[LAU] Looking for Audio Watermarking Advice & Tools

[Florian Paul Schmidt]

On 10/25/2011 04:33 AM, Paul Davis wrote:
> On Mon, Oct 24, 2011 at 10:00 PM, Al Thompson<althompson58 at gmail.com>  wrote:
>>   MP3s take away a lot of "good" information.
> Al, I have a huge amount of respect for your technical knowledge but
> offhand remarks like this require some countering in an online forum.
> Its true that low bit rate psycho-acoustic lossy compression does
> remove some "good" information. But my impression is that at
> "appropriate" bit rates, an overwhelming majority of humans cannot
> differentiate between an mp3 and the original recorded audio. I'm not
> entirely clear what "appropriate" means, but I believe that its hard
> for most people to differentiate (in a double blind test) at 128kbps,
> very hard at 192kbps and essentially impossible at rates above
> 256kbps. Should I update my understanding of this?
>
> i'm relatively skeptical of any claims for audio steganography that
> can survive arbitrary psycho-acoustic compression. in addition, random
> permutations of the least significant bits of a PCM encoding will
> almost certainly eliminate or at least reduce the confidence level
> associated with the presence or absence of the watermark), in a way
> that will be inaudible to more or less anyone.

While I don't know exactly what Al meant with "good information" 
exactly, here's maybe a way to interpret it: The information that is 
removed with lossy compression is in the best case exactly that 
information that is redundant with respect to human perception. It would 
be "good" in the sense that this redundant information would be a great 
place to hide watermarking. With a "perfect" lossy compression scheme, 
there's no bandwidth left to alter the signal without the human 
perception noticing.. So any watermark would be audible.

Flo

Flo

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