Do not take watermarking lightly. (Score 1)

Do not take watermarking lightly. This has been a research topic for video for at least a decade, by the companies that store 50GB video data using invisible to the naked eye pits on 12cm discs using blue light - not the RIAA. This is *analogue* signal processing not bits and bytes and bar codes. One aim has been for the watermark to survive cinema screen->camcorder->avi... its not about hiding the information in bits and bytes in the stream, its about hiding the information in the image (or audio). Its a challenge, but its only a very small amount of information that needs to be hidden, 64bits would be more than enough, and over a 2 hour film, it can be hidden *many* times. Its not unimaginable that imperceptible low frequency variations could be inserted into the image and extracted several times overlayed with high frequency variations. Of course it would have to be adapatable to the type of film, it may only encode during dark scenes, it may only encode duting light scenes, in a dark corner... and then add a similar mechanism in the audio. This is done in the mastering. You might filter some of it out, but certainly not all. Diff it? You're having a laugh. The only way to guarantee removal would be to have access to the profile used for the master of that particular movie. You could get hold of a pre-master. But would you know it was 100% clean?