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

[Floyd L. Davidson]

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.

It wasn't analog until you ran it through an analog amplifier.

If you want to amplify a
signal in the digital domain, you must perform maths on the numbers.
Can you really not see the difference?

Non-sequitur. When you quantize an analog signal you
have a digital signal. Just as it is possible to
convert an analog signal to a digital signal, it is
possible to convert a digital signal to analog.

One way to do it is to generate a digital PAM signal and
pass it through an analog channel.

Sorry, but you are wrong. And any reference you have found that makes
such a claim is not authoritative; it is also wrong.

As if *you* are an authority! Bullshit son.

The NTIA is an authority, and MilStd specifications are
also authoritative. That is the reason I cited them.
And the *fact* is that you have not and cannot cite any
authoritative standards body that does not agree with
them.

 

[Radium]

You can also
reduce the temporal frequency in the case of motion video.

That's what I was talking about. Reducing the temporal frequency of
the video w/out low-pass filtering or increasing the length of the
movie.

 

[Floyd L. Davidson]

No it isn't -

It is by definition. You can stand there and deny it all
you like, but that just makes *you* look damned silly.

I've cited impeccable and authoritative sources. You have not
and cannnot cite anything that supports your opinion.

it can simply be a signal where the smooth curve has
been replaced by steps. If you want to process that signal you must do
so with analogue circuitry - amplifiers, filters etc. Representing
those steps by numbers is a different matter. Once you have done that,
you can no longer process in the analogue domain, you must use maths
on the numbers; that is what makes it digital.

No it isn't. It is an analogue signal, because it is no longer
represented by digits.

Keep denying all you like Don. You can't cite anyone credible
that supports your whacko definitions.

 

[Don Bowey]

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.

Which means you still do not understand basics.

 

[Floyd L. Davidson]

[email protected] (Floyd L. Davidson) wrote in


Wouldn't this make the output of a D/A converter digital by definition?

It is in fact! It's a digital PAM signal. Indeed, v.90 modems
make use of it.

However, just as you can convert an analog signal to digital, you
can indeed convert digital to analog. One method is to produce a
digital PAM signal and run it through an analog channel. What
you get directly from the D/A is technically called "quasi-analog"
because of that.

 

[Floyd L. Davidson]

It certainly would. But apparently there are those that can't see the
difference between a limited set of values, and a set of numbers
describing those values.

You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...

 

[Floyd L. Davidson]

[email protected] (Don Pearce) writes:
[...]
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.

Are you kidding? It is *the* industry standard
definition. It is not something that I made up, I
merely looked it up.

http://ntia.its.bldrdoc.gov/fs-1037/

That is, since you seem unable to grasp or investigate
it, the web site of the National Telecommunications and
Information Administration, a part of the US Federal
Department of Commerce, in Boulder Colorado. Which is
to say they are next door to and under that same
management as the NIST (the National Institute of
Standards and Technology), and NOAA (National Oceanic
and Atmospheric Administration) which you may also have
heard of...

Or, to put it another way, you will not find anywhere in
the world a valid definition that disagrees with that
one. If yours is not in agreement, you are *wrong*.

You have misunderstood what is meant by the definition. It is not
intended to describe quantized signals, but data where sequential time
steps represent data. It is very clear that when those definitions
were being written, nobody on the committee was thinking of quantized
analogue signals.

You get funnier all the time. Not meant to describe
quantized signals??? Were do you come up with this stuff?

The "steps" in digital signals are not sequential time
steps, the are signal *value* steps. What they were in
fact thinking of *was* "quantized analogue signals"!
For goodness sakes, it is the National
*Telecommunications* and Information Administration.

Tell me which industry used quantized analog signals, and
studied the theory of exactly that?

of course not. They can start life in a computer or whatever. Are you
trying to confuse the issue with a red herring?

You are the one who claimed DSP is necessarily done on output
of an A/D converter. It isn't true.

You can do arithmetic on the output of a quantizer? How do you do
that, it is not in a numeric form. If you want to do arithmetic on it,
you must first digitize it.

It is a digital PAM signal. If you have ever used a v.90 modem,
*you* have done it. Don't say it can't be done, it is commonly
done.

Well, that is a start!

Yes. Now if we can only get you to cease this laziness with your
use of nomenclature and get you a few clues about what you keep
talking about.

 

[Radium]

Radium wrote:

I am talking about:
1. Decreasing the temporal frequency of the video signal without low-
pass filtering or decreasing the playback speed - an example of which
would be decreasing the rate at which a bird [in the movie] flaps its
wings. Hummingbirds flap their wings too fast for the human eye to
see. So the flap-rate of the wings could be decreased until the
flapping is visible to the human eye - without decreasing the playback
speed of the video. This decrease in flap-rate without slowing
playback is visually-analogous to decreasing the pitch of a recorded
sound without decreasing the playback speed. In this case, low-pass
filter would involve attenuating rapidly-changing images while
amplifying slowly-changing images -- I don't want this.

