[mythtv-users] AV-Sync problem

[David Wong]

----- "Jean-Yves Avenard" <jyavenard at gmail.com> wrote:
> Hi
> 
> 2009/4/15 David Wong <david.wong at marvel.com.hk>:
> >> 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.
> 
> Does this apply?
> 
> Q: I get stuttering  every few seconds with errors like "NVP: Video
> is
> 3.12705 frames behind audio (too slow), dropping frame to catch up."
> 
> A: Check your settings: In General: make sure "Aggressive sound card
> buffering" is unckecked
> In TV -> Playback "Extra audio buffering" is checked.
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Should be applied, 'though I am not in front of my machine to confirm it at the moment.

I read the code and "already 75 video frames queued" error message seems very related
to the gap between video packet and audio after multiplex. It checks the difference 
between video PTS and audio PTS.

On the other hand, when I study FFMPEG few months ago with the up-to-date repository code that time,
the reported PTS from FFMPEG is not exact the PTS of the PES packet it represent.
I tried parse TS and PES packet myself and found that observation. I don't know if it is related,
to the MythTV problem I am facing.

BTW, I really hate that function AvFormatDecoder::GetFrame(). It is ridiculously long,
with over nine hundred lines of code. I can't fully understand that yet.
Allman style indentation is also a cause to be blamed too.

David