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You may have read
about the HEPC project of Metaxas Audio Systems in an article of some
weeks ago here on TNT, where Kostas Metaxas himself explained his
views and projects about the Future
of the source for Hi-end audio.
To
cut a long story short, the main idea behind this project is: design
and build a Personal Computer aimed to reproduce Music, which reads
it as files from a CD-rom, directly from the Net or from *external*
peripherals like DAT, DVD or any other digital source, present or
next-to-come.
This of course requires hi-end level audio boards,
hi-end power supply circuits and a general rethinking of the whole
concept of PC.
Now, one of the possibilities to store Music into
files that are reasonably sized (in order to make them downloadable
from the Web, for example), compression algorithms are a must.
Thanks to the kind
collaboration of Metaxas Audio I've had the possibility to listen to
a direct comparision between standard CD audio recording and MPEG3
compressed tracks.
In particular I've received a CD with four
tracks *standard* (called *raw*) each one followed by the relative
compressed counterparts, one with a compression ratio of 10:1 and the
other with 5:1.
The tracks were recorded via a standard
Pentium-based CD (no HEPC was involved during the process) and taken
from CD's *Harry Belafonte at Carnegie Hall* and *The Cowboy Junkies*
- well-known recordings among audiophiles.
Let's admit it: the
MPEG3 compression is CLEVER but the performance depends strongly (and
obviously) on the choosen rate.
The 10:1 compression rate
is clearly excessive: it cuts both low and high frequencies, flattens
the virtual perspective and subtracts liveliness to the
recording.
The sound becomes harsh and artificial, dynamics
diminish and it seems you're listening to a bad copy on a bad Compact
Cassette.
But please remeber we're talkin' of a 10:1 compression
rate which is a HEAVY one.
Still MPEG3 succeeds giving you an idea
of how the recording will sound like and I'm pretty sure that on
cheap low-fi systems it will be considered more than sufficient by
most customers.
The 5:1 compression rate is another story.
Though you can always *tell* which track is playing, the compressed
or the uncompressed one, here the differences become subtler.
The
first thing one can notice is the reduced soundstage, depth, width
and height. Especially depth.
Then the air amiong the instruments:
it seems everything has been *compacted*, losing the breath of the
otherwise very good recording.
Also it seems the pace changes a
bit (I know this is a psychoacoustic effect), and the compressed
tracks sound somewhat faster, as if the players were late for dinner
:-)
Despite of this, the overall effect is incredible and, without
comparing it to the uncompressed version, you wouldn't believe you're
listening to a 5:1 compressed data.
Clearly, if you give people a
compressed recording, few of them will argue if it is compressed or
not. They would probably say: well, the soundstage isn't so
realistic or there's not enough *air* among instruments
but how many commercial recordings sound this way? Tons of 'em,
sadly.
Compression is
compression, you just can't avoid this. We're sadly going towards a
compressed version of our universe, compressed pictures, movies and
audio.
Since the digital revolution (involution) started it was
clear that the uncompressed HUGE analog data were doomed to an
end.
The new DVD audio standard seems now to be the 96 kHz/24 (or
less) bits instead of what we have now (44.1/16) so it seems there's
still hope for a more analogue :-) digital sound.
But once you can
use clever compression algorithms and hence store more data in a
given medium, well, our ears will be required to decide which kind of
compression is better or worse.
MPEG3 works fine and clearly can
be already used to store small excerpts of Music into Web servers,
for faster downloads and quick evaluation of what you're going to
buy, so that you can decide if the recording is worth the money or
not.
I simply can't wait to test-listen to the first samples of
the HEPCs.
For more details please refer to Metaxas
Audio Systems
Copyright © 1998 Lucio Cadeddu
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