On Mon, 11 Aug 1997, daniel wrote:
quoted 4 lines The sound quality of an mp3 is close to that of a cd <which have a high
> The sound quality of an mp3 is close to that of a cd <which have a high
> sampling rate (44.1k per second to be exact)>. So the mp3 is close
> to how the record really sounded. Note I am not saying that mp3 uses
> sample rates in the traditional sense.
Actually, MP3 does use sample rates in the traditional sense. Most MP3s
use the same sample rate (44100 khz) and bittage (16 bits/sample) as a CD.
The lame old way of of data reduction was reducing the sample-rate and/or
bittage (so basically it's just throwing out all frequencies above a
certain threshhold). The way MP3, ATRAC, and (I think) RealAudio works is
by selectively removing frequencies we can't hear anyway (because of
psychoacoustical effects such as masking, where a frequency that's a lot
quieter than a nearby frequency is ignored by the brain).
Most MP3s are encoded at 112 kbps (because that's the best the
unregistered shareware encoder will do), while 44.1 khz/16 bit/2 channel
uncompressed data from a CD is 1411.2 kbps, which is (approx.) 12:1
compression, so for every frequency in the original, 11 have been removed
for the MP3. For some reason, 128 kbps MP3s sound quite noticably better
even though their compression ratio isn't much lower.
An MP3 with the same bit rate as a RealAudio file will sound better than
the RealAudio, because MP3 uses a better (much slower) algorithm for
compression. ATRAC is supposed to be even better than MP3, but it's
proprietry and there aren't any software encoders/decoders (it's what
MiniDisc recorders use.. I just had to mention MiniDisc somewhere :-))
For speech you can use vocoding for amazing compression ratios with very
little loss in clarity. That's actually the original reason vocoders were
invented. Their use as a musical instrument is just a side effect.
onNow: Exist Dance - Transmitting From Heaven (there was a documentary on
the (Canadian) Discovery Channel last night called Synthetic Pleasures
that used lots of the tracks from this comp.)
By the way, I'm starting to like the new Jega a lot better now.
--
Emanuel Borsboom -- Victoria, B.C., Canada -- "complete with surface noise"
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