I've had a Mythbuntu installation that was first installed somewhere around version 9 or so, and has been upgraded ever since. It has played pretty much every video in every format I've thrown at it.

However, since upgrading to 12.04, some video files do not play, and I can't determine why. It might be particular to .AVI files, but some .AVI files do play, so I'm not sure.

I've checked all the logs in /var/log/mythv, but found no errors.

What can I do to determine what the problem is and fix it?

Also note, I tried following these intructions, which claim to be a comprehensive installation of all codecs and software necessary to play any video, but it did not solve the problem.

Update: As suggested, I ran the program mediainfo to compare two video files, one that works and one that doesn't, and here is the output, trimmed down to just the output that is different.

This is a video that works:

Overall bit rate                         : 1 289 Kbps

Bit rate                                 : 1 142 Kbps

Maximum bit rate                         : 5 892 Kbps

Frame rate                               : 29.970 fps

Bits/(Pixel*Frame)                       : 0.131

Stream size                              : 740 MiB (89%)

Encoding settings                        : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=crf / mbtree=1 / crf=22.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

Bit rate                                 : 144 Kbps

Maximum bit rate                         : 179 Kbps

Stream size                              : 92.2 MiB (11%)

This is a video that doesn't:

Overall bit rate                         : 1 555 Kbps

Bit rate                                 : 1 437 Kbps

Maximum bit rate                         : 3 651 Kbps

Frame rate                               : 23.976 fps

Bits/(Pixel*Frame)                       : 0.206

Stream size                              : 221 MiB (92%)

Encoding settings                        : cabac=1 / ref=5 / deblock=1:2:2 / analyse=0x3:0x133 / me=umh / subme=9 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=14 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=crf / mbtree=1 / crf=20.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

Bit rate                                 : 114 Kbps

Maximum bit rate                         : 142 Kbps

Stream size                              : 17.5 MiB (7%)