[MPlayer-users] 2-pass HQ encoding with libavcodec

Louis Tsui louis at eea188.ee.ust.hk
Fri Mar 29 11:19:02 CET 2002

On Fri, Mar 29, 2002 at 11:24:13AM +0200, Costas Gargerakis wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> > i got no big improvement in quality doing 2-pass compared to 1-pass.
> > with divx4 there is big difference between 1 and 2-pass encoding in
> quality
> >
> > to be more exact: encoding with libavcodec 1-pass was as good as with
> > 2-pass.
> Then lavc 2-pass does not work as it should...because i've noticed huge
> quality differences between the 1-pass avi and the 2nd-pass avi with
> divx4.

I think the quality depends on the file size (average bit rate) if the
encoding parameters are the same for both 1-pass and 2-pass. If the
file size of 1-pass avi is small than that of the 2nd-pass avi,
quality improvement is obvious.

If libavcodec produces same file size with similar quality for both
1-pass and 2-pass, then it already did a good job for bit rate control
and 2-pass method is not needed provided that the average bit rate is
close to what we set.


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