ALSA project - the C library reference
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
Modules | Macros | Typedefs | Enumerations | Functions
Mixer Interface

Modules

 Simple Mixer Interface

Macros

#define snd_mixer_class_alloca(ptr)
 allocate an invalid snd_mixer_class_t using standard alloca

Typedefs

typedef struct _snd_mixer snd_mixer_t
typedef struct _snd_mixer_class snd_mixer_class_t
typedef struct _snd_mixer_elem snd_mixer_elem_t
typedef int(* snd_mixer_callback_t )(snd_mixer_t *ctl, unsigned int mask, snd_mixer_elem_t *elem)
 Mixer callback function.
typedef int(* snd_mixer_elem_callback_t )(snd_mixer_elem_t *elem, unsigned int mask)
 Mixer element callback function.
typedef int(* snd_mixer_compare_t )(const snd_mixer_elem_t *e1, const snd_mixer_elem_t *e2)
 Compare function for sorting mixer elements.
typedef int(* snd_mixer_event_t )(snd_mixer_class_t *class_, unsigned int mask, snd_hctl_elem_t *helem, snd_mixer_elem_t *melem)
 Event callback for the mixer class.

Enumerations

enum  snd_mixer_elem_type_t { SND_MIXER_ELEM_SIMPLE, SND_MIXER_ELEM_LAST = SND_MIXER_ELEM_SIMPLE }

