Questions about equivalents of audio/video and digital/analog.

[Randy Yates]

[...]
Nyquist's theorem:
A theorem, developed by H. Nyquist, which states
that an analog signal waveform may be uniquely
reconstructed, without error, from samples taken at
equal time intervals. The sampling rate must be
equal to, or greater than, twice the highest
frequency component in the analog signal. Synonym
sampling theorem.

[...]
You are looking at the definition of the Theorem, not
the definition of the rate, and then saying the
definition of "Nyquist Rate" should not have the words
"equal to".

I agree this is a definition of the theorem, but in the definition of
the theorem it states the definition of the rate, and that statement
is wrong.

I can see, though, that you and others in this thread have become very
unbalanced. It's not good for your mental health. You're in Alaska,
right? Get outside and go bear hunting or something! Pull your chair
away from the computer!
--
% Randy Yates % "She has an IQ of 1001, she has a jumpsuit
%% Fuquay-Varina, NC % on, and she's also a telephone."
%%% 919-577-9882 %
%%%% <[email protected]> % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

 

[Floyd L. Davidson]

I guessed you would think it was correct. You can't sample at a rate
equal to twice the frequency you are sampling. The wanted signal has
collided with its image and you can't disambiguate them. Thank you for
showing us that you are clueless.

The definition they have for Nyquist Rate does not suggest
anything different.

Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note: The
actual sampling rate required to reconstruct the
original signal will be somewhat higher than the
Nyquist rate, because of quantization errors
introduced by the sampling process.

It does not say what you claimed it does.

 

[Floyd L. Davidson]

No need. You claim your definitions to be correct because they appear
to be borne out by a list you claim to be definitive. The list has
been shown to be errored, so your authority has vanished. Deal with
it.

All you would need to show the definitions I posted are
not valid is provide a conflicting definition of each
from an authoritative source.

You haven't, because there are none.

You claim that the list itself is errored, but you
cannot show an error in it other than one of your own
imagination, where you think one definition implies that
of another... except it does not and the specific
"error" that you claim exists is not part of the
definition given for the term in question.

The point still remains that even if you can find some
error some place in the list, the agrument from
authority is valid for the definitions of the terms
"analog" and "digital" until you can show some other
expert source that disagrees.

You can't.

You apparently can't learn the rules of logic either,
as that has all been explained previously.

 

[Don Pearce]

The definition they have for Nyquist Rate does not suggest
anything different.

Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note: The
actual sampling rate required to reconstruct the
original signal will be somewhat higher than the
Nyquist rate, because of quantization errors
introduced by the sampling process.

It does not say what you claimed it does.

--

Floyd, be a good boy and piss off you lying little toad. Don't bother
replying any more because you are now in my killfile along with Phil
Alison. Why is it always the six-fingered inbreds from the outback
that cause the most grief around here?

d

 

[Floyd L. Davidson]

Floyd L. Davidson wrote:
..
..

This only addresses values, it does not address time. So
how would you classify this signal:

the output of a standard 1V/oct (voltage control) music
keyboard - a monophonic (= non-overlapping) series of

Monophonic measn one channel. The output could be
monophonic and still be overlapping.

stepped voltages corresponding precisely to the 12-tone
equal-termperament subdivisions of the octave. This

It is a digital output if there are precisely 12 voltages
per octave.

control signal is typically applied to the frequency
control input of an analogue voltage-controlled
oscillator (VCO; think MiniMoog), in order to synthesise
tones at the specified frequency.

An analog output device, that has a digital control circuit.

Thus, values are
quantized.

The DC control voltage is quantized. It is digital.
The tone output from the VCO is not quantized and is
analog.

from it the notion of "digital". And manifestly, making
a digital signal is ~not~ the only purpose for
quantization!

And if the Federal Standard had meant to make it mean
"digital" surely, given its importance, they would have
said so.

I believe that what you had to say there demonstrates
why you are so utterly confused on the topic of analog
and digital.

 

[Floyd L. Davidson]

[email protected] (Floyd L. Davidson) writes:

[...]
Nyquist's theorem:
A theorem, developed by H. Nyquist, which states
that an analog signal waveform may be uniquely
reconstructed, without error, from samples taken at
equal time intervals. The sampling rate must be
equal to, or greater than, twice the highest
frequency component in the analog signal. Synonym
sampling theorem.

[...]
You are looking at the definition of the Theorem, not
the definition of the rate, and then saying the
definition of "Nyquist Rate" should not have the words
"equal to".

I agree this is a definition of the theorem, but in the definition of
the theorem it states the definition of the rate, and that statement
is wrong.

