RE: oversampling

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2 total messages Started by Dzung Hoang Wed, 27 Sep 1989 02:15

#409

Author: Dzung Hoang
Date: Wed, 27 Sep 1989 02:15

26 lines
1826 bytes

In article <1737@draken.nada.kth.se>, d88-jwa@nada.kth.se (Jon W{tte) writes:
> The solution is to "fake" a higher sample pitch, causing the CD to
> interpolate the samples between the actual samples. The waveform
> now looks like this: (4-fold oversampling)
. . .
> And requres much less steep filters (typically 30 dB/octave) which means
> no phase shifting. Good CD players use more bits in the output stage
> than is recorded on the CD (i.e. 18 or 20 instead of 16) to get better
> resolution in the oversampling if the variation between each sample is
> small (i.e. low output) so that they don't have to interpolate 47 -> 48
> as 47 47 47 48 48 but could use 47 47.25 47.5 47.75 48 and thus get a
> smoother, cleaner output.

	My DSP professor discussed CD oversampling and his explanation was
different from the above in the details.  Oversampling does not directly
interpolate the sample values to 47 47.25 47.5, etc.  Instead, 0's are
inserted as appropriate between samples.  The LPF takes care of recovering
the signal.  There is no distortion at all.

Dzung Hoang
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Re: oversampling

#411

Author: Jonathan Flamm
Date: Wed, 27 Sep 1989 03:27

16 lines
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In article <1122@rex.cs.tulane.edu> hoang@rex.UUCP (Dzung Hoang) writes:
>	My DSP professor discussed CD oversampling and his explanation was
>different from the above in the details.  Oversampling does not directly
>interpolate the sample values to 47 47.25 47.5, etc.  Instead, 0's are
>inserted as appropriate between samples.  The LPF takes care of recovering
>the signal.  There is no distortion at all.
>
>Dzung Hoang

Actually zeroes are inserted but interpolation is performed using a digital
filter -- hence the jargon "digital filtering" so prevelant on CD players.
The LPF is done (as usual) in the analog domain and can be accomplished
with a much shallower, more linear filter.  At least this is what I believed
to be true.
Jonathan Flamm
jef@apple.com

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