 |
Search Sci.Electronics.Basics |
|
|
|
|
|
|
 |
|
|
Sci.Electronics.Basics -> Questions about equivalents of audio/video and digital/analog.
There are 304 messages in this thread.
You are currently looking at messages 80 to 100.
|
Author: Don BoweyDate: 14:07 20-08-07
|
|
On 8/20/07 8:41 AM, in article faccmf$sfh$1@usenet01.boi.hp.com, "Bob Myers"
<nospamplease@address.invalid> wrote:
>
> "Floyd L. Davidson" <floyd@apaflo.com> wrote in message
> news:87r6lyjp3o.fld@apaflo.com...
>
>> A "quantized analogue signal" is digital by definition.
>
> No, Don had it right. A quantized analog signal
> remains analog as long as the relative values of the
> quantization levels, one to the other have significance;
> they thus can carry information, which is the fundamental
> goal of any such system.
No, it becomes a digitally encoded representative of a sample of an analog
voltage. First the continuously variable analog signal is sampled,
becoming, for example PAM, which is still analog, which is then quantized
and may be fit to whatever digital or analog coding that is desired. If
it's to a digital code, the signal is digital. If to an analog code, the
signal is analog.
>
> Now, we could certainly assign values to those levels
> which (for instance) are NOT in order from "top to
> bottom" (or whichever direction you choose to use),
> which might be done to distribute the susceptibility of
> any given "bit" in said value to noise evenly. In this
> case, the levels MUST be interpreted as the intended
> numeric values in order to recover the original
> information, and hence this would be a "digital"
> encoding system.
>
>> QUANTIZATION:
>> A process in which the continuous range of values
>> of an analog signal is sampled and divided into
>> nonoverlapping (but not necessarily equal)
>> subranges, and *a* *discrete*, *unique* *value* *is*
>> *assigned* to each subrange.
>>
>> http://ntia.its.bldrdoc.gov/fs-1037/
>
> Exactly. But mere quantization by itself does not
> suffice to render a signal "digitally encoded," no
> matter what a given government "expert" may claim.
>
> Bob M.
>
>
|
|
|
|
Author: Bob MyersDate: 14:11 20-08-07
|
|
"Nobody" <nobody@nowhere.com> wrote in message
news:pan.2007.08.20.17.22.21.125000@nowhere.com...
>
> Those discrete levels *are* digits.
>
No, because it is the relative change between levels
which contains the information, not *necessarily* the
levels themselves.
Suppose you have an "analog" representation of an
audio signal, which is coming out of a D/A converter
and therefore DOES have discrete levels which it
may assume. As output by the D/A, this signal
ranges between 0 and +1.0V. Now suppose I
shift the signal so that it is now between -0.5 and
+0.5V, or amplify so that it is now between 0 and
+100V. What has changed in terms of the information
content in either case? Note that the discrete levels
most definitely have changed!
Now suppose I have developed an encoding system
which uses the following definitions (never mind WHY
I chose this encoding, we can just assume that I had
my reasons:
0V = "3"
1V = "1"
2V = "7"
3V = "4"
4V = "2"
5V = "0"
6V = "5"
7V = "6"
This is quite clearly a system which conveys three
bits of information per sample (symbol), but the
encoding is such that the levels themselves are NOT
related to each other in an "analog" fashion. Further,
a decoder which would be built to understand the
above would produce an erroneous output if, say,
the signal carrying this information were attenuated
or amplified by a factor of two. This is a "digital"
system (it's just not a *binary* encoding, which is
of course the most common form of "digital" in use
today), as the symbols themselves carry a defined
meaning which is not directly dependent on the
signal which carries them varying in a manner analogous
to the original.
Finally, consider the following, which you see on
an oscilloscope screen; for readability here, I will
use "L" for a low state in the wave form, and "H"
for high:
LLHHHLHLLLHHHHLLHHHH
Now, exactly what is this? If we assume it's carrying
information, it appears to be "sampled" in time - although
we can't be certain that the shortest low or high state
in this wave represents a single symbol - it might be that
we are happening to see a period where the shortest
continuous high or low is actually two, three, or twenty
symbol times. Is it a "digital" signal? Perhaps; you might
be tempted to say that you could interpret this string of
highs and lows as binary digits (again, if only you knew
how long a "digit" was), and it certainly appears to be
"quantized" in that it only exhibits two states.
However, it might also be a snapshot of a single line
of video, which happens to be varying between black
and white vertical bars - there is again, no way of knowing.
The bottom line - both "digital" and "analog" refer to
different means of encoding information, and you CANNOT
reliably distinguish one from the other without knowing
something about the intent of the encoding going on at
the transmitting end. You can take an educated guess
based on the most commonly-seen implementations of
these two, but you cannot be absolutely certain that your
guess is correct.