It does not define the rate. There *is* a formal
definition of the rate provided, and it is absolutely
correct.

If *you* read something into it that is clearly in
conflict with what they say, it is time to question your
interpretation of what you read into it.

I can see, though, that you and others in this thread have become very
unbalanced.

Sorry sonny, but gratuitous insults are almost always a
reflection of the mental state of the people who make
them. They indicate self fears by those who make them.

One of the things that should be obvious from the length
of this thread is that *I* am not the one wallowing all
over creation with a variety of different and
conflicting attempts, all of which fail, to prove
something that obviously isn't true. I have simply been able
to followup on the initial statements that I made with
*logical* and rational continuations of exactly the same
thing, without contradictions, without variations, and
without wearing a tin foil hat.

It's not good for your mental health. You're in Alaska,
right? Get outside and go bear hunting or something! Pull your chair
away from the computer!

You might be right about mental health problems. Given
the amount of therapeutic noise that you and others have
generated as you slam back and forth trying to imagine a
hole in the basic wall you've butted up against... you
probably should seek a professional evaluation.

 

[Floyd L. Davidson]

Floyd, be a good boy and piss off you lying little toad. Don't bother
replying any more because you are now in my killfile along with Phil
Alison. Why is it always the six-fingered inbreds from the outback
that cause the most grief around here?

I see that you find it difficult to handle facts and
logic when you meet up with someone who can sort them
out at the drop of a hat.

Gratuitous insults are virtually always a fair
indication of the reflection the writer sees in a
mirror, so my only comment on your statements above is
that you seem to have a truly horrifying mental image of
yourself to use as an example when you want to insult
someone.

Whatever, if you had had your facts straight to begin
with, you wouldn't feel so crushed now.

 

[Don Bowey]

Floyd, be a good boy and piss off you lying little toad. Don't bother
replying any more because you are now in my killfile along with Phil
Alison. Why is it always the six-fingered inbreds from the outback
that cause the most grief around here?

d

The problem with people like Floyd is that, when you get frustrated from his
moronic misleading replies and lies, he will internalize that he has "won,"
and will feel empowered to continue in kind. Someone else posted that his
goal is to win at any cost (including his veracity) and facts will be
twisted or ignored to meet that goal. It would be unfortunate if he posts
his views to Wikapedia.

Phil, on the other hand, seems to be technically correct, though sometimes
vague. The latter is, I believe, to leave something for the OP to finish.
I always read his posts.

 

[Al in Dallas]

Here are some valid standard defintions:

"quantize - to subdivide into small but measurable increments."
(Merriam Webster's Collegiate Dictionary, Tenth Edition)

Note that in the definition, there appears no mention of assigning a
value. Assigning a value would then be considered a part of a
separate and distinct process of converting to digital form, as in

"digital - of, or relating to data in the form of numerical digits",

and as opposed to

"analog - of, relating to, or being a mechanism in which data is
represented by continuously variable physical quantities."

There's a huge difference between the jargon of experts and the
language of common people. Doctors and surgeons don't restrict
themselves to the definitions found in ordinary dictionaries. Neither
do experts in communications theory. If that's the best cite the
audiophiles have, then they're admitting they're hobbiests.

 

[Don Pearce]

The problem with people like Floyd is that, when you get frustrated from his
moronic misleading replies and lies, he will internalize that he has "won,"
and will feel empowered to continue in kind. Someone else posted that his
goal is to win at any cost (including his veracity) and facts will be
twisted or ignored to meet that goal. It would be unfortunate if he posts
his views to Wikapedia.

Phil, on the other hand, seems to be technically correct, though sometimes
vague. The latter is, I believe, to leave something for the OP to finish.
I always read his posts.

Indeed Phil is usually technically correct, but his posts are simply
so strewn with the filthiest invective that I am prepared to forego
the occasional nugget. Floyd, unfortunately, doesn't have even that
redeeming feature.

d

 

[Al in Dallas]

Monophonic measn one channel. The output could be
monophonic and still be overlapping.

"Monophonic" is a term of art in the music world. In that world, it
means one note at a time, in contrast with polyphony, which was the
revolution that gave the world Western Music as we know it today.

It is a digital output if there are precisely 12 voltages
per octave.


An analog output device, that has a digital control circuit.


The DC control voltage is quantized. It is digital.
The tone output from the VCO is not quantized and is
analog.


I believe that what you had to say there demonstrates
why you are so utterly confused on the topic of analog
and digital.

They seem to be experts in music, not communications theory. Perhpas
their definition of "digital" is extremely useful for them. However, I
don't understand why they've come into an electronics group and
started an argument about electronics terms of art.

