[MPlayer-users] libavcodec vbitrate problem

[Michael Niedermayer]

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)

[...]

Michael