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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 60 to 80.
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Author: Bob MyersDate: 11:26 20-08-07
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"Radium" <glucegen1@gmail.com> wrote in message
news:1187586179.764532.267740@i38g2000prf.googlegroups.com...
> On Aug 19, 8:34 pm, "Bob Myers" <nospample...@address.invalid>
wrote:
>
>> Sampled analog systems are certainly
>> not very common today (unless you count certain forms of
>> modulation as "sampling," and in fact there are some very close
>> parallels there), but the theory remains the same no matter which
>> form of encoding is used. In any event, you must sample the
>> original signal at a rate equal to at least twice its bandwidth
>> (actually,
>> very slightly higher, to avoid a particular degenerate case which
>> could occur at EXACTLY 2X the bandwidth) in order to preserve
>> the information in the original and avoid "aliasing."
>
> Is the CCD [Charge Coupled Device] a "sampled analog system"?
It's certainly one example of such, being essentially an
analog shift register.
Bob M.
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Author: Jerry AvinsDate: 11:28 20-08-07
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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 matters; it's good
enough in context. A signal can be quantized without any need to measure
it or describe it with a number. An example is the signal being measured
in a quantum Hall-effect experiment.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
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Author: Bob MyersDate: 11:31 20-08-07
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"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.
"Quantized" and "sampled" are terms which are really not all
that closely associated (at least in theory) with either of the
above, 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.
Bob M.
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Author: Randy YatesDate: 11:31 20-08-07
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nospam@nospam.com (Don Pearce) writes:
> [...]
> On Mon, 20 Aug 2007 05:46:19 -0800, floyd@apaflo.com (Floyd L.
> Davidson) wrote:
>
>>A "quantized analogue signal" is digital by definition.
>>
>
> 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".
I've never seen that definition, while I have seen the definition
Floyd is proposing, and I think it is a reasonable one.
I've also seen many contexts in which "digital" means
"discrete-time,"
i.e., there is no amplitude quantization at all. Take for example any
of a number of books on the subject which have "digital signal
processing" in the title - they are referring to signals that have
been sampled in time, but not quantized (generally, although
quantization effects are also analyzed in several such texts).
Do you have a reference for your definition?
--
% Randy Yates % "I met someone who looks alot like you,
%% Fuquay-Varina, NC % she does the things you do,
%%% 919-577-9882 % but she is an IBM."
%%%% <yates@ieee.org> % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr
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Author: Bob MyersDate: 11:32 20-08-07
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"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.
Bob M.
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Author: Bob MyersDate: 11:36 20-08-07
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"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. 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." It is certainly
possible to conceive of a quantized analog system, although
such things are rarely if ever seen in practice.
"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...;-)
Bob M.
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Author: Bob MyersDate: 11:41 20-08-07
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"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.
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.
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Author: Jerry AvinsDate: 11:42 20-08-07
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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.
>
> (Emphasis added)
>
> 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/
The government declares it so it must be true? I can demonstrate a
circuit using analog components that transforms a continuous ramp input
into a staircase output. Moreover, the output levels can be individually
adjusted. Is the output digital? (We're discussing an arbitrary
definition here. There is no wrong answer.)
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
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Author: Randy YatesDate: 11:46 20-08-07
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Randy Yates <yates@ieee.org> writes:
> nospam@nospam.com (Don Pearce) writes:
>> [...]
>> On Mon, 20 Aug 2007 05:46:19 -0800, floyd@apaflo.com (Floyd L.
>> Davidson) wrote:
>>
>>>A "quantized analogue signal" is digital by definition.
>>>
>>
>> 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".
>
> I've never seen that definition, while I have seen the definition
> Floyd is proposing, and I think it is a reasonable one.
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).
--
% Randy Yates % "The dreamer, the unwoken fool -
%% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..."
%%% 919-577-9882 %
%%%% <yates@ieee.org> % 'Eldorado Overture', *Eldorado*, ELO
http://home.earthlink.net/~yatescr
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Author: Don PearceDate: 11:47 20-08-07
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On Mon, 20 Aug 2007 11:31:16 -0400, Randy Yates <yates@ieee.org>
wrote:
>nospam@nospam.com (Don Pearce) writes:
>> [...]
>> On Mon, 20 Aug 2007 05:46:19 -0800, floyd@apaflo.com (Floyd L.
>> Davidson) wrote:
>>
>>>A "quantized analogue signal" is digital by definition.
