[XviD-devel] XviD waterkmark?

[Jakub Piotrowski]

Hi,

In general idea of watermarking is that they do not interfere with the standard - its only modification of payload. In my case, it is changing least significant bits of macroblocks - this results in probably slight (not yet tested:)) changes to the film. So I'm not changing bitstream sythax (this would be useless), I'm only messing with bits vaules.Changes are based on selected bits xor function (determined by a random number, which acts like an encryption-key).

Benefits are: You get extra data channel without incrasing bitrate, and (not yet but maybe in future) You get robust marking tool. Of course robustness can ba achieved only by increasing number of bits that are involved in marking process, and to avoid lowering visual quality it would require some kind of visual-adapting algorithm to be implemented (just like phillips did for JAWS), but this is good direction, and I'll try this way - after I complete first stage.

And of course main target is not to include subtitlest. It is supposed to become a fingerprinting/authentication system. For now, it may act as a part of broadcast control system - but this can also be done with media containers (btw. there are also a few projected watermarks for media containers as well, e.g. for xmt scene structure in mpeg-4).

Jakub