The video encoder board:

Closeup picture and pin assignment:

Some MPEG2 decoders output BT601 digital video, which does not have embedded sync signal. Since the commercial SDI transmitters are based on BT656 not BT601, it is much more difficult to modify this kind of devices to output SDI.

Mavromatis has designed a BT601 to BT656 converter based on FPGA and this makes more DVD players and set-top boxes become SDI-modifiable. 

The above pictures were originally posted by Mavromatis in the "Poor Man's SDI" thread at AVS Forum.