[XviD-devel] xvid decoding in high definition (bug?)

[Mauro Borghi]

(I'm re-sending this mail, because the first I tried is still awaiting 
moderator approval after a couple of days)


Hello all,
for a benchmarking activity on HDTV, I'm encoding short sequences of
1080i content using XviD (and other codecs).
I did a 2-pass encoding, enabling up to 2 consecutive B-frames.

Using XviD to decode the sequence, I get a crash on various players
(both on win32 and linux).
I placed the start of this sequence on the web (~5MB), so you can
download it if you want to reproduce the crash:
<http://tao.tilab.com/hd-tests/>

For example, mplayer on linux exits like this:
[...]
MPlayer interrupted by signal 8 in module: decode_video
- MPlayer crashed by bad usage of CPU/FPU/RAM.
[...]

which should be a division by zero or some other floating point exception.

Btw, mplayer on linux needs to be run with the following command:
$ mplayer -vo x11 -vc xvid hd-1080-xvid-2b.avi
[trying to use the x11 xvideo (-vo xv) extension results in an earlier 
exit of the player, because of allocation errors in xv]

Decoding using a different decoder (-vc ffodivx), the decoding crash
disappears (though artifacts appear on the frames).
Re-encoding the same sequence, but this time disabling B-frames, the
decoding crash disappears.

Another difference between "-vc ffodivx" and "-vc xvid" is that while
with the former the colorspace and image size are ok, with the latter
the colors are messed up and the image size is half in width of what
should be. (But probably this is an mplayer issue, as with other players
this does not happen).

Hope this helps finding the bug... if it's actually a bug!

Ciao,
Mauro.