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Re: mp3 and the perceptual coding demo
Brian Gygi, Ph.D.
A related demo is to subtract the spectrum of the mp3 coded sound from the original, and do an inverse fft, to show all the sounds that they are not "hearing." Werner Deutsch used to do this with symphonic recordings and joke that this showed that most of the musicians in the symphony were not needed.
Speech and Hearing Research
Veterans Affairs Northern California Health Care System
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Martinez, CA 94553
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From: Laszlo Toth [mailto:tothl@xxxxxxxxxxxxxxx]
Sent: Thursday, March 25, 2010 05:37 AM
Subject: Re: mp3 and the perceptual coding
On Thu, 25 Mar 2010, Massimo Grassi wrote:
> I would like to convince to my students that psychophysics can (seldom)
> be useful. For this reason, I want to talk about mp3 and perceptual coding.
I usually do the following demonstration: take a speech sample, compress
it with an mp3 codec at the highest possible compression rate, then
decompress it and display the spectrogram of the original and the
processed signal. The spectral valleys are wiped out,
while there is minimal perceptual difference. I think this quite
convincingly demonstrates that masking indeed works, and that the industry
can make use of the results of psychophysics.
Hungarian Academy of Sciences *
Research Group on Artificial Intelligence * "Failure only begins
e-mail: tothl@xxxxxxxxxxxxxxx * when you stop trying"