a #snd_pcm_access_mask_t

Parameters

mask	pointer to mask
val	access type

snd_pcm_access_mask_set()

void snd_pcm_access_mask_set	(	snd_pcm_access_mask_t *	mask,
		snd_pcm_access_t	val )

make an access type present in a #snd_pcm_access_mask_t

Parameters

mask	pointer to mask
val	access type

snd_pcm_access_mask_sizeof()

size_t snd_pcm_access_mask_sizeof

(

)

get size of #snd_pcm_access_mask_t

Returns

size in bytes

snd_pcm_access_mask_test()

int snd_pcm_access_mask_test	(	const snd_pcm_access_mask_t *	mask,
		snd_pcm_access_t	val )

test the presence of an access type in a #snd_pcm_access_mask_t

Parameters

mask	pointer to mask
val	access type

snd_pcm_access_name()

const char * snd_pcm_access_name

(

const snd_pcm_access_t

acc

)

get name of PCM access type

Parameters

acc	PCM access type

Returns

ascii name of PCM access type

snd_pcm_area_copy()

int snd_pcm_area_copy	(	const snd_pcm_channel_area_t *	dst_area,
		snd_pcm_uframes_t	dst_offset,
		const snd_pcm_channel_area_t *	src_area,
		snd_pcm_uframes_t	src_offset,
		unsigned int	samples,
		snd_pcm_format_t	format )

Copy an area.

Parameters

dst_area	destination area specification
dst_offset	offset in frames inside destination area
src_area	source area specification
src_offset	offset in frames inside source area
samples	samples to copy
format	PCM sample format

Returns

0 on success otherwise a negative error code

snd_pcm_area_silence()

int snd_pcm_area_silence	(	const snd_pcm_channel_area_t *	dst_area,
		snd_pcm_uframes_t	dst_offset,
		unsigned int	samples,
		snd_pcm_format_t	format )

Silence an area.

Parameters

dst_area	area specification
dst_offset	offset in frames inside area
samples	samples to silence
format	PCM sample format

Returns

0 on success otherwise a negative error code

snd_pcm_areas_copy()

int snd_pcm_areas_copy	(	const snd_pcm_channel_area_t *	dst_areas,
		snd_pcm_uframes_t	dst_offset,
		const snd_pcm_channel_area_t *	src_areas,
		snd_pcm_uframes_t	src_offset,
		unsigned int	channels,
		snd_pcm_uframes_t	frames,
		snd_pcm_format_t	format )

Copy one or more areas.

Parameters

dst_areas	destination areas specification (one for each channel)
dst_offset	offset in frames inside destination area
src_areas	source areas specification (one for each channel)
src_offset	offset in frames inside source area
channels	channels count
frames	frames to copy
format	PCM sample format

Returns

0 on success otherwise a negative error code

snd_pcm_areas_copy_wrap()

int snd_pcm_areas_copy_wrap	(	const snd_pcm_channel_area_t *	dst_channels,
		snd_pcm_uframes_t	dst_offset,
		const snd_pcm_uframes_t	dst_size,
		const snd_pcm_channel_area_t *	src_channels,
		snd_pcm_uframes_t	src_offset,
		const snd_pcm_uframes_t	src_size,
		const unsigned int	channels,
		snd_pcm_uframes_t	frames,
		const snd_pcm_format_t	format )

Copy one or more areas.

Parameters

dst_channels	destination areas specification (one for each channel)
dst_offset	offset in frames inside destination area
dst_size	size in frames of the destination buffer
src_channels	source areas specification (one for each channel)
src_offset	offset in frames inside source area
src_size	size in frames of the source buffer
channels	channels count
frames	frames to copy
format	PCM sample format

Returns

0 on success otherwise a negative error code

snd_pcm_areas_silence()

int snd_pcm_areas_silence	(	const snd_pcm_channel_area_t *	dst_areas,
		snd_pcm_uframes_t	dst_offset,
		unsigned int	channels,
		snd_pcm_uframes_t	frames,
		snd_pcm_format_t	format )

Silence one or more areas.

Parameters

dst_areas	areas specification (one for each channel)
dst_offset	offset in frames inside area
channels	channels count
frames	frames to silence
format	PCM sample format

Returns

0 on success otherwise a negative error code

snd_pcm_avail()

snd_pcm_sframes_t snd_pcm_avail

(

snd_pcm_t *

pcm

)

Return number of frames ready to be read (capture) / written (playback)

Parameters

pcm	PCM handle

Returns

a positive number of frames ready otherwise a negative error code

On capture does all the actions needed to transport to application level all the ready frames across underlying layers.

The position is synced with hardware (driver) position in the sound ring buffer in this functions.

The function is thread-safe when built with the proper option.

Examples

/test/latency.c.

snd_pcm_avail_delay()

int snd_pcm_avail_delay	(	snd_pcm_t *	pcm,
		snd_pcm_sframes_t *	availp,
		snd_pcm_sframes_t *	delayp )

Combine snd_pcm_avail and snd_pcm_delay functions.

Parameters

pcm	PCM handle
availp	Number of available frames in the ring buffer
delayp	Total I/O latency in frames

Returns

zero on success otherwise a negative error code

The avail and delay values returned are in sync.

The function is thread-safe when built with the proper option.

snd_pcm_avail_update()

snd_pcm_sframes_t snd_pcm_avail_update

(

snd_pcm_t *

pcm

)

Return number of frames ready to be read (capture) / written (playback)

Parameters

pcm	PCM handle

Returns

a positive number of frames ready otherwise a negative error code

On capture does all the actions needed to transport to application level all the ready frames across underlying layers.

The position is not synced with hardware (driver) position in the sound ring buffer in this function. This function is a light version of snd_pcm_avail() .

Using this function is ideal after poll() or select() when audio file descriptor made the event and when application expects just period timing.

Also this function might be called after snd_pcm_delay() or snd_pcm_hwsync() functions to move private ring buffer pointers in alsa-lib (the internal plugin chain).

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_bytes_to_frames()

snd_pcm_sframes_t snd_pcm_bytes_to_frames	(	snd_pcm_t *	pcm,
		ssize_t	bytes )

Convert bytes in frames for a PCM.

Parameters

pcm	PCM handle
bytes	quantity in bytes

Returns

quantity expressed in frames

snd_pcm_bytes_to_samples()

long snd_pcm_bytes_to_samples	(	snd_pcm_t *	pcm,
		ssize_t	bytes )

Convert bytes in samples for a PCM.

Parameters

pcm	PCM handle
bytes	quantity in bytes

Returns

quantity expressed in samples

snd_pcm_chmap_from_string()

unsigned int snd_pcm_chmap_from_string

(

const char *

str

)

!brief Convert from string to channel position

Parameters

str	The string to parse

Returns

The channel position value or -1 as an error

snd_pcm_chmap_long_name()

const char * snd_pcm_chmap_long_name

(

enum snd_pcm_chmap_position

val

)

!brief Get a longer name string for a standard channel map position

Parameters

val	Channel position

Returns

The string corresponding to the given position, or NULL

snd_pcm_chmap_name()

const char * snd_pcm_chmap_name

(

enum snd_pcm_chmap_position

val

)

!brief Get a name string for a standard channel map position

Parameters

val	Channel position

Returns

The string corresponding to the given position, or NULL

snd_pcm_chmap_parse_string()

snd_pcm_chmap_t * snd_pcm_chmap_parse_string

(

const char *

str

)

!brief Convert from string to channel map

Parameters

str	The string to parse

Returns

The channel map

Note: the caller is requested to release the returned value via free()

snd_pcm_chmap_print()

int snd_pcm_chmap_print	(	const snd_pcm_chmap_t *	map,
		size_t	maxlen,
		char *	buf )

!brief Print the channels in chmap on the buffer

Parameters

map	The channel map to print
maxlen	The maximal length to write (including NUL letter)
buf	The buffer to write

Returns

The actual string length or a negative error code

snd_pcm_chmap_type_name()

const char * snd_pcm_chmap_type_name

(

enum snd_pcm_chmap_type

val

)

!brief Get a name string for a channel map type as query results

Parameters

val	Channel position

Returns

The string corresponding to the given type, or NULL

snd_pcm_close()

int snd_pcm_close

(

snd_pcm_t *

pcm

)

close PCM handle

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

Closes the specified PCM handle and frees all associated resources.

Examples

/test/latency.c, /test/pcm.c, and /test/pcm_min.c.

snd_pcm_delay()

int snd_pcm_delay	(	snd_pcm_t *	pcm,
		snd_pcm_sframes_t *	delayp )

Obtain delay for a running PCM handle.

Parameters

pcm	PCM handle
delayp	Returned delay in frames

Returns

0 on success otherwise a negative error code

For playback the delay is defined as the time that a frame that is written to the PCM stream shortly after this call will take to be actually audible. It is as such the overall latency from the write call to the final DAC.

For capture the delay is defined as the time that a frame that was digitized by the audio device takes until it can be read from the PCM stream shortly after this call returns. It is as such the overall latency from the initial ADC to the read call.

Please note that hence in case of a playback underrun this value will not necessarily got down to 0.

If the application is interested in the fill level of the playback buffer of the device, it should use snd_pcm_avail*() functions. The value returned by that call is not directly related to the delay, since the latter might include some additional, fixed latencies the former does not.

Note this function does not update the actual r/w pointer for applications. The function snd_pcm_avail_update() have to be called before any begin+commit operation.

The function is thread-safe when built with the proper option.

snd_pcm_drain()

int snd_pcm_drain

(

snd_pcm_t *

pcm

)

Stop a PCM preserving pending frames.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

Return values

-ESTRPIPE

a suspend event occurred

For playback wait for all pending frames to be played and then stop the PCM. For capture stop PCM permitting to retrieve residual frames.

For stopping the PCM stream immediately, use ::snd_pcm_drop() instead.

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, and /test/pcm_min.c.

snd_pcm_drop()

int snd_pcm_drop

(

snd_pcm_t *

pcm

)

Stop a PCM dropping pending frames.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

This function stops the PCM immediately. The pending samples on the buffer are ignored.

For processing all pending samples, use ::snd_pcm_drain() instead.

The function is thread-safe when built with the proper option.

Examples

/test/latency.c.

snd_pcm_dump()

int snd_pcm_dump	(	snd_pcm_t *	pcm,
		snd_output_t *	out )

Dump PCM info.

Parameters

pcm	PCM handle
out	Output handle

Returns

0 on success otherwise a negative error code

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_dump_hw_setup()

int snd_pcm_dump_hw_setup	(	snd_pcm_t *	pcm,
		snd_output_t *	out )

Dump current hardware setup for PCM.

Parameters

pcm	PCM handle
out	Output handle

Returns

0 on success otherwise a negative error code

snd_pcm_dump_setup()

int snd_pcm_dump_setup	(	snd_pcm_t *	pcm,
		snd_output_t *	out )

Dump current setup (hardware and software) for PCM.

Parameters

pcm	PCM handle
out	Output handle

Returns

0 on success otherwise a negative error code

snd_pcm_dump_sw_setup()

int snd_pcm_dump_sw_setup	(	snd_pcm_t *	pcm,
		snd_output_t *	out )

Dump current software setup for PCM.

