Walt,
I will now leave you alone and no longer waste my time on your mad phantasy=
.
Raimund
> From: Gianni Pavan <>
>
> >
> > Raimund,
> > it is difficult to say something about the spectrogram you
> show:
> >
> >
> >>http://www.avisoft-saslab.com/compression/MDtest2MD.gif
> >>
> >>As you can see clearly on the waveform, there is for sure no clipping a=
t
> >>that location (the amplitude is much higher at the start of the call).
> >
> >
> > The "missing" harmonic maybe an artifact or maybe it is real.
>
> A pattern of anything like that nature has not occurred in all the years=
> I've been staring at sonograms of my minidisc recordings. I'd say to be
> ATRAC caused would make it extremely rare, with odds of occurring like
> winning the big lottery.
>
> I vote for processing artifact of some kind. It covers 0.35 seconds,
> that's over 15,000 samples wide. A huge amount of time in sound
> processing. ATRAC works in much shorter frames, and has little
> connection downstream like that. The premise proposed that the louder
> sound just before blanked it out would simply not occur, no connection.
>
> Even as a processing artifact it's interesting, and rare. The sonogram
> is very crude, and the explanation may be in there.
>
> > To have a better view of what ATRAC or MP3 do on a recording I suggest
> to
> > plot the spectrogram with 96dB or more dynamic range: this way it is
> easy
> > to see all the portions that are cut by the system because "believed"
> > unaudible for the human ear. If the recording has a background noise, a=
s
> > most nature recordings have, you'll easily see (and demonstrate) all th=
e
> > "holes" created by psychoacoustic compression.
> > I'm sorry I can't now post an example.
>
> Doing this can also induce all kinds of artifacts. Remember the analysis=
> software is a form of sound compression. It's extremely crude, and has
> artifacts much bigger than those of a very highly refined compression
> like ATRAC. At one point one of the shareware programs that floated
> around would make a sonogram for you, a pretty good sonogram. But, the
> fun part was it would also take a sonogram and convert it back to sound.=
> Fun to play with, but a single round would produce really poor sound
> compared to the original. Yes going both ways probably at least doubled
> the errors. That would produce obvious holes easily.
>
> I should note that I've managed a few times to produce ATRAC/no ATRAC
> soundfile pairs a few times that were in accurate enough sync along
> their entire length to produce a quality difference file. In other
> words, what ATRAC removed. I did not find a batch of holes, selected
> faint calls hidden by louder foreground or anything like that when I
> looked by sonogram and listened to the sound in those difference files.
> What I did find was that the difference file was a very close duplicate
> of either the ATRAC or no ATRAC file, but at a much reduced volume.
> Especially obvious if the gain is matched to the original files. In
> other words what ATRAC removed was what it left (and what it left was
> what it removed, kind of zen like). Exactly what we want a quality
> compressor to do if you think about it. Note the only ATRAC I've managed=
> to test this way was ATRAC 4, not the ATRAC 4.5 I now use.
>
> So, the idea that there are "holes" from ATRAC seems a little strange.
> Such holes would be very obvious in a difference file. In my experience
> that not only are not obvious, but appear to not exist.
>
> Walt
>
>
>
>
>
> "Microphones are not ears,
> Loudspeakers are not birds,
> A listening room is not nature."
> Klas Strandberg
> Yahoo! Groups Links
>
>
>
>=20
>
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