[mythtv] Help requested: fixing MythTV's support for MPEG4 AVI files

[Will Dormann]

I started this discussion in mythtv-users, but I think it's more
relavent to this list.   My goal is to be able to do an "in-place"
transoding of my recorded shows.   That is, take my MPEG2 files from my
PVR-250 and convert them to XVID AVI files and overwrite the original
.NUV file with that.  That way, the recording will be much more highly
compressed, but still be in the same spot as the other live recordings.
(rather than having to switch back and forth between MythTV and
MythVideo, based upon whether or not the show has been transcoded yet)

I've transcoded a file and copied it over, but when I go to play it
back, mythfrontend exits.   Originally I thought it was a segfault, but
according to gdb, it's a clean exit:
Input #0, avi, from '/mnt/store//1003_20030726233000_20030727010100.nuv':
 Stream #0.0: Video: mpeg4, 640x480, 29.97 fps, 800 kb/s
 Stream #0.1: Audio: mp3, 48000 Hz, stereo, 160 kb/s
[New Thread 393241 (LWP 21567)]
header damaged
decoding error

Program exited normally.

I've tried XVID and DivX AVI files, and they both behave the same way.
Oddly enough, an MSMP4V2 file seems to work fine.  Isaac mentioned that
this is because of the decoder's limited support for other formats.

I don't really know the MythTV code too well, so this is where I need
help.  Does anybody have an idea of how I might be able to fix MythTV so
that it can handle an XVID AVI?   If I were to guess, there's something
that needs to be fixed in h263dec.c ?   MPlayer plays my XVID files
fine, so maybe some sort of merge to make MythTV's h263dec.c file more
like the one in MPlayer?  I'm just drawing straws here....    If the fix
is truly as simple as Isaac says it should be, maybe some kind sould
could give this a shot?

I have a sample XVID avi file here:   (about 500KB in size)
http://dormcam.org/snl_test.avi

Thanks!
-WD