Nicolas Alvarez wrote:
> Tor Olav Kristensen escribió:
>> Jim Henderson wrote:
>>> 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.
>>
>> Yes, I know. And to overcome that, just don't make the changes to the
>> sound THAT small.
> 
> Yeah, encode the username in the lyrics. Hey, I can hear my name if I 
> play this song backwards!

=)

-- 
Tor Olav
http://subcube.com

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