Hi all,
I have a lot of respect for both Raimund and Walt. I learned a lot from
both and I'll like to read again their postings.
On the technical side, I should agree more with Raimund than with Walt.
ATRAC artifacts "may" be negligible to our ears, though they "are" there in
unpredictable ways as unpredictable are the infinite combination
possibilities of incoming sounds. Though I've no direct experience with MD
as I never found an ATRAC software to make my own tests without all the
possible artifacts induced by the other components of a recording chain.
Probably next winter I'll buy a MD machine to play with as I played (...for
testing, of course) with a lot of DAT decks and sound boards (I discovered
a lot of interesting things but I never had the time to publish my results).
I made some tests with MP3 and I found that it behaves (apparently)
unpredictably when different and non musical sounds combine together. I got
artifacts very similar to those showed by Raimund. MP3 and ATRAC are both
based on psychoacoustic models to cut details supposed negligible to our
ears. By definition, they are based on algorithms that must cut something.
And now just an example of one of the artifacts in MP3 I found intolerable
for my needs.
I compressed sperm whale clicks in recordings with >90dB dynamic! Clicks
are very loud, very short (and thus broadband) impulsive sounds. Just after
the main click there are low level components generated inside the head of
the whale, including reflections that carry an information about the size
of the spermaceti organ. The reflection to be used for assessing the
spermaceti size is after 4 to 7 ms the main click with a level that is
often 60 dB less than the main click!! The MP3 encoder "thinks" we can't
hear anything after a loud broadband click and thus cuts everything for
more than 10 ms! Thus after each click I have a short silence instead of
the subtle components I'm looking for. Unfortunately, I never made the
same test with ATRAC.
This example is just to say that absolute perfection is not of this world
and that each real technical solution 1) may have different negative and
positive aspects and 2) may fit well certain tasks and not others.
Walt and Raimund, I hope to learn more from both you,
Gianni
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Gianni Pavan
Email
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel/Fax +39-0382-525234
Web http://www.unipv.it/cibra
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