Re: hacksdmi?

[Robert Johnson <rjohnson () ASTRO OX AC UK>]

Don't really see how this is on topic unless we're talking about the
vulnerability of the digital watermark to forgery, etc., but anyways...

On Thu, 12 Oct 2000, David Knaack wrote:

> From: "Steve Mosher" <farq () KILN ISN NET>
> > The only way to really make it work (as I see it) is to make the
> > watermark a *fundamental* portion of the sound, but that would be entirely
> > moot since there's no way to apply the watermark to existing sound, thus
> > it's useless.

Someone's comments earlier about using a discrete wavelet transform
sounded potentially viable.  What seems possible to me is taking a
DWT of the entire track, then retaining only the highest order
coefficients, then creating the watermark by applying those coefficients
(or the sum or mean or some other reduction transform) to the lowest
order(s of) wavelet--essentially taking a snapshot of the high frequency
information and coding it at the lowest possible frequencies supported by
the devices the track might be processed through.  That should make a
virtually inaudible watermark.

> I'm very curious what use the watermark has.  It seems that
> image recognition techniques could be applied to music such
> that a particular performance could be reliably identifed
> without adding anything to the format.

The watermark is supposed to be robust against DA->AD->DA->etc and any
other processing.  However, what if someone applied a freq dependent
selective/random phase filter, subtly altering the shape of the waveform
but producing negligible audio artefacts?  That might be a means of
watermark removal...

> Of course destroying the recognizable patterns bypasses
> this; then you have what I would consider a different
> (possably derivate) work.
>
> The only other use I can think of for a watermarke is to
> 'personalize' a recording with a digital ID of the person
> that has aquired the right to play it.  But, I think that
> is a silly thing to do.

Corporations have been known to do much sillier things...

> > > Ps. Thanks to everyone who hasn't participated in the hacksdmi contest.
> > > Your efforts to defend civil rights & fair use all over the earth is
> much
> > > appriciated :)
>
> I'm guessing that its already been hacked and the code to
> write and remove the watermark will be released shortly
> after technology using it is released.
>
> DK

This ain't my field, so I'll leave it to those who know...
later,
RJ