[MPlayer-users] RFC: docs update for "how to create a high quality DVD rip"

[D Richard Felker III]

On Tue, Jun 08, 2004 at 03:00:32PM -0700, Jack wrote:
> D Richard Felker III wrote:
> 
> >>On Sun, 2004-06-06 at 19:46 -0400, D Richard Felker III wrote:
> >>   
> >>
> >>>It doesn't work with inverse telecine or other filters that drop
> >>>frames (or add them), it doesn't work with field-coded DVDs (and it's
> >>>difficult to tell in advance which ones are field-coded), and it
> >>>causes A/V desync. Also it has no useful purpose.
> >>>     
> >>>
> >Nope, the first (frameno) pass does the a/v sync (choosing which
> >frames to drop or duplicate) which can't be done correctly without
> >decoding and filtering them. And it doesn't decode them. So it's
> >broken.
> >
> > 
> >
> Odd... I've never had any A/V desync problems using 3-pass encoding and 
> inverse telecine, even though I've seen this mentioned here many times 
> before.  Nearly all of my encoding is done this way, and the only sync 
> problems I ever see are there with or without 3-pass.  For instance, I 
> almost always see that the audio is off by 1 or 2 frames for the whole 
> video, but going to 2-pass doesn't fix it.

The problem isn't that it will desync. The problem is that the inverse
telecine will be performed totally wrong and you'll lose lots of
frames! It _might_ be fixed with vf_softskip, but it's hard to say.

> What kind of dvd would make frameno freak out?

A field-coded one (fairly common for PAL, for some reason).

> >If you want to do the same sort of thing correctly, you should encode
> >the audio separately with lame, then mux it with -oac copy and
> >-audiofile during the normal 2 passes. This is actually the best way
> >since bugs in mencoder cause slight a/v desync with modern versions of
> >lame due to lack of buffer measurement.
> > 
> >
> ... Is this why I see that 1 or 2 frame offset?  I thought I was just 
> going crazy over here.

Yes.

Rich