"rickman" wrote in message
...
On 2/24/2015 12:37 PM, gareth wrote:
"Spike" wrote in message
...
Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter,
with
the phasing notching out any nearby signal, and you realise that DSP
just
isn't necessary due to the quality of the 80-year-old technology
employed.

WHS.

The Eddystone EA12 does not have a phasing control as that part of the
cct
is fixed-tuned, but it does have a tunable notch in the 100kHz IF to
achieve the same effect.

Mind you, there seems to be a diminishing band of people who know how to
do this, so the simplistic approach of using someone else's
ever-upgraded
software to do something less effective is about as far as the tick-box
Amateur seems to go. Heavens - they even buy ready-made wire aerials!

And going from previous threads, there are even fewer who understand that
setting up for single-signal reception means that the notional carrier
frequency has
to lie half-way between the peak of the Xtal and the notch of the phasing
control.

We should not forget that he who sneers loud and long about others' grasp
of
the mathematics of DSP maintains that changing the direction of a
rotating
vector
(A Phasor, and not related to the weapons of Star Trek!) causes it to
decrease in sixe.

What is "sixe"???

Typo - adjacent key - size

On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the 1970s
and 1980s digital transmissions used a much greater bandwidth than their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.

A friend worked in sonar where the data was collected on ships and
transmitted via satellite to shore for signal processing rather than
doing any compression on the data and sending the useful info. As the
signal was nearly all "noise" trying to do any compression on it, even
the aspects that weren't "pure" white noise, would potentially have
masked the signals. Sonar is all about pulling the signal out of the
noise.


You mean the signal can't be compressed? No way. Any non-random signal
can be compressed to some extent. How much depends on the signal and
the amount of processing power required to compress it. However, in
your example, the processing power to compress the signal would probably
have been greater than that required to process the original signal. So
if there wasn't enough power to process the signal on the ship, there
wouldn't be enough power to compress the near-white noise signal, either.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On 2/24/2015 6:35 PM, gareth wrote:
"rickman" wrote in message
...
On 2/24/2015 12:37 PM, gareth wrote:
"Spike" wrote in message
...
Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter,
with
the phasing notching out any nearby signal, and you realise that DSP
just
isn't necessary due to the quality of the 80-year-old technology
employed.

WHS.

The Eddystone EA12 does not have a phasing control as that part of the
cct
is fixed-tuned, but it does have a tunable notch in the 100kHz IF to
achieve the same effect.

Mind you, there seems to be a diminishing band of people who know how to
do this, so the simplistic approach of using someone else's
ever-upgraded
software to do something less effective is about as far as the tick-box
Amateur seems to go. Heavens - they even buy ready-made wire aerials!

And going from previous threads, there are even fewer who understand that
setting up for single-signal reception means that the notional carrier
frequency has
to lie half-way between the peak of the Xtal and the notch of the phasing
control.

We should not forget that he who sneers loud and long about others' grasp
of
the mathematics of DSP maintains that changing the direction of a
rotating
vector
(A Phasor, and not related to the weapons of Star Trek!) causes it to
decrease in sixe.

What is "sixe"???

Typo - adjacent key - size

I thought it might be that, but it still makes no sense to me. Who or
how does changing the direction of rotation of a rotating vector change
its "size". Are you defining size as the rotation so that going from a
+ to a - is like reversing the direction of a vector? I think most
people would consider the "size" of a vector to be the magnitude which
is independent of phase angle and so rotation, no?

Perhaps you can explain this with a little math?

--

Rick

On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the 1970s
and 1980s digital transmissions used a much greater bandwidth than their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.

Why does it not "exist"? That is not at all clear. You don't
understand compression. Compression is a means of removing the part of
a signal that is unimportant and sending only the part that is
important. In most cases of "pure" noise, you can just send a statement
that the signal is "noise" without caring about the exact voltages over
time. So, yes, even noise can be compressed depending on your
requirements.


A friend worked in sonar where the data was collected on ships and
transmitted via satellite to shore for signal processing rather than
doing any compression on the data and sending the useful info. As the
signal was nearly all "noise" trying to do any compression on it, even
the aspects that weren't "pure" white noise, would potentially have
masked the signals. Sonar is all about pulling the signal out of the
noise.


You mean the signal can't be compressed? No way. Any non-random signal
can be compressed to some extent. How much depends on the signal and
the amount of processing power required to compress it. However, in
your example, the processing power to compress the signal would probably
have been greater than that required to process the original signal. So
if there wasn't enough power to process the signal on the ship, there
wouldn't be enough power to compress the near-white noise signal, either.

