[mythtv-users] A/V out of sync due to dropped frames

[mary wright]

There's a really good program called ProjectX it's a java app with fixes
most errors in av sync'ing .It hasn't failed to work on eveything I have
thrown at it .once I get the output from Project X I use Avidemux2 to edit
and re-encode to what ever format needed

I also have a wrapper script that output's *.mpg but haven't worked out a
way to get mythtv to run it on recorded programs

If you want the link to a compiled ProjectX email me


On 7/4/05 12:21 PM, "Justin Gombos" <mindfuq at fairfieldi.com> wrote:

> * Ian Trider <iantri at gmail.com> [2005-04-05 20:58]:
>> 
>> BTW, essentially if the problem you are referring to is audio sync,
>> it is because of how the PVR-250 outputs streams -- the video and
>> audio are aligned with via the PTS data, essentially timestaps,
>> which dicates the temporal relationship between audio and video in
>> an MPEG elementary stream.  If something bad happens (i.e. a frame
>> drop) the PVR-250 takes no notice of it; it will be indicated in the
>> PTS data and the player deals with keeping the sync locked together.
>> 
>> This isn't really wrong, and in fact seems like a good way to
>> produce perfectly synced audio (because the temporal position of
>> each frame of audio or video is indicated), but because most editing
>> programs simply disregard this and work on the raw video and audio
>> streams, you get 'issues' -- the lengths won't be exactly the same
>> due to recording flaws (like frame drops) and it will go out of
>> sync.
>> 
>> The way to fix it is to have a program go through and readjust lengths
>> of the audio and video so that the raw streams sync properly -- by
>> dropping audio or video frames to make the actual video and audio
>> streams match the PTS data.
> 
> Wouldn't it be better in that case to reconstruct the missing video
> frames, rather than drop audio frames?  Missing video frames can
> probably be reconstructed by interpolating the 'before' and 'after'
> frames, no?
> 
> BTW- I'd like to point out that this problem seems to occurr with the
> Plextor tv402u.  Sometimes part way into a capture video will get
> quite choppy, and audio out of sync, which is probably a symptom of
> the problem you describe.  I just wanted to point that out, so folks
> buying a Plextor ConvertX are aware that the bundled software is not
> smart enough to resolve this problem.
> 
> Does MythTV resolve this problem?
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