[MPlayer-users] Re: Low bitrate using 2-pass with libavcodec

[marcogi at libero.it]

On Sun, 21 Apr 2002, Rémi Guyomarch wrote:

> > I'm try to make some test encoding a dvd.
> > I made first and second pass using:
> > mencoder -dvd 1 -aid 131 -ovc frameno -lameopts q=4 -o frameno.avi
> > mencoder -dvd 1 -oac copy -vop scale=512:256,crop=720:346:0:112 -ovc lavc
> > -lavcopts vcodec=mpeg4:vbitrate=785:vhq:vme=5:vqmin=2 -pass 1 -o pass1.avi
> > 
> > Everything seems to work.
> > But, when I try to do thirth pass mencoder drops video bitrate to about one
> > half I set. The bitrate seems stable around 780 for the first frames; after
> > about 300 frames bitrate drops quikly to 370. The obtained video quality
> > is visibly lower then first pass one.
> 
> Don't use vhq on the first pass. The second pass will still be encoded
> with a lower bitrate than the first, but the difference will be
> minimal (less than 10%). Adjust the bitrate accordingly. For example,
> on a 10 minutes sample I specified vbitrate=858 and got 797 on the
> second pass. The ratio may depend on what you encode.

I did so, but still second pass video has lower quality than first pass.

--
Regards,  Marco Gigante
Student at Pisa University - Computer Engineering