[MPlayer-users] 2 pass divx encoding from .VOB/dvd - Targeted filesize (bitrate) ends up way way wrong

[Øyvind Stegard]

Hey

I'm trying to encode a ~2 hour DVD, targeting two 80 min CDRs (about 
1400MB). My problem is essentially that the bitrate I specify to 
libavcodec is not respected at all and the movie ended up at half of the 
filesize I had targeted(resulting in rather poor quality). (It turned 
out to be ~700MB when I specified an average bitrate that should result 
in a file close to 1400MB (audio stream taken into consideration)). To 
clear things up, here are the two command lines I used:

1. pass:
mencoder dogma.vob -nosound -ovc lavc -lavcopts 
vcodec=mpeg4:vbitrate=1400:vhq:vpass=1 -vop scale=672:288,crop=701:429 
-sws 2 -o /dev/null

This resulted, as expected, in a lavc_stats.txt file. (I threw away the 
video to /dev/null in this pass, wrong??)

2. pass
mencoder dogma.vob -oac mp3lame -lameopts abr:br=128:aq=0:mode=1:vol=3 
-aid 128 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1400:vhq:vpass=2 
-vobsubout dogmasub -ifo vts_01_0.ifo -sid 5 -vop 
scale=672:288,crop=701:429 -sws 2 -o dogma.avi

This time I included the audio, naturally, as this was to be the final 
avi before splitting. (and I extracted some subtitles in vobsub format). 
The resulting average bitrate was NOT 1400, but rather around 
600-700kbit. Why does it end up so wrong ? I know mencoder/libavcodec 
loaded the statsfile, because of the startup time of mencoder and the 
size of the mencoder process (the stats file was about 15MB large).

Finally, some more details:
The movie is 720x576 PAL 25fps, about two hours long. I also got 
indications (from a reply to a previous post I sent), that the movie 
probably was a field based interlaced stream. It was ripped using Smart 
Ripper on a windows box, and the .vob file (concatenated all vobs to 
one) is about 6GIGs, and contains video, two ac3 streams (one 2.0 and 
one 5.1), and some subtitle stuff.

Also, when I try to use the external -pass 1/2 parameter (instead of 
libavcodec internal vpass), the bitrate goes much much higher than it 
should, so that's a no-no. (Does the external -pass 1/2 really work well 
with libavcodec ?? It looks very DivX5 oriented)

mplayer 0.90pre6-gcc3.1

Thanks in advance for all help/tips, it's all appreciated.

--
Øyvind S.