Re: [alsa-devel] snd_pcm_delay, hw buffers and driver api (v2)

Kai Vehmanen wrote:

... In both cases, this value (hw_ptr) shows the status of sending data to an separate entity, and one that has its own buffer (multiple ms) before the actual DAC/ADC.

So when application developer uses snd_pcm_delay(), the result is not quite what the ALSA API says: ...

snd_pcm_avail() returns the free part of the buffer. snd_pcm_delay() returns the filled part of the buffer plus the additional delay imposed by the device.

The additional delay can be set by the driver in pcm_substream->runtime->delay. (Currently, only the USB audio driver bothers to set this.)

HTH Clemens