>>>
>>
>> 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".
>
>I've never seen that definition, while I have seen the definition
>Floyd is proposing, and I think it is a reasonable one.
>
No, it isn't. It misses the fact that sampled and digital are
different things. Digits are numbers.
>I've also seen many contexts in which "digital" means
"discrete-time,"
>i.e., there is no amplitude quantization at all. Take for example any
>of a number of books on the subject which have "digital signal
>processing" in the title - they are referring to signals that have
>been sampled in time, but not quantized (generally, although
>quantization effects are also analyzed in several such texts).
>
Really? Can you point me at something that does DSP on signals that
have been merely sampled in time? I've never come across any such
thing.
>Do you have a reference for your definition?
Logic will do. If you are doing digital signal processing, you are
doing arithmetic on the numbers that come out of an AtoD converter.
You can't do that with some voltage levels out of a quantizer.
As for discrete time, that is simply sampled, like a class D
amplifier, and nothing to do with digits. There is plenty of laziness
in the use of nomenclature (as well as misuse by people who simply
have no idea what they are talking about).
d
--
Pearce Consulting
http://www.pearce.uk.com
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Author: Bob MyersDate: 11:47 20-08-07
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"Radium" <glucegen1@gmail.com> wrote in message
news:1187591359.045722.145790@i38g2000prf.googlegroups.com...
>
> The purpose of this visual "pitch-shifting" is like a way to record/
> playback/transmit/receive/store supreme-quality video while using the
> least bandwidth and storage space necessary when low-pass filtering is
> not an option.
And as you have been told countless times before, you REALLY
need to read up on the basics of compression, and specifically
the differences between "lossy" and "lossless" compression, and
what forces the differences between these two and what enables
the latter. Until you do, you'll never really understand any of
this.
> Hence, if you want to get decent imagery in a low-bandwidth imaging
> device, your best bet is to decrease the spatial frequency because
> transferring it into the imaging device.
Or use fewer bits per sample, or just fewer bits for certain parts
of the information you're trying to capture (for instance, chroma
information vs. luma), or remove redundant information. (Think
about this: how efficient is it, if we have a section of an image which
is just a blank white area, to have each and every pixel there carry
information that equates to "I'm white!" "So am I!" "So am
I"....
and so forth? Just one example to consider...). You can also
reduce the temporal frequency in the case of motion video. And
these are just the simpler approaches.
Bob M.
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Author: Don PearceDate: 12:02 20-08-07
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On Mon, 20 Aug 2007 11:46:41 -0400, Randy Yates <yates@ieee.org>
wrote:
>Randy Yates <yates@ieee.org> writes:
>
>> nospam@nospam.com (Don Pearce) writes:
>>> [...]
>>> On Mon, 20 Aug 2007 05:46:19 -0800, floyd@apaflo.com (Floyd L.
>>> Davidson) wrote:
>>>
>>>>A "quantized analogue signal" is digital by definition.
>>>>
>>>
>>> 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".
>>
>> I've never seen that definition, while I have seen the definition
>> Floyd is proposing, and I think it is a reasonable one.
>
>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).
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. The signal can be reconverted to an
analogue one later by a D to A. 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.
d
--
Pearce Consulting
http://www.pearce.uk.com
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Author: Randy YatesDate: 12:03 20-08-07
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nospam@nospam.com (Don Pearce) writes:
> On Mon, 20 Aug 2007 11:31:16 -0400, Randy Yates <yates@ieee.org>
> wrote:
>
>>nospam@nospam.com (Don Pearce) writes:
>>> [...]
>>> On Mon, 20 Aug 2007 05:46:19 -0800, floyd@apaflo.com (Floyd L.
>>> Davidson) wrote:
>>>
>>>>A "quantized analogue signal" is digital by definition.
>>>>
>>>
>>> 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".
>>
>>I've never seen that definition, while I have seen the definition
>>Floyd is proposing, and I think it is a reasonable one.
>>
> No, it isn't. It misses the fact that sampled and digital are
> different things. Digits are numbers.
It isn't reaonable to you. Don't publish opinion as fact.
>>I've also seen many contexts in which "digital" means
"discrete-time,"
>>i.e., there is no amplitude quantization at all. Take for example any
>>of a number of books on the subject which have "digital signal
>>processing" in the title - they are referring to signals that have
>>been sampled in time, but not quantized (generally, although
>>quantization effects are also analyzed in several such texts).