 

[Richard Dobson]

Floyd L. Davidson wrote:
...

It is a digital output if there are precisely 12 voltages
per octave.

Users may insert a simple control (may be called "Key Follow" but is
basically just an analogue level control) that can reduce/expand the
size of the steps so that 24 notes, say, cover one octave; or 11 notes
cover an octave and a fifth. This is of course an analogue control, as
the amount of key follow (and hence the division of the octave achieved
by each step) is continuously variable. Which is another way of saying
that the quantization itself is infinitely variable. The VCO is
calibrated such that a change of one octave results in a pitch change of
one octave. Users may well subvert that calibration (and the whole
12-note octave convention) for creative purposes.

An analog output device, that has a digital control circuit.

The key aspect of Voltage Control (as designed by Robert Moog) is that
any module can control (and be controlled by) any other. Inputs are
content-agnostic - the VCO does not have a "digital control circuit" -
just a control circuit to which can be connected any analogue input. In
short - the VCO's control inputs are all analogue; so that, for example,
by inserting a filter (slew-rate limiter) between the keyboard output
and the VCO input, you get a portamento from one note to the next, not a
straight jump. You can equally connect the output of one VCO to the
frequency input of another one, to do FM (Vibrato etc). These are ~all~
analogue signals, being handled by analogue electronics. The
electronics, indeed, on many early synths was notorious for being
somewhat unstable, so that oscillator frequencies adn voltage ranges
could drift as the machine warmed up or cooled down. Later technology
brought in the DCO - the Digitally-Controlled analogue Oscillator, to
eliminate such instabilities.

You might find this company's products interesting:

http://www.analoguesystems.co.uk/modules.htm

See for example the "Voltage Quantiser" and "Voltage controlled slew
limiter" modules.

Richard Dobson

 

[Floyd L. Davidson]

Floyd L. Davidson wrote:
..

Users may insert a simple control (may be called "Key
Follow" but is basically just an analogue level control)
that can reduce/expand the size of the steps so that 24

So there are not precisely 12 voltages per octave, but
rather there are now ever many you choose, and the
adjustment is continuously variable.

You described one device before, and now describe
a different device...

How do you expect a valid answer if you purposely
distort the question with false information?

 

[Eric Jacobsen]

Don Pearce wrote:
..

Well, I seem to have spent my life doing that, as much as I am able. But
agreeing upon terminology, the core vocabulary of the subject, is by
definition a group exercise. Otherwise, people take a term and
arbitrarily make it mean what they want it to mean, which seems to be
the issue here. Converging to an agreement would be great, but after an
avalanche of posts on this thread, people seem no closer now that at the
start. Calling each other "delusional"! First principles? Which ones?!

Richard Dobson

Floyd's been beaten up about this before, but he just keeps coming
back for more.

"Standards" and associated definitions are created for their own use
in a specific context within the scope of the standard, and no
further. Stating that there is "a standard" definition that should
apply to everyone, everywhere, belies a substantial misunderstanding
of what "standards" are and how they work.

Get enough experienced, competent, expert comm people in the same room
and pretty soon you'll have enough different points of view that
you'll have some pretty substantial disagreements on the meaning of
things as fundamental as SNR.

All that means is that it's smart to have a short dialogue to synch up
contexts and definitions before you proceed, and if you do sense that
communication is breaking down due to different definitions, you stop
for just long enough to synch up and then move on. Pounding one's
fist on the table and demanding that one definition is superior to
another is not productive, IMHO. Clearly it's important to
understand what one means when using a term, but there's certainly no
central global clearinghouse that magically decides what terms mean.
If there was it'd be obsolete in a week because the technology and the
areas where it's used is constantly changing.

If one can't just express what they mean or manage to synch up somehow
with the folks with whom they're communicating, then that individual
is just going to have a harder time making progress with people. I
think the current thread is a pretty good example of that. For those
sick bastards among us that like this sort of thing it's been pretty
doggone amusing, too.

Ah, well, this is the sort of thing that'll just always be an issue as
long as people are involved.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

 

[Richard Dobson]

Floyd L. Davidson wrote:
...

So there are not precisely 12 voltages per octave, but
rather there are now ever many you choose, and the
adjustment is continuously variable.

You described one device before, and now describe
a different device...

How do you expect a valid answer if you purposely
distort the question with false information?

Good grief man, it's the SAME DEVICE! The same cable, the same modules,
the same everything. All that changes is that the user tweaks a pot.

So I suppose we have to define "device" now as well as everything else.

