Main Page   Modules   Data Structures   File List   Data Fields   Globals   Related Pages   Examples  

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_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_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_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_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_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_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_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_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.


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_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 Software Parameters 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 whole ring buffer is filled with silence at start. Later, only just processed 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

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


Generated on Mon Oct 27 12:34:48 2003 for ALSA project - the C library reference by doxygen1.2.18