[mythtvnz] Audio sync issued with DVBS, mythbunut 12.04 and mythtv 0.25

[David Moore]

On 18/06/12 21:53, Stephen Worthington wrote:
> On Mon, 18 Jun 2012 20:53:44 +1200 (NZST), you wrote:
>
>>
>> On Sun, June 17, 2012 7:15 pm, Steven Ellis wrote:
>>> Hi Guys
>>>
>>> Ran an upgrade over the weekend and I noticed that David had the same
>>> issue over on the MythTV Users list.
>>>
>>> Basically if I ffwd or jump within a DVB-S recording, in particular a TVNZ
>>> stream, audio sync is lost unless I exit playback and re-open the file.
>>>
>>> He's already raised a ticket for the issue
>>> http://code.mythtv.org/trac/ticket/10797
>>>
>>> Anyone else here seeing wit with DVB-S material
>>>
>>> I'm currently running 2:0.25.0+fixes.20120614
>>>
>>> Tried the usual obvious stuff. Any other ideas?
>>
>> Looks like I've got a fix and updated the ticket with the details. Argh
>> Alsa buffers.
>
> I thought I remembered something about ALSA buffer problems with 0.24.
> A search of my /etc files turned up this in my rc.local:
>
> # Fix for getting these errors in mythfrontend.log:
> #   ALSA, Error: Setting hardware audio buffer size to 6016
> #   ALSA, Error: Error opening /proc/asound/card0/pcm0p/sub0/prealloc:
> Permission denied.
> #   ALSA, Error: Try to manually increase audio buffer with: echo 6016
> | sudo tee /proc/asound/card0/pcm0p/sub0/prealloc
> #   ALSA, Error: Unable to sufficiently increase ALSA hardware buffer
> size - underruns are likely
> #   ALSA, Error: WriteAudio: buffer underrun
> chmod a+rwx /proc/asound/card0/pcm0p/sub0/prealloc
> chgrp audio /proc/asound/card0/pcm0p/sub0/prealloc
>
> With that fix in place, I did a
>
>    cat /proc/asound/card0/pcm0p/sub0/prealloc
>
> and got a value of 4096.
>
> What sort of default value does Mythbuntu 12.04 have for this?  Would
> the same fix help?
>

Tried that even though I wasn't getting buffer underruns. Still major 
unsync when seeking back to recording start and minor unsync when 
seeking forward.