Our business currently moves video around as MPEG-2 Long GOP.

For high definition, one of my clients is insisting that we use a bitrate of 135Mbps. On further investigation, I found that they are insisting on this bitrate because this is the bitrate HDCAM uses, and supposedly HDCAM uses MPEG-2.

I don't believe this is correct - but I'm having trouble finding information which disproves this theory. All I can find is that HDCAM uses intra-frame compression (does this mean it is I-Frame only?), while Long GOP (obviously) is inter-frame compression.

It will cause us major headaches to use 135Mbps (none of our equipment goes past 80Mbps). Anybody have any info which can help convince our client otherwise?

HDCAM uses DCT-based compression and it's only intraframe compression (which is similar to I frames only). It doesn't use MPEG2 compression, although MPEG2 is similar since it is DCT-based. Charles Poynton's book (see poynton.com) has a little bit of information on the HDCAM format.

XDCAM uses MPEG-2 compression. In higher rates than HDV, but they only go up to 35MB/s. Still, many people choose that format and many networks accept it.

DVCPRO HD is 100MB/s...and yes, HDCAM is 135MB/s.