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

[Martin Collins]

On Wed, 6 Jul 2005 12:29:40 +0200
Joachim Jautz <lists.mplayer-users at jay-jay.net> wrote:

> But, let's look at it from a practical point of view. The problem
> is that using the frameno.avi _seems_ to be the only way to
> achieve these goals:
> 
> - the video is to be encoded only once (in two passes, of course)
> - multiple audio tracks (e.g. `en' and `de') are desired; moreover
>   it would be nice if these audio tracks were
>   * MP3 encoded (instead of -oac copy)
>   * `normalized' or in other words: not so silent that you have to
>     pump up your stereo to volume `blow it' ;)
> - each audio track is to be mixed to the video resulting in one
>   stand-alone movie file
> - target format is MPEG4 / DivX5
> 
> My assumption is that the recommended way that is described in the
> mplayer documentation requires to encode the video twice if you
> want to get two different language versions.

You can do this with a final muxing stage. First split out the audio
tracks and process them as you please. I suggest you look into
replaygain rather than normalizing. Then encode the video using -oac
copy to maintain sync. Then mux your audio into the video replacing
the copied audio. You can do this for each language.
 
> Regretfully I cannot see why there should occur distortion when
> - dumping audio to a wave file
> - adjusting the file so that its maximum sample is at full scale
>   which just gives a file the maximum volume possible without
>   clipping (cf. [1])
> - encoding the wave file into MPEG Layer 3
> 
> Do I miss some important technical detail? If the distortion were
> `SERIOUS', it would be audible, I assume? To me the result sounds
> perfect.

Distortion will likely only occur in the loudest portions such as explosions so may not be obvious, especially with cheap speakers.

Martin