I think you might mean SCMS (serial copy management system), which is what's in DATs, Minidiscs, CD players, etc.

SDMI was a consortium trying to make a single industry-wide (an possibly very onerous) DRM complete with watermarking to nab people who did the decode-reencode trick.

Not suprisingly, it fell apart. This wasn't until after lots of lavish meetings at far flung (and usually hot) resorts, as far as I heard.

Hugo