Re: mp3 and the perceptual coding demo (Brian Gygi )


Subject: Re: mp3 and the perceptual coding demo
From:    Brian Gygi  <bgygi@xxxxxxxx>
Date:    Thu, 25 Mar 2010 20:43:17 +0000
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

----=_vm_0011_W4961218475_3027_1269549797 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable A related demo is to subtract the spectrum of the mp3 coded sound from th= e original, and do an inverse fft, to show all the sounds that they are n= ot "hearing." Werner Deutsch used to do this with symphonic recordings an= d joke that this showed that most of the musicians in the symphony were n= ot needed. Brian Gygi, Ph.D. Speech and Hearing Research Veterans Affairs Northern California Health Care System 150 Muir Road Martinez, CA 94553 (925) 372-2000 x5653 -----Original Message----- From: Laszlo Toth [mailto:tothl@xxxxxxxx Sent: Thursday, March 25, 2010 05:37 AM To: AUDITORY@xxxxxxxx Subject: Re: mp3 and the perceptual coding On Thu, 25 Mar 2010, Massimo Grassi wrote:> I would like to convince to m= y 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, compressit with an mp3 codec at the = highest possible compression rate, thendecompress it and display the spec= trogram of the original and theprocessed signal. The spectral valleys are= wiped out,while there is minimal perceptual difference. I think this qui= teconvincingly demonstrates that masking indeed works, and that the indus= trycan make use of the results of psychophysics. Laszlo Toth Hungarian Ac= ademy of Sciences * Research Group on Artificial Intelligence * "Failure = only begins e-mail: tothl@xxxxxxxx * when you stop trying" http://= www.inf.u-szeged.hu/~tothl * ----=_vm_0011_W4961218475_3027_1269549797 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable <html><div><font face=3D"Verdana" size=3D"2"><br>A related demo is to sub= tract the spectrum of the mp3 coded sound from the original, and do an in= verse fft, to show all the sounds that they are not "hearing."&nbsp; Wern= er Deutsch used to do this with symphonic recordings and joke that this s= howed that most of the musicians in the symphony were not needed.<br>&nbs= p;</font></div> Brian Gygi, Ph.D. <br> Speech and Hearing Research <br> Veterans Affairs Northern California Health Care System <br> 150 Muir Road <br> Martinez, CA 94553 <br> (925) 372-2000 x5653<div><font color=3D"#0000ff" face=3D"Verdana" size=3D= "2"></font>&nbsp;</div> <blockquote style=3D"border-left: 2px solid rgb(0, 0, 255); padding-left:= 5px; margin-left: 5px; margin-right: 0px;"><font face=3D"Tahoma" size=3D= "2">-----Original Message-----<br><b>From:</b> Laszlo Toth [mailto:tothl@xxxxxxxx= INF.U-SZEGED.HU]<br><b>Sent:</b> Thursday, March 25, 2010 05:37 AM<br><b>= To:</b> AUDITORY@xxxxxxxx<br><b>Subject:</b> Re: mp3 and the perce= ptual coding<br><br></font>On Thu, 25 Mar 2010, Massimo Grassi wrote: &gt; I would like to convince to my students that psychophysics can (seld= om) &gt; 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 industr= y can make use of the results of psychophysics. Laszlo Toth Hungarian Academy of Sciences * Research Group on Artificial Intelligence * "Failure only begins e-mail: tothl@xxxxxxxx * when you stop trying" http://www.inf.u-szeged.hu/~tothl * </blockquote></html> ----=_vm_0011_W4961218475_3027_1269549797--


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