Parameters

pcm	PCM handle
out	Output handle

Returns

0 on success otherwise a negative error code

snd_pcm_format_description()

const char * snd_pcm_format_description

(

const snd_pcm_format_t

format

)

get description of PCM sample format

Parameters

format

PCM sample format

Returns

ascii description of PCM sample format

snd_pcm_format_mask_any()

void snd_pcm_format_mask_any

(

snd_pcm_format_mask_t *

mask

)

set all bits in a #snd_pcm_format_mask_t

Parameters

mask	pointer to mask

snd_pcm_format_mask_copy()

void snd_pcm_format_mask_copy	(	snd_pcm_format_mask_t *	dst,
		const snd_pcm_format_mask_t *	src )

copy one #snd_pcm_format_mask_t to another

Parameters

dst	pointer to destination
src	pointer to source

snd_pcm_format_mask_empty()

int snd_pcm_format_mask_empty

(

const snd_pcm_format_mask_t *

mask

)

test, if given a #snd_pcm_format_mask_t is empty

Parameters

mask	pointer to mask

Return values

0	not empty
1	empty

snd_pcm_format_mask_free()

void snd_pcm_format_mask_free

(

snd_pcm_format_mask_t *

obj

)

frees a previously allocated #snd_pcm_format_mask_t

Parameters

obj	pointer to object to free

snd_pcm_format_mask_malloc()

int snd_pcm_format_mask_malloc

(

snd_pcm_format_mask_t **

ptr

)

allocate an empty #snd_pcm_format_mask_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_format_mask_none()

void snd_pcm_format_mask_none

(

snd_pcm_format_mask_t *

mask

)

reset all bits in a #snd_pcm_format_mask_t

Parameters

mask	pointer to mask

snd_pcm_format_mask_reset()

void snd_pcm_format_mask_reset	(	snd_pcm_format_mask_t *	mask,
		snd_pcm_format_t	val )

make a format missing from a #snd_pcm_format_mask_t

Parameters

mask	pointer to mask
val	format

snd_pcm_format_mask_set()

void snd_pcm_format_mask_set	(	snd_pcm_format_mask_t *	mask,
		snd_pcm_format_t	val )

make a format present in a #snd_pcm_format_mask_t

Parameters

mask	pointer to mask
val	format

snd_pcm_format_mask_sizeof()

size_t snd_pcm_format_mask_sizeof

(

)

get size of #snd_pcm_format_mask_t

Returns

size in bytes

snd_pcm_format_mask_test()

int snd_pcm_format_mask_test	(	const snd_pcm_format_mask_t *	mask,
		snd_pcm_format_t	val )

test the presence of a format in a #snd_pcm_format_mask_t

Parameters

mask	pointer to mask
val	format

snd_pcm_format_name()

const char * snd_pcm_format_name

(

const snd_pcm_format_t

format

)

get name of PCM sample format

Parameters

format

PCM sample format

Returns

ascii name of PCM sample format

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_format_value()

snd_pcm_format_t snd_pcm_format_value

(

const char *

name

)

get PCM sample format from name

Parameters

name	PCM sample format name (case insensitive)

Returns

PCM sample format

Examples

/test/latency.c.

snd_pcm_forward()

snd_pcm_sframes_t snd_pcm_forward	(	snd_pcm_t *	pcm,
		snd_pcm_uframes_t	frames )

Move application frame position forward.

Parameters

pcm	PCM handle
frames	wanted skip in frames

Returns

a positive number for actual skip otherwise a negative error code

Return values

0	means no action

The function is thread-safe when built with the proper option.

snd_pcm_forwardable()

snd_pcm_sframes_t snd_pcm_forwardable

(

snd_pcm_t *

pcm

)

Get safe count of frames which can be forwarded.

Parameters

pcm	PCM handle

Returns

a positive number of frames or negative error code

Note: The snd_pcm_forward() can accept bigger value than returned by this function. But it is not guaranteed that output stream will be consistent with bigger value.

The function is thread-safe when built with the proper option.

snd_pcm_frames_to_bytes()

ssize_t snd_pcm_frames_to_bytes	(	snd_pcm_t *	pcm,
		snd_pcm_sframes_t	frames )

Convert frames in bytes for a PCM.

Parameters

pcm	PCM handle
frames	quantity in frames

Returns

quantity expressed in bytes

snd_pcm_free_chmaps()

void snd_pcm_free_chmaps

(

snd_pcm_chmap_query_t **

maps

)

!brief Release the channel map array allocated via snd_pcm_query_chmaps

Parameters

maps	the array pointer to release

snd_pcm_get_chmap()

snd_pcm_chmap_t * snd_pcm_get_chmap

(

snd_pcm_t *

pcm

)

!brief Get the current channel map

Parameters

pcm	PCM instance

Returns

the current channel map, or NULL if error

Note: the caller is requested to release the returned value via free()

snd_pcm_get_params()

int snd_pcm_get_params	(	snd_pcm_t *	pcm,
		snd_pcm_uframes_t *	buffer_size,
		snd_pcm_uframes_t *	period_size )

Get the transfer size parameters in a simple way.

Parameters

pcm	PCM handle
buffer_size	PCM ring buffer size in frames
period_size	PCM period size in frames

Returns

0 on success otherwise a negative error code

snd_pcm_htimestamp()

int snd_pcm_htimestamp	(	snd_pcm_t *	pcm,
		snd_pcm_uframes_t *	avail,
		snd_htimestamp_t *	tstamp )

Obtain last position update hi-res timestamp.

Parameters

pcm	PCM handle
avail	Number of available frames when timestamp was grabbed
tstamp	Hi-res timestamp

Returns

0 on success otherwise a negative error code

Note this function does not update the actual r/w pointer for applications.

The function is thread-safe when built with the proper option.

snd_pcm_hw_free()

int snd_pcm_hw_free

(

snd_pcm_t *

pcm

)

Remove PCM hardware configuration and free associated resources.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

The function will also report success if no configuration is set.

Examples

/test/latency.c.

snd_pcm_hw_params()

int snd_pcm_hw_params	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params )

Install one PCM hardware configuration chosen from a configuration space and snd_pcm_prepare it.

Parameters

pcm	PCM handle
params	Configuration space definition container

Returns

0 on success otherwise a negative error code

The configuration is chosen fixing single parameters in this order: first access, first format, first subformat, min channels, min rate, min period time, max buffer size, min tick time. If no mutually compatible set of parameters can be chosen, a negative error code will be returned.

After this call, snd_pcm_prepare() is called automatically and the stream is brought to #SND_PCM_STATE_PREPARED state.

The hardware parameters cannot be changed when the stream is running (active). The software parameters can be changed at any time.

The configuration space will be updated to reflect the chosen parameters.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_any()

int snd_pcm_hw_params_any	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params )

Fill params with a full configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space

The configuration space will be filled with all possible ranges for the PCM device.

Note that the configuration space may be constrained by the currently installed configuration on the PCM device. To remove any constrains, free the configuration with snd_pcm_hw_free first.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_can_disable_period_wakeup()

int snd_pcm_hw_params_can_disable_period_wakeup

(

const snd_pcm_hw_params_t *

params

)

Check if hardware can disable period wakeups.

Parameters

params

Configuration space

Return values

0	Hardware cannot disable period wakeups
1	Hardware can disable period wakeups

Examples

/test/latency.c.

snd_pcm_hw_params_can_mmap_sample_resolution()

int snd_pcm_hw_params_can_mmap_sample_resolution

(

const snd_pcm_hw_params_t *

params

)

Check if hardware supports sample-resolution mmap for given configuration.

Parameters

params

Configuration space

Return values

0	Hardware doesn't support sample-resolution mmap
1	Hardware supports sample-resolution mmap

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_can_overrange()

int snd_pcm_hw_params_can_overrange

(

const snd_pcm_hw_params_t *

params

)

Check if hardware supports overrange detection.

Parameters

params

Configuration space

Return values

0	Hardware doesn't support overrange detection
1	Hardware supports overrange detection

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_can_pause()

int snd_pcm_hw_params_can_pause

(

const snd_pcm_hw_params_t *

params

)

Check if hardware supports pause.

Parameters

params

Configuration space

Return values

0	Hardware doesn't support pause
1	Hardware supports pause

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_can_resume()

int snd_pcm_hw_params_can_resume

(

const snd_pcm_hw_params_t *

params

)

Check if hardware supports resume.

Parameters

params

Configuration space

Return values

0	Hardware doesn't support resume
1	Hardware supports resume

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_can_sync_start()

int snd_pcm_hw_params_can_sync_start

(

const snd_pcm_hw_params_t *

params

)

Check if hardware supports synchronized start with sample resolution.

Parameters

params

Configuration space

Return values

0	Hardware doesn't support synchronized start
1	Hardware supports synchronized start

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_copy()

void snd_pcm_hw_params_copy	(	snd_pcm_hw_params_t *	dst,
		const snd_pcm_hw_params_t *	src )

copy one #snd_pcm_hw_params_t to another

Parameters

dst	pointer to destination
src	pointer to source

Examples

/test/latency.c.

snd_pcm_hw_params_current()

int snd_pcm_hw_params_current	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params )

Retreive current PCM hardware configuration chosen with snd_pcm_hw_params.

Parameters

pcm	PCM handle
params	Configuration space definition container

Returns

0 on success otherwise a negative error code

Return values

-EBADFD

no hardware configuration is set

snd_pcm_hw_params_dump()

int snd_pcm_hw_params_dump	(	snd_pcm_hw_params_t *	params,
		snd_output_t *	out )

Dump a PCM hardware configuration space.

Parameters

params	Configuration space
out	Output handle

Returns

0 on success otherwise a negative error code

snd_pcm_hw_params_free()

void snd_pcm_hw_params_free

(

snd_pcm_hw_params_t *

obj

)

frees a previously allocated #snd_pcm_hw_params_t

Parameters

obj	pointer to object to free

snd_pcm_hw_params_get_access()

int snd_pcm_hw_params_get_access	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_access_t *	access )

Extract access type from a configuration space.

Parameters

params	Configuration space
access	Returned value

Returns

access type otherwise a negative error code if the configuration space does not contain a single value

snd_pcm_hw_params_get_access_mask()

int snd_pcm_hw_params_get_access_mask	(	snd_pcm_hw_params_t *	params,
		snd_pcm_access_mask_t *	mask )

Get access mask from a configuration space.

Parameters

params	Configuration space
mask	Returned Access mask

snd_pcm_hw_params_get_buffer_size()

int snd_pcm_hw_params_get_buffer_size	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Extract buffer size from a configuration space.

Parameters

params	Configuration space
val	Returned buffer size in frames

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_get_buffer_size_max()

int snd_pcm_hw_params_get_buffer_size_max	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Extract maximum buffer size from a configuration space.

Parameters

params	Configuration space
val	Returned approximate maximum buffer size in frames

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_buffer_size_min()

int snd_pcm_hw_params_get_buffer_size_min	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Extract minimum buffer size from a configuration space.

Parameters

params	Configuration space
val	Returned approximate minimum buffer size in frames

Returns

0 otherwise a negative error code

snd_pcm_hw_params_get_buffer_time()

int snd_pcm_hw_params_get_buffer_time	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract buffer time from a configuration space.

Parameters

params	Configuration space
val	Returned buffer time in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_get_buffer_time_max()

int snd_pcm_hw_params_get_buffer_time_max	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract maximum buffer time from a configuration space.

Parameters

params	Configuration space
val	approximate maximum buffer duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_buffer_time_min()

int snd_pcm_hw_params_get_buffer_time_min	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract minimum buffer time from a configuration space.

Parameters

params	Configuration space
val	approximate minimum buffer duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_channels()

int snd_pcm_hw_params_get_channels	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract channels from a configuration space.

Parameters

params	Configuration space
val	Returned channels count

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

snd_pcm_hw_params_get_channels_max()

int snd_pcm_hw_params_get_channels_max	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract maximum channels count from a configuration space.

Parameters

params	Configuration space
val	maximum channels count

Returns

0 otherwise a negative error code

snd_pcm_hw_params_get_channels_min()

int snd_pcm_hw_params_get_channels_min	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract minimum channels count from a configuration space.

Parameters

params	Configuration space
val	minimum channels count

Returns

0 otherwise a negative error code

snd_pcm_hw_params_get_drain_silence()

int snd_pcm_hw_params_get_drain_silence	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract drain with the filling of silence samples from a configuration space.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disabled, 1 = enabled

Returns

0 otherwise a negative error code

snd_pcm_hw_params_get_export_buffer()

int snd_pcm_hw_params_get_export_buffer	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract buffer accessibility from a configuration space.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disable, 1 = enable exporting buffer

Returns

0 otherwise a negative error code

snd_pcm_hw_params_get_fifo_size()

int snd_pcm_hw_params_get_fifo_size

(

const snd_pcm_hw_params_t *

params

)

Get hardware FIFO size info from a configuration space.

Parameters

params

Configuration space

Returns

FIFO size in frames otherwise a negative error code if the info is not available

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_get_format()

int snd_pcm_hw_params_get_format	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_format_t *	format )

Extract format from a configuration space.

Parameters

params	Configuration space
format	returned format

Returns

format otherwise a negative error code if the configuration space does not contain a single value

snd_pcm_hw_params_get_format_mask()

void snd_pcm_hw_params_get_format_mask	(	snd_pcm_hw_params_t *	params,
		snd_pcm_format_mask_t *	mask )

Get format mask from a configuration space.

