Karl Uppiano
Guest
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 Posted:
Mon Nov 01, 2004 2:20 am Post subject:
Re: Encoding of Stereo CD's |
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"KellyClarksonTV" <kellyclarksontv@cs.com> wrote in message
news:20041031012238.04253.00002044@mb-m23.news.cs.com...
| Quote: | Just curious, were Stereo CD's encoded as L and R (like in phonograph) or
L+R
and L-R (like in radio transmission)? My guess is L and R, because by the
time
CD's were around everything was stereo. How about quadraphonic CD's? I
think
they had the extra channels modulated on an ultrasonic frequency, but not
sure.
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CDs always encode the channels as discrete data (not encoded sum and
difference, although the channel data is interleaved. See
http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/95x7.htm). I am not
aware of a quad format in the CD "red book" standard. In any event, it would
*not* use an ultrasonic frequency. CDs can't reproduce any frequency above
1/2 the sample rate of 44.1KHz, i.e, 22.05KHz. The ultrasonic carrier you
would need would have to be at least 30KHz, even to approach FM-quality
sound. CD-4 was a format for discrete quad on vinyl. The name might cause
confusion today. See http://en.wikipedia.org/wiki/Quadraphonic |
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