>>
>
> Really? Can you point me at something that does DSP on signals that
> have been merely sampled in time? I've never come across any such
> thing.
You haven't looked very far. Here is an example (a power calculation):
Px = \sum_{n=-\infty}^{+\infty} x^2[n],
where x[n] \in \R.
>>Do you have a reference for your definition?
>
> Logic will do. If you are doing digital signal processing, you are
> doing arithmetic on the numbers that come out of an AtoD converter.
> You can't do that with some voltage levels out of a quantizer.
>
> As for discrete time, that is simply sampled, like a class D
> amplifier, and nothing to do with digits. There is plenty of laziness
> in the use of nomenclature (as well as misuse by people who simply
> have no idea what they are talking about).
I won't argue that the current usage isn't good nomenclature, but that's
the way historically things have developed.
--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% <yates@ieee.org> % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr
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Author: Jerry AvinsDate: 12:08 20-08-07
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Doug McDonald wrote:
> ... It's very hard to STORE signals purely analog without
> moving parts. In fact, I had a hard time thinking of any such
> device that is or was purely analog. However, the old analog
> storage oscilloscopes would meet your criteria if you don't
> include electrons in a vacuum as moving parts. There the limit to the
> frequency response is the size of the focus spot .... i.e.
> the quality of the lenses! (Such device of course uses analog
> electron lenses). If you don't intend to store forever, there
> were things like analog mercury delay lines which stored signals
> as sound waves travelling through mercury.
I mentioned mercury delay lines in an earlier post that probably hadn't
seen when you wrote that. There's another way that uses only common
electrical components -- capacitors and inductors. Cascaded low-pass T
(or pi) sections approximate a transmission line very well up to a
frequency determined by the product of 1/LC, while the characteristic
impedance is sqrt(L/C). Such "synthetic lines" were staples in telephone
research labs. The Bell Labs exhibit at the 1939-40 Worlds Fair included
such a line driven by a microphone into which a visitor could speak,
feeding headphones (s)he wore while speaking. Most visitors were reduced
to stammering by the delay, which I'm guessing was about two seconds; my
memory on that point is hazy. I impressed my parents (much like Radium
probably impressed his) by doggedly ignoring the feedback and speaking
clearly and deliberately. The demonstrator, a Bell Labs researcher,
asked us to wait while he fetched his boss to show me off. I do remember
being told that delays up to ten seconds were feasible, but that long
delays allowed the brain to more easily decouple speech and hearing, so
they weren't used in the demo. Bossman showed us the closet where the
delay line was stored. The parts were housed in two large relay racks.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
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Author: Jerry AvinsDate: 12:42 20-08-07
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Don Pearce wrote:
> ... If you are doing digital signal processing, you are
> doing arithmetic on the numbers that come out of an AtoD converter.
> You can't do that with some voltage levels out of a quantizer.
Transversal and recursive filters and correlators have been built that
operate on unquantized samples. Fourier transforms have been "computed"
with lenses. Do you remember the early days of side-looking radar?
> As for discrete time, that is simply sampled, like a class D
> amplifier, and nothing to do with digits. There is plenty of laziness
> in the use of nomenclature (as well as misuse by people who simply
> have no idea what they are talking about).
Agreed. Sometimes I'm guilty of sloppiness. It's the flip side of
explanatory excess.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
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Author: NobodyDate: 12:49 20-08-07
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On Mon, 20 Aug 2007 04:47:00 -0800, glen herrmannsfeldt wrote:
>>> Well, some types of RAM bits are stored as analog voltages
>>> on a MOS gate capacitor.
> (snip)
>
>> These are/were the so-called "bucket-brigade" nominally analog
devices
>> used as delay lines for audio effects such as phasers. Based on storing
>> audio in a chain of capacitors (typ. NMOS, in VLSI chips). Sort of an
>> analogue shift register.
> (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.
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Author: NobodyDate: 12:55 20-08-07
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On Mon, 20 Aug 2007 07:11:34 +0000, Don Pearce wrote:
>>"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. It's not just that the
>>signal amplitude is quantized, but that the quantization uses a
>>power-of-two representation and storage system of some sort.
>
> My reading of the possible systems goes like this.
>
> analogue - a continuous representation of the original signal
> sampled - a representation of the signal at discrete time points
Both of these are analogue; if you want to distinguish the first case, use
"continuous".
"Analogue" = "how much", "digital" = "how many".