Parameters

params	Configuration space
mask	Returned Format mask

snd_pcm_hw_params_get_min_align()

int snd_pcm_hw_params_get_min_align	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get the minimum transfer align value in samples.

Parameters

params	Configuration space
val	Returned minimum align value

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

snd_pcm_hw_params_get_period_size()

int snd_pcm_hw_params_get_period_size	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Extract period size from a configuration space.

Parameters

params	Configuration space
val	Returned approximate period size in frames
dir	Sub unit direction

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_get_period_size_max()

int snd_pcm_hw_params_get_period_size_max	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Extract maximum period size from a configuration space.

Parameters

params	Configuration space
val	approximate minimum period size in frames
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_period_size_min()

int snd_pcm_hw_params_get_period_size_min	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Extract minimum period size from a configuration space.

Parameters

params	Configuration space
val	approximate minimum period size in frames
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_period_time()

int snd_pcm_hw_params_get_period_time	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract period time from a configuration space.

Parameters

params	Configuration space
val	Returned approximate period duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

Examples

/test/latency.c.

snd_pcm_hw_params_get_period_time_max()

int snd_pcm_hw_params_get_period_time_max	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract maximum period time from a configuration space.

Parameters

params	Configuration space
val	approximate maximum period duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_period_time_min()

int snd_pcm_hw_params_get_period_time_min	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract minimum period time from a configuration space.

Parameters

params	Configuration space
val	approximate minimum period duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_period_wakeup()

int snd_pcm_hw_params_get_period_wakeup	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract period wakeup flag from a configuration space.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disabled, 1 = enabled period wakeups

Returns

Zero on success, otherwise a negative error code.

snd_pcm_hw_params_get_periods()

int snd_pcm_hw_params_get_periods	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract periods from a configuration space.

Parameters

params	Configuration space
val	approximate periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_get_periods_max()

int snd_pcm_hw_params_get_periods_max	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract maximum periods count from a configuration space.

Parameters

params	Configuration space
val	approximate maximum periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_periods_min()

int snd_pcm_hw_params_get_periods_min	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract minimum periods count from a configuration space.

Parameters

params	Configuration space
val	approximate minimum periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

Examples

/test/latency.c.

snd_pcm_hw_params_get_rate()

int snd_pcm_hw_params_get_rate	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract rate from a configuration space.

Parameters

params	Configuration space
val	Returned approximate rate
dir	Sub unit direction

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_get_rate_max()

int snd_pcm_hw_params_get_rate_max	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract maximum rate from a configuration space.

Parameters

params	Configuration space
val	Returned approximate maximum rate
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_rate_min()

int snd_pcm_hw_params_get_rate_min	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Extract minimum rate from a configuration space.

Parameters

params	Configuration space
val	Returned approximate minimum rate
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_rate_numden()

int snd_pcm_hw_params_get_rate_numden	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	rate_num,
		unsigned int *	rate_den )

Get rate exact info from a configuration space.

Parameters

params	Configuration space
rate_num	Pointer to returned rate numerator
rate_den	Pointer to returned rate denominator

Returns

0 otherwise a negative error code if the info is not available

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_get_rate_resample()

int snd_pcm_hw_params_get_rate_resample	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Extract resample state from a configuration space.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disable, 1 = enable rate resampling

Returns

0 otherwise a negative error code

snd_pcm_hw_params_get_sbits()

int snd_pcm_hw_params_get_sbits

(

const snd_pcm_hw_params_t *

params

)

Get sample resolution info from a configuration space.

Parameters

params

Configuration space

Returns

sample resolution (in bits) otherwise a negative error code if the info is not available

For linear formats, this function returns sample resolution - used bits starting from the first usable significant bit defined by the format (e.g. bit 31 for S32_LE format or bit 23 for S24_LE format - starting from bit zero). Application may use full sample bit range defined by the format, but additional bits (outside this sample resolution) are stripped (not processed).

For non-linear formats, this value may have a special meaning which may be defined in future.

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_get_subformat()

int snd_pcm_hw_params_get_subformat	(	const snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_t *	subformat )

Extract subformat from a configuration space.

Parameters

params	Configuration space
subformat	Returned subformat value

Returns

subformat otherwise a negative error code if the configuration space does not contain a single value

snd_pcm_hw_params_get_subformat_mask()

void snd_pcm_hw_params_get_subformat_mask	(	snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_mask_t *	mask )

Get subformat mask from a configuration space.

Parameters

params	Configuration space
mask	Returned Subformat mask

snd_pcm_hw_params_get_sync()

const unsigned char * snd_pcm_hw_params_get_sync

(

const snd_pcm_hw_params_t *

params

)

Get hardware synchronization ID from a PCM info container.

Parameters

params

Configuration space

Returns

16-byte synchronization ID (use #SND_PCM_HW_PARAMS_SYNC_SIZE)

This synchronization ID determines the similar clocks for the PCM stream between multiple devices (including different cards). "All zeros" means "not set". The contents of the ID can be used only for a comparison with the contents of another ID returned from this function. Applications should not do a comparison with hard-coded values, because the implementation generating such synchronization IDs may be changed in future.

snd_pcm_hw_params_get_tick_time()

int snd_pcm_hw_params_get_tick_time	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Extract tick time from a configuration space

Parameters

params	Configuration space
val	Returned approximate tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if the configuration space does not contain a single value

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_get_tick_time_max()

int snd_pcm_hw_params_get_tick_time_max	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Extract maximum tick time from a configuration space

Parameters

params	Configuration space
val	Returned approximate maximum tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_get_tick_time_min()

int snd_pcm_hw_params_get_tick_time_min	(	const snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Extract minimum tick time from a configuration space

Parameters

params	Configuration space
val	Returned approximate minimum tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Exact value is <,=,> the returned one following dir (-1,0,1)

snd_pcm_hw_params_is_batch()

int snd_pcm_hw_params_is_batch

(

const snd_pcm_hw_params_t *

params

)

Check if hardware does double buffering for data transfers for given configuration.

Parameters

params

Configuration space

Return values

0	Hardware doesn't do double buffering for data transfers
1	Hardware does double buffering for data transfers

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_is_block_transfer()

int snd_pcm_hw_params_is_block_transfer

(

const snd_pcm_hw_params_t *

params

)

Check if hardware does block transfers for samples for given configuration.

Parameters

params

Configuration space

Return values

0	Hardware doesn't block transfers
1	Hardware does block transfers

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_is_double()

int snd_pcm_hw_params_is_double

(

const snd_pcm_hw_params_t *

params

)

Check if hardware does double buffering for start/stop for given configuration.

Parameters

params

Configuration space

Return values

0	Hardware doesn't do double buffering for start/stop
1	Hardware does double buffering for start/stop

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_is_half_duplex()

int snd_pcm_hw_params_is_half_duplex

(

const snd_pcm_hw_params_t *

params

)

Check if hardware does half-duplex only.

Parameters

params

Configuration space

Return values

0	Hardware doesn't do half-duplex
1	Hardware does half-duplex

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_is_joint_duplex()

int snd_pcm_hw_params_is_joint_duplex

(

const snd_pcm_hw_params_t *

params

)

Check if hardware does joint-duplex (playback and capture are somewhat correlated)

Parameters

params

Configuration space

Return values

0	Hardware doesn't do joint-duplex
1	Hardware does joint-duplex

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_is_monotonic()

int snd_pcm_hw_params_is_monotonic

(

const snd_pcm_hw_params_t *

params

)

Check if timestamps are monotonic for given configuration.

Parameters

params

Configuration space

Return values

0	Device doesn't do monotomic timestamps
1	Device does monotonic timestamps

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_is_perfect_drain()

int snd_pcm_hw_params_is_perfect_drain

(

const snd_pcm_hw_params_t *

params

)

Check if hardware is capable of perfect drain.

Parameters

params

Configuration space

Return values

0	Hardware doesn't do perfect drain
1	Hardware does perfect drain

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

Perfect drain means that the hardware does not use samples beyond the stream application pointer.

snd_pcm_hw_params_malloc()

int snd_pcm_hw_params_malloc

(

snd_pcm_hw_params_t **

ptr

)

allocate an invalid #snd_pcm_hw_params_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_hw_params_set_access()

int snd_pcm_hw_params_set_access	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_access_t	access )

Restrict a configuration space to contain only one access type.

Parameters

pcm	PCM handle
params	Configuration space
access	access type

Returns

0 otherwise a negative error code if configuration space would become empty

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_set_access_first()

int snd_pcm_hw_params_set_access_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_access_t *	access )

Restrict a configuration space to contain only its first access type.

Parameters

pcm	PCM handle
params	Configuration space
access	Returned first access type

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_access_last()

int snd_pcm_hw_params_set_access_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_access_t *	access )

Restrict a configuration space to contain only its last access type.

Parameters

pcm	PCM handle
params	Configuration space
access	Returned last access type

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_access_mask()

int snd_pcm_hw_params_set_access_mask	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_access_mask_t *	mask )

Restrict a configuration space to contain only a set of access types.

Parameters

pcm	PCM handle
params	Configuration space
mask	Access mask

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_buffer_size()

int snd_pcm_hw_params_set_buffer_size	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t	val )

Restrict a configuration space to contain only one buffer size.

Parameters

pcm	PCM handle
params	Configuration space
val	buffer size in frames

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_buffer_size_first()

int snd_pcm_hw_params_set_buffer_size_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Restrict a configuration space to contain only its minimum buffer size.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned minimum buffer size in frames

Returns

buffer size in frames

snd_pcm_hw_params_set_buffer_size_last()

int snd_pcm_hw_params_set_buffer_size_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Restrict a configuration space to contain only its maximum buffer size.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned maximum buffer size in frames

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_buffer_size_max()

int snd_pcm_hw_params_set_buffer_size_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Restrict a configuration space with a maximum buffer size.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum buffer size in frames (on return filled with actual maximum)

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_buffer_size_min()

int snd_pcm_hw_params_set_buffer_size_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Restrict a configuration space with a minimum buffer size.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum buffer size in frames (on return filled with actual minimum)

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_buffer_size_minmax()

int snd_pcm_hw_params_set_buffer_size_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	min,
		snd_pcm_uframes_t *	max )

Restrict a configuration space to have buffer sizes in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum buffer size in frames (on return filled with actual minimum)
max	approximate maximum buffer size in frames (on return filled with actual maximum)

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_buffer_size_near()

int snd_pcm_hw_params_set_buffer_size_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val )

Restrict a configuration space to have buffer size nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target buffer size in frames / returned chosen approximate target buffer size in frames

Returns

0 otherwise a negative error code if configuration space is empty

Examples

/test/latency.c.

snd_pcm_hw_params_set_buffer_time()

int snd_pcm_hw_params_set_buffer_time	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Restrict a configuration space to contain only one buffer time.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate buffer duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_buffer_time_first()

int snd_pcm_hw_params_set_buffer_time_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its minimum buffer time.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate minimum buffer duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_buffer_time_last()

int snd_pcm_hw_params_set_buffer_time_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its maximum buffered time.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate maximum buffer duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_buffer_time_max()

int snd_pcm_hw_params_set_buffer_time_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a maximum buffer time.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum buffer duration in us (on return filled with actual maximum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact maximum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_buffer_time_min()

int snd_pcm_hw_params_set_buffer_time_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a minimum buffer time.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum buffer duration in us (on return filled with actual minimum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_buffer_time_minmax()

int snd_pcm_hw_params_set_buffer_time_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	min,
		int *	mindir,
		unsigned int *	max,
		int *	maxdir )

Restrict a configuration space to have buffer times in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum buffer duration in us (on return filled with actual minimum)
mindir	Sub unit direction for minimum (on return filled with actual direction)
max	approximate maximum buffer duration in us (on return filled with actual maximum)
maxdir	Sub unit direction for maximum (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact min/max is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_buffer_time_near()

int snd_pcm_hw_params_set_buffer_time_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to have buffer time nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target buffer duration in us / returned chosen approximate target buffer duration
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space is empty

target/chosen exact value is <,=,> val following dir (-1,0,1)

Examples

/test/pcm.c.

snd_pcm_hw_params_set_channels()

int snd_pcm_hw_params_set_channels	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val )

Restrict a configuration space to contain only one channels count.

Parameters

pcm	PCM handle
params	Configuration space
val	channels count

Returns

0 otherwise a negative error code if configuration space would become empty

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_set_channels_first()

int snd_pcm_hw_params_set_channels_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Restrict a configuration space to contain only its minimum channels count.

