[MEncoder-users] Problem with encoding on _every_ cvs snapshot after 2005/03/06

[treponemanichols at ecn.org]

> Why don't you show us the command line you used? W e have absolutely
> no idea what you did...
> 

Thanks for your answer, Rich. 

I'm trying to encode into an avi file a regular vob obtained from a PAL dvd
with "vobcopy -l -n 7 -o ./ -i /mnt/dvd". The vob is ~4.8GB in size.
The problem is there both when playing the vob and when encoding it, and
actually the errors are more informative when playing it.

When playing the vob, the simplest command lines like "gmplayer in.vob"  or
"mplayer in.vob" will produce the burst of errors I reported yesterday, after 
247 seconds (this is only important because it's very near the beginning of 
the file, so it's not likely to have something to do the file being very big).

To encode, I use this command line:

nice -n 0 /usr/local/bin/mencoder in.vob  -o /dev/null   -oac mp3lame \
-lameopts vbr=3:br=128:vol=2.666 -ovc lavc \
-lavcopts
vcodec=mpeg4:vbitrate=945:mbd=2:vmax_b_frames=2:v4mv:trell:autoaspect:psnr:turbo:vrc_override=131500,500000,20-31:vpass=1
 \
 -vf crop=712:436:6:70,scale=592:256:0:0:0.00:0.75 -sws 2

for the first pass and similar lines for the second and third passes. Mencoder
reports a duplicate frame at second 247,1 and a CRC error shortly after on
each of the three passes.

Now, all this is clearly very dependent on the particular vob file I'm playing
and encoding, and I'm afraid it will be of little help in understanding what's
happening. I wouldn't have bothered writing about it here if I hadn't found
that these errors were introduced by some change in the 03/06 CVS.

The important thing, I think, is that there are some errors generated by the 
libavcodec's mpeg code that were not generated by version of that code
earlier than 03/07. As far as I know this could well be a _feature_, a better
error detecting routine or whatever. Yet from a user point of view, this
also seems to cause some corrupted frames when encoding.

I'll just encoding this particular file using 03/06 CVS, then go on using
one of the latest CVS and see if this error comes up again, so I don't really
need that this problem is sorted out. But I thought it was worth pointing
it out.

If you need any other info, I'm there. If anybody can suggest me some switch
to let mencoder output some more meaningful error messages, please do.


Thanks again,
Enrico



________________________________________________________________
Mailbox hosted by Isole nella Rete - http://www.ecn.org/