[MPlayer-users] introducing DVD-to-DivX approach that fixes A/V sync problems

[Rich Felker]

On Sun, Jul 03, 2005 at 07:35:00PM +0200, Joachim Jautz wrote:
> Hi MPlayer Users,
> 
> when converting a DVD into DivX using MEncoder it can (under
> certain circumstances) happen that the resulting movie's audio and
> video are out of sync. Usually the delay is about 300ms which is
> enough to be annoying.
> 
> The purpose of this mail is to introduce my solution to this
> problem for those who are interested.
> 
> When I myself ran into this problem in early 2004 there was
> neither a definitive explanation why this problem sometimes
> occures nor a good solution except one: encode and mix audio and
> video at once.
> But this solution was inacceptable for me because I wanted to
> encode the video only once and then mix it with different audio
> tracks.
> After days of experimenting I finally came to the solution that
> extracting the audio track to a wave file and then re-including it
> while encoding is doing the trick (example follows below).
> 
> Since then I successfully use this method and therefore can call
> it `thoroughly tested' with MPlayer/MEncoder 1.0pre5-2.95.4 .
> I extended my dvd2divx script so that it works according to that
> solution; it is available at:
> 
> http://www.jay-jay.net/src/bash/dvd2divx/index.html

This guide seems to recommend some very bad things.

1, using frameno.avi. STRONGLY discouraged. it will not work with any
inverse telecine, frame decimation, etc., which are needed for most
movies.

2, 'normalizing' audio. if you normalize to maximize peak, you WILL
generate SERIOUS distortion when encoding with any frequency-domain
audio codec (i.e. any decent non-lossless codec). the headroom away
from peak is needed to prevent clipping in the transformations. you
should either normalize rms instead (to a moderate value, not high),
or do no normalization at all!

rich