Hardware vs software encoders
Can you get raw video from hardware encoder cards?
For card combos where the decoder is on the PCI bus (Conexant Blackbird, Philips Empress, ATI Theatre, etc.), you can grab either the raw video or the compressed video. These cards register two devices, one for raw video (/dev/video0) and one for compressed (/dev/video1).
Cards with the encoder on the PCI bus (PVR-350/250, DVB, etc.) only provide compressed streams. This is because the decoder is not accessable on the PCI bus, so you can't grab the raw stream from it.
Some cards, like the Pinnacle PCTV Stereo have the capability to output raw and compressed streams, but the compressed stream is only available if you're running Windows and pay Pinnacle for a special activation code.