Software Parameters

Overview

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

// global functions

size_t
snd_pcm_sw_params_sizeof(void);

int
snd_pcm_sw_params_malloc(snd_pcm_sw_params_t** ptr);

void
snd_pcm_sw_params_free(snd_pcm_sw_params_t* obj);

void
snd_pcm_sw_params_copy(
    snd_pcm_sw_params_t* dst,
    const snd_pcm_sw_params_t* src
);

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
);

int
snd_pcm_sw_params_get_tstamp_mode(
    const snd_pcm_sw_params_t* params,
    snd_pcm_tstamp_t* val
);

int
snd_pcm_sw_params_set_tstamp_type(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_tstamp_type_t val
);

int
snd_pcm_sw_params_get_tstamp_type(
    const snd_pcm_sw_params_t* params,
    snd_pcm_tstamp_type_t* val
);

int
snd_pcm_sw_params_set_avail_min(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t val
);

int
snd_pcm_sw_params_get_avail_min(
    const snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t* val
);

int
snd_pcm_sw_params_set_period_event(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    int val
);

int
snd_pcm_sw_params_get_period_event(
    const snd_pcm_sw_params_t* params,
    int* val
);

int
snd_pcm_sw_params_set_start_threshold(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t val
);

int
snd_pcm_sw_params_get_start_threshold(
    const snd_pcm_sw_params_t* paramsm,
    snd_pcm_uframes_t* val
);

int
snd_pcm_sw_params_set_stop_threshold(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t val
);

int
snd_pcm_sw_params_get_stop_threshold(
    const snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t* val
);

int
snd_pcm_sw_params_set_silence_threshold(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t val
);

int
snd_pcm_sw_params_get_silence_threshold(
    const snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t* val
);

int
snd_pcm_sw_params_set_silence_size(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t val
);

int
snd_pcm_sw_params_get_silence_size(
    const snd_pcm_sw_params_t* params,
    snd_pcm_uframes_t* val
);

// macros

#define snd_pcm_sw_params_alloca(ptr)

Detailed Documentation

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

Global Functions

size_t
snd_pcm_sw_params_sizeof(void)

get size of snd_pcm_sw_params_t

Returns:

size in bytes

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

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

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

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
val	Returned boundary in frames

Returns:

0 otherwise a negative error code

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_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_set_tstamp_type(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    snd_pcm_tstamp_type_t val
)

Set timestamp type inside a software configuration container.

Parameters:

pcm	PCM handle
params	Software configuration container
val	Timestamp type

Returns:

0 otherwise a negative error code

int
snd_pcm_sw_params_get_tstamp_type(
    const snd_pcm_sw_params_t* params,
    snd_pcm_tstamp_type_t* val
)

Get timestamp type from a software configuration container.

Parameters:

params	Software configuration container
val	Returned timestamp type

Returns:

0 otherwise a 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.

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.

Parameters:

pcm	PCM handle
params	Software configuration container
val	Minimum avail frames to consider PCM ready

Returns:

0 otherwise a negative error code

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_set_period_event(
    snd_pcm_t* pcm,
    snd_pcm_sw_params_t* params,
    int val
)

Set period event inside a software configuration container.

An poll (select) wakeup event is raised if enabled.

Parameters:

pcm	PCM handle
params	Software configuration container
val	0 = disable period event, 1 = enable period event

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
val	returned period event state

Returns:

0 otherwise a negative error code

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.

PCM is automatically started when playback frames available to PCM are >= threshold or when requested capture frames are >= threshold

Parameters:

pcm	PCM handle
params	Software configuration container
val	Start threshold in frames

Returns:

0 otherwise a negative error code

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.

PCM is automatically started when playback frames available to PCM are >= threshold or when requested capture frames are >= threshold

Parameters:

params	Software configuration container
val	Returned start threshold in frames

Returns:

0 otherwise a negative error code

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.

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).

Parameters:

pcm	PCM handle
params	Software configuration container
val	Stop threshold in frames

Returns:

0 otherwise a negative error code

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.

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).

Parameters:

params	Software configuration container
val	Returned stop threshold in frames

Returns:

0 otherwise a negative error code

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.

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.

Parameters:

pcm	PCM handle
params	Software configuration container
val	Silence threshold in frames

Returns:

0 otherwise a negative error code

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.

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.

Parameters:

params	Software configuration container
val	Returned silence threshold in frames

Returns:

0 otherwise a negative error value

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.

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.

Parameters:

pcm	PCM handle
params	Software configuration container
val	Silence size in frames (0 for disabled)

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.

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)

Parameters:

params	Software configuration container
val	Returned silence size in frames (0 for disabled)

Returns:

0 otherwise a negative error code

Macros

#define snd_pcm_sw_params_alloca(ptr)

allocate an invalid snd_pcm_sw_params_t using standard alloca

Parameters:

ptr	returned pointer