Re: [LAU] Looking for Audio Watermarking Advice & Tools

On 23 October 2011 at 22:09, Jeremy Salwen <jeremysalwen@email-addr-hidden> 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
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