Forum Moderators: not2easy
For example, when the 'images' are transmitted for digital terestrial in the UK they use an MPEG2 stream (at least I'm pretty sure they do).
If you capture the stream using a video capture card it will be in whatever video codec you choose to use or your hardware is capable of. So it might be an avi an mpeg or a mov.
After capturing, you can convert individual frames to any format you choose, psd, bmp, jpeg, whatever.
I'd guess if you elaborate a bit a better answer will be offered.
Cheers
Stretch