I have a hd dvr from the cable company (no dvd burning ability). Am interested in getting a jpg snapshot of what is recorded and showing on my hdtv screen download to a pc. Any chance of this? I read months ago that cable companies have to provide fire wire output on a dvr box. If so is this at all feasable? I am interested in a high quality picture as it shows on my hd tv.
The IEEE-1394 (FireWire) port won't let you do that. The only thing you can do is play back a recording or watch a live show, and transport the raw MPEG transport stream over FireWire (if it's not flagged as copy-once, you can capture it on a computer, otherwise it'll be encrypted using 5C DTCP-1394 encryption). The menu screens aren't part of that, so you won't be able to see that via the FireWire port.
When this data ends up recorded on a pc, is it stored in a common format? Is it still high definition when it gets to the pc?
The stream is an MPEG transport stream, containing MPEG-2 video and Dolby Digital audio; the video will be whatever was sent to your cable box. If you just want a screencap of a specific frame of video, many players should be able to do that. Again, as long as it's not protected content (flagged "copy-once"), assuming the FireWire port is active (you'll find out pretty quickly, if it's not it just won't selfID on the FireWire bus at all), you should be able to capture. I'm not sure of what tools to use - that depends on the OS, but I know there are threads about it.