I understand several lines in the NTSC transmission are used to encode closed captioning? I can view closed captions fine if I'm watching "live tv", but if I'm watching a recording and I toggle closed captioning it doesn't work. Why is this?

If you're transcoding them that information usually gets lost. It's very annoying, and I've been meaning to check in the MythTV Trac DB to see if anyone has filed a bug about it.

I wonder why this doesn't happen when I watch live tv, though. Isn't live tv just a 3 second delay between recording and playback of the same file? If it encodes it for live TV, I wonder why not if I watch it later.

Are you using a BTTV driver (software encoder) capture card? Those are typically set up to do initial encoding using RTJPG (fast but fat) and then transcode to MPEG4 (much smaller but also more compute intensive) later. Watching live TV you're watching the original untranscoded format.

With a PVR (IVTV driver) card this would be unusual but might happen if you've got some kind of auto transcoding setup there to convert the MPEG2 output of the card to another format or do commercial cutting.

I'm using a PVR-350, although I have a second PVR-150 tuner in there. I don't do commercial cutting but I do flag for them. Does it depend on the type of enconding? MPEG-PS, DVD, etc?

Some things to check:

1. There are separate recording profiles for "livetv" and recording. Check to see if there are any differences between your "livetv" and "default" recording profiles.

2. In the myth setup utility (entered by hitting "alt-s" on the keyboard), on the third screen of the "general" section, make sure that VBI format is set to "NTSC closed caption" (assuming you are in NTSC land).l

Marc