copyright information

Why not add the copyright information into the file format?

One could define a new audio file format, in which the watermark is a part of the header block but is not removable without destroying the original signal, because part of the definition of the file format requires the watermark to be therein. In this case the signal would not really be literally 'destroyed' but any application using this file format would not touch it without a valid photo watermark. Some electronic copyright management system propose mechanisms like this. Such schemes are weak as anyone with a computer or a digital editing workstation would be able to convert the information to another format and remove the watermark images at the same time. Finally this new audio format would be incompatible with the existing one. Thus the watermark should really be embedded in the audio signal.

This is very similar to S.C.M.S (Serial Code Management System). When Philips and Sony introduced the 'S/PDIF' (Sony/Phillips Digital Interchange Format), they included the S.C.M.S. which provides a way to regulate copies of digital music in the consumer market. This information is added to the stream of data that contains the music when one makes a digital copy (a 'clone'). This is in fact just a bit saying: digital copy prohibited or permitted. Some professional equipment are exempt for needing S.C.M.S.

With watermarking however, the copy control information is part of the audio-visual signal and aim at surviving file format conversion and other transformations.