You really like your all encompassing assumptions. No, all signals can
not be compressed, even non-noise signals can't be compressed if the
signal is not appropriate for the compressor. This is really a very
large topic and I think you are used to dealing with the special cases
without understanding the general case.

Try visiting comp.compression and offering them your opinions. There
are many there who are happy to explain the details to you.

--

Rick

On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the 1970s
and 1980s digital transmissions used a much greater bandwidth than their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.

Here is a white noise signal... 4. That number was chosen at random,
courtesy of XKCD.com. http://xkcd.com/221/

--

Rick

On 2/24/2015 7:03 PM, rickman wrote:
On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the
1970s
and 1980s digital transmissions used a much greater bandwidth than
their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer
so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth
resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it
digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.

Why does it not "exist"? That is not at all clear. You don't
understand compression. Compression is a means of removing the part of
a signal that is unimportant and sending only the part that is
important. In most cases of "pure" noise, you can just send a statement
that the signal is "noise" without caring about the exact voltages over
time. So, yes, even noise can be compressed depending on your
requirements.


Pure white noise is a concept only. There is no perfect white noise
source, just as there is no pure resistor or capacitor.

And yes, I do understand compression. One of the things it depends on
is predictability and repeatability of the incoming signal. That does
not exist with white noise. The fact you don't understand that pure
white noise is only a concept and cannot exist in the real world shows
your lack of understanding.

Some compression algorithms (i.e. mp3) remove what they consider is
"unimportant". However, the result after decompressing is a poor
recreation of the original signal.

But for perfect recreation, nothing is "unimportant". Voice/video
compression is no different than file compression on a computer. Can
you imaging what would happen if your favorite program was not perfectly
recreated?


A friend worked in sonar where the data was collected on ships and
transmitted via satellite to shore for signal processing rather than
doing any compression on the data and sending the useful info. As the
signal was nearly all "noise" trying to do any compression on it, even
the aspects that weren't "pure" white noise, would potentially have
masked the signals. Sonar is all about pulling the signal out of the
noise.


You mean the signal can't be compressed? No way. Any non-random signal
can be compressed to some extent. How much depends on the signal and
the amount of processing power required to compress it. However, in
your example, the processing power to compress the signal would probably
have been greater than that required to process the original signal. So
if there wasn't enough power to process the signal on the ship, there
wouldn't be enough power to compress the near-white noise signal, either.

You really like your all encompassing assumptions. No, all signals can
not be compressed, even non-noise signals can't be compressed if the
signal is not appropriate for the compressor. This is really a very
large topic and I think you are used to dealing with the special cases
without understanding the general case.


Which is just the opposite of what you claimed above. Please make up
your mind.

Try visiting comp.compression and offering them your opinions. There
are many there who are happy to explain the details to you.


I understand the details, thank you. Much better than you do,
obviously. But that's not surprising, either.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On 2/24/2015 7:07 PM, rickman wrote:
On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the
1970s
and 1980s digital transmissions used a much greater bandwidth than
their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer
so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth
resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it
digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.

Here is a white noise signal... 4. That number was chosen at random,
courtesy of XKCD.com. http://xkcd.com/221/


No, that is not a white noise signal. And the number, by definition,
being computer generated, is only pseudo-random.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On 2/24/2015 7:32 PM, Brian Reay wrote:
Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the 1970s
and 1980s digital transmissions used a much greater bandwidth than their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.


To be more accurate, it has an infinite bandwidth and constant power
density/Hz.

As you say, it doesn't really exist.

In practice, lab noise sources are specified over a bandwidth and to be
within a given limit of power variation across that.

Darn useful devices to have around.


Brian,

Thank you - you are much more accurate in describing it than I was able to.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On Tue, 24 Feb 2015, gareth wrote:

What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Because it's something new, at least to amateur radio.

The phasing method of sideband was common in the early days of amateur
SSB (I recall reading the first rigs were filter type, but with really low
IFs, then phasing, then crystal and mechanical filters took over from
phasing). It offered up a lot on transmit and receive, though not
perfection.

But now phasing is used a lot, because digital circuitry has made it
viable. I remember seeing some of the potential when phasing was still
analog, but I also remember reading articles where it was clear others
didn't see the potential. Sometimes ideