snd_pcm_channel_prepare()

Signal the driver to ready the specified channel

Synopsis:

#include <sys/asoundlib.h>

int snd_pcm_channel_prepare( snd_pcm_t *handle, 
                             int channel );

Arguments:

handle

The handle for the PCM device, which you must have opened by calling snd_pcm_open() or snd_pcm_open_preferred().

channel

The channel; SND_PCM_CHANNEL_CAPTURE or SND_PCM_CHANNEL_PLAYBACK.

Library:

libasound.so

Description:

The snd_pcm_channel_prepare() function prepares hardware to operate in a specified transfer direction by calling snd_pcm_capture_prepare() or snd_pcm_playback_prepare(), depending on the value of channel.

This call is responsible for all parts of the hardware's startup sequence that require additional initialization time, allowing the final “GO” (usually from writes into the buffers) to execute more quickly.

This function may be called in all states except SND_PCM_STATUS_NOTREADY (returns -EBADFD) and SND_PCM_STATUS_RUNNING state (returns -EBUSY). If the operation is successful (zero is returned), the driver state is changed to SND_PCM_STATUS_PREPARED.

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If your channel has underrun (during playback) or overrun (during capture), you have to reprepare it before continuing. For an example, see wave.c and waverec.c in the appendix.

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Returns:

Zero on success, or a negative error code.

Errors:

-EINVAL

Invalid handle.

-EBUSY

Channel is running.

Classification:

QNX Neutrino

See also:

snd_pcm_capture_prepare(), snd_pcm_playback_prepare(), snd_pcm_plugin_prepare()