Parameters

pcm	PCM handle
params	Configuration space
val	minimum channels count

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_channels_last()

int snd_pcm_hw_params_set_channels_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Restrict a configuration space to contain only its maximum channels count.

Parameters

pcm	PCM handle
params	Configuration space
val	maximum channels count

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_channels_max()

int snd_pcm_hw_params_set_channels_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Restrict a configuration space with a maximum channels count.

Parameters

pcm	PCM handle
params	Configuration space
val	maximum channels count (on return filled with actual maximum)

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_channels_min()

int snd_pcm_hw_params_set_channels_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Restrict a configuration space with a minimum channels count.

Parameters

pcm	PCM handle
params	Configuration space
val	minimum channels count (on return filled with actual minimum)

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_channels_minmax()

int snd_pcm_hw_params_set_channels_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	min,
		unsigned int *	max )

Restrict a configuration space to have channels counts in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	minimum channels count (on return filled with actual minimum)
max	maximum channels count (on return filled with actual maximum)

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_channels_near()

int snd_pcm_hw_params_set_channels_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val )

Restrict a configuration space to have channels count nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	target channels count, returned chosen channels count

Returns

0 otherwise a negative error code if configuration space is empty

snd_pcm_hw_params_set_drain_silence()

int snd_pcm_hw_params_set_drain_silence	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val )

Restrict a configuration space to fill the end of playback stream with silence when drain() is invoked.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disabled, 1 = enabled (default) fill the end of the playback stream with silence when drain() is invoked

Returns

Zero on success, otherwise a negative error code.

When disabled, the application should handle the end of stream gracefully (fill the silent samples to align to the period size plus some extra samples for hardware / driver without perfect drain). Note that the rewind may be used for this purpose or the sw_params silencing mechanism.

snd_pcm_hw_params_set_export_buffer()

int snd_pcm_hw_params_set_export_buffer	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val )

Restrict a configuration space to allow the buffer to be accessible from outside.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disable, 1 = enable (default) exporting buffer

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_format()

int snd_pcm_hw_params_set_format	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_format_t	format )

Restrict a configuration space to contain only one format.

Parameters

pcm	PCM handle
params	Configuration space
format	format

Returns

0 otherwise a negative error code

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_set_format_first()

int snd_pcm_hw_params_set_format_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_format_t *	format )

Restrict a configuration space to contain only its first format.

Parameters

pcm	PCM handle
params	Configuration space
format	Returned first format

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_format_last()

int snd_pcm_hw_params_set_format_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_format_t *	format )

Restrict a configuration space to contain only its last format.

Parameters

pcm	PCM handle
params	Configuration space
format	Returned last format

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_format_mask()

int snd_pcm_hw_params_set_format_mask	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_format_mask_t *	mask )

Restrict a configuration space to contain only a set of formats.

Parameters

pcm	PCM handle
params	Configuration space
mask	Format mask

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_period_size()

int snd_pcm_hw_params_set_period_size	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t	val,
		int	dir )

Restrict a configuration space to contain only one period size.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate period size in frames
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_size_first()

int snd_pcm_hw_params_set_period_size_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Restrict a configuration space to contain only its minimum period size.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned maximum approximate period size in frames
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_period_size_integer()

int snd_pcm_hw_params_set_period_size_integer	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params )

Restrict a configuration space to contain only integer period sizes.

Parameters

pcm	PCM handle
params	Configuration space

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_period_size_last()

int snd_pcm_hw_params_set_period_size_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Restrict a configuration space to contain only its maximum period size.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned maximum approximate period size in frames
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_period_size_max()

int snd_pcm_hw_params_set_period_size_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Restrict a configuration space with a maximum period size.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum period size in frames (on return filled with actual maximum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_size_min()

int snd_pcm_hw_params_set_period_size_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Restrict a configuration space with a minimum period size.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum period size in frames (on return filled with actual minimum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_size_minmax()

int snd_pcm_hw_params_set_period_size_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	min,
		int *	mindir,
		snd_pcm_uframes_t *	max,
		int *	maxdir )

Restrict a configuration space to have period sizes in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum period size in frames (on return filled with actual minimum)
mindir	Sub unit direction for minimum (on return filled with actual direction)
max	approximate maximum period size in frames (on return filled with actual maximum)
maxdir	Sub unit direction for maximum (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact min/max is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_size_near()

int snd_pcm_hw_params_set_period_size_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t *	val,
		int *	dir )

Restrict a configuration space to have period size nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target period size in frames / returned chosen approximate target period size
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space is empty

target/chosen exact value is <,=,> val following dir (-1,0,1)

Examples

/test/latency.c.

snd_pcm_hw_params_set_period_time()

int snd_pcm_hw_params_set_period_time	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Restrict a configuration space to contain only one period time.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate period duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_time_first()

int snd_pcm_hw_params_set_period_time_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its minimum period time.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate period duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_period_time_last()

int snd_pcm_hw_params_set_period_time_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its maximum period time.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned maximum approximate period time
dir	Sub unit direction

Returns

approximate period duration in us

snd_pcm_hw_params_set_period_time_max()

int snd_pcm_hw_params_set_period_time_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a maximum period time.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum period duration in us (on return filled with actual maximum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact maximum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_time_min()

int snd_pcm_hw_params_set_period_time_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a minimum period time.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum period duration in us (on return filled with actual minimum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_time_minmax()

int snd_pcm_hw_params_set_period_time_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	min,
		int *	mindir,
		unsigned int *	max,
		int *	maxdir )

Restrict a configuration space to have period times in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum period duration in us (on return filled with actual minimum)
mindir	Sub unit direction for minimum (on return filled with actual direction)
max	approximate maximum period duration in us (on return filled with actual maximum)
maxdir	Sub unit direction for maximum (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact min/max is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_period_time_near()

int snd_pcm_hw_params_set_period_time_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to have period time nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target period duration in us / returned chosen approximate target period duration
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space is empty

target/chosen exact value is <,=,> val following dir (-1,0,1)

Examples

/test/pcm.c.

snd_pcm_hw_params_set_period_wakeup()

int snd_pcm_hw_params_set_period_wakeup	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val )

Restrict a configuration space to settings without period wakeups.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disable, 1 = enable (default) period wakeup

Returns

Zero on success, otherwise a negative error code.

This function must be called only on devices where non-blocking mode is enabled.

To check whether the hardware does support disabling period wakeups, call snd_pcm_hw_params_can_disable_period_wakeup(). If the hardware does not support this mode, standard period wakeups will be generated.

Even with disabled period wakeups, the period size/time/count parameters are valid; it is suggested to use snd_pcm_hw_params_set_period_size_last().

When period wakeups are disabled, the application must not use any functions that could block on this device. The use of poll should be limited to error cases. The application needs to use an external event or a timer to check the state of the ring buffer and refill it apropriately.

Examples

/test/latency.c.

snd_pcm_hw_params_set_periods()

int snd_pcm_hw_params_set_periods	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Restrict a configuration space to contain only one periods count.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_periods_first()

int snd_pcm_hw_params_set_periods_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its minimum periods count.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate minimum periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_periods_integer()

int snd_pcm_hw_params_set_periods_integer	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params )

Restrict a configuration space to contain only integer periods counts.

Parameters

pcm	PCM handle
params	Configuration space

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_periods_last()

int snd_pcm_hw_params_set_periods_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its maximum periods count.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate maximum periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_periods_max()

int snd_pcm_hw_params_set_periods_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a maximum periods count.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum periods per buffer (on return filled with actual maximum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact maximum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_periods_min()

int snd_pcm_hw_params_set_periods_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a minimum periods count.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum periods per buffer (on return filled with actual minimum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_periods_minmax()

int snd_pcm_hw_params_set_periods_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	min,
		int *	mindir,
		unsigned int *	max,
		int *	maxdir )

Restrict a configuration space to have periods counts in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum periods per buffer (on return filled with actual minimum)
mindir	Sub unit direction for minimum (on return filled with actual direction)
max	approximate maximum periods per buffer (on return filled with actual maximum)
maxdir	Sub unit direction for maximum (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact min/max is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_periods_near()

int snd_pcm_hw_params_set_periods_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to have periods count nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target periods per buffer / returned chosen approximate target periods per buffer
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space is empty

target/chosen exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_rate()

int snd_pcm_hw_params_set_rate	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Restrict a configuration space to contain only one rate.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate rate
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_rate_first()

int snd_pcm_hw_params_set_rate_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its minimum rate.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned minimum approximate rate
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_rate_last()

int snd_pcm_hw_params_set_rate_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to contain only its maximum rate.

Parameters

pcm	PCM handle
params	Configuration space
val	Returned maximum approximate rate
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_rate_max()

int snd_pcm_hw_params_set_rate_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a maximum rate.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum rate (on return filled with actual maximum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact maximum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_rate_min()

int snd_pcm_hw_params_set_rate_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space with a minimum rate.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum rate (on return filled with actual minimum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_rate_minmax()

int snd_pcm_hw_params_set_rate_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	min,
		int *	mindir,
		unsigned int *	max,
		int *	maxdir )

Restrict a configuration space to have rates in a given range.

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum rate (on return filled with actual minimum)
mindir	Sub unit direction for minimum (on return filled with actual direction)
max	approximate maximum rate (on return filled with actual maximum)
maxdir	Sub unit direction for maximum (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact min/max is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_rate_near()

int snd_pcm_hw_params_set_rate_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

Restrict a configuration space to have rate nearest to a target.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target rate / returned approximate set rate
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space is empty

target/chosen exact value is <,=,> val following dir (-1,0,1)

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_set_rate_resample()

int snd_pcm_hw_params_set_rate_resample	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val )

Restrict a configuration space to contain only real hardware rates.

Parameters

pcm	PCM handle
params	Configuration space
val	0 = disable, 1 = enable (default) rate resampling

Returns

0 otherwise a negative error code

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_hw_params_set_subformat()

int snd_pcm_hw_params_set_subformat	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_t	subformat )

Restrict a configuration space to contain only one subformat.

Parameters

pcm	PCM handle
params	Configuration space
subformat	subformat value

Returns

0 otherwise a negative error code if configuration space would become empty

snd_pcm_hw_params_set_subformat_first()

int snd_pcm_hw_params_set_subformat_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_t *	subformat )

Restrict a configuration space to contain only its first subformat.

Parameters

pcm	PCM handle
params	Configuration space
subformat	Returned subformat

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_subformat_last()

int snd_pcm_hw_params_set_subformat_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_t *	subformat )

Restrict a configuration space to contain only its last subformat.

Parameters

pcm	PCM handle
params	Configuration space
subformat	Returned subformat

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_subformat_mask()

int snd_pcm_hw_params_set_subformat_mask	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_mask_t *	mask )

Restrict a configuration space to contain only a set of subformats.

Parameters

pcm	PCM handle
params	Configuration space
mask	Subformat mask

Returns

0 otherwise a negative error code

snd_pcm_hw_params_set_tick_time()

int snd_pcm_hw_params_set_tick_time	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

(DEPRECATED) Restrict a configuration space to contain only one tick time

Parameters

pcm	PCM handle
params	Configuration space
val	approximate tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_tick_time_first()

int snd_pcm_hw_params_set_tick_time_first	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Restrict a configuration space to contain only its minimum tick time

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate minimum tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_tick_time_last()

int snd_pcm_hw_params_set_tick_time_last	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Restrict a configuration space to contain only its maximum tick time

Parameters

pcm	PCM handle
params	Configuration space
val	Returned approximate maximum tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code

Actual exact value is <,=,> the approximate one following dir (-1, 0, 1)

snd_pcm_hw_params_set_tick_time_max()

int snd_pcm_hw_params_set_tick_time_max	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Restrict a configuration space with a maximum tick time

Parameters

pcm	PCM handle
params	Configuration space
val	approximate maximum tick duration in us (on return filled with actual maximum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact maximum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_tick_time_min()

int snd_pcm_hw_params_set_tick_time_min	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Restrict a configuration space with a minimum tick time

Parameters

pcm	PCM handle
params	Configuration space
val	approximate minimum tick duration in us (on return filled with actual minimum)
dir	Sub unit direction (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact minimum is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_tick_time_minmax()

int snd_pcm_hw_params_set_tick_time_minmax	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	min,
		int *	mindir,
		unsigned int *	max,
		int *	maxdir )

(DEPRECATED) Restrict a configuration space to have tick times in a given range

Parameters

pcm	PCM handle
params	Configuration space
min	approximate minimum tick duration in us (on return filled with actual minimum)
mindir	Sub unit direction for minimum (on return filled with actual direction)
max	approximate maximum tick duration in us (on return filled with actual maximum)
maxdir	Sub unit direction for maximum (on return filled with actual direction)

Returns

0 otherwise a negative error code if configuration space would become empty

Wanted/actual exact min/max is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_set_tick_time_near()

int snd_pcm_hw_params_set_tick_time_near	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int *	val,
		int *	dir )

(DEPRECATED) Restrict a configuration space to have tick time nearest to a target

Parameters

pcm	PCM handle
params	Configuration space
val	approximate target tick duration in us / returned chosen approximate target tick duration in us
dir	Sub unit direction

Returns

0 otherwise a negative error code if configuration space is empty

target/chosen exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_sizeof()

size_t snd_pcm_hw_params_sizeof

(

)

get size of #snd_pcm_hw_params_t

Returns

size in bytes

snd_pcm_hw_params_supports_audio_ts_type()

int snd_pcm_hw_params_supports_audio_ts_type	(	const snd_pcm_hw_params_t *	params,
		int	type )

Check if hardware supports type of audio timestamps.

