[zapu]

Also [1], which relies on watermarking audio of content, which then can be detected by hardware players and the playback can be stopped if it discovers that e.g. you play a BluRay rip from USB stick. It survives encoding with different codecs. I'm not sure if it has been cracked yet or not.

[1] https://en.wikipedia.org/wiki/Cinavia

[grw_]

Appears to be 'cracked' as far as is possible- i.e, can remove the watermark itself, but not possible to undo the degradation to the original signal that the watermarking introduces.

http://cyberside.net.ee/ripping/cinex_wp_release1.pdf