On 23 October 2011 at 22:09, Jeremy Salwen <jeremysalwen@xxxxxxxxx> wrote: > Hmm... it seems to me that if the watermark does not cause audible > distortion, then shouldn't there be a simple algorithm to remove the > watermark: namely, to watermark the same file again with different > information? > > I suppose this requires you to know the algorithm used to watermark the file > in the first place. All the algorithms discussed here: > http://www.ece.uvic.ca/~aupward/w/watermarking.htm seem like they would be > pretty trivially removed by the applying them again with different watermark > data. > > I could imagine that one could choose from different frequency bands, and > hide the data in only one of them, so that in order to remove it you'd need > to know which band it's in, or over-write the data in *all* bands. But in > order to make the ratio of noise generated by watermark-all-bands vs > watermark-one-band large enough that watermarking all bands would introduce > unreasonable noise, but just watermarking one wouldn't, it seems the bands > would have to be very small. How much data could you really fit in them > (and what are the chances that any one of the bands happens to look > "watermarked" with something meaningful)? > > But perhaps there is some other way to parametrize the algorithm so that if > the parameters are not equal, the watermarks can coexist. I would be > interested in seeing it. But my feeling is that the amount of data you can > robustly store is small enough that splitting it into a reasonable number of > bands to thwart removers would make the capacity unreasonably small. I'd been wondering if some sort of spread-spectrum code would be an applicable technology. -- Kevin _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
