[LAU] Looking for Audio Watermarking Advice & Tools

Monty Montgomery xiphmont at gmail.com
Thu Oct 27 11:40:36 UTC 2011


> A variation on this is used to check the authenticity of some
> recordings in forensic audio. Almost all 'surveillance' audio
> contains some low level 50/60 Hz. If the recording is done on
> a digital device then its clock can be assumed to be more stable
> than the mains frequency

At least in NA, mains frequency is very very stable. The entire
continent is in phase and clocked with very high precision.  It's more
stable than a free-running digital clock.

...I used this fact to 'cheat' in a high school physics contest where
we had to build a clock and the winner was the most stable.  Ours had
a CdS cell that watched the 120Hz flicker of the lights in the room.

Monty


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