[MPlayer-users] mencoder, libavcodec and b-frames

[Oeystein Olsen]

Hi, I've recently started experimenting with b-frames and libavcodec. With 
b-frames I always get a segmentation fault. I do not get the message saying 
mplayer/mencoder has crashed and I should read the manual and about 
testing/bugreporting. That has happened, it has always been me doing 
something stupid. 

I'm using vmax_b_frames option to get b-frames. The crash happens independent 
of what value this option is set equal to, and always in pass 2. I've 
downloaded the latest cvs from mplayer and ffmpeg. This doesn't change 
anything. I've downloaded and installed gcc-2.95.3. I'm using redhat 8.0, so 
I thought that they might done something similar to their 2.96-version.
The crashes happens at the exact same moment. 
	So for a given set of options, mencoder crashes at a time independent 
of the version of mplayer/mencoder, libavcodec and gcc. With different options 
and different movies the time changes, but is not affect by the versions of 
mplayer, gcc, libavcodec. 

The part encoded before the crash looks perfectly good, but is usally only 
10-60s long.

I've included an example on how I've tried to use b-frames. The encoding works 
extremly well without b-frames. I've tried turning off cropping, and scaling 
but it still crashes in pass 2. I usually use ac3-sound instead of mp3, but 
that does not affect the result.

1: Can anybody see if I do something wrong?
2: If not, should I file a bugreport? I'll make one later this evening. (The 
machine is back home and I must reread the documents on bugreporting first.)

#Ripping the movie
> mplayer -dvd 1 -dumpstream -dumpfile ripped_dvd

# Soundfile
> mencoder -ovc frameno -o frameno.avi -oac mp3lame -lameopts cbr:br=192 
-alang en ripped_dvd

# First pass
>mencoder -ovc lavc -lavcopts 
vcodec=mpeg4:vbitrate=1494:vhq:vmax_b_frames=2:vpass=1 -vop 
crop=632:264:2:48,scale -zoom -xy 640 -sws 2 -oac copy -o /dev/null 
ripped_dvd

# Second pass, crashes with a segmention fault.
> mencoder -ovc lavc -lavcopts 
vcodec=mpeg4:vbitrate=1494:vhq:vmax_b_frames=2:vpass=2 -vop 
crop=632:264:2:48,scale -zoom -xy 640 -sws 2 -oac copy -o the_movie.avi  
ripped_dvd


-- 
Øystein Olsen, oystein.olsen at astro.uio.no, http://folk.uio.no/oeysteio
Institute of Theoretical Astrophysics, http://www.astro.uio.no
University of Oslo, Norway