> 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
These are the same thing. Digital values *can* be represented by numbers,
but in practice they're represented by physical quantities. You can
the states of binary logic as 0 and 1, but in practice they're
represented by voltages.
> Aliasing is going to happen as soon as you move beyond the first line
> of that list.
Yep; aliasing is a consequence of sampling, not quantisation.
It's the quantisation which makes something "digital".
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Author: NobodyDate: 13:22 20-08-07
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On Mon, 20 Aug 2007 13:56:36 +0000, Don Pearce wrote:
>>>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.
Those discrete levels *are* digits.
> You need an analogue to digital converter to take each of those
> quantized levels and convert it into a digital word
The circuit which performs the quantisation *is* an analogue to digital
converter.
Note that an analogue circuit with a "step" transfer curve
(e.g. a comparator) doesn't necessarily perform "quantisation". Whether or
not quantisation occurs is conceptual, and depends upon context (i.e. how
you intend to use that signal).
> (of 1s and 0s).
Although binary is the most common base for digital systems, any base is
possible.
> Digital means "represented by digits", not "in discrete voltage
> steps".
The concept of "digit" is more general than you realise.
In essence, if you have a signal where the exact value (voltage etc)
doesn't matter, only the "category" (e.g. voltage band) in which it falls,
then it's digital, regardless of whether you have 2 categories or 10 or
100.
An important property of practical digital components is that they
regenerate the signal. If you define e.g. the range 0V-2V as "zero" and
3V-5V as "one", then each component will accept outputs which are near the
edges of the range and produce outputs which are further from the edges
(i.e. less ambiguous).
This property allows you to connect components together into arbitrarily
complex circuits without imposing extremely low tolerances on the inputs.
Moreover, it also allows the construction of feedback loops (sequential
logic), where a signal has to pass through an infinite number of
components (it passes through a finite number of components infinitely
many times).
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Author: Bob MyersDate: 13:47 20-08-07
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"Randy Yates" <yates@ieee.org> wrote in message
news:m31wdytcq2.fsf@ieee.org...
>>>I've never seen that definition, while I have seen the definition
>>>Floyd is proposing, and I think it is a reasonable one.
>>>
>> No, it isn't. It misses the fact that sampled and digital are
>> different things. Digits are numbers.
>
> It isn't reaonable to you. Don't publish opinion as fact.
OK, it's not reasonable to ME, either, if you're impressed
by taking a vote on this sort of thing.
The problem with the definition that you and Floyd seem to
want to use is that it leads to several problems in both
theory and practice, in addition to the fact that there are
numerous counter-examples one can point to.
"Reasonable" would seem (at least to me) to mean that you
can justify your definition *through reason*, which Don has
done. Simply pointing to a published work, including a
standard, as a reference to support your definition is what's
called an "argument from authority," and it has exactly zero
weight in light of an opposing argument based on evidence
and logic. However, if you like, I can also point to several
references which support the definition that Don and I (and
I believe others) are proposing. You might claim the list to
be invalid, however, since it would contain works that I
myself wrote for publication. Which is, of course, the whole
point - simply having your statements published does NOT
make them any more or less correct; the deciding factor is
whether or not they can be shown to be true through evidence
and logic.
Bob M.
>> Really? Can you point me at something that does DSP on signals that
>> have been merely sampled in time? I've never come across any such
>> thing.
>
> You haven't looked very far. Here is an example (a power calculation):
The question was flawed to being with, though - "DSP" stands
for "DIGITAL signal processing," which by definition could
not have been done on information that was simply "sampled
in time." Such information would also have to be digitally encoded
in order to be subject to "DSP.:
> I won't argue that the current usage isn't good nomenclature, but that's
> the way historically things have developed.
A common misuse or misunderstanding does not become
less so merely because it IS common.
Bob M.
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Author: Bob MyersDate: 13:54 20-08-07
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"Nobody" <nobody@nowhere.com> wrote in message
news:pan.2007.08.20.16.55.35.828000@nowhere.com...
>
> It's the quantisation which makes something "digital".
>
So is the output of an ideal D/A converter "digital,"
then? It is most certainly quantized; it cannot take
on any values between adjacent output levels,
which are themselves separated by one "LSB" step
size.
What makes something "digital" is the representation
of information by numeric values ("digits"), or their equivalent,
as opposed to its representation by analogous variations
in some other quantity (which is "analog"). This is the
only definition which consistently makes sense.
Bob M.
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