On Sat, 09 Feb 2008 16:47:22 +0100, Tor Olav Kristensen wrote:

> Jim Henderson wrote:
>> On Fri, 08 Feb 2008 23:20:53 +0100, Tor Olav Kristensen wrote:
>> 
>>> Jim Henderson wrote:
>>> ...
>>>> Actually, I was surprised that the Amazon downloadable Complete LOTR
>>>> soundtracks are in MP3 format.  I don't *think* there's any DRM
>>>> involved (which was really surprising).
>>> But maybe they can tell who bought the mp3 file by looking at it...
>>>
>>> http://www.google.com/search?q=mp3+watermark+amazon
>> 
>> I'm sure they probably can.  That's a bit different than DRM, though,
>> which has the explicit stated goal of preventing people from
>> "inappropriate use".  Watermarking allows them to act reactivley - and
>> I believe is fairly easy to remove anyways...
>> 
>> mplayer -ao pcm:file=temp.wav file.mp3 lame -h temp.wav
>> file-without-watermark.mp3
> 
> Yes, but then you assume that the watermarking is done on the bit-level.
> 
> What if they change the music somewhat in a way that will survive format
> conversion ? (E.g. tiny changes in volume levels within a frequency
> band, small phase shifts, changes in the dynamic range, added noise or a
> combination of some of these.)
> 
> There will only have to be minor changes to the sound, as they will only
> have to encode something like e.g. 30 bits into more than 100s of sound
> in 2 channels.

I'd think that the conversion back and forth would modify an attempt like 
this enough.  Remember that mp3 encoding is lossy, not lossless.

Of course, though, the best option is to not give the files away.

Jim

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