[mythtv-users] audio buffer underruns [partly solved]

Jean-Yves Avenard jyavenard at gmail.com
Sat Mar 17 20:58:43 UTC 2012


On Sunday, 18 March 2012, Ross Boylan <RossBoylan at stanfordalumni.org> wrote:

>
> I'm pretty sure I used the same recording each time.  So why is it now
> trying for 320 when before is was 192?  Does the code try progressively
> larger buffer sizes til it gets where it wants to go?  If so, what is
> the final size I should use?
>

The way that figure is reported/calculated is as follow.
Myth asks alsa for 500ms audio. Say it only gets 250ms.
Myth looks at the size of the existing alsa kernel buffer, and sees that
it's set to 64kB
As myth only got half the time it wanted, it assumes the audio buffer
should have been 128kB instead.

So myth could have guessed that you needed 192kB buffer, but alsa continues
to return a different buffer than what we ask. So the value reported
changes.

I wouldn't worry about it unless you do get buffer underruns. The message
is harmless, but does help finding the cause of buffer underruns when they
do happen.

> Also, not being able to reset the sound without disabling other sound
> seems like a problem if different recordings have different
> requirements, which I gather they do.
>

You can only modify the card if it's not in use elsewhere.

> mythtv 0.24-2.
> linux kernel 2.6.26-2-686
> 00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High
> Definition Audio Controller (rev 01) on motherboard.

Try upgrading your alsa drivers.
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