[alsa-devel] snd_pcm_avail_update returns 0

Singaravelan Nallasellan singaravelann at gmail.com
Thu Jan 14 15:41:31 CET 2010


Our audio driver uses the indirect PCM data transfer mechanism to
transfer the buffer pointers and the size of the buffer to the Audio
engine which DMAs the PCM data to the sound card.

The driver uses the .ack callback to receive the buffer pointer and
the size. It also sends it to the audio engine.

We are facing a problem when we play long wav file using our driver.

The application has written the PCM data and the ring buffer is full.
snd_pcm_avail_update returns 0 sporadically. But the .ack callback was
not called. The playback is stuck. It is not progressing.

I have tried with pulseaudio (0.9.15) and with my own player. Both
gives the same result.

I would appreciate if somebody could provide some pointer to identify
the cause of this issue. Let me know if anybody needs more info.


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