Parameters

params	Configuration space
type	Audio timestamp type

Return values

0	Hardware doesn't support type of audio timestamps
1	Hardware supports type of audio timestamps

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_supports_audio_wallclock_ts()

int snd_pcm_hw_params_supports_audio_wallclock_ts

(

const snd_pcm_hw_params_t *

params

)

Check if hardware supports audio wallclock timestamps.

Parameters

params

Configuration space

Return values

0	Hardware doesn't support audio wallclock timestamps
1	Hardware supports audio wallclock timestamps

This function should only be called when the configuration space contains a single configuration. Call snd_pcm_hw_params to choose a single configuration from the configuration space.

snd_pcm_hw_params_test_access()

int snd_pcm_hw_params_test_access	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_access_t	access )

Verify if an access type is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
access	access type

Returns

0 if available a negative error code otherwise

snd_pcm_hw_params_test_buffer_size()

int snd_pcm_hw_params_test_buffer_size	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t	val )

Verify if a buffer size is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	buffer size in frames

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_test_buffer_time()

int snd_pcm_hw_params_test_buffer_time	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Verify if a buffer time is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate buffer duration in us
dir	Sub unit direction

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_test_channels()

int snd_pcm_hw_params_test_channels	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val )

Verify if a channels count is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	channels count

Returns

0 if available a negative error code otherwise

snd_pcm_hw_params_test_format()

int snd_pcm_hw_params_test_format	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_format_t	format )

Verify if a format is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
format	format

Returns

0 if available a negative error code otherwise

snd_pcm_hw_params_test_period_size()

int snd_pcm_hw_params_test_period_size	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_uframes_t	val,
		int	dir )

Verify if a period size is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate period size in frames
dir	Sub unit direction

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_test_period_time()

int snd_pcm_hw_params_test_period_time	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Verify if a period time is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate period duration in us
dir	Sub unit direction

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_test_periods()

int snd_pcm_hw_params_test_periods	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Verify if a periods count is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate periods per buffer
dir	Sub unit direction

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_test_rate()

int snd_pcm_hw_params_test_rate	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

Verify if a rate is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
val	approximate rate
dir	Sub unit direction

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hw_params_test_subformat()

int snd_pcm_hw_params_test_subformat	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		snd_pcm_subformat_t	subformat )

Verify if a subformat is available inside a configuration space for a PCM.

Parameters

pcm	PCM handle
params	Configuration space
subformat	subformat value

Returns

0 if available a negative error code otherwise

snd_pcm_hw_params_test_tick_time()

int snd_pcm_hw_params_test_tick_time	(	snd_pcm_t *	pcm,
		snd_pcm_hw_params_t *	params,
		unsigned int	val,
		int	dir )

(DEPRECATED) Verify if a tick time is available inside a configuration space for a PCM

Parameters

pcm	PCM handle
params	Configuration space
val	approximate tick duration in us
dir	Sub unit direction

Returns

0 if available a negative error code otherwise

Wanted exact value is <,=,> val following dir (-1,0,1)

snd_pcm_hwsync()

int snd_pcm_hwsync

(

snd_pcm_t *

pcm

)

(DEPRECATED) Synchronize stream position with hardware

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

Note this function does not update the actual r/w pointer for applications. The function snd_pcm_avail_update() have to be called before any mmap begin+commit operation.

The function is thread-safe when built with the proper option.

This function is deprecated. Use snd_pcm_avail_update() instead.

snd_pcm_info()

int snd_pcm_info	(	snd_pcm_t *	pcm,
		snd_pcm_info_t *	info )

Obtain general (static) information for PCM handle.

Parameters

pcm	PCM handle
info	Information container

Returns

0 on success otherwise a negative error code

snd_pcm_info_copy()

void snd_pcm_info_copy	(	snd_pcm_info_t *	dst,
		const snd_pcm_info_t *	src )

copy one #snd_pcm_info_t to another

Parameters

dst	pointer to destination
src	pointer to source

snd_pcm_info_free()

void snd_pcm_info_free

(

snd_pcm_info_t *

obj

)

frees a previously allocated #snd_pcm_info_t

Parameters

obj	pointer to object to free

snd_pcm_info_get_card()

int snd_pcm_info_get_card

(

const snd_pcm_info_t *

obj

)

Get card from a PCM info container.

Parameters

obj	PCM info container

Returns

card number otherwise a negative error code if not associable to a card

snd_pcm_info_get_class()

snd_pcm_class_t snd_pcm_info_get_class

(

const snd_pcm_info_t *

obj

)

Get class from a PCM info container.

Parameters

obj	PCM info container

Returns

class of PCM

snd_pcm_info_get_device()

unsigned int snd_pcm_info_get_device

(

const snd_pcm_info_t *

obj

)

Get device from a PCM info container.

Parameters

obj	PCM info container

Returns

device number

snd_pcm_info_get_id()

const char * snd_pcm_info_get_id

(

const snd_pcm_info_t *

obj

)

Get id from a PCM info container.

Parameters

obj	PCM info container

Returns

short id of PCM

snd_pcm_info_get_name()

const char * snd_pcm_info_get_name

(

const snd_pcm_info_t *

obj

)

Get name from a PCM info container.

Parameters

obj	PCM info container

Returns

name of PCM

snd_pcm_info_get_stream()

snd_pcm_stream_t snd_pcm_info_get_stream

(

const snd_pcm_info_t *

obj

)

Get stream (direction) from a PCM info container.

Parameters

obj	PCM info container

Returns

stream

snd_pcm_info_get_subclass()

snd_pcm_subclass_t snd_pcm_info_get_subclass

(

const snd_pcm_info_t *

obj

)

Get subclass from a PCM info container.

Parameters

obj	PCM info container

Returns

subclass of PCM

snd_pcm_info_get_subdevice()

unsigned int snd_pcm_info_get_subdevice

(

const snd_pcm_info_t *

obj

)

Get subdevice from a PCM info container.

Parameters

obj	PCM info container

Returns

subdevice number

snd_pcm_info_get_subdevice_name()

const char * snd_pcm_info_get_subdevice_name

(

const snd_pcm_info_t *

obj

)

Get subdevice name from a PCM info container.

Parameters

obj	PCM info container

Returns

name of used PCM subdevice

snd_pcm_info_get_subdevices_avail()

unsigned int snd_pcm_info_get_subdevices_avail

(

const snd_pcm_info_t *

obj

)

Get available subdevices count from a PCM info container.

Parameters

obj	PCM info container

Returns

available subdevices count of PCM

snd_pcm_info_get_subdevices_count()

unsigned int snd_pcm_info_get_subdevices_count

(

const snd_pcm_info_t *

obj

)

Get subdevices count from a PCM info container.

Parameters

obj	PCM info container

Returns

subdevices total count of PCM

snd_pcm_info_get_sync()

snd_pcm_sync_id_t snd_pcm_info_get_sync

(

const snd_pcm_info_t *

obj

)

(DEPRECATED) Get hardware synchronization ID from a PCM info container

Parameters

obj	PCM info container

Returns

hardware synchronization ID

snd_pcm_info_malloc()

int snd_pcm_info_malloc

(

snd_pcm_info_t **

ptr

)

allocate an invalid #snd_pcm_info_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_info_set_device()

void snd_pcm_info_set_device	(	snd_pcm_info_t *	obj,
		unsigned int	val )

Set wanted device inside a PCM info container (see snd_ctl_pcm_info)

Parameters

obj	PCM info container
val	Device number

snd_pcm_info_set_stream()

void snd_pcm_info_set_stream	(	snd_pcm_info_t *	obj,
		snd_pcm_stream_t	val )

Set wanted stream inside a PCM info container (see snd_ctl_pcm_info)

Parameters

obj	PCM info container
val	Stream

snd_pcm_info_set_subdevice()

void snd_pcm_info_set_subdevice	(	snd_pcm_info_t *	obj,
		unsigned int	val )

Set wanted subdevice inside a PCM info container (see snd_ctl_pcm_info)

Parameters

obj	PCM info container
val	Subdevice number

snd_pcm_info_sizeof()

size_t snd_pcm_info_sizeof

(

)

get size of #snd_pcm_info_t

Returns

size in bytes

snd_pcm_link()

int snd_pcm_link	(	snd_pcm_t *	pcm1,
		snd_pcm_t *	pcm2 )

Link two PCMs.

Parameters

pcm1	first PCM handle
pcm2	first PCM handle

Returns

0 on success otherwise a negative error code

The two PCMs will start/stop/prepare in sync.

Examples

/test/latency.c.

snd_pcm_mmap_begin()

int snd_pcm_mmap_begin	(	snd_pcm_t *	pcm,
		const snd_pcm_channel_area_t **	areas,
		snd_pcm_uframes_t *	offset,
		snd_pcm_uframes_t *	frames )

Application request to access a portion of direct (mmap) area.

Parameters

pcm	PCM handle
areas	Returned mmap channel areas
offset	Returned mmap area offset in area steps (== frames)
frames	mmap area portion size in frames (wanted on entry, contiguous available on exit)

Returns

0 on success otherwise a negative error code

It is necessary to call the snd_pcm_avail_update() function directly before this call. Otherwise, this function can return a wrong count of available frames.

The function should be called before a sample-direct area can be accessed. The resulting size parameter is always less or equal to the input count of frames and can be zero, if no frames can be processed (the ring buffer is full).

See the snd_pcm_mmap_commit() function to finish the frame processing in the direct areas.

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_mmap_commit()

snd_pcm_sframes_t snd_pcm_mmap_commit	(	snd_pcm_t *	pcm,
		snd_pcm_uframes_t	offset,
		snd_pcm_uframes_t	frames )

Application has completed the access to area requested with snd_pcm_mmap_begin.

Parameters

pcm	PCM handle
offset	area offset in area steps (== frames)
frames	area portion size in frames

Returns

count of transferred frames otherwise a negative error code

You should pass this function the offset value that snd_pcm_mmap_begin() returned. The frames parameter should hold the number of frames you have written or read to/from the audio buffer. The frames parameter must never exceed the contiguous frames count that snd_pcm_mmap_begin() returned. Each call to snd_pcm_mmap_begin() must be followed by a call to snd_pcm_mmap_commit().

Example:

 double phase = 0;
 const snd_pcm_area_t *areas;
 snd_pcm_sframes_t avail, size, commitres;
 snd_pcm_uframes_t offset, frames;
 int err;
 
 avail = snd_pcm_avail_update(pcm);
 if (avail < 0)
   error(avail);
 // at this point, we can transfer at least 'avail' frames
 
 // we want to process frames in chunks (period_size)
 if (avail < period_size)
   goto _skip;
 size = period_size;
 // it is possible that contiguous areas are smaller, thus we use a loop
 while (size > 0) {
   frames = size;
 
   err = snd_pcm_mmap_begin(pcm_handle, &areas, &offset, &frames);
   if (err < 0)
     error(err);
   // this function fills the areas from offset with count of frames
   generate_sine(areas, offset, frames, &phase);
   commitres = snd_pcm_mmap_commit(pcm_handle, offset, frames);
   if (commitres < 0 || commitres != frames)
     error(commitres >= 0 ? -EPIPE : commitres);
     
   size -= frames;
 }
_skip:

Look to the Sine-wave generator example for more details about the generate_sine function.

