>> Well, the article states that it's supposed to resist somebody 
>> pointing a video camera at their TV screen, so a 1-pixel alteration 
>> won't do.
> 
> Probably different watermarks encoded, without actually looking visibly 
> different in a way you could tell. Otherwise, someone might just rip it 
> twice and change the file to use (say) 1364 frames of ocian.

Well, to lots of people digital watermarking is the Holy Grail of 
digital technology, the thing that will finally stop the pirates. 
Trouble is... it's extremely hard.

If the watermark is encoded in a way that's perceptually 
insignificant... well guess what lossy codecs are specifically designed 
to do? Yes, that's right: *remove* perceptually insignificant information!

I'm thinking things like small timing differences would be too subtle to 
notice, but significant enough for encoding to not screw them up. And 
you could try to correct it yourself, but you'd have to know exactly 
which bits of timing are varied in order to know what to change...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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