Functions

int snd_mixer_open (snd_mixer_t **mixer, int mode)
 Opens an empty mixer.
int snd_mixer_close (snd_mixer_t *mixer)
 Close a mixer and free all related resources.
snd_mixer_elem_tsnd_mixer_first_elem (snd_mixer_t *mixer)
 get first element for a mixer
snd_mixer_elem_tsnd_mixer_last_elem (snd_mixer_t *mixer)
 get last element for a mixer
int snd_mixer_handle_events (snd_mixer_t *mixer)
 Handle pending mixer events invoking callbacks.
int snd_mixer_attach (snd_mixer_t *mixer, const char *name)
 Attach an HCTL specified with the CTL device name to an opened mixer.
int snd_mixer_attach_hctl (snd_mixer_t *mixer, snd_hctl_t *hctl)
 Attach an HCTL to an opened mixer.
int snd_mixer_detach (snd_mixer_t *mixer, const char *name)
 Detach a previously attached HCTL to an opened mixer freeing all related resources.
int snd_mixer_detach_hctl (snd_mixer_t *mixer, snd_hctl_t *hctl)
 Detach a previously attached HCTL to an opened mixer freeing all related resources.
int snd_mixer_get_hctl (snd_mixer_t *mixer, const char *name, snd_hctl_t **hctl)
 Obtain a HCTL pointer associated to given name.
int snd_mixer_poll_descriptors_count (snd_mixer_t *mixer)
 get count of poll descriptors for mixer handle
int snd_mixer_poll_descriptors (snd_mixer_t *mixer, struct pollfd *pfds, unsigned int space)
 get poll descriptors
int snd_mixer_poll_descriptors_revents (snd_mixer_t *mixer, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
 get returned events from poll descriptors
int snd_mixer_load (snd_mixer_t *mixer)
 Load a mixer elements.
void snd_mixer_free (snd_mixer_t *mixer)
 Unload all mixer elements and free all related resources.
int snd_mixer_wait (snd_mixer_t *mixer, int timeout)
 Wait for a mixer to become ready (i.e. at least one event pending)
int snd_mixer_set_compare (snd_mixer_t *mixer, snd_mixer_compare_t msort)
 Change mixer compare function and reorder elements.
void snd_mixer_set_callback (snd_mixer_t *obj, snd_mixer_callback_t val)
 Set callback function for a mixer.
void * snd_mixer_get_callback_private (const snd_mixer_t *obj)
 Get callback private value for a mixer.
void snd_mixer_set_callback_private (snd_mixer_t *obj, void *val)
 Set callback private value for a mixer.
unsigned int snd_mixer_get_count (const snd_mixer_t *obj)
 Get elements count for a mixer.
int snd_mixer_class_unregister (snd_mixer_class_t *clss)
 Unregister mixer element class and remove all its elements.
snd_mixer_elem_tsnd_mixer_elem_next (snd_mixer_elem_t *elem)
 get next mixer element
snd_mixer_elem_tsnd_mixer_elem_prev (snd_mixer_elem_t *elem)
 get previous mixer element
void snd_mixer_elem_set_callback (snd_mixer_elem_t *obj, snd_mixer_elem_callback_t val)
 Set callback function for a mixer element.
void * snd_mixer_elem_get_callback_private (const snd_mixer_elem_t *obj)
 Get callback private value for a mixer element.
void snd_mixer_elem_set_callback_private (snd_mixer_elem_t *obj, void *val)
 Set callback private value for a mixer element.
snd_mixer_elem_type_t snd_mixer_elem_get_type (const snd_mixer_elem_t *obj)
 Get type for a mixer element.
int snd_mixer_class_register (snd_mixer_class_t *class_, snd_mixer_t *mixer)
 Register mixer element class.
int snd_mixer_elem_new (snd_mixer_elem_t **elem, snd_mixer_elem_type_t type, int compare_weight, void *private_data, void(*private_free)(snd_mixer_elem_t *elem))
 Allocate a new mixer element.
int snd_mixer_elem_add (snd_mixer_elem_t *elem, snd_mixer_class_t *class_)
 Add an element for a registered mixer element class.
int snd_mixer_elem_remove (snd_mixer_elem_t *elem)
 Remove a mixer element.
void snd_mixer_elem_free (snd_mixer_elem_t *elem)
 Free a mixer element.
int snd_mixer_elem_info (snd_mixer_elem_t *elem)
 Mixer element informations are changed.
int snd_mixer_elem_value (snd_mixer_elem_t *elem)
 Mixer element values is changed.
int snd_mixer_elem_attach (snd_mixer_elem_t *melem, snd_hctl_elem_t *helem)
 Attach an HCTL element to a mixer element.
int snd_mixer_elem_detach (snd_mixer_elem_t *melem, snd_hctl_elem_t *helem)
 Detach an HCTL element from a mixer element.
int snd_mixer_elem_empty (snd_mixer_elem_t *melem)
 Return true if a mixer element does not contain any HCTL elements.
void * snd_mixer_elem_get_private (const snd_mixer_elem_t *melem)
 Get private data associated to give mixer element.
size_t snd_mixer_class_sizeof (void)
 get size of snd_mixer_class_t
int snd_mixer_class_malloc (snd_mixer_class_t **ptr)
 allocate an invalid snd_mixer_class_t using standard malloc
void snd_mixer_class_free (snd_mixer_class_t *obj)
 frees a previously allocated snd_mixer_class_t
void snd_mixer_class_copy (snd_mixer_class_t *dst, const snd_mixer_class_t *src)
 copy one snd_mixer_class_t to another
snd_mixer_tsnd_mixer_class_get_mixer (const snd_mixer_class_t *class_)
 Get a mixer associated to given mixer class.
snd_mixer_event_t snd_mixer_class_get_event (const snd_mixer_class_t *class_)
 Get mixer event callback associated to given mixer class.
void * snd_mixer_class_get_private (const snd_mixer_class_t *class_)
 Get mixer private data associated to given mixer class.
snd_mixer_compare_t snd_mixer_class_get_compare (const snd_mixer_class_t *class_)
 Get mixer compare callback associated to given mixer class.
int snd_mixer_class_set_event (snd_mixer_class_t *class_, snd_mixer_event_t event)
 Set mixer event callback to given mixer class.
int snd_mixer_class_set_private (snd_mixer_class_t *class_, void *private_data)
 Set mixer private data to given mixer class.
int snd_mixer_class_set_private_free (snd_mixer_class_t *class_, void(*private_free)(snd_mixer_class_t *))
 Set mixer private data free callback to given mixer class.
int snd_mixer_class_set_compare (snd_mixer_class_t *class_, snd_mixer_compare_t compare)
 Set mixer compare callback to given mixer class.

Detailed Description

The mixer interface.


Macro Definition Documentation

#define snd_mixer_class_alloca (   ptr)

allocate an invalid snd_mixer_class_t using standard alloca

Parameters:
ptrreturned pointer

Typedef Documentation

typedef int(* snd_mixer_callback_t)(snd_mixer_t *ctl, unsigned int mask, snd_mixer_elem_t *elem)

Mixer callback function.