There are some mixed metaphors here. There is a video equivalent to
audio pitch shifting. think of the latter represetned in the frequency
domain (spectrum) - the peak correspindsing to the source partial moves
down (or up). the video equivalent is colour cycling or shifting. But
most simply, reds would be shifted to orange, green shifted to blue,
violet to ultra-violet (and hence llost to view). An alternatyive
stratgy is colour rotation using the artists colour wheel, where,
ideally, diametrically opposite colours are complementary. There is no
equivalent that I know of to colour complemenariness in audio.

Never thought of it this way. My description of visual "pitch-
shifting" is to alter the temporal and spatial frequencies of a video
signal without using low/high-pass-filtering, changing the speed of
the video or changing the size of the images that make up the movie.

Real-time pitch-shifting is done for audio on the phone. Certain voice-
changing devices allow women to sound like men on the phone, without
decreasing the speed at which they talk. The pitch of the audio is
decreased but the speed remains the same.

I would like something similar to be done with the spatial and
temporal of a video signal in real-time. I would like to be able to
work not only for recorded video but also for video signals that are
being transmitted/received in real-time -- such as a live TV show.

I ~think~ I get what Radium wants - he wants to be able to modify a
recorded scene the way one can modify a CGI virtual scene, e.g. by
setting a slower wing flapping rate while leaving other parts of the
scene unchanged.

Actually I don't want other parts to be unchanged. What I would like
is the temporal frequencies [of all parts of the video] to be
decreased but without decreasing the speed of the video signal.

The only audio parallel I can think
of is wanting to pitch shift just one instrument in a polyphonic
texture, leaving other voices unchanged.

The audio parallel is the following:

http://www.adobe.com/products/audition/overview2.html#kmhead3

"Time and pitch processing: shift pitch without changing tempo - and
never introduce audio artifacts."

 

[Floyd L. Davidson]

No I'm not. Let me explain with an example. Suppose I have a ramp that
changes smoothly from 0 to 1 volt. Now I quantize it in steps of 0.1
volts. I now have a staircase that rises in 0.1V steps from 0 to 1
volt.

You just digitized it. You can no longer have a value of 0.15 volts.

If I put that through an amplifier with a gain of 2, I will get
a staircase from 0 to 2 volts. I can put it through an amplifier
because it is still an analogue signal.

It isn't. You cannot determine the difference between an input voltage
of 0.15 and 0.17, even if you amplify the signal times two, you still
have one value. You can call it 0.2 if you like, or 0.4 after the
amplfier, but it is just one value.

If I digitize the signal, I will get a set of signals which might be
0000, 0001, 0010, 0011 etc. If I want to apply a gain of 2, I can't
use an amplifier, I will have to use maths. In the case of applying a
gain of 2 it is easy - the result is 0000, 0010, 000, 0110 etc.

You can't get values that show the difference between an input of
0.15 and 0.17. That is just exactly the same as above.

That is the difference between an analogue signal (whether quantized
or not) and a digital one.

No. By definition it is not. With an analogue signal you have
(technically) an infinite number of values between an input of
0.1 and 0.2. With digital you do not.

A digit is a number.

That is a discrete value. We might note that it doesn't
have to be a number either. It could be a red flag as
opposed to a blue flag, a large cloud of smoke as
opposed to a small puff, a dah instead of a dit, and on
and on.

Digital doesn't mean numbers, it means discrete values.

 

[Floyd L. Davidson]

Floyd L. Davidson wrote:

...


So the output of a fresh C cell is a digit? Talk about
digging a hole for oneself!

Is that supposed to have meaning? It doesn't.

How do you translate "discrete value" into C cells?

You really shouldn't crawl into holes like that one!

 

[Floyd L. Davidson]

The big problem here is that you have misunderstood what NTIA is
saying.

Sure Don. The National Telecommunications Information
Association doesn't know diddly about quantized analog
signals and didn't mean that at all, or so you said in
another post. I'm the only one who thinks that is what
they are talking about... (Which is why _you_ can't cite
any credible sources to support your fantasy claims.)

Do you have any other funny stories. It is getting
mighty absurd when you go to that degree to deny
reality.

 

[Dave Platt]

Actually I don't want other parts to be unchanged. What I would like
is the temporal frequencies [of all parts of the video] to be
decreased but without decreasing the speed of the video signal.

That might be harder. For audio, it can be chopped, such as
removing 1/60th of a second every 1/20th to speed it up by 1.5.
If that is done faster than the modulation (vocalization),
and slower than the frequencies of interest (maybe 400Hz-3.5kHz
for voice) it works pretty well. Probably less well for music.

As far as I know, that is usually done asynchronously to the
source signal. One could imagine removing cycles of a 1.23kHz
voice, for example.