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_name()

const char * snd_pcm_name

(

snd_pcm_t *

pcm

)

get identifier of PCM handle

Parameters

pcm	PCM handle

Returns

ascii identifier of PCM handle

Returns the ASCII identifier of given PCM handle. It's the same identifier specified in snd_pcm_open().

snd_pcm_nonblock()

int snd_pcm_nonblock	(	snd_pcm_t *	pcm,
		int	nonblock )

set nonblock mode

Parameters

pcm	PCM handle
nonblock	0 = block, 1 = nonblock mode, 2 = abort

Returns

0 on success otherwise a negative error code

The function is thread-safe when built with the proper option.

Examples

/test/latency.c.

snd_pcm_open()

int snd_pcm_open	(	snd_pcm_t **	pcmp,
		const char *	name,
		snd_pcm_stream_t	stream,
		int	mode )

Opens a PCM.

Parameters

pcmp	Returned PCM handle
name	ASCII identifier of the PCM handle
stream	Wanted stream
mode	Open mode (see #SND_PCM_NONBLOCK, #SND_PCM_ASYNC)

Returns

0 on success otherwise a negative error code

Examples

/test/latency.c, /test/pcm.c, and /test/pcm_min.c.

snd_pcm_open_fallback()

int snd_pcm_open_fallback	(	snd_pcm_t **	pcmp,
		snd_config_t *	root,
		const char *	name,
		const char *	orig_name,
		snd_pcm_stream_t	stream,
		int	mode )

Opens a fallback PCM.

Parameters

pcmp	Returned PCM handle
root	Configuration root
name	ASCII identifier of the PCM handle
orig_name	The original ASCII name
stream	Wanted stream
mode	Open mode (see #SND_PCM_NONBLOCK, #SND_PCM_ASYNC)

Returns

0 on success otherwise a negative error code

snd_pcm_open_lconf()

int snd_pcm_open_lconf	(	snd_pcm_t **	pcmp,
		const char *	name,
		snd_pcm_stream_t	stream,
		int	mode,
		snd_config_t *	lconf )

Opens a PCM using local configuration.

Parameters

pcmp	Returned PCM handle
name	ASCII identifier of the PCM handle
stream	Wanted stream
mode	Open mode (see #SND_PCM_NONBLOCK, #SND_PCM_ASYNC)
lconf	Local configuration

Returns

0 on success otherwise a negative error code

snd_pcm_pause()

int snd_pcm_pause	(	snd_pcm_t *	pcm,
		int	enable )

Pause/resume PCM.

Parameters

pcm	PCM handle
enable	0 = resume, 1 = pause

Returns

0 on success otherwise a negative error code

Note that this function works only on the hardware which supports pause feature. You can check it via ::snd_pcm_hw_params_can_pause() function.

The function is thread-safe when built with the proper option.

snd_pcm_poll_descriptors()

int snd_pcm_poll_descriptors	(	snd_pcm_t *	pcm,
		struct pollfd *	pfds,
		unsigned int	space )

get poll descriptors

Parameters

pcm	PCM handle
pfds	array of poll descriptors
space	space in the poll descriptor array

Returns

count of filled descriptors

This function fills the given poll descriptor structs for the specified PCM handle. The poll desctiptor array should have the size returned by ::snd_pcm_poll_descriptors_count() function.

The result is intended for direct use with the poll() syscall.

For reading the returned events of poll descriptor after poll() system call, use ::snd_pcm_poll_descriptors_revents() function. The field values in pollfd structs may be bogus regarding the stream direction from the application perspective (POLLIN might not imply read direction and POLLOUT might not imply write), but the ::snd_pcm_poll_descriptors_revents() function does the right "demangling".

You can use output from this function as arguments for the select() syscall, too. Do not forget to translate POLLIN and POLLOUT events to corresponding FD_SET arrays and demangle events using ::snd_pcm_poll_descriptors_revents() .

It is guaranteed that for the given PCM handle, the output poll descriptor structs (and their count) will not change after hardware and software parameters setup. Thus it is valid to call the function once when all parameters are set and reuse its output for the lifetime of the stream parameters.

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_poll_descriptors_count()

int snd_pcm_poll_descriptors_count

(

snd_pcm_t *

pcm

)

get count of poll descriptors for PCM handle

Parameters

pcm	PCM handle

Returns

count of poll descriptors

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_poll_descriptors_revents()

int snd_pcm_poll_descriptors_revents	(	snd_pcm_t *	pcm,
		struct pollfd *	pfds,
		unsigned int	nfds,
		unsigned short *	revents )

get returned events from poll descriptors

Parameters

pcm	PCM handle
pfds	array of poll descriptors
nfds	count of poll descriptors
revents	pointer to the returned (single) event

Returns

zero if success, otherwise a negative error code

This function does "demangling" of the revents mask returned from the poll() syscall to correct semantics (POLLIN = read, POLLOUT = write).

Note: The null event also exists. Even if poll() or select() syscall returned that some events are waiting, this function might return empty set of events. In this case, application should do next event waiting using poll() or select().

Note: Even if multiple poll descriptors are used (i.e. pfds > 1), this function returns only a single event.

The passed in count of poll descriptors must be equal to ::snd_pcm_poll_descriptors_count() and the passed in array must match the array returned by ::snd_pcm_poll_descriptors() (in its full length and original order) with the revent fields updated according to the poll() result. This function will not modify the file descriptor or event field of any element of the given poll descriptor array.

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_prepare()

int snd_pcm_prepare

(

snd_pcm_t *

pcm

)

Prepare PCM for use.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_query_chmaps()

snd_pcm_chmap_query_t ** snd_pcm_query_chmaps

(

snd_pcm_t *

pcm

)

!brief Query the available channel maps

Parameters

pcm	PCM handle to query

Returns

the NULL-terminated array of integer pointers, each of which contains the channel map. A channel map is represented by an integer array, beginning with the channel map type, followed by the number of channels, and the position of each channel. Return NULL in case of an error.

Note: the caller is requested to release the returned value via snd_pcm_free_chmaps().

snd_pcm_readi()

snd_pcm_sframes_t snd_pcm_readi	(	snd_pcm_t *	pcm,
		void *	buffer,
		snd_pcm_uframes_t	size )

Read interleaved frames from a PCM.

Parameters

pcm	PCM handle
buffer	frames containing buffer
size	frames to be read

Returns

a positive number of frames actually read otherwise a negative error code

Return values

-EBADFD	PCM is not in the right state (#SND_PCM_STATE_PREPARED or #SND_PCM_STATE_RUNNING)
-EPIPE	an overrun occurred
-ESTRPIPE	a suspend event occurred (stream is suspended and waiting for an application recovery)

If the blocking behaviour was selected and it is running, then routine waits until all requested frames are filled. The returned number of frames can be less only if a signal or underrun occurred.

If the non-blocking behaviour is selected, then routine doesn't wait at all.

The function is thread-safe when built with the proper option.

Examples

/test/latency.c.

snd_pcm_readn()

snd_pcm_sframes_t snd_pcm_readn	(	snd_pcm_t *	pcm,
		void **	bufs,
		snd_pcm_uframes_t	size )

Read non interleaved frames to a PCM.

Parameters

pcm	PCM handle
bufs	frames containing buffers (one for each channel)
size	frames to be read

Returns

a positive number of frames actually read otherwise a negative error code

Return values

-EBADFD	PCM is not in the right state (#SND_PCM_STATE_PREPARED or #SND_PCM_STATE_RUNNING)
-EPIPE	an overrun occurred
-ESTRPIPE	a suspend event occurred (stream is suspended and waiting for an application recovery)

If the blocking behaviour was selected and it is running, then routine waits until all requested frames are filled. The returned number of frames can be less only if a signal or underrun occurred.

If the non-blocking behaviour is selected, then routine doesn't wait at all.

The function is thread-safe when built with the proper option.

snd_pcm_recover()

int snd_pcm_recover	(	snd_pcm_t *	pcm,
		int	err,
		int	silent )

Recover the stream state from an error or suspend.

Parameters

pcm	PCM handle
err	error number
silent	do not print error reason

Returns

0 when error code was handled successfuly, otherwise a negative error code

This a high-level helper function building on other functions.

This functions handles -EINTR (interrupted system call), -EPIPE (overrun or underrun) and -ESTRPIPE (stream is suspended) error codes trying to prepare given stream for next I/O.

Note that this function returns the original error code when it is not handled inside this function (for example -EAGAIN is returned back).

Examples

/test/pcm_min.c.

snd_pcm_reset()

int snd_pcm_reset

(

snd_pcm_t *

pcm

)

Reset PCM position.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

Reduce PCM delay to 0.

The function is thread-safe when built with the proper option.

snd_pcm_resume()

int snd_pcm_resume

(

snd_pcm_t *

pcm

)

Resume from suspend, no samples are lost.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

Return values

-EAGAIN	resume can't be proceed immediately (audio hardware is probably still suspended)
-ENOSYS	hardware doesn't support this feature

This function can be used when the stream is in the suspend state to do the fine resume from this state. Not all hardware supports this feature, when an -ENOSYS error is returned, use the ::snd_pcm_prepare() function to recovery.

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_rewind()

snd_pcm_sframes_t snd_pcm_rewind	(	snd_pcm_t *	pcm,
		snd_pcm_uframes_t	frames )

Move application frame position backward.

Parameters

pcm	PCM handle
frames	wanted displacement in frames

Returns

a positive number for actual displacement otherwise a negative error code

The function is thread-safe when built with the proper option.

snd_pcm_rewindable()

snd_pcm_sframes_t snd_pcm_rewindable

(

snd_pcm_t *

pcm

)

Get safe count of frames which can be rewinded.

Parameters

pcm	PCM handle

Returns

a positive number of frames or negative error code

Note: The snd_pcm_rewind() can accept bigger value than returned by this function. But it is not guaranteed that output stream will be consistent with bigger value.

The function is thread-safe when built with the proper option.

snd_pcm_samples_to_bytes()

ssize_t snd_pcm_samples_to_bytes	(	snd_pcm_t *	pcm,
		long	samples )

Convert samples in bytes for a PCM.

Parameters

pcm	PCM handle
samples	quantity in samples

Returns

quantity expressed in bytes

snd_pcm_set_chmap()

int snd_pcm_set_chmap	(	snd_pcm_t *	pcm,
		const snd_pcm_chmap_t *	map )

!brief Configure the current channel map

Parameters

pcm	PCM instance
map	the channel map to write

Returns

zero if succeeded, or a negative error code

snd_pcm_set_params()

int snd_pcm_set_params	(	snd_pcm_t *	pcm,
		snd_pcm_format_t	format,
		snd_pcm_access_t	access,
		unsigned int	channels,
		unsigned int	rate,
		int	soft_resample,
		unsigned int	latency )

Set the hardware and software parameters in a simple way.

Parameters

pcm	PCM handle
format	required PCM format
access	required PCM access
channels	required PCM channels
rate	required sample rate in Hz
soft_resample	0 = disallow alsa-lib resample stream, 1 = allow resampling
latency	required overall latency in us

Returns

0 on success otherwise a negative error code

Examples

/test/pcm_min.c.

snd_pcm_start()

int snd_pcm_start

(

snd_pcm_t *

pcm

)

Start a PCM.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_start_mode_name()

const char * snd_pcm_start_mode_name

(

snd_pcm_start_t

mode

)

(DEPRECATED) get name of PCM start mode setting

Parameters

mode	PCM start mode

Returns

ascii name of PCM start mode setting

snd_pcm_state()

snd_pcm_state_t snd_pcm_state

(

snd_pcm_t *

pcm

)

Return PCM state.

Parameters

pcm	PCM handle

Returns

PCM state #snd_pcm_state_t of given PCM handle

This is a faster way to obtain only the PCM state without calling ::snd_pcm_status().

Note that this function always returns one of the #snd_pcm_state_t enum variants. It will never return a negative error code.

The function is thread-safe when built with the proper option.

