[mythtv-users] Video is behind audio, dropping frames to catch up (VDPAU, HD content)

[Richard]

On 12/03/13 22:04, Thomas Börkel wrote:
> HI!
>
> On 12.03.2013 21:07, Richard wrote:
>
>> I'm no audio expert but maybe the audio buffers were set too low on the
>> PCI card?
>>
>> Do you see anything like the following in your frontend logs?
>>
>> ALSA: Try to manually increase audio buffer with...
>
> 2013-03-12 21:13:36.313758 E  ALSA: Requested 500000us got 170666 buffer
> time
> 2013-03-12 21:13:36.313838 E  ALSA: Try to manually increase audio
> buffer with: echo 192 | sudo tee /proc/asound/card0/pcm0p/sub0/prealloc
>
> This message I get since switching to onboard audio. Should I do this?

If it ain't broke... :)  If you're sticking with the internal audio and 
aren't having problems with it, I'd leave it.  At least you're aware of 
it in case you do start having problems.

If you want to go back to the PCI sound card, or just for curiosity's 
sake, you could see whether that message appears when you select the PCI 
card.  As I said, depending on how I select the card, I don't always see 
that message.  Only when I *don't* see it does the value in 
..../prealloc *seem* to make a difference.

>> Interestingly, if I select 'ALSA:default', I don't see that message but
>> if the buffers are set too low, playback stutters terribly and I see the
>> same error message you originally reported.
>
> Hmm, maybe that would have fixed it.
>
>> If I select something else like 'ALSA:dmix:CARD=PCH,DEV=0', I get the
>> 'Try to manually increase...' message but playback seems fine regardless
>> of what size I set the buffers to.
>>
>> Both settings select the same (and only) sound card so I don't know
>> exactly what's going on but maybe you have a similar issue.
>
> Could be, although I did not get the hiccup that often. Mostly it played
> fine.

I could imagine that if the buffer size were a bit border-line, it could 
play fine most of the time until there was a bit of extra load of one 
sort or another, at which point the buffer size would turn out to be a 
bit too small to maintain error-free playback.

Richard.