For video the modulation (wing flapping) is not separate from
the source frequency. If you know you are trying to separate
wing flapping, it could be done by cutting out whole flap
cycles, assuming only one bird is in the scene, and is doing
most of the motion. Otherwise, I don't think there is anything
you could do.[/QUOTE]

Some of the TV networks are speeding up syndicated reruns by using
this sort of technique. They appear to be using the "chop out audio
samples" method to speed up the dialog (without pitch-shifting it) and
dropping out complete frames of the video. This works fairly well
when watching scenes with little action, but causes an odd
stuttering-jerk effect when the camera pans or somebody walks across
the screen.

I think I prefer it to the old technique of cutting out whole scenes
or sub-scenes, though.

 

[Jerry Avins]

...


The output is apparenlty analog. At least you have said
*nothing* that indicates otherwise.

Apparently analog but actually digital? That would be in keeping with
your assertion that quantizing an otherwise analog signal digitizes it.

Do you think all digital signals are square waves and
anything that has square waves is digital? Your example
above suggests that you might, but it simply isn't true.

By old vacuum-tube signal generator was certainly analog. It produced
square waves among other wave shapes.

Jerry

 

[Jerry Avins]

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.


Explain.

http://www.warwick.ac.uk/~phsbm/qhe.htm

Jerry

 

[Jerry Avins]

Floyd L. Davidson wrote:

...

Anything that is quantized is digitized.

A signal can be quantized without having been measured. How doe that fit
your scheme?

Jerry

 

[Radium]

For video the modulation (wing flapping) is not separate from
the source frequency. If you know you are trying to separate
wing flapping, it could be done by cutting out whole flap
cycles, assuming only one bird is in the scene, and is doing
most of the motion. Otherwise, I don't think there is anything
you could do.

I don't want to separate the wing-flapping or anything from the video.
I want all temporal components of the video signal to be slowed
without changing the length or speed of the video. Just like Adobe
Audition and certain voice-changers allow the pitch of the audio
signal to be decreased without changing the length or speed of the
audio.

 

[Jerry Avins]

Radium wrote:

...

Actually I don't want other parts to be unchanged. What I would like
is the temporal frequencies [of all parts of the video] to be
decreased but without decreasing the speed of the video signal.
...

The audio parallel is the following:

http://www.adobe.com/products/audition/overview2.html#kmhead3

"Time and pitch processing: shift pitch without changing tempo - and
never introduce audio artifacts."

The video analog of acoustic pitch is color. Both are our biological
response to frequency.

Jerry

 

[Jerry Avins]

Is that supposed to have meaning? It doesn't.

How do you translate "discrete value" into C cells?

You really shouldn't crawl into holes like that one!

Surely, the voltage of a fresh C cell has a discrete value! Or you
really claim otherwise? Have you noticed that the values of commonly
available battery voltages are quantized? 1.5, 3, 4.5, 6, 9, and 12 are
all common values. 22.5 and 45 were once available but are now
exceedingly hard to find. By your definition (quantized = digital) those
are digital batteries.

Jerry

 

[Radium]

Radium wrote:

Don't be sorry. If you work out the details, I'll help you to see the
inherent contradictions they impose, but I won't argue with you about it.

The problem is, I have a hard time accepting when I'm told that there
is no video-equivalent to pitch-shifting-without-changing-tempo.

That's true only if you mean spatial aliasing. Otherwise, you're using
"distortion" in a non-standard way.
Okay.

How does that make for "decent imagery? It amounts to a low-pass filter,
about which you remarked, "ugh".

Well, the image looked bad. It's similar to what happens when you set
the "sharpness" setting on a PC-monitor or TV-screen too low.

Stop with analogies. Say what you mean.

I am saying what I mean -- or at least what I think I mean.

Here's the picture of you that I have in my head: You were a precocious
kid, and impressed those around by asking questions that were further
out than what most kids asked. (Reading a lot leads one to do that.) The
adults around you patted you on the head and praised you for digging
into subjects they knew little or nothing about.* They knew so little
about it that they didn't understand much of what you talked about, and
so couldn't set you back on the rails when you wandered away from
reality. No matter, the praise kept coming anyway, and you learned that
if you imagined something, it was golden. It wasn't really, but those
around you taught you to believe that it was. Now you find yourself
going on about your imaginings with people who _do_ understand the
subject you fantasize about and their reaction hurts, but you're finding
it very hard to get out of bullshit mode and ask basic questions. It
hasn't sunk in yet that you don't even have basic answers because you
still believe that the fantasies you construct are real. I hope you get
over that. In the meanwhile, I feel sorry for you.

Well, I've always had a special interest in things that I find
difficult to answer or make sense of. Video-equivalents-of-audio-
entities are certainly one of them.

 

[Radium]

The video analog of acoustic pitch is color. Both are our biological
response to frequency.

True. Maybe I am just using the wrong words.

Instead of "pitch-shift", I should say "frequency-shift" because that
is what I really mean.