Examples

/test/pcm.c.

snd_pcm_state_name()

const char * snd_pcm_state_name

(

const snd_pcm_state_t

state

)

get name of PCM state

Parameters

state

PCM state

Returns

ascii name of PCM state

snd_pcm_status()

int snd_pcm_status	(	snd_pcm_t *	pcm,
		snd_pcm_status_t *	status )

Obtain status (runtime) information for PCM handle.

Parameters

pcm	PCM handle
status	Status container

Returns

0 on success otherwise a negative error code

The function is thread-safe when built with the proper option.

Examples

/test/latency.c.

snd_pcm_status_copy()

void snd_pcm_status_copy	(	snd_pcm_status_t *	dst,
		const snd_pcm_status_t *	src )

copy one #snd_pcm_status_t to another

Parameters

dst	pointer to destination
src	pointer to source

snd_pcm_status_dump()

int snd_pcm_status_dump	(	snd_pcm_status_t *	status,
		snd_output_t *	out )

Dump status.

Parameters

status	Status container
out	Output handle

Returns

0 on success otherwise a negative error code

Examples

/test/latency.c.

snd_pcm_status_free()

void snd_pcm_status_free

(

snd_pcm_status_t *

obj

)

frees a previously allocated #snd_pcm_status_t

Parameters

obj	pointer to object to free

snd_pcm_status_get_audio_htstamp()

void snd_pcm_status_get_audio_htstamp	(	const snd_pcm_status_t *	obj,
		snd_htimestamp_t *	ptr )

Get "now" hi-res audio timestamp from a PCM status container.

Parameters

obj	pointer to #snd_pcm_status_t
ptr	Pointer to returned timestamp

snd_pcm_status_get_audio_htstamp_report()

void snd_pcm_status_get_audio_htstamp_report	(	const snd_pcm_status_t *	obj,
		snd_pcm_audio_tstamp_report_t *	audio_tstamp_report )

Get audio_tstamp_report from a PCM status container.

Parameters

obj	pointer to #snd_pcm_status_t
audio_tstamp_report	Pointer to returned report

snd_pcm_status_get_avail()

snd_pcm_uframes_t snd_pcm_status_get_avail

(

const snd_pcm_status_t *

obj

)

Get number of frames available from a PCM status container (see snd_pcm_avail_update)

Returns

Number of frames ready to be read/written

snd_pcm_status_get_avail_max()

snd_pcm_uframes_t snd_pcm_status_get_avail_max

(

const snd_pcm_status_t *

obj

)

Get maximum number of frames available from a PCM status container after last snd_pcm_status call.

Returns

Maximum number of frames ready to be read/written

This value returns the peak for the available frames between snd_pcm_status calls.

snd_pcm_status_get_delay()

snd_pcm_sframes_t snd_pcm_status_get_delay

(

const snd_pcm_status_t *

obj

)

Get delay from a PCM status container (see snd_pcm_delay)

Returns

Delay in frames

Delay is distance between current application frame position and sound frame position. It's positive and less than buffer size in normal situation, negative on playback underrun and greater than buffer size on capture overrun.

snd_pcm_status_get_driver_htstamp()

void snd_pcm_status_get_driver_htstamp	(	const snd_pcm_status_t *	obj,
		snd_htimestamp_t *	ptr )

Get "now" hi-res driver timestamp from a PCM status container. Defines when the status was generated by driver, may differ from normal timestamp.

Parameters

obj	pointer to #snd_pcm_status_t
ptr	Pointer to returned timestamp

snd_pcm_status_get_htstamp()

void snd_pcm_status_get_htstamp	(	const snd_pcm_status_t *	obj,
		snd_htimestamp_t *	ptr )

Get "now" hi-res timestamp from a PCM status container.

Parameters

obj	pointer to #snd_pcm_status_t
ptr	Pointer to returned timestamp

snd_pcm_status_get_overrange()

snd_pcm_uframes_t snd_pcm_status_get_overrange

(

const snd_pcm_status_t *

obj

)

Get count of ADC overrange detections since last call.

Returns

Count of ADC overrange detections

snd_pcm_status_get_state()

snd_pcm_state_t snd_pcm_status_get_state

(

const snd_pcm_status_t *

obj

)

Get state from a PCM status container (see snd_pcm_state)

Parameters

obj	#snd_pcm_status_t pointer

Returns

PCM state

snd_pcm_status_get_trigger_htstamp()

void snd_pcm_status_get_trigger_htstamp	(	const snd_pcm_status_t *	obj,
		snd_htimestamp_t *	ptr )

Get trigger hi-res timestamp from a PCM status container.

Parameters

obj	#snd_pcm_status_t pointer
ptr	Pointer to returned timestamp

Trigger means a PCM state transition (from stopped to running or versa vice). It applies also to pause and suspend. In other words, timestamp contains time when stream started or when it was stopped.

snd_pcm_status_get_trigger_tstamp()

void snd_pcm_status_get_trigger_tstamp	(	const snd_pcm_status_t *	obj,
		snd_timestamp_t *	ptr )

Get trigger timestamp from a PCM status container.

Parameters

obj	#snd_pcm_status_t pointer
ptr	Pointer to returned timestamp

Trigger means a PCM state transition (from stopped to running or versa vice). It applies also to pause and suspend. In other words, timestamp contains time when stream started or when it was stopped.

Examples

/test/latency.c.

snd_pcm_status_get_tstamp()

void snd_pcm_status_get_tstamp	(	const snd_pcm_status_t *	obj,
		snd_timestamp_t *	ptr )

Get "now" timestamp from a PCM status container.

Parameters

obj	#snd_pcm_status_t pointer
ptr	Pointer to returned timestamp

snd_pcm_status_malloc()

int snd_pcm_status_malloc

(

snd_pcm_status_t **

ptr

)

allocate an invalid #snd_pcm_status_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_status_set_audio_htstamp_config()

void snd_pcm_status_set_audio_htstamp_config	(	snd_pcm_status_t *	obj,
		snd_pcm_audio_tstamp_config_t *	audio_tstamp_config )

set audio_tstamp_config from a PCM status container

Parameters

obj	pointer to #snd_pcm_status_t
audio_tstamp_config	Pointer to config (valid fields are type_requested and report_delay)

snd_pcm_status_sizeof()

size_t snd_pcm_status_sizeof

(

)

get size of #snd_pcm_status_t

Returns

size in bytes

snd_pcm_stream()

snd_pcm_stream_t snd_pcm_stream

(

snd_pcm_t *

pcm

)

get stream for a PCM handle

Parameters

pcm	PCM handle

Returns

stream of PCM handle

Returns the type #snd_pcm_stream_t of given PCM handle.

snd_pcm_stream_name()

const char * snd_pcm_stream_name

(

const snd_pcm_stream_t

stream

)

get name of PCM stream type

Parameters

stream

PCM stream type

Returns

ascii name of PCM stream type

snd_pcm_subformat_description()

const char * snd_pcm_subformat_description

(

const snd_pcm_subformat_t

subformat

)

get description of PCM sample subformat

Parameters

subformat

PCM sample subformat

Returns

ascii description of PCM sample subformat

snd_pcm_subformat_mask_any()

void snd_pcm_subformat_mask_any

(

snd_pcm_subformat_mask_t *

mask

)

set all bits in a #snd_pcm_subformat_mask_t

Parameters

mask	pointer to mask

snd_pcm_subformat_mask_copy()

void snd_pcm_subformat_mask_copy	(	snd_pcm_subformat_mask_t *	dst,
		const snd_pcm_subformat_mask_t *	src )

copy one #snd_pcm_subformat_mask_t to another

Parameters

dst	pointer to destination
src	pointer to source

snd_pcm_subformat_mask_empty()

int snd_pcm_subformat_mask_empty

(

const snd_pcm_subformat_mask_t *

mask

)

test, if given a #snd_pcm_subformat_mask_t is empty

Parameters

mask	pointer to mask

Return values

0	not empty
1	empty

snd_pcm_subformat_mask_free()

void snd_pcm_subformat_mask_free

(

snd_pcm_subformat_mask_t *

obj

)

frees a previously allocated #snd_pcm_subformat_mask_t

Parameters

obj	pointer to object to free

snd_pcm_subformat_mask_malloc()

int snd_pcm_subformat_mask_malloc

(

snd_pcm_subformat_mask_t **

ptr

)

allocate an empty #snd_pcm_subformat_mask_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_subformat_mask_none()

void snd_pcm_subformat_mask_none

(

snd_pcm_subformat_mask_t *

mask

)

reset all bits in a #snd_pcm_subformat_mask_t

Parameters

mask	pointer to mask

snd_pcm_subformat_mask_reset()

void snd_pcm_subformat_mask_reset	(	snd_pcm_subformat_mask_t *	mask,
		snd_pcm_subformat_t	val )

make a subformat missing from a #snd_pcm_subformat_mask_t

Parameters

mask	pointer to mask
val	subformat

snd_pcm_subformat_mask_set()

void snd_pcm_subformat_mask_set	(	snd_pcm_subformat_mask_t *	mask,
		snd_pcm_subformat_t	val )

make a subformat present in a #snd_pcm_subformat_mask_t

Parameters

mask	pointer to mask
val	subformat

snd_pcm_subformat_mask_sizeof()

size_t snd_pcm_subformat_mask_sizeof

(

)

get size of #snd_pcm_subformat_mask_t

Returns

size in bytes

snd_pcm_subformat_mask_test()

int snd_pcm_subformat_mask_test	(	const snd_pcm_subformat_mask_t *	mask,
		snd_pcm_subformat_t	val )

test the presence of a subformat in a #snd_pcm_subformat_mask_t

Parameters

mask	pointer to mask
val	subformat

snd_pcm_subformat_name()

const char * snd_pcm_subformat_name

(

const snd_pcm_subformat_t

subformat

)

get name of PCM sample subformat

Parameters

subformat

PCM sample subformat

Returns

ascii name of PCM sample subformat

snd_pcm_subformat_value()

snd_pcm_subformat_t snd_pcm_subformat_value

(

const char *

name

)

get PCM sample subformat from name

Parameters

name	PCM sample subformat name (case insensitive)

Returns

PCM sample subformat

snd_pcm_sw_params()

int snd_pcm_sw_params	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params )

Install PCM software configuration defined by params.

Parameters

pcm	PCM handle
params	Configuration container

Returns

0 on success otherwise a negative error code

The software parameters can be changed at any time. The hardware parameters cannot be changed when the stream is running (active).

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_sw_params_copy()

void snd_pcm_sw_params_copy	(	snd_pcm_sw_params_t *	dst,
		const snd_pcm_sw_params_t *	src )

copy one #snd_pcm_sw_params_t to another

Parameters

dst	pointer to destination
src	pointer to source

snd_pcm_sw_params_current()

int snd_pcm_sw_params_current	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params )

Return current software configuration for a PCM.

Parameters

pcm	PCM handle
params	Software configuration container

Returns

0 on success otherwise a negative error code

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_sw_params_dump()

int snd_pcm_sw_params_dump	(	snd_pcm_sw_params_t *	params,
		snd_output_t *	out )

Dump a software configuration.

Parameters

params	Software configuration container
out	Output handle

Returns

0 on success otherwise a negative error code

snd_pcm_sw_params_free()

void snd_pcm_sw_params_free

(

snd_pcm_sw_params_t *

obj

)

frees a previously allocated #snd_pcm_sw_params_t

Parameters

obj	pointer to object to free

snd_pcm_sw_params_get_avail_min()

int snd_pcm_sw_params_get_avail_min	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get avail min from a software configuration container.

Parameters

params	Software configuration container
val	returned minimum available frames to consider PCM ready

Returns

0 otherwise a negative error code

This is a threshold value when the PCM stream is considered as ready for another read/write operation or poll event.

snd_pcm_sw_params_get_boundary()

int snd_pcm_sw_params_get_boundary	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get boundary for ring pointers from a software configuration container.

Parameters

params	Software configuration container
val	Returned boundary in frames

Returns

0 otherwise a negative error code

snd_pcm_sw_params_get_period_event()

int snd_pcm_sw_params_get_period_event	(	const snd_pcm_sw_params_t *	params,
		int *	val )

Get period event from a software configuration container.

Parameters

params	Software configuration container
val	returned period event state

Returns

0 otherwise a negative error code

snd_pcm_sw_params_get_silence_size()

int snd_pcm_sw_params_get_silence_size	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get silence size from a software configuration container.