Bob M.
|
|
|
|
Author: Scott SeidmanDate: 14:38 20-08-07
|
|
glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote in
news:E6ednXh1JIkcRlTbnZ2dnUVZ_hynnZ2d@comcast.com:
> 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.
>
> -- glen
>
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"?
--
Scott
Reverse name to reply
|
|
|
|
Author: Richard CrowleyDate: 14:58 20-08-07
|
|
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.
|
|
|
|
Author: Jerry AvinsDate: 15:09 20-08-07
|
|
glen herrmannsfeldt wrote:
> Jerry Avins wrote:
>
> (snip)
>
>> I believe that's also a borderline area where definitions become
>> smudged. I know that the Russians built a computer with trinary logic,
>> but all the decimal systems I know, whether BCD, excess-three, or
>> something more exotic, encode the numbers on sets of four wires that
>> carry two-state signals. Making a case that that isn't binary opens
>> the door to claiming that hexadecimal is distinct from binary.
>
> I believe that some of the early machines used 10 wires.
With ten neon lamps stacked vertically for each digit at first, then
Nixie tubes.
> Biquinary, with seven wires, one of two and one of five, has
> also been used.
That was so entrenched that TI's first IC decimal counter could be
configured as a biquinary device. It had divide-by-two and
divide-by-five sections.
> In both cases each wire has one of two values, but it isn't very
> "binary like".
It really depends on context. From a circuit viewpoint, I think of
"binary" as implying a single receiver threshold.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
|
|
|
|
Author: glen herrmannsfeldtDate: 15:16 20-08-07
|
|
Nobody wrote:
(snip)
>>I believe there is a device more like an analog RAM used for
>>sound recording in toys. One can record up to about a
>>minute of voice and replay it many times.
> That's just normal (digital) RAM with an ADC and DAC.
No, they have ones that store analog voltages in memory
cells, instead of digitized bits.
See the ISD MICROTAD-16M for example:
http://www.datasheets.org.uk/search.php?q=ISD+MICROTAD-16M&sType=part&ExactDS=St
arts
-- glen
|
|
|
|
Author: Martin HeffelsDate: 15:17 20-08-07
|
|
On Mon, 20 Aug 2007 11:58:32 -0700, "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.
I vote: aye
--
Official website "Jonah's Quid" http://www.jonahsquids.co.uk
|
|
|
|
Author: Bob MyersDate: 15:18 20-08-07
|
|
"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.
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"?
Bob M.
|
|
|
|
Author: glen herrmannsfeldtDate: 15:19 20-08-07
|
|
Randy Yates wrote:
(snip)
> Let me back-pedal a little and say that, yeah, colloquially, digital
> is related to "digits." But the term "digital signal" as used
in texts
> and industry does not hold to this colloquial usage. That is, a signal
> that is completely unquantized in amplitude and represented in base 10
> as an element of the real numbers could well be called a digital
> signal. The key property of such a signal is that it is *discrete-time*
> (i.e., sampled in time).
I would say that "digitized signal" also implies quantization.
There are analog sampled storage systems, such as:
http://www.datasheets.org.uk/search.php?q=ISD+MICROTAD-16M&sType=part&ExactDS=St
arts
-- glen
|
|
|
|
Author: Bob MyersDate: 15:20 20-08-07
|
|
|
|
|
|
Author: glen herrmannsfeldtDate: 15:23 20-08-07
|
|
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.
-- glen
|
|
|
|
Author: Richard CrowleyDate: 15:26 20-08-07
|
|
"Martin Heffels" wrote ...
> "Richard Crowley" 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.
>
> I vote: aye
I don't mean to imply that there may not be idiot-savants
on the interweb. Al Einstein himself may easily have been
perceived as a troll if he were online :-)
|
|
|
|
Author: glen herrmannsfeldtDate: 15:36 20-08-07
|
|
Jerry Avins wrote:
(snip)
> I believe that's also a borderline area where definitions become
> smudged. I know that the Russians built a computer with trinary logic,
> but all the decimal systems I know, whether BCD, excess-three, or
> something more exotic, encode the numbers on sets of four wires that
> carry two-state signals. Making a case that that isn't binary opens the
> door to claiming that hexadecimal is distinct from binary.
I believe that some of the early machines used 10 wires.
Biquinary, with seven wires, one of two and one of five, has
also been used.
In both cases each wire has one of two values, but it isn't very
"binary like".
-- glen
|
|
|
|
Author: glen herrmannsfeldtDate: 15:43 20-08-07
|
|
Don Pearce wrote:
(snip)
> No, you haven't. You merely have a signal at a set of discrete levels.
