Hi Walt,
Thanks for such a considered response, you've caused me to reconsider some
of my assumptions about exactly what I might be hearing.
> > I had two or three ideas about the differences I'm hearing:
> > (a) the Sony is doing some un-specified post-processing to handle case=
s
> > where it must generate a lot of 'filler' white noise, to insure that it=
's
> > either masked by higher frequency noise, or as non-periodic as possible=
;
>
> It needs to generate no filler. I've not seen any sonograms of any ATRAC
> recording where deliberate filler was introduced. It does not do this,
> it only works to reproduce what it got not invent new stuff.
I had recalled that there was a "masking" interval following transients,
in which the original waveform could be safely discarded and low-volume
noise synthesized to replace it on decode -- as long as a certain ratio of
transient volume to noise volume was maintained... I was supposing that
perhaps what I think I'm hearing might be a periodicity that was making
these (hypothesized) "masked" noise samples more audible.
But this was pretty much uninformed speculation!
> > (b) EDL is not implementing the ATRAC decode recipe correctly;
>
> Or just differently, note that the difference could also be hardware,
It's the "differently" that comes as a surprise, I'd read somewhere that
the de-code was fixed and inferred that for a given ATRAC block there was
only one legal "decode", no post-filtering, waveshaping, etc. allowed by
the decoder -- whatever "allowed" means.
One interesting thing about the EDL system btw is that there isn't any
clocking, it reads the disk as a data disk and I presume (perhaps
erroneously) that it does this with essentially perfect accuracy -- then
the transfer is lossless over SCSI (it better be!) and the decode is all
done in software on the PC.
> The compression is not even getting into heavy breathing on this stuff.
Of this one point I'm not 100% convinced; I certainly stand corrected on
my inaccurate use of the phrase "white noise" ~ but I intuit that there is
something "complex" about water/wind flap recordings (or even traffic
noise), in which a lot of non-tonal noise seems to approach, to my ear
anyway, genuinely random noise...
Perhaps its time to go back and study some "complex" recordings to hear if
that artifacts I detect are in fact completely dependent on the decoding
device, as they may well be -- it'd be nice to know that some recordings
I've lamented hearing "ATRAC artifacts" (emphasis on quotes) in are in
fact capable of very clean decompression under better circumstances.
> parts, for instance. Differences in exactly what the software really
> does, which is usually different from what we think it does, and even
> different from the official description of what it does. The trickery in
Exactly my suspicion -- as a professional programmer... :)
> Ok, here's a sonogram:
> http://wwknapp.home.mindspring.com/images/Flagsono.jpg
Thanks!!! Remarkable how 'invisible' the differences I are in this, they
sound so pronounced on my monitors -- in particular I hear a higher-
frequency hiss in the Sony decode that I don't hear much at all in the
MDTE version... and I can only just see more energy on the top of the Sony
(if it is in fact the middle).
> slight intensity difference rather than structural. Look at how closely
> the difference part mimics the louder parts of the others.
I had wondered about that, perhaps I will try to hand-normalize them one
to the other (regardless of my a priori assumptions that they should be at
the same level) and listen again.
> synthesizer for the decode. It is known that slight differences do exist
> between the output of the decoders for various versions. Slight
That was my real question to EDL -- I haven't been able to find anything
online about the specifics, I assume it's all under NDA or something.
Which is really too bad, I'd happily pay someone to write a decoder for my
files that "sounds like" the Sony! In the meantime, I'm back to using it
for sensitive transfers -- sigh. I do so like the 5x speed benefit of the
EDL system... and the fact that it's essentially a drag-and-drop endeavor
to transfer files. :/
b e st
aaron
http://www.quietamerican.org
________________________________________________________________________
________________________________________________________________________
|
