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

Jerry Avins <jya@ieee.org> wrote:
>Floyd L. Davidson wrote:
>> Jerry Avins <jya@ieee.org> wrote:
>>> I like your categories. It is possible in concept to
>>> have a signal that is quantized in magnitude and
>>> continuous in time, but (unless we resort to counting
>>> electrons) I don't think it's possible in practice.
>> If you quantize the magnitude, it is digital. That is
>> by definition.
>
>I believe that the definition is flawed. Not that it

Your opinion of standard definitions is worthless.

If you want to communicate with the rest of the technical
world, use standard definitions and cease claiming they
are flawed.

Your opinion is where the flaw exists.

>matters; it's good enough in context. A signal can be
>quantized without any need to measure it or describe it
>with a number.

That isn't true. In order to quantize it you *must*
decide on non-overlapping ranges of *values*, and a
specific quantity value that equates to those values.

>An example is the signal being measured
>in a quantum Hall-effect experiment.

Explain.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

"Bob Myers" <nospamplease@address.invalid> wrote:
>"Dave Platt" <dplatt@radagast.org> wrote in message
>news:8ponp4-gfd.ln1@radagast.org...
>> >Come on, Dave, a CCD is a digital device, subject to aliasing. The
>>>charges represent the signal at a particular instant of its average over
>>>a particular interval. (My CCD digital camera can take time exposures.)
>>>A CCD's content may not be quantized in amount, but it is quantized in
>>>time. In a camera, where the charges pertain to individual pixels, the
>>>result is also quantized in space.
>>
>> "Digital" and "subject to aliasing" are two different things.
>>
>> As I believe the term "digital" is usually meant, it implies a
>> two-state (on/off) storage representation.
>
>Not necessarily; a two-state representation is most properly
>referred to as "binary." The best definition of "digital" I've
>managed to come up with comes in the word itself - it
>is the encoding system whereby information is stored as
>"digits," i.e., numeric values, as opposed to a system in which
>the information is stored "analogously" in the form of one
>parameter (voltage, say) which varies in a like manner as the
>original.

Your definition is flawed. Digital implies a finite set
of values, which might well be a voltage that varies in
a like manner (granted not continuously) as the
original.

Analog inplies the variation is continuous.

>"Quantized" and "sampled" are terms which are really not all
>that closely associated (at least in theory) with either of the
>above,

Again, not really true. Quantized is necessarily
digitized.

But sampled can be either.

>although admittedly most systems seen today which
>employ sampling and/or quantization are also "digital" in the
>nature of the encoding of the information carried.

Anything that is quantized is digitized.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

"Bob Myers" <nospamplease@address.invalid> wrote:
>"Don Pearce" <nospam@nospam.com> wrote in message
>news:46cd3d5b.233043828@news.plus.net...
>> analogue - a continuous representation of the original signal
>
>A CCD is an example of a device which stores information
>in an analog manner, but non-continuously.

The output signal is analog, and is able to vary *continuously*
over the range in which it functions.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

"Bob Myers" <nospamplease@address.invalid> wrote:
>"Floyd L. Davidson" <floyd@apaflo.com> wrote in message
>news:87zm0mjrfy.fld@apaflo.com...
>>>digital - a quantized signal, with the individual levels represented
>>>by numbers
>>
>> It makes no difference how the levels are represented.
>
>Sure it does.

Look up the definition of "quantization" again. It simply
makes no difference. If an analog signal is quantized, the
result is a digital signal. That is by definition, and you
cannot escape that with mumbo-jumbo and faulty logic.

>If the levels of the original signal (or rather,
>whatever parameter of the original information is being
>recorded/stored/process are represented by analogous
>levels of some other parameter (e.g., sound represented
>by voltage), then the system is "analog."

And that necessarily means that the "analogous levels"
can vary continuously.

(Your example is poor, becuase sound can be represented
by a voltage that has been digitally encoded.)

>It is certainly
>possible to conceive of a quantized analog system, although

It is not possible by definition. If you quantize something,
you have a finite set of discrete values, and it *is* digital.

>such things are rarely if ever seen in practice.

Understatement of the day.

>"Analog" also does not imply "infinite" precision or
>adjustability, since, as is the case in ALL systems, the achievable
>precision (and thus the information capacity) is ultimately limited
>by noise. See the Gospel According to St. Shannon for
>further details...;-)

True. It means only continuously variable over an
infinite set of values. Your ability to determine
exactly which value (accuracy) is not guaranteed, nor is
your ability to reset to any specific value (precision)
guaranteed.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:
>Bob Myers wrote:
>
>(snip)
>
>> "Analog" also does not imply "infinite" precision or
>> adjustability, since, as is the case in ALL systems, the achievable
>> precision (and thus the information capacity) is ultimately limited
>> by noise. See the Gospel According to St. Shannon for
>> further details...;-)
>
>How about, Analog implies "infinite" precision in the absence of
>noise, including fundamental quantum noise.
>
>Note, for example, that an analog current is quantized in units
>of the charge on the electron.

No, in fact it is not. Electrons do not necessarily all move
at the same speed...

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

"Bob Myers" <nospamplease@address.invalid> wrote:
>"Scott Seidman" <namdiesttocs@mindspring.com> wrote in message
>news:Xns999294E6D651Fscottseidmanmindspri@130.133 .1.4...
>
>> Doesn't "analog" also imply that x(t) exists for all t in range, and not
>> just at nT for all n in range? Or would people just call that "sampled"?
>
>Assuming "t" is time here, no - that would require
>that there be no such thing as a sampled analog
>representation, and we already have noted examples
>of that very thing.
>
>"Analog" != "continuous," even though most commonly
>"analog" signals are also continuous in nature.

Analog signals are by *definition* continous.

You have misunderstood what that means though. The
analog value of a signal is continuous, but that does
not imply that the signal continuously exists or that
it even changes at all.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

"Bob Myers" <nospamplease@address.invalid> wrote:
>"glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote in message
>news:E6ednXh1JIkcRlTbnZ2dnUVZ_hynnZ2d@comcast.com ...
>
>> How about, Analog implies "infinite" precision in the absence of
>> noise, including fundamental quantum noise.
>
>Except that "absence of noise" is a condition which
>doesn't exist, even in theory.

Apparenlty Claude Shannon didn't agree with you on that.

Part I of "A Mathematical Theory of Communications" carries
the title "Discrete Noiseless Systems". Section 1 of that
part is titled "The Discrete Noiseless Channel". It turns
out that is a very important theoretical model.

>ALL systems, digital, analog, or whatever, are limited in
>information capacity by (a) the bandwidth of the channel
>in question and (b) the level of noise within that channel,
>per the aforementioned Gospel According to Shannon.
>This is exactly the same thing as saying that there is a limit
>to "precision" or "accuracy," as infinite precision implies
>an infinite information capacity (i.e., given infinite precision,
>I could encode the entire Library of Congress as a single
>value, since I have as many effective "bits of resolution"
>as I would ever need).
>
>> Note, for example, that an analog current is quantized in units
>> of the charge on the electron.
>
>Sure is. So isn't it a good thing that we don't confuse either
>"analog" or "digital" with either "quantized" or "continuous"?

Backwards.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

On 8/20/07 11:58 AM, in article 5iu6iuF3qsf7aU1@mid.individual.net, "Richard
Crowley" <rcrowley@xp7rt.net> wrote:

> Radium's ability to suck so many people into attempting to
> answer insane questions is reaching legendary heights.
> I hereby nominate him for the Troll Hall of Fame with special
> endorsement for use of technical gobeldygook.
>
>

He does have a knack for getting into esoteric points before having an
understanding foundation. Not insane, but all over the map.

I'll vote for your candidate, in any case.

On Aug 20, 12:11 am, nos...@nospam.com (Don Pearce) wrote:

> analogue - a continuous representation of the original signal
> sampled - a representation of the signal at discrete time points
> quantized - a sampled signal, but with the possible levels constrained
> to a limited set of values
> digital - a quantized signal, with the individual levels represented
> by numbers

I agree with your list.

That means the device in the link below is neither analog nor
digital.

http://www.winbond-usa.com/mambo/content/view/36/140/

I'd like to see a purely-analog device which can record, store, and
playback electric audio signals [AC currents at least 20 Hz but no
more than 20,000 Hz] without having any moving parts [except of course
for the diaphragms present in the microphone and speaker and the
electrons that make up the electric signal] and without any amount of
sampling.

The CCD is out of the question as it uses sampling.

Radium <glucegen1@gmail.com> wrote in news:1187655470.606369.55890
@j4g2000prf.googlegroups.com:

> That means the device in the link below is neither analog nor
> digital.

Or more accurately, both analog and digital.

--
Scott
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