Parameters:
mixerMixer handle
maskevent mask
elemrelated mixer element (if any)
Returns:
0 on success otherwise a negative error code
typedef struct _snd_mixer_class snd_mixer_class_t

Mixer elements class handle

typedef int(* snd_mixer_compare_t)(const snd_mixer_elem_t *e1, const snd_mixer_elem_t *e2)

Compare function for sorting mixer elements.

Parameters:
e1First element
e2Second element
Returns:
-1 if e1 < e2, 0 if e1 == e2, 1 if e1 > e2
typedef int(* snd_mixer_elem_callback_t)(snd_mixer_elem_t *elem, unsigned int mask)

Mixer element callback function.

Parameters:
elemMixer element
maskevent mask
Returns:
0 on success otherwise a negative error code
typedef struct _snd_mixer_elem snd_mixer_elem_t

Mixer element handle

typedef int(* snd_mixer_event_t)(snd_mixer_class_t *class_, unsigned int mask, snd_hctl_elem_t *helem, snd_mixer_elem_t *melem)

Event callback for the mixer class.

Parameters:
class_Mixer class
maskEvent mask (SND_CTL_EVENT_*)
helemHCTL element which invoked the event
melemMixer element associated to HCTL element
Returns:
zero if success, otherwise a negative error value
typedef struct _snd_mixer snd_mixer_t

Mixer handle


Enumeration Type Documentation

Mixer element type


Function Documentation

int snd_mixer_attach ( snd_mixer_t mixer,
const char *  name 
)

Attach an HCTL specified with the CTL device name to an opened mixer.

Parameters:
mixerMixer handle
nameHCTL name (see snd_hctl_open)
Returns:
0 on success otherwise a negative error code
int snd_mixer_attach_hctl ( snd_mixer_t mixer,
snd_hctl_t hctl 
)

Attach an HCTL to an opened mixer.

Parameters:
mixerMixer handle
hctlthe HCTL to be attached
Returns:
0 on success otherwise a negative error code
void snd_mixer_class_copy ( snd_mixer_class_t dst,
const snd_mixer_class_t src 
)

copy one snd_mixer_class_t to another

Parameters:
dstpointer to destination
srcpointer to source
void snd_mixer_class_free ( snd_mixer_class_t obj)

frees a previously allocated snd_mixer_class_t

Parameters:
objpointer to object to free
snd_mixer_compare_t snd_mixer_class_get_compare ( const snd_mixer_class_t obj)

Get mixer compare callback associated to given mixer class.

Parameters:
objMixer simple class identifier
Returns:
event callback pointer
snd_mixer_event_t snd_mixer_class_get_event ( const snd_mixer_class_t obj)

Get mixer event callback associated to given mixer class.

Parameters:
objMixer simple class identifier
Returns:
event callback pointer
snd_mixer_t* snd_mixer_class_get_mixer ( const snd_mixer_class_t obj)

Get a mixer associated to given mixer class.

Parameters:
objMixer simple class identifier
Returns:
mixer pointer
void* snd_mixer_class_get_private ( const snd_mixer_class_t obj)

Get mixer private data associated to given mixer class.

Parameters:
objMixer simple class identifier
Returns:
event callback pointer
int snd_mixer_class_malloc ( snd_mixer_class_t **  ptr)

allocate an invalid snd_mixer_class_t using standard malloc

Parameters:
ptrreturned pointer
Returns:
0 on success otherwise negative error code
int snd_mixer_class_register ( snd_mixer_class_t class,
snd_mixer_t mixer 
)

Register mixer element class.

Parameters:
classMixer element class
mixerMixer handle
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

int snd_mixer_class_set_compare ( snd_mixer_class_t obj,
snd_mixer_compare_t  compare 
)

Set mixer compare callback to given mixer class.

Parameters:
objMixer simple class identifier
comparethe compare callback to be used
Returns:
zero if success, otherwise a negative error code
int snd_mixer_class_set_event ( snd_mixer_class_t obj,
snd_mixer_event_t  event 
)

Set mixer event callback to given mixer class.

Parameters:
objMixer simple class identifier
eventEvent callback
Returns:
zero if success, otherwise a negative error code
int snd_mixer_class_set_private ( snd_mixer_class_t obj,
void *  private_data 
)

Set mixer private data to given mixer class.

