[mythtv] AVSync Problem on entering recorded playback

Stephen Williams stephen.gw at gmail.com
Tue Mar 28 23:00:12 UTC 2006


On 3/28/06, Stephen Williams <stephen.gw at gmail.com> wrote:
> Okay, i've been making some progress on this now. Disabling the
> dropping of frames / doubling of frame times and allowing the AVSync
> code to settle down (takes a few minutes to stabilise) it has become
> apparent that on initial entry to recorded playback it is trying the
> play the video at 30fps (note that this is PAL content at 25fps).
>
> After pausing / unpausing it then starts to play the content correctly at 25fps.
>
> Now for the million dollar question, why are we initially defaulting to 30fps?
>
> Stephen

OK, I have a 'fix' but may be treating the symptom and not the cause.

It appears that the AVD (avformatdecoder) it detecting _two_ video
streams in each of my mpg files (note, these are all DVB-T in the UK).
One of the video streams looks legit whilst the other apparently has a
bit-rate of 0 and seems to just pick up some default params from AVD
(e.g. 30fps, 640x480).

NVP::SetVideoParams was being called for both video streams and was
clearly just getting confused.

For the time being I have added a check in AVD::ScanStreams that
discards any video streams with a bit-rate of 0, as I said previously,
this 'fixes' my problem.

Is there any other tool I can use to look at the mpeg file and double
check the existence of this second video stream? My hunch is that the
stream doesn't really exist and there may be a problem with
AVD::ScanStreams.

Any advice greatly appreciated.
Stephen


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