snd_pcm_playback

Signal the driver to ready the playback channel

Synopsis:

#include <sys/asoundlib.h>

int snd_pcm_playback_prepare( snd_pcm_t *handle);

Arguments:

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

Library:

libasound.so

Use the -l asound option with qcc to link against this library.

Description:

The snd_pcm_playback_prepare() function prepares hardware to operate in a specified transfer direction. This call is responsible for all parts of the hardware's startup sequence that require additional initialization time, allowing the final “GO” (either from writes into the buffers or snd_pcm_channel_go()) to execute more quickly.

You can call this function in all states except SND_PCM_STATUS_NOTREADY (returns -EBADFD) and SND_PCM_STATUS_RUNNING (returns -EBUSY). If the operation is successful (zero is returned), the driver state is changed to SND_PCM_STATUS_PREPARED.

Note: If your channel has underrun, you have to reprepare it before continuing. For an example, see wave.c in the appendix.

Returns:

EOK on success, a negative error code, or a negative errno upon failure. The errno values are available in the errno.h file.

Errors:

-EINVAL: The state of handle is invalid or an invalid state change occurred. You can call snd_pcm_channel_status() to check if the state change was invalid.
-EBUSY: The channel is already running.
-EIO: The channel was not set to SND_PCM_CHANNEL_PLAYBACK or SND_PCM_CHANNEL_CAPTURE.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Read the Caveats

Caveats:

This function is not thread safe if handle (snd_pcm_t) is used across multiple threads.