Parameters:
objMixer simple class identifier
private_dataclass private data
Returns:
zero if success, otherwise a negative error code
int snd_mixer_class_set_private_free ( snd_mixer_class_t obj,
void(*)(snd_mixer_class_t *)  private_free 
)

Set mixer private data free callback to given mixer class.

Parameters:
objMixer simple class identifier
private_freeMixer class private data free callback
Returns:
zero if success, otherwise a negative error code
size_t snd_mixer_class_sizeof ( void  )

get size of snd_mixer_class_t

Returns:
size in bytes
int snd_mixer_class_unregister ( snd_mixer_class_t class)

Unregister mixer element class and remove all its elements.

Parameters:
classMixer element class
Returns:
0 on success otherwise a negative error code

Note that the class structure is also deallocated!

int snd_mixer_close ( snd_mixer_t mixer)

Close a mixer and free all related resources.

Parameters:
mixerMixer handle
Returns:
0 on success otherwise a negative error code
int snd_mixer_detach ( snd_mixer_t mixer,
const char *  name 
)

Detach a previously attached HCTL to an opened mixer freeing all related resources.

Parameters:
mixerMixer handle
nameHCTL previously attached
Returns:
0 on success otherwise a negative error code
int snd_mixer_detach_hctl ( snd_mixer_t mixer,
snd_hctl_t hctl 
)

Detach a previously attached HCTL to an opened mixer freeing all related resources.

Parameters:
mixerMixer handle
hctlHCTL previously attached
Returns:
0 on success otherwise a negative error code

Note: The hctl handle is not closed!

int snd_mixer_elem_add ( snd_mixer_elem_t elem,
snd_mixer_class_t class 
)

Add an element for a registered mixer element class.

Parameters:
elemMixer element
classMixer element class
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

int snd_mixer_elem_attach ( snd_mixer_elem_t melem,
snd_hctl_elem_t helem 
)

Attach an HCTL element to a mixer element.

Parameters:
melemMixer element
helemHCTL element
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

int snd_mixer_elem_detach ( snd_mixer_elem_t melem,
snd_hctl_elem_t helem 
)

Detach an HCTL element from a mixer element.

Parameters:
melemMixer element
helemHCTL element
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

int snd_mixer_elem_empty ( snd_mixer_elem_t melem)

Return true if a mixer element does not contain any HCTL elements.

Parameters:
melemMixer element
Returns:
0 if not empty, 1 if empty

For use by mixer element class specific code.

void snd_mixer_elem_free ( snd_mixer_elem_t elem)

Free a mixer element.

Parameters:
elemMixer element
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

void* snd_mixer_elem_get_callback_private ( const snd_mixer_elem_t mixer)

Get callback private value for a mixer element.

Parameters:
mixermixer element
Returns:
callback private value
void* snd_mixer_elem_get_private ( const snd_mixer_elem_t elem)

Get private data associated to give mixer element.

Parameters:
elemMixer element
Returns:
private data

For use by mixer element class specific code.

snd_mixer_elem_type_t snd_mixer_elem_get_type ( const snd_mixer_elem_t mixer)

Get type for a mixer element.

Parameters:
mixermixer element
Returns:
mixer element type
int snd_mixer_elem_info ( snd_mixer_elem_t elem)

Mixer element informations are changed.

Parameters:
elemMixer element
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

int snd_mixer_elem_new ( snd_mixer_elem_t **  elem,
snd_mixer_elem_type_t  type,
int  compare_weight,
void *  private_data,
void(*)(snd_mixer_elem_t *elem)  private_free 
)

Allocate a new mixer element.

Parameters:
elemReturned mixer element
typeMixer element type
compare_weightMixer element compare weight
private_dataPrivate data
private_freePrivate data free callback
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

snd_mixer_elem_t* snd_mixer_elem_next ( snd_mixer_elem_t elem)

get next mixer element

Parameters:
elemmixer element
Returns:
pointer to next element
snd_mixer_elem_t* snd_mixer_elem_prev ( snd_mixer_elem_t elem)

get previous mixer element

Parameters:
elemmixer element
Returns:
pointer to previous element
int snd_mixer_elem_remove ( snd_mixer_elem_t elem)

Remove a mixer element.

