Today I was goofing around with hooking a firewire cable to the Motorola DCT-6412 DVR that Comcast provides, and seeing if I could capture HD content onto my MacBook. I could, with some caveats. (Click on the image below to get the full resolution png file of a frame from the capture.)
The problem is that many channels (including most HD channels) are set up with copy protection. They will record, but no open source playback solution exists because of encryption. TNT and our local PBS station are
transmitted in the clear however.
I’ll play with this some more. If anyone is interested, I’ll summarize here at a later date.
Engadget had a nice guide to recording HD material onto your PC, and includes a lot of information.