[MPlayer-users] libavcodec vbitrate problem

[Kresimir Kukulj]

Quoting Michael Niedermayer (michaelni at gmx.at):
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Hi
> 
> On Thursday 09 May 2002 15:41, Kresimir Kukulj wrote:
> > [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> > Hi
> >
> > I switched from transcode to mencoder because I heard that libavcodec is
> > giving good results.
> >
> > I don't know if this is a bug of my misinterpretation but:
> >
> > I encode movies as this:
> > tccat -i /ext/tmp/S -T 1,1-2 -t dvd | mencoder -ovc lavc \
> > -lavcopts vcodec=mpeg4:vhq:vbitrate=800 -nosound \
> > -vop scale=704:304,crop=704:416:8:80 -o X.1-2.800b.avi -lavcopts vpass=1 -
> >
> > tccat is transcode util I am found of :) Basically it will dump first two
> > chapters from title 1. I use this because it allows me to have DVD copied
> > to disk with navigational data preserved so I can skip chapters & stuff...
> > I think mencoder cannot do that ?
> >
> > I tried vbitrate=800, 1600 and 2000. Corresponding filesizes and actual
> > bitrate (shown by mplayer) is:
> >
> > vbitrate|actual bitrate|filesize
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 800     |719.6         |24549218
> > 1600    |883.5         |30101746
> > 2000    |886.0         |30185878
> >
> > I confused here :) It seems to be stuck around 800kbps (default).
> > It's not that I am dissapointed by libavcodec quality. I has shown
> > extraordinary results in first pass (XviD is very blocky on fast moving
> > scenes). In second pass difference between lavc and XviD is less visible,
> > I'd say XviD is a little bit more detailed but libavcodec has no (visible)
> > blocky artifacts at all (nor smearing).
> -lavcopts vqmin=2
> should allow higher bitrates & looks better (isnt the default cuz it causes 
> clipping in the quantizer for h263 but is ok for mpeg4)

Ok. I tried and it helped. Thanks.
Now I get (first two chapters):

vbitrate|actual bitrate|filesize
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
800     |796.2         |24549218
1600    |1500.8        |51020492
2000    |1706.0        |57971188

This is much closer bitrate.
Although, quality was very good even at 800Kbps.
libavcodec gives suprisingly good first pass.

Are there any more tips like that for libavcodec ? I have read the man page
(-lavcopts), but tips are always welcome.

Also, is there a way to specify different name for lavc_stats.txt ?
-passlogfile doesn't work. It's probably DiVX4,5/XviD only ?

-- 
Kresimir Kukulj                      madmax at iskon.hr
+--------------------------------------------------+
Old PC's never die. They just become Unix terminals.