2010/12/13 Clemens Ladisch clemens@ladisch.de
louis@museresearch.com wrote:
Hi everyone, I'm having some difficulty improving a full-duplex MMAP ALSA routine. ALSA sometimes reports more samples available for input than my buffer can take, or asks for more samples than I have available. Is this a buffer overrun/underrun?
Yes. (And this should happen only when you've disabled stopping on an xrun, so you've asked for it. :-)
If I restart the streams in the case that too much input is available (on the assumption that it's an xrun) it seems to happen at the drop of a hat and makes things worse. If I discard the excess input, that doesn't work well either.
What is the appropriate way to deal with this situation?
The best way would be to prevent this situation from happening, i.e., read the captured data from the buffer before it overflows.
(In the case of capturing, latency does _not_ depend on the buffer size, so you should make the buffer as big as possible.)
Refer to http://thread.gmane.org/gmane.linux.alsa.devel/66826/focus=66954
you mention that snd_pcm_forward can be used to recover from an underrun condition for playback
In underrun/overrun of playback/capture , the hardware pointer is ahead of the application pointer
Can snd_pcm_forward be used to recover from overrun in capture when automatic stop is disabled ?
Why does Pulseaudio server request rewind at the end of underrun ?
D: protocol-native.c: Requesting rewind due to *end of underrun*