Parameters

params	Software configuration container
val	Returned silence size in frames (0 for disabled)

Returns

0 otherwise a negative error code

A portion of playback buffer is overwritten with silence when playback underrun is nearer than silence threshold (see snd_pcm_sw_params_set_silence_threshold)

snd_pcm_sw_params_get_silence_threshold()

int snd_pcm_sw_params_get_silence_threshold	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get silence threshold from a software configuration container.

Parameters

params	Software configuration container
val	Returned silence threshold in frames

Returns

0 otherwise a negative error value

A portion of playback buffer is overwritten with silence (see snd_pcm_sw_params_set_silence_size) when playback underrun is nearer than silence threshold.

snd_pcm_sw_params_get_sleep_min()

int snd_pcm_sw_params_get_sleep_min	(	const snd_pcm_sw_params_t *	params,
		unsigned int *	val )

(DEPRECATED) Get minimum numbers of ticks to sleep from a software configuration container

Parameters

params	Software configuration container
val	returned minimum number of ticks to sleep or 0 if tick timer is disabled

Returns

0 otherwise a negative error code

snd_pcm_sw_params_get_start_mode()

snd_pcm_start_t snd_pcm_sw_params_get_start_mode

(

const snd_pcm_sw_params_t *

params

)

(DEPRECATED) Get start mode from a software configuration container

Parameters

params

Software configuration container

Returns

start mode

snd_pcm_sw_params_get_start_threshold()

int snd_pcm_sw_params_get_start_threshold	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get start threshold from a software configuration container.

Parameters

params	Software configuration container
val	Returned start threshold in frames

Returns

0 otherwise a negative error code

PCM is automatically started when playback frames available to PCM are >= threshold or when requested capture frames are >= threshold

snd_pcm_sw_params_get_stop_threshold()

int snd_pcm_sw_params_get_stop_threshold	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

Get stop threshold from a software configuration container.

Parameters

params	Software configuration container
val	Returned stop threshold in frames

Returns

0 otherwise a negative error code

PCM is automatically stopped in #SND_PCM_STATE_XRUN state when available frames is >= threshold. If the stop threshold is equal to boundary (also software parameter - sw_param) then automatic stop will be disabled (thus device will do the endless loop in the ring buffer).

snd_pcm_sw_params_get_tstamp_mode()

int snd_pcm_sw_params_get_tstamp_mode	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_tstamp_t *	val )

Get timestamp mode from a software configuration container.

Parameters

params	Software configuration container
val	Returned timestamp

Returns

0 otherwise a negative error code

snd_pcm_sw_params_get_tstamp_type()

int snd_pcm_sw_params_get_tstamp_type	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_tstamp_type_t *	val )

Get timestamp type from a software configuration container.

Parameters

params	Software configuration container
val	Returned timestamp type

Returns

0 otherwise a negative error code

snd_pcm_sw_params_get_xfer_align()

int snd_pcm_sw_params_get_xfer_align	(	const snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t *	val )

(DEPRECATED) Get xfer align from a software configuration container

Parameters

params	Software configuration container
val	returned chunk size (frames are attempted to be transferred in chunks)

Returns

0 otherwise a negative error code

snd_pcm_sw_params_get_xrun_mode()

snd_pcm_xrun_t snd_pcm_sw_params_get_xrun_mode

(

const snd_pcm_sw_params_t *

params

)

(DEPRECATED) Get xrun mode from a software configuration container

Parameters

params

Software configuration container

Returns

xrun mode

snd_pcm_sw_params_malloc()

int snd_pcm_sw_params_malloc

(

snd_pcm_sw_params_t **

ptr

)

allocate an invalid #snd_pcm_sw_params_t using standard malloc

Parameters

ptr	returned pointer

Returns

0 on success otherwise negative error code

snd_pcm_sw_params_set_avail_min()

int snd_pcm_sw_params_set_avail_min	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t	val )

Set avail min inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Minimum avail frames to consider PCM ready

Returns

0 otherwise a negative error code

Note: This is similar to setting an OSS wakeup point. The valid values for 'val' are determined by the specific hardware. Most PC sound cards can only accept power of 2 frame counts (i.e. 512, 1024, 2048). You cannot use this as a high resolution timer - it is limited to how often the sound card hardware raises an interrupt.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_sw_params_set_period_event()

int snd_pcm_sw_params_set_period_event	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		int	val )

Set period event inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	0 = disable period event, 1 = enable period event

Returns

0 otherwise a negative error code

An poll (select) wakeup event is raised if enabled.

Examples

/test/pcm.c.

snd_pcm_sw_params_set_silence_size()

int snd_pcm_sw_params_set_silence_size	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t	val )

Set silence size inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Silence size in frames (0 for disabled)

Returns

0 otherwise a negative error code

A portion of playback buffer is overwritten with silence when playback underrun is nearer than silence threshold (see snd_pcm_sw_params_set_silence_threshold)

When drain silence (see snd_pcm_hw_params_get_drain_silence) is disabled, this will also apply for draining, i.e. silence is written also when the drain end is nearer than the silence threshold.

The special case is when silence size value is equal or greater than boundary. The unused portion of the ring buffer (initial written samples are untouched) is filled with silence at start. Later, only just processed sample area is filled with silence. Note: silence_threshold must be set to zero.

snd_pcm_sw_params_set_silence_threshold()

int snd_pcm_sw_params_set_silence_threshold	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t	val )

Set silence threshold inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Silence threshold in frames

Returns

0 otherwise a negative error code

A portion of playback buffer is overwritten with silence (see snd_pcm_sw_params_set_silence_size) when playback underrun is nearer than silence threshold.

snd_pcm_sw_params_set_sleep_min()

int snd_pcm_sw_params_set_sleep_min	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		unsigned int	val )

(DEPRECATED) Set minimum number of ticks to sleep inside a software configuration container

Parameters

pcm	PCM handle
params	Software configuration container
val	Minimum ticks to sleep or 0 to disable the use of tick timer

Returns

0 otherwise a negative error code

snd_pcm_sw_params_set_start_mode()

int snd_pcm_sw_params_set_start_mode	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_start_t	val )

(DEPRECATED) Set start mode inside a software configuration container

Parameters

pcm	PCM handle
params	Software configuration container
val	Start mode

Returns

0 otherwise a negative error code

snd_pcm_sw_params_set_start_threshold()

int snd_pcm_sw_params_set_start_threshold	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t	val )

Set start threshold inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Start threshold in frames

Returns

0 otherwise a negative error code

PCM is automatically started when playback frames available to PCM are >= threshold or when requested capture frames are >= threshold

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_sw_params_set_stop_threshold()

int snd_pcm_sw_params_set_stop_threshold	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t	val )

Set stop threshold inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Stop threshold in frames

Returns

0 otherwise a negative error code

PCM is automatically stopped in #SND_PCM_STATE_XRUN state when available frames is >= threshold. If the stop threshold is equal to boundary (also software parameter - sw_param) then automatic stop will be disabled (thus device will do the endless loop in the ring buffer).

snd_pcm_sw_params_set_tstamp_mode()

int snd_pcm_sw_params_set_tstamp_mode	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_tstamp_t	val )

Set timestamp mode inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Timestamp mode

Returns

0 otherwise a negative error code

snd_pcm_sw_params_set_tstamp_type()

int snd_pcm_sw_params_set_tstamp_type	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_tstamp_type_t	val )

Set timestamp type inside a software configuration container.

Parameters

pcm	PCM handle
params	Software configuration container
val	Timestamp type

Returns

0 otherwise a negative error code

snd_pcm_sw_params_set_xfer_align()

int snd_pcm_sw_params_set_xfer_align	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_uframes_t	val )

(DEPRECATED) Set xfer align inside a software configuration container

Parameters

pcm	PCM handle
params	Software configuration container
val	Chunk size (frames are attempted to be transferred in chunks)

Returns

0 otherwise a negative error code

snd_pcm_sw_params_set_xrun_mode()

int snd_pcm_sw_params_set_xrun_mode	(	snd_pcm_t *	pcm,
		snd_pcm_sw_params_t *	params,
		snd_pcm_xrun_t	val )

(DEPRECATED) Set xrun mode inside a software configuration container

Parameters

pcm	PCM handle
params	Software configuration container
val	Xrun mode

Returns

0 otherwise a negative error code

snd_pcm_sw_params_sizeof()

size_t snd_pcm_sw_params_sizeof

(

)

get size of #snd_pcm_sw_params_t

Returns

size in bytes

snd_pcm_tstamp_mode_name()

const char * snd_pcm_tstamp_mode_name

(

const snd_pcm_tstamp_t

mode

)

get name of PCM tstamp mode setting

Parameters

mode	PCM tstamp mode

Returns

ascii name of PCM tstamp mode setting

snd_pcm_tstamp_type_name()

const char * snd_pcm_tstamp_type_name

(

snd_pcm_tstamp_type_t

type

)

get name of PCM tstamp type setting

Parameters

type	PCM tstamp type

Returns

ascii name of PCM tstamp type setting

snd_pcm_type()

snd_pcm_type_t snd_pcm_type

(

snd_pcm_t *

pcm

)

get type of PCM handle

Parameters

pcm	PCM handle

Returns

type of PCM handle

Returns the type #snd_pcm_type_t of given PCM handle.

snd_pcm_type_name()

const char * snd_pcm_type_name

(

snd_pcm_type_t

type

)

get name of PCM type

Parameters

type

PCM type

Returns

ascii name of PCM type

snd_pcm_unlink()

int snd_pcm_unlink

(

snd_pcm_t *

pcm

)

Remove a PCM from a linked group.

Parameters

pcm	PCM handle

Returns

0 on success otherwise a negative error code

Examples

/test/latency.c.

snd_pcm_wait()

int snd_pcm_wait	(	snd_pcm_t *	pcm,
		int	timeout )

Wait for a PCM to become ready.

Parameters

pcm	PCM handle
timeout	maximum time in milliseconds to wait, a -1 value means infinity (SND_PCM_WAIT_INFINITE), see also SND_PCM_WAIT_IO and SND_PCM_WAIT_DRAIN

Returns

a positive value on success otherwise a negative error code (-EPIPE for the xrun and -ESTRPIPE for the suspended status, others for general errors)

Return values

0	timeout occurred
1	PCM stream is ready for I/O

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, and /test/pcm.c.

snd_pcm_writei()

snd_pcm_sframes_t snd_pcm_writei	(	snd_pcm_t *	pcm,
		const void *	buffer,
		snd_pcm_uframes_t	size )

Write interleaved frames to a PCM.

Parameters

pcm	PCM handle
buffer	frames containing buffer
size	frames to be written

Returns

a positive number of frames actually written otherwise a negative error code

Return values

-EBADFD	PCM is not in the right state (#SND_PCM_STATE_PREPARED or #SND_PCM_STATE_RUNNING)
-EPIPE	an underrun occurred
-ESTRPIPE	a suspend event occurred (stream is suspended and waiting for an application recovery)

If the blocking behaviour is selected and it is running, then routine waits until all requested frames are played or put to the playback ring buffer. The returned number of frames can be less only if a signal or underrun occurred.

If the non-blocking behaviour is selected, then routine doesn't wait at all.

The function is thread-safe when built with the proper option.

Examples

/test/latency.c, /test/pcm.c, and /test/pcm_min.c.

snd_pcm_writen()

snd_pcm_sframes_t snd_pcm_writen	(	snd_pcm_t *	pcm,
		void **	bufs,
		snd_pcm_uframes_t	size )

Write non interleaved frames to a PCM.

Parameters

pcm	PCM handle
bufs	frames containing buffers (one for each channel)
size	frames to be written

Returns

a positive number of frames actually written otherwise a negative error code

Return values

-EBADFD	PCM is not in the right state (#SND_PCM_STATE_PREPARED or #SND_PCM_STATE_RUNNING)
-EPIPE	an underrun occurred
-ESTRPIPE	a suspend event occurred (stream is suspended and waiting for an application recovery)

If the blocking behaviour is selected and it is running, then routine waits until all requested frames are played or put to the playback ring buffer. The returned number of frames can be less only if a signal or underrun occurred.

If the non-blocking behaviour is selected, then routine doesn't wait at all.

The function is thread-safe when built with the proper option.

snd_pcm_xrun_mode_name()

const char * snd_pcm_xrun_mode_name

(

snd_pcm_xrun_t

mode

)

(DEPRECATED) get name of PCM xrun mode setting

Parameters

mode	PCM xrun mode

Returns

ascii name of PCM xrun mode setting