[MPlayer-users] mencoder 2-pass

[Loren Merritt]

On Sun, 11 Apr 2004, cmisip wrote:
> On Sun, 2004-04-11 at 12:14, D Richard Felker III wrote:
> > On Sun, Apr 11, 2004 at 04:38:55PM +0200, Matthias Wieser wrote:
> > > Hi,
> > >
> > > what's the preferred method for 2-pass encoding into mpeg4?
> > >
> > > Documentation only says:
> > > mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac copy -o
> > > movie.avi
> > > mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac copy -o
> > > movie.avi
> > >
> > > Some people recommend to use constant quantisizer for the first pass, some
> > > recommend to use the same variable bitrate as in pass two.
> > >
> > > What should produce better quality nowadays?
> >
> > Using the same or similar bitrate for the first pass has produced
> > slightly better results in all the tests I've seen.
> >
> > Rich
>
> I thought the point of two pass is that the first pass generates a log
> file that is used to plan the bitrate use for the second pass.  Then it
> only makes sense to have the same settings for the quantizer on both
> passes.  I could be wrong.

Yes, that is the point. But there are different ways to get that initial
estimate of bitrate. You could encode the first pass at ABR and then
adjust distribution of bits (divx, recommended for lavc), or you could
encode at fixed quantizer, and then adjust total size (xvid).

--
Loren Merritt