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MIDI Sequencer

Modules

 Sequencer Client Interface
 Sequencer Port Interface
 Sequencer Port Subscription
 Sequencer Queue Interface
 Sequencer Event API
 Sequencer Miscellaneous
 Sequencer Event Type Checks
 Sequencer Event Definitions
 Sequencer Middle Level Interface
 Sequencer event <-> MIDI byte stream coder

Macros

#define SND_SEQ_DLSYM_VERSION   _dlsym_seq_001
#define SND_SEQ_OPEN_OUTPUT   1
#define SND_SEQ_OPEN_INPUT   2
#define SND_SEQ_OPEN_DUPLEX   (SND_SEQ_OPEN_OUTPUT|SND_SEQ_OPEN_INPUT)
#define SND_SEQ_NONBLOCK   0x0001
#define SND_SEQ_ADDRESS_UNKNOWN   253
#define SND_SEQ_ADDRESS_SUBSCRIBERS   254
#define SND_SEQ_ADDRESS_BROADCAST   255
#define SND_SEQ_CLIENT_SYSTEM   0
#define snd_seq_system_info_alloca(ptr)   __snd_alloca(ptr, snd_seq_system_info)

Typedefs

typedef struct _snd_seq snd_seq_t
typedef struct _snd_seq_system_info snd_seq_system_info_t

Enumerations

enum  snd_seq_type_t { SND_SEQ_TYPE_HW, SND_SEQ_TYPE_SHM, SND_SEQ_TYPE_INET }

Functions

int snd_seq_open (snd_seq_t **handle, const char *name, int streams, int mode)
 Open the ALSA sequencer.
int snd_seq_open_lconf (snd_seq_t **handle, const char *name, int streams, int mode, snd_config_t *lconf)
 Open the ALSA sequencer using local configuration.
const char * snd_seq_name (snd_seq_t *seq)
 get identifier of sequencer handle
snd_seq_type_t snd_seq_type (snd_seq_t *seq)
 get type of sequencer handle
int snd_seq_close (snd_seq_t *handle)
 Close the sequencer.
int snd_seq_poll_descriptors_count (snd_seq_t *handle, short events)
 Returns the number of poll descriptors.
int snd_seq_poll_descriptors (snd_seq_t *handle, struct pollfd *pfds, unsigned int space, short events)
 Get poll descriptors.
int snd_seq_poll_descriptors_revents (snd_seq_t *seq, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
 get returned events from poll descriptors
int snd_seq_nonblock (snd_seq_t *handle, int nonblock)
 Set nonblock mode.
int snd_seq_client_id (snd_seq_t *handle)
 Get the client id.
size_t snd_seq_get_output_buffer_size (snd_seq_t *handle)
 Return the size of output buffer.
size_t snd_seq_get_input_buffer_size (snd_seq_t *handle)
 Return the size of input buffer.
int snd_seq_set_output_buffer_size (snd_seq_t *handle, size_t size)
 Change the size of output buffer.
int snd_seq_set_input_buffer_size (snd_seq_t *handle, size_t size)
 Resize the input buffer.
size_t snd_seq_system_info_sizeof (void)
 Get size of snd_seq_system_info_t.
int snd_seq_system_info_malloc (snd_seq_system_info_t **ptr)
 Allocate an empty snd_seq_system_info_t using standard malloc.
void snd_seq_system_info_free (snd_seq_system_info_t *ptr)
 Frees a previously allocated snd_seq_system_info_t.
void snd_seq_system_info_copy (snd_seq_system_info_t *dst, const snd_seq_system_info_t *src)
 Copy one snd_seq_system_info_t to another.
int snd_seq_system_info_get_queues (const snd_seq_system_info_t *info)
 Get maximum number of queues.
int snd_seq_system_info_get_clients (const snd_seq_system_info_t *info)
 Get maximum number of clients.
int snd_seq_system_info_get_ports (const snd_seq_system_info_t *info)
 Get maximum number of ports.
int snd_seq_system_info_get_channels (const snd_seq_system_info_t *info)
 Get maximum number of channels.
int snd_seq_system_info_get_cur_clients (const snd_seq_system_info_t *info)
 Get the current number of clients.
int snd_seq_system_info_get_cur_queues (const snd_seq_system_info_t *info)
 Get the current number of queues.
int snd_seq_system_info (snd_seq_t *handle, snd_seq_system_info_t *info)
 obtain the sequencer system information

Detailed Description

MIDI Sequencer Interface. See Sequencer interface page for more details.