I gave you a picture, a micrograph, of a system that ~can~ produce a
signal of precisely stepped voltages. You promptly pronounce that as
"digital". Then I zoom out, give you a broader picture of the same
system, and all of a sudden we discover sginals that can morph
seamlessly between stepped and non-stepped - between "digital" and
"analogue". Perhaps that simply doesn't arise in your universe.

Away now for a week, so you will have to figure the rest out by yourself!

Richard Dobson

 

[Randy Yates]

[email protected] (Floyd L. Davidson) writes:

Floyd: Have a nice day. Come visit me if you're ever in Fuquay, NC,
and I think you'll find me somewhat different than the usenet monster
you seem to imagine me to be.
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% <[email protected]> % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr

 

[Eric Jacobsen]

I don't believe you understand the theorem.
Incidentally, Nyquist didn't come up with the theorem,
hence you really don't want to look at what Nyquist
wrote much as at Shannon's mathematical proof of what
Nyquist proposed.

Floyd, you're out of your league here.

Nyquist's and Shannon's careers overlapped a little bit at Bell Labs
and they collaborated a bit on some things...Nyquist reviewed a lot of
Shannon's early work, IIRC.

In any case, Nyquist clearly created the defining early work in this
area, and the correctness of that work has given it a lot of staying
power. It's not really been superceded by anything. Saying "you
really don't want to look at what Nyquist wrote" belies a deficiency
in your own understanding and makes me suspect that your motivation is
primarily to poison that well for anyone else who might want to
reference it. You seem to like to define your own playing field
smaller and smaller and claim "I'm absolutely correct in this tiny
little circle" and somehow try to make that relevant to everybody
else. At least, that's my take on it.

Shannon's work was primarily in laying the foundation for Information
Theory, and his sampling theorem was pretty much just re-working
Nyquist's theorem from an Information Theory perspective. That's
important partly because context changes interpretation. e.g., you
can't expect a single definition of a term to apply universally to all
possible cases when the contexts and technologies are constantly
changing.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

 

[John E. Hadstate]

"Pearls before swine". However, I understand that the
reason you do it is to keep people like Floyd from confusing
the less-informed readers who will come along later.

I have a rule that changes the color of messages from
certain posters to Hot Pink, and marks them Read and
Ignored. Floyd is a charter member of that group and he is
really very pretty in pink ;-)

 

[Bob Myers]

The standard definition of Nyquist Rate from the
glossary is not incorrect.

It is most definitely incorrect, and since you've now had
more than adequate time to identify and discuss the error,
I guess I'll have to point it out. The key item in question
from the definition you gave is:

....and it contains a very common misunderstanding of
Nyquist's theorem. The sampling rate is NOT required
to be "equal to or greater than twice the highest frequency
component in the analog signal," even ignoring the
problematic "equal to" case in the above. Rather, the
sampling rate must be > twice the BANDWIDTH of the
signal in question. For example, if one is sampling an
AM signal which comprises a 10 MHz carrier modulated
by an audio signal of 0 - 5 kHz, the highest frequency
component would be expected to be at 10.005 MHz -
yet sampling at 20.010 MHz or higher is NOT required
to fully recover the information contained within this
signal. The carrier itself carries no information, so
that's all there is to it. The AM signal in question could
be sampled at a MUCH lower rate (in this case, a bit
greater than 10 kHz would suffice), and still be fully
captured. This in fact forms the basis for what's often
referred to as "digital downcoversion" in receivers, and
also is the basis for the "equivalent-time sampling" operation
of digital sampling oscilloscopes.

To be sure, if you were trying to accurately capture
the form of a single cycle (or even a few cycles) of
a "10 MHz signal," you'd need a sampling rate
far in excess of 20 MHz - but that is also per the
theorem, since such signals' complete spectrums are
very, very wide.

As you seem to accept such things only if "authoritative
sources" are cited, I'd suggest you check the application
notes provided by either Agilent Technologies or
Tektronix on their web sites, re their digital oscilloscopes.
Hopefully, you will consider either of these companies as
knowing a bit about what they're talking about in this area.


Bob M.

 

[Bob Myers]

Floyd's been beaten up about this before, but he just keeps coming
back for more.

"Standards" and associated definitions are created for their own use
in a specific context within the scope of the standard, and no
further. Stating that there is "a standard" definition that should
apply to everyone, everywhere, belies a substantial misunderstanding
of what "standards" are and how they work.

Yes, if there's one thing that's become adequately clear from
this discussion, it's the fact that Floyd has never ever seen any
actual standards-setting body at work.

It puts one in mind of what is traditionally said about not wanting
to watch either sausage or law being made...

Bob M.