[Imc-tech] Re: [Imc] U-C IMC on INN--14 Feb

[David Young]

Compounding data loss notwithstanding, it's strange to me that an MP3
would degrade a long-distance telephone call, which is such a "data-poor"
signal.  For the curious, here's one way you might get at the bottom of
this compression strangeness:

It is possible to visualize the effects of audio compression by comparing
charts of the original and compressed recording, the charts showing
the power in different sound frequencies as it changes over time. (Some
call these charts "sonograms.") It's not hard to learn to read sonograms,
and without reading the sonogram very "deeply" at all, you may be able to
figure out the trouble with your compressed recordings.  If you discover
in time that certain sounds in your original recordings do not compress
well, you may be able to rub them out on the sonogram. I would not be
the least surprised if Brian Hagy has a program on Sergei that lets you
see sonograms, and "rub-out" parts of them, too.

There are rigorous (but unnecessarily technical) analyses of popular
MP3 encoders, using sonograms, here:

    http://www.airwindows.com/encoders/index.html

Dave

On Wed, Feb 14, 2001 at 11:30:43AM -0600, Paul Riismandel wrote:
> Hey, I think the piece sounded good.  It's tough to cram all that info into 
> 1'15" and I think you all did a great job.
> 
> Phone recordings can be really problematic--phones are subject to all sorts 
> of abnormalities and interference.  Actually, most phone calls are now 
> digital and they are compressed somewhere in the system, which introduces 
> problems with minidiscs and mp3.  In short when you record something onto a 
> medium that uses compression, like minidisc, you lose some data, though 
> it's typically inaudible.  If you transfer that sound into another 
> compression format, like mp3, you lose more data.  But because they're not 
> the same compression schema they throw out different data, and that can 
> have audible results.  Since you started with a phone call, which probably 
> was compressed digitally, you probably had 3 compression/decompression 
> cycles with 3 completely different schemas (codecs).  I hear similar 
> problems all the time on Pacifica and even the BBC, especially when 
> correspondents phone in their story.
> 
> The best way to avoid this problem is to record directly to the computer if 
> you think the file will be mp3'd.
> 
> --Paul
> 
> At 09:59 AM 2/14/01 -0600, brent john mcdonald wrote:
> 
> >A 1'15'' news piece on recent community support for the retirement of
> >Chief Illiniwek airs today on INN (Independent Native News).  It was
> >produced by myself with help from Brian Hagy, Peter Miller and Pauline
> >Bartolone.  The 5min. news bit can be downloaded at www.nativevoice.org.
> >
> >Peter, our telephone interview with Rev. Jack must have converted poorly
> >from Wave to MP3, there's an electronic echo I hadn't noticed before.  So,
> >they've edited that part down.
> >
> >Granted, I stand to improve on my radio news technique.  Unfortunately, I
> >didn't speak with the producer again until Monday, at which time he
> >informed me of their "normal procedure" for gathering news (i.e.
> >overseeing production of the script).  Anyway, they seemed to like it
> >and are enthusiastic about working with the U-C IMC in the future.
> >
> >Please send any feedback/criticism my way.
> >
> >Brent McDonald
> >
> >
> >
> >On Tue, 13 Feb 2001, Peter Miller wrote:
> >
> > > Hi, Brent-
> > >
> > > How did your Independent Native News piece go?  Did you manage to put 
> > it all together and send it off?
> > >
> > > -Peter
> > >
> >
> >
> >_______________________________________________
> >Imc mailing list
> >Imc at urbana.indymedia.org
> >http://lists.groogroo.com/cgi-bin/listinfo/imc
> 
> 
> _______________________________________________
> Imc mailing list
> Imc at urbana.indymedia.org
> http://lists.groogroo.com/cgi-bin/listinfo/imc

-- 
Didn't you hear? Commentary and Dissent merged and became Dissentary.
  -- Woody Allen