Macro Definition Documentation

#define SND_SEQ_ADDRESS_BROADCAST   255

send event to all queues/clients/ports/channels

#define SND_SEQ_ADDRESS_SUBSCRIBERS   254

send event to all subscribed ports

#define SND_SEQ_ADDRESS_UNKNOWN   253

special client (port) ids unknown source

#define SND_SEQ_CLIENT_SYSTEM   0

known client numbers system client

#define SND_SEQ_DLSYM_VERSION   _dlsym_seq_001

dlsym version for interface entry callback

#define SND_SEQ_NONBLOCK   0x0001

sequencer opening mode non-blocking mode (flag to open mode)

#define SND_SEQ_OPEN_DUPLEX   (SND_SEQ_OPEN_OUTPUT|SND_SEQ_OPEN_INPUT)

open for both input and output (read/write)

#define SND_SEQ_OPEN_INPUT   2

open for input (read)

#define SND_SEQ_OPEN_OUTPUT   1

sequencer opening stream types open for output (write)

#define snd_seq_system_info_alloca (   ptr)    __snd_alloca(ptr, snd_seq_system_info)

allocate a snd_seq_system_info_t container on stack


Typedef Documentation

typedef struct _snd_seq_system_info snd_seq_system_info_t

system information container

typedef struct _snd_seq snd_seq_t

Sequencer handle


Enumeration Type Documentation

sequencer handle type

Enumerator:
SND_SEQ_TYPE_HW 

hardware

SND_SEQ_TYPE_SHM 

shared memory (NYI)

SND_SEQ_TYPE_INET 

network (NYI)


Function Documentation

int snd_seq_client_id ( snd_seq_t seq)

Get the client id.

Parameters:
seqsequencer handle
Returns:
the client id

Returns the id of the specified client. If an error occurs, function returns the negative error code. A client id is necessary to inquiry or to set the client information. A user client is assigned from 128 to 191.

See also:
snd_seq_open()
int snd_seq_close ( snd_seq_t seq)

Close the sequencer.

Parameters:
seqHandle returned from snd_seq_open()
Returns:
0 on success otherwise a negative error code

Closes the sequencer client and releases its resources. After a client is closed, an event with SND_SEQ_EVENT_CLIENT_EXIT is broadcast to announce port. The connection between other clients are disconnected. Call this just before exiting your program.

See also:
snd_seq_close()
size_t snd_seq_get_input_buffer_size ( snd_seq_t seq)

Return the size of input buffer.

Parameters:
seqsequencer handle
Returns:
the size of input buffer in bytes

Obtains the size of input buffer. This buffer is used to read byte-stream of input events from sequencer.

See also:
snd_seq_set_input_buffer_size()
size_t snd_seq_get_output_buffer_size ( snd_seq_t seq)

Return the size of output buffer.

Parameters:
seqsequencer handle
Returns:
the size of output buffer in bytes

Obtains the size of output buffer. This buffer is used to store decoded byte-stream of output events before transferring to sequencer.

See also:
snd_seq_set_output_buffer_size()
const char* snd_seq_name ( snd_seq_t seq)

get identifier of sequencer handle

Parameters:
seqsequencer handle
Returns:
ASCII identifier of sequencer handle

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

See also:
snd_seq_open()
int snd_seq_nonblock ( snd_seq_t seq,
int  nonblock 
)

Set nonblock mode.

Parameters:
seqsequencer handle
nonblock0 = block, 1 = nonblock mode
Returns:
0 on success otherwise a negative error code

Change the blocking mode of the given client. In block mode, the client falls into sleep when it fills the output memory pool with full events. The client will be woken up after a certain amount of free space becomes available.

See also:
snd_seq_open()
int snd_seq_open ( snd_seq_t **  seqp,
const char *  name,
int  streams,
int  mode 
)

Open the ALSA sequencer.

Parameters:
seqpPointer to a snd_seq_t pointer. This pointer must be kept and passed to most of the other sequencer functions.
nameThe sequencer's "name". This is not a name you make up for your own purposes; it has special significance to the ALSA library. Usually you need to pass "default" here.
streamsThe read/write mode of the sequencer. Can be one of three values:
Note:
Internally, these are translated to O_WRONLY, O_RDONLY and O_RDWR respectively and used as the second argument to the C library open() call.
Parameters:
modeOptional modifier. Can be either 0, or SND_SEQ_NONBLOCK, which will make read/write operations non-blocking. This can also be set later using snd_seq_nonblock().
Returns:
0 on success otherwise a negative error code

Creates a new handle and opens a connection to the kernel sequencer interface. After a client is created successfully, an event with SND_SEQ_EVENT_CLIENT_START is broadcast to announce port.

See also:
snd_seq_open_lconf(), snd_seq_close(), snd_seq_type(), snd_seq_name(), snd_seq_nonblock(), snd_seq_client_id()
int snd_seq_open_lconf ( snd_seq_t **  seqp,
const char *  name,
int  streams,
int  mode,
snd_config_t lconf 
)

Open the ALSA sequencer using local configuration.

Parameters:
seqpPointer to a snd_seq_t pointer.
nameThe name to open
streamsThe read/write mode of the sequencer.
modeOptional modifier
lconfLocal configuration
Returns:
0 on success otherwise a negative error code

See the snd_seq_open() function for further details. The extension is that the given configuration is used to resolve abstract name.

See also:
snd_seq_open()
int snd_seq_poll_descriptors ( snd_seq_t seq,
struct pollfd *  pfds,
unsigned int  space,
short  events 
)

Get poll descriptors.

Parameters:
seqsequencer handle
pfdsarray of poll descriptors
spacespace in the poll descriptor array
eventspolling events to be checked (POLLIN and POLLOUT)
Returns:
count of filled descriptors

Get poll descriptors assigned to the sequencer handle. Since a sequencer handle can duplex streams, you need to set which direction(s) is/are polled in events argument. When POLLIN bit is specified, the incoming events to the ports are checked.

To check the returned poll-events, call snd_seq_poll_descriptors_revents() instead of reading the pollfd structs directly.

See also:
snd_seq_poll_descriptors_count(), snd_seq_poll_descriptors_revents()
int snd_seq_poll_descriptors_count ( snd_seq_t seq,
short  events 
)

Returns the number of poll descriptors.

Parameters:
seqsequencer handle
eventsthe poll events to be checked (POLLIN and POLLOUT)
Returns:
the number of poll descriptors.

Get the number of poll descriptors. The polling events to be checked can be specified by the second argument. When both input and output are checked, pass POLLIN|POLLOUT

See also:
snd_seq_poll_descriptors()
int snd_seq_poll_descriptors_revents ( snd_seq_t seq,
struct pollfd *  pfds,
unsigned int  nfds,
unsigned short *  revents 
)

get returned events from poll descriptors

Parameters:
seqsequencer handle
pfdsarray of poll descriptors
nfdscount of poll descriptors
reventsreturned events
Returns:
zero if success, otherwise a negative error code
See also:
snd_seq_poll_descriptors()
int snd_seq_set_input_buffer_size ( snd_seq_t seq,
size_t  size 
)

Resize the input buffer.

Parameters:
seqsequencer handle
sizethe size of input buffer to be changed in bytes
Returns:
0 on success otherwise a negative error code

Changes the size of input buffer.

See also:
snd_seq_get_input_buffer_size()
int snd_seq_set_output_buffer_size ( snd_seq_t seq,
size_t  size 
)

Change the size of output buffer.

Parameters:
seqsequencer handle
sizethe size of output buffer to be changed in bytes
Returns:
0 on success otherwise a negative error code

Changes the size of output buffer.

See also:
snd_seq_get_output_buffer_size()
int snd_seq_system_info ( snd_seq_t seq,
snd_seq_system_info_t info 
)

obtain the sequencer system information

Parameters:
seqsequencer handle
infothe pointer to be stored
Returns:
0 on success otherwise a negative error code

Stores the global system information of ALSA sequencer system. The returned data contains the maximum available numbers of queues, clients, ports and channels.

void snd_seq_system_info_copy ( snd_seq_system_info_t dst,
const snd_seq_system_info_t src 
)

Copy one snd_seq_system_info_t to another.

Parameters:
dstpointer to destination
srcpointer to source
void snd_seq_system_info_free ( snd_seq_system_info_t obj)

Frees a previously allocated snd_seq_system_info_t.

Parameters:
objpointer to object to free
int snd_seq_system_info_get_channels ( const snd_seq_system_info_t info)

Get maximum number of channels.

Parameters:
infosnd_seq_system_info_t container
Returns:
maximum number of channels
See also:
snd_seq_system_info()
int snd_seq_system_info_get_clients ( const snd_seq_system_info_t info)

Get maximum number of clients.

Parameters:
infosnd_seq_system_info_t container
Returns:
maximum number of clients
See also:
snd_seq_system_info()
int snd_seq_system_info_get_cur_clients ( const snd_seq_system_info_t info)

Get the current number of clients.

Parameters:
infosnd_seq_system_info_t container
Returns:
current number of clients
See also:
snd_seq_system_info()
int snd_seq_system_info_get_cur_queues ( const snd_seq_system_info_t info)

Get the current number of queues.

Parameters:
infosnd_seq_system_info_t container
Returns:
current number of queues
See also:
snd_seq_system_info()
int snd_seq_system_info_get_ports ( const snd_seq_system_info_t info)

Get maximum number of ports.

Parameters:
infosnd_seq_system_info_t container
Returns:
maximum number of ports
See also:
snd_seq_system_info()
int snd_seq_system_info_get_queues ( const snd_seq_system_info_t info)

Get maximum number of queues.

Parameters:
infosnd_seq_system_info_t container
Returns:
maximum number of queues
See also:
snd_seq_system_info()
int snd_seq_system_info_malloc ( snd_seq_system_info_t **  ptr)

Allocate an empty snd_seq_system_info_t using standard malloc.

Parameters:
ptrreturned pointer
Returns:
0 on success otherwise negative error code
size_t snd_seq_system_info_sizeof ( void  )

Get size of snd_seq_system_info_t.

Returns:
size in bytes
snd_seq_type_t snd_seq_type ( snd_seq_t seq)

get type of sequencer handle

Parameters:
seqsequencer handle
Returns:
type of sequencer handle

Returns the type snd_seq_type_t of the given sequencer handle.

See also:
snd_seq_open()