Parameters:
elemMixer element
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

void snd_mixer_elem_set_callback ( snd_mixer_elem_t mixer,
snd_mixer_elem_callback_t  val 
)

Set callback function for a mixer element.

Parameters:
mixermixer element
valcallback function
void snd_mixer_elem_set_callback_private ( snd_mixer_elem_t mixer,
void *  val 
)

Set callback private value for a mixer element.

Parameters:
mixermixer element
valcallback private value
int snd_mixer_elem_value ( snd_mixer_elem_t elem)

Mixer element values is changed.

Parameters:
elemMixer element
Returns:
0 on success otherwise a negative error code

For use by mixer element class specific code.

snd_mixer_elem_t* snd_mixer_first_elem ( snd_mixer_t mixer)

get first element for a mixer

Parameters:
mixerMixer handle
Returns:
pointer to first element
void snd_mixer_free ( snd_mixer_t mixer)

Unload all mixer elements and free all related resources.

Parameters:
mixerMixer handle
void* snd_mixer_get_callback_private ( const snd_mixer_t mixer)

Get callback private value for a mixer.

Parameters:
mixermixer handle
Returns:
callback private value
unsigned int snd_mixer_get_count ( const snd_mixer_t mixer)

Get elements count for a mixer.

Parameters:
mixermixer handle
Returns:
elements count
int snd_mixer_get_hctl ( snd_mixer_t mixer,
const char *  name,
snd_hctl_t **  hctl 
)

Obtain a HCTL pointer associated to given name.

Parameters:
mixerMixer handle
nameHCTL previously attached
hctlHCTL pointer
Returns:
0 on success otherwise a negative error code
int snd_mixer_handle_events ( snd_mixer_t mixer)

Handle pending mixer events invoking callbacks.

Parameters:
mixerMixer handle
Returns:
Number of events that occured on success, otherwise a negative error code on failure
snd_mixer_elem_t* snd_mixer_last_elem ( snd_mixer_t mixer)

get last element for a mixer

Parameters:
mixerMixer handle
Returns:
pointer to last element
int snd_mixer_load ( snd_mixer_t mixer)

Load a mixer elements.

Parameters:
mixerMixer handle
Returns:
0 on success otherwise a negative error code
int snd_mixer_open ( snd_mixer_t **  mixerp,
int  mode 
)

Opens an empty mixer.

Parameters:
mixerpReturned mixer handle
modeOpen mode
Returns:
0 on success otherwise a negative error code
int snd_mixer_poll_descriptors ( snd_mixer_t mixer,
struct pollfd *  pfds,
unsigned int  space 
)

get poll descriptors

Parameters:
mixerMixer handle
pfdsarray of poll descriptors
spacespace in the poll descriptor array
Returns:
count of filled descriptors
int snd_mixer_poll_descriptors_count ( snd_mixer_t mixer)

get count of poll descriptors for mixer handle

Parameters:
mixerMixer handle
Returns:
count of poll descriptors
int snd_mixer_poll_descriptors_revents ( snd_mixer_t mixer,
struct pollfd *  pfds,
unsigned int  nfds,
unsigned short *  revents 
)

get returned events from poll descriptors

Parameters:
mixerMixer handle
pfdsarray of poll descriptors
nfdscount of poll descriptors
reventsreturned events
Returns:
zero if success, otherwise a negative error code
void snd_mixer_set_callback ( snd_mixer_t obj,
snd_mixer_callback_t  val 
)

Set callback function for a mixer.

Parameters:
objmixer handle
valcallback function
void snd_mixer_set_callback_private ( snd_mixer_t mixer,
void *  val 
)

Set callback private value for a mixer.

Parameters:
mixermixer handle
valcallback private value
int snd_mixer_set_compare ( snd_mixer_t mixer,
snd_mixer_compare_t  compare 
)

Change mixer compare function and reorder elements.

Parameters:
mixerMixer handle
compareElement compare function
Returns:
0 on success otherwise a negative error code
int snd_mixer_wait ( snd_mixer_t mixer,
int  timeout 
)

Wait for a mixer to become ready (i.e. at least one event pending)

Parameters:
mixerMixer handle
timeoutmaximum time in milliseconds to wait
Returns:
0 otherwise a negative error code on failure