So a little while ago I wanted to pull up a Chuck I had recorded OTA from our local NBC affiliate using MythTV. Seeing as how my home theater PC is Windows currently (VLC, and therefore Linux can't handle Dolby TrueHD or DTS-HD Master yet unfortunately), I used MythWeb to download the episode to my hard drive, and tried to play it using VLC for Windows.
I was greeted with no audio, and a video track that went through the entire ~hour episode in a matter of minutes. It would show a couple seconds of a scene, then skip forward a number of minutes, rinse and repeat.
I tried downloading the file again, and then tried opening on Linux VLC on a different computer. No go, same issues. A friend of mine who originally got me into MythTV suggested I try reencoding the video using mythtranscode. A bit of research later, and I entered the following command into the Linux command line:
mythtranscode --infile /var/lib/mythtv/recordings/1061_20081110185800.mpg --mpeg2 --showprogress --outfile /home/pcjjman/videos/chuck.mpg
Most of the options are self-explanatory. The --mpeg2 tells mythtranscode to convert the TS stream to a PS stream, and reencode any frames next to commercials. The end result of the operation was the reencoded file played perfectly and I was able to enjoy Chuck in 1080i and 5.1. It also allowed me to skip through the episode using the Alt-Arrow Keys shortcuts in VLC, which didn't work previously.
So if you download a file straight off MythWeb and it's not playing correctly, try reencoding it. It might just do the trick.