Software Parameters
[PCM Interface]

Defines

#define snd_pcm_sw_params_alloca(ptr)
 allocate an invalid snd_pcm_sw_params_t using standard alloca

Functions

size_t snd_pcm_sw_params_sizeof (void)
 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_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_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_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 *paramsm, 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.

Detailed Description

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

Define Documentation

#define snd_pcm_sw_params_alloca ( ptr   ) 

allocate an invalid snd_pcm_sw_params_t using standard alloca

Parameters:
ptr returned pointer
Examples:
/test/latency.c, and /test/pcm.c.

Function Documentation

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
Parameters:
src pointer to source
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
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
Parameters:
val returned minimum available frames to consider PCM ready
Returns:
0 otherwise a negative error code
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
Parameters:
val Returned boundary in frames
Returns:
0 otherwise a negative error code
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
Parameters:
val returned period event state
Returns:
0 otherwise a negative error code
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
Parameters:
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)
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
Parameters:
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.
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
Parameters:
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
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
Parameters:
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).
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
Parameters:
val Returned timestamp
Returns:
0 otherwise a negative error code
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
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
Parameters:
params Software configuration container
Parameters:
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.
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
Parameters:
params Software configuration container
Parameters:
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.
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
Parameters:
params Software configuration container
Parameters:
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)
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.
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
Parameters:
params Software configuration container
Parameters:
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.
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
Parameters:
params Software configuration container
Parameters:
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.
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
Parameters:
params Software configuration container
Parameters:
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).
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
Parameters:
params Software configuration container
Parameters:
val Timestamp mode
Returns:
0 otherwise a negative error code
size_t snd_pcm_sw_params_sizeof ( void   ) 

get size of snd_pcm_sw_params_t

Returns:
size in bytes
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Defines
Generated on Fri Jan 27 14:19:57 2012 for ALSA project - the C library reference by  doxygen 1.6.3