Transfer PCM data from the capture channel
#include <sys/asoundlib.h> ssize_t snd_pcm_read( snd_pcm_t *handle, void *buffer, size_t size );
The snd_pcm_read() function reads samples from the device, which must be in the proper format specified by snd_pcm_channel_prepare() or snd_pcm_capture_prepare().
This function may suspend the client application if blocking mode is active (see snd_pcm_nonblock_mode()) and no data is available for read.
When the subdevice is in blocking mode (SND_PCM_MODE_BLOCK), then the number of read bytes must fulfill the N × fragment-size expression, where N > 0.
If the stream format is noninterleaved (i.e. the interleave member of the snd_pcm_format_t structure isn't set), then the driver returns data that's separated to single voice blocks encapsulated to fragments. For example, imagine you have two voices, and the fragment size is 512 bytes. The number of bytes per one voice is 256. The driver returns the first 256 bytes that contain samples for the first voice, and the second 256 bytes from the fragment size that contains samples for the second voice.
A positive value that represents the number of bytes that were successfully read from the device if the capture was successful, or a negative value if an error occurred.
snd_pcm_capture_prepare(), snd_pcm_channel_prepare(), snd_pcm_format_t, snd_pcm_plugin_read(), snd_pcm_write()