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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)
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_sleep_min (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, unsigned int val)
 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)
 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_xfer_align (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val)
 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)
 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 *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
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:
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
val returned minimum available frames to consider PCM ready
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
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
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_sleep_min const snd_pcm_sw_params_t params,
unsigned int *  val
 

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

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

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).

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

int snd_pcm_sw_params_get_xfer_align const snd_pcm_sw_params_t params,
snd_pcm_uframes_t val
 

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)
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
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. Note that you can greatly improve the reponses using snd_pcm_sw_params_set_sleep_min where another timing source is used.
Examples:
/test/latency.c, and /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
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)

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
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.

int snd_pcm_sw_params_set_sleep_min snd_pcm_t pcm,
snd_pcm_sw_params_t params,
unsigned int  val
 

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
Examples:
/test/latency.c.

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.

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).

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

int snd_pcm_sw_params_set_xfer_align snd_pcm_t pcm,
snd_pcm_sw_params_t params,
snd_pcm_uframes_t  val
 

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

size_t snd_pcm_sw_params_sizeof void   ) 
 

get size of snd_pcm_sw_params_t

Returns:
size in bytes


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