On Friday, February 15, 2013 8:16:30 PM UTC-8, KH wrote:
On 2/14/2013 8:06 AM, Scott wrote:
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On Wednesday, February 13, 2013 8:05:12 PM UTC-8, KH wrote:
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On 2/13/2013 3:10 PM, Scott wrote:
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On Wednesday, February 13, 2013 11:54:15 AM UTC-8, Dick Pierce wrote:
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Scott wrote:
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Maybe in some other neck of the woods. But all too often I
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see some folks dragging out Shannon/Nyquist and saying "see digital
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IS perfect."
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I would like to see a direct quote from someone who
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made this assertion.
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If you are asking for one I'll just show you one from one of my
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favorite sources of misinformation.
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"The Nyquist theorem (which is mathematically proven) says that
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the exact waveform can be reproduced if the original signal is
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frequency limited to less than half the sampling frequency."
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http://www.hydrogenaudio.org/forums/...3D98761&hl=3D=
nyquist+perfect
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IMO "exact" and "perfect" are synonymous as used here. I can find
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more but you only asked for one.
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You seem to have left out the clear caveat in the very next sentence;
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"The word "exact" gets a little shaky if the initial assumptions aren'=
t
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met (example: each sample is taken exactly on time.)"
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Seriously? You think that makes it correct? You think that is all it ta=
kes?
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Well, yes. In fact that is all that is required to make it "correct".=20
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It still says *nothing* about "digital is perfect".
No "in fact" that is not all it takes. If that were all it took then bit de=
pth would be irrelevant to resolution.=20
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from which it is
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abundantly clear that the OP was decidedly Not implying "digital is
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perfect", merely that if "done perfectly" - an impossibility - the
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resulting waveform would be perfect, which IS clearly supported by
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information theory.
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Really? So you don't believe in quantization error?
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In "sampling"? No. And sampling is what that statement relates to. I=20
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believe Dick Pierce has sufficiently addressed that.
Well that seems to be the problem. The statement is limited to sampling rat=
es and ignores the fact that quantization error is also a factor when it co=
mes to Nyquist. There can be no quanitization error for Nyquist to give us =
an "exact" copy of an analog signal. There is always some quantization erro=
r. So the claim "The Nyquist theorem (which is mathematically proven) says =
that the exact waveform can be reproduced if the original signal is frequen=
cy limited to less than half the sampling frequency." Is an "audio" myth.It=
doesn't happen in real AD conversion. Nyquist works perfectly and gives ex=
act waveforms on a mathematical level not on a practical level. but heck, a=
sine wave has infinite resolution on a mathematical level. On a mathematic=
al level both *audio myths* are actually true. Now I look forward to the ar=
guments that a sine wave doesn't have infinite resolution on a mathematical=
level. That will be fun.=20
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And of course, you excised the context of the statement as well, in th=
at
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it was a response to the ludicrous claim that "...converting an analog
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signal into a discrete-time one (as it happens when converting from
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analog to digital) destroys the phase information in the two top octav=
es
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of the resulting spectrum. In a CD-standard digital recording, all pha=
se
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information are lost from 5.5kHz up to 22kHz,"
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I don't see how the quote you provided has ANY relevance to your claim=
..
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People often see what they want to see.
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Yes, they do. And no one, with even a superficial objective reading,=20
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would construe the post you cited as saying "digital is perfect".
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You really don't get to speak for anyone other than yourself.=20