[mythtv-users] AV-Sync problem

R. G. Newbury newbury at mandamus.org
Wed Apr 15 13:35:07 UTC 2009

David Wong wrote:
> ----- Original Message -----
> From: "greg" <greg12866 at nycap.rr.com>
> To: "Discussion about mythtv" <mythtv-users at mythtv.org>
> Sent: Wednesday, April 15, 2009 3:09:11 AM (GMT+0800) Asia/Hong_Kong
> Subject: Re: [mythtv-users] AV-Sync problem
> David Wong wrote:
>> Hi all,
>> I am running 0.21 branch with VDPAU patch #r20300, on NVidia 9400 IGP with Intel Q2D E7400 2.8GHz.
>> When I play some of DTV channel in my living place, I got lots of following warnings:
>> "Audio 686 ms behind video but already 75 video frames queued. AV-Sync might be broken. "
>> and some audio buffer underrun error, both video and audio are not smooth.
>> Video output resolution is not important too.
>> It only happens in 2 SD H.264 channels from same broadcaster here.
>> It looks like that audio packet, in form of libavformat packet?, is very lag behind video.
>> It is not very surprising as the two channels are rather low bit rate. Broadcaster makes very extreme
>>  configuration to accommodate 1 HD and 3 SD channels in a 21Mbps carrier.
>> I check into the code. It seems the playback engine only checks enough video when pre-buffering,
>>  and left audio buffer unchecked. Is my observation valid? Are there anyway to both ensure enough
>>  video and audio before playback?
>> Or anyway to buffer more data? I think it is better to be measured in time rather than in data size.

> I used to have this problem until i removed pulseaudio... Try removing 
> it and see if that resolves your problem..

> I tried "sudo /etc/init.d/pulseaudio stop" in my Mythbuntu 8.10.
> Unfortunately, it doesn't help.
> Thanks anyway.
> David

Try 'apt-get remove  alsa-plugins-pulseaudio' and reboot

alsa-plugins-pulseaudio io the name of the package in Fedora, and it's 
likely the same in Ubuntu.


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