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!

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