> You need an analogue to digital converter to take each of those
> quantized levels and convert it into a digital word (of 1s and 0s).
> Digital means "represented by digits", not "in discrete voltage
> steps".
Now it is getting complicated. Once it is quantized it "could"
be represented by digits. Whether you actually have to do that,
I am not so sure.
I haven't followed quantum computing so carefully, but it might
be possible to do computing on discrete voltage levels that
haven't been converted to digits. (And note that the usual
representation of a digital signal is by voltages on wires.)
-- glen
|
|
|
|
Author: Bob MyersDate: 15:57 20-08-07
|
|
"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:5iu86vF3ogf25U1@mid.individual.net...
> I don't mean to imply that there may not be idiot-savants
> on the interweb. Al Einstein himself may easily have been
> perceived as a troll if he were online :-)
And let's not forget Alfred Nobel's half-brother
Ignatz, the benefactor behind the Ig Nobel prize,
awarded for outstanding contributions to that
very field...;-)
Bob M.
|
|
|
|
Author: glen herrmannsfeldtDate: 16:12 20-08-07
|
|
Scott Seidman wrote:
(snip)
> 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"?
Yes, that would be "sampled". Since analog tends to imply continuous
(non-sampled) it would probably be best to use "sampled analog" for
non-continuous non-quantized data.
-- glen
|
|
|
|
|
|
On Aug 20, 3:26 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote:
> "Martin Heffels" wrote ...
>
> > "Richard Crowley" 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.
>
> > I vote: aye
>
> I don't mean to imply that there may not be idiot-savants
> on the interweb. Al Einstein himself may easily have been
> perceived as a troll if he were online :-)
There is NO mistaking Albert Einstein for Radium. Even
if you disagreed with Einstein, his math was impeccable
and self-consistent and provided a plausible explanation
for observed phenomenon that was at variance with
Netwonian physics.
Radium, on the other hand, is simply a blithering idiot.
|
|
|
|
Author: Floyd L. DavidsonDate: 17:33 20-08-07
|
|
nospam@nospam.com (Don Pearce) wrote:
>On Mon, 20 Aug 2007 05:46:19 -0800, floyd@apaflo.com (Floyd L.
>Davidson) wrote:
>
>>nospam@nospam.com (Don Pearce) wrote:
>>>On Mon, 20 Aug 2007 04:57:03 -0800, floyd@apaflo.com (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.
>>>
>>>No it isn't. It isn't digital until you assign numerical values to
>>>those quantized levels. Until then it is simply a quantized analogue
>>>signal.
>>
>>If you quantize it, you *have* assigned a value to it,
>>and that value is not from a continuous set, but from a
>>discrete finite set, and therefore it is digital.
>>
>>A "quantized analogue signal" is digital by definition.
>>
>
>No, you haven't. You merely have a signal at a set of discrete levels.
Sheesh! That *is*, by definition a digital signal.
>You need an analogue to digital converter to take each of those
>quantized levels and convert it into a digital word (of 1s and 0s).
>
>Digital means "represented by digits", not "in discrete voltage
>steps".
Bullshit son. Look it up. I've provided you with
quotes from an authoritative reference, twice now. You
don't have to take my word for it, that *is* the agreed
technical definition of the term.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>;
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
|
|
|
|
Author: Floyd L. DavidsonDate: 17:38 20-08-07
|
|
nospam@nospam.com (Don Pearce) wrote:
>Sorry, but that is simply nonsense. A signal that is sampled in time,
>but not quantized is an analogue signal. It is treated and processed
>by analogue circuits. For a signal to be digital its sampled levels
>must be represented by numbers, which are processed mathematically by
>some sort of microprocessor.
That is, it must actually be quantized.
Perhaps that is what you meant to say earlier, but you
actually didn't, and said that the quantized signal has
to be represented by numbers, which it is by definition.
>The signal can be reconverted to an
>analogue one later by a D to A.
It's best to call that a quasi-analog signal...
>The output of a D to A is still a
>time-sampled signal, but since it is now a set of varying levels, we
>again call it an analogue signal.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>;
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
|
|
|
|
Author: Scott SeidmanDate: 17:42 20-08-07
|
|
floyd@apaflo.com (Floyd L. Davidson) wrote in
news:87zm0mjrfy.fld@apaflo.com:
>>quantized - a sampled signal, but with the possible levels constrained
>>to a limited set of values
>
> That is by definition a digital siganl. As soon as the possible values
> are "constrained to a limited set", it is by definition digital data.
>
>
Wouldn't this make the output of a D/A converter digital by definition?
--
Scott
Reverse name to reply
|
|
|
|
|
|
|
|
|
Contact | Electronic Portal
|
|
|
