[MPlayer-users] libavcodec vbitrate problem
Kresimir Kukulj
madmax at iskon.hr
Thu May 9 21:15:02 CEST 2002
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.
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