[gentoo-user] DVD authoring and AV sync problems with mpeg2 source

[gentoo-user] DVD authoring and AV sync problems with mpeg2 source

[Ezequiel Tolnay]

Dear all,

    I've been trying to author my first DVD on my Gentoo box, and after 
many attempts I couldn't get the audio and video properly synchronised 
as it is in the original mpeg2/mp2 video.

    I made the video using an old camera, and captured it on a Windows 
PC, using a TV capture card, using 352x288 and mpeg2 for video and audio.

    I've used several tools to try to get the final DVD video format 
with ac3, mostly following guidelines from 
http://forums.gentoo.org/viewtopic-t-117709-highlight-authoring.html. If 
if follow those guidelines, the audio loses sync. Whenever I convert the 
.mpg to AVI format with any tools the audio goes out of sync again, just 
the same. The only tool I used that managed to maintain the audio and 
video in sync is mpgtx, but I can only use it this one to extract and 
join mpeg segments, therefore limiting somehow the problem by chunking 
the the video in say 20 min segments, but it still by the end the 
desynchronised audio is quite anoying.

    I was wondering if any of you has had a similar problem and figured 
a way to maintain the AV in sync after converting an mpeg to AVI format, 
or if any of you can give me any clues as to why is this happening and a 
way to prevent/solve it.

Thanks in advance to you all,

Ezequiel
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Re: [gentoo-user] DVD authoring and AV sync problems with mpeg2 source

[Ezequiel Tolnay]

Ezequiel Tolnay wrote:

>    I was wondering if any of you has had a similar problem and figured 
> a way to maintain the AV in sync after converting an mpeg to AVI 
> format, or if any of you can give me any clues as to why is this 
> happening and a way to prevent/solve it.

After much fidling with it, I found a solution for it, and would like to 
share it with whoever has this problem in the future. The problem is 
basically that the mpeg2 source has repeated frames, and the transcode 
utility filters them without compensating with the audio, thus creating 
a synching issue. If the source is already mpeg2 for video and audio but 
the dvdauthor doesn't like it, that's because the video also needs to be 
built for DVD (some kind of meta information between frames, or 
something like that). The same for other formats such as SVCD.

    In my case the video had already the proper codecs (both mpeg2), the 
proper size (352x288 for PAL, which is fine), and the proper audio 
bitrate (224), but not formatted for DVD. To format it properly, use the 
following:

mencoder -oac copy -ovc copy -of mpeg -mpegopts format=dvd -vf harddup 
-o dvdformatted.mpg original.mpg

    Should your source be in a different format, mencoder can take care 
of the proper transformations, there is a tutorial and a series of 
examples about  it at 
www.mplayerhq.hu/DOCS/HTML/en/menc-feat-vcd-dvd.html (the page takes an 
eternity to load, by the way...). To create the DVD I used qdvdauthor, 
which is quite primitive but gets the job done quite nicely.

Happy authoring!

Ezequiel
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