Compression of sound that is.
I have been prompted to post this by all the talk here of using the pitch
shift and speed rate settings of home MD decks to effectively sample
onto MD at a lower rate. I personally think that's a pointless thing to
do, notwithstanding compatability issues.
Peeps often say that the Diamond Rio sounds c**p because it uses MP3
at 128kbps. I agree that isn't the same as your home hi-fi setup, but if
you're using your Rio on a bus, train, plane (if allowed), or any outdoor
environment with significant noise like any town or city, the background
noise will be such that a $20 cassette walkman will sound as good as
a fancy MZ-R50. And probably better than any MD on the planet which
has been recorded at double-speed then played back at half-speed.
I've tried MP3 at 96kbps (tolerable-- but fine for "noisy" places), 64kbps
(very iffy-- but okay still for "noisy" on the move listening), and have
tried
RealAudio at higher compression levels. Remember 64kbps is 22x
compression compared with CD.
Provided the audio levels are correctly set in the recording, and yes, in
this special case I would approve some compression, much tighter
compression is possible and still gives listenable sound. I'll assume now
the recording is of something like an audiobook in mono, so the 64kbps
above now becomes a 32kbps mono file.
At 20kbps, it still sounds pretty good, certainly fine if you had a long
trip
ahead and wanted something interesting to listen to. By 16kbps things
are detiriorating a bit but still okay though from now on it gets steadily
worse. The most compressed file I've heard is 8.5kbps (yeah 8.5 kbits
per sec) which has a s/n ratio of about 20-30dB and a frequency range
of... well let's say it's like a poor telephone line but hey, it's still
listenable
and if you wanted to listen to an audiobook while driving, on the bus,
train, in a busy city or whatever, you'd hardly notice the noise.
Do remember that the 8.5kbps mono file is compressed about 80x
compared with a single (left or right) CD channel, ie a CD could fit roughly
200 hours of dialogue on it, and a method adapted for MD about 40 hours.
We're talking extreme compression here and I think a 16kbps "dictaphone"
format would be great for recording audiobooks and suchlike. Imagine
having 20 hours of passable quality "reading" on one MD for long journeys.
I know it'll never happen, just like my "ideal" portable MD device won't,
unless a major manufacturer spotted a hole in the market around the
$2000 mark, which would be more than I would pay for it.
Cheers,
PrinceGaz -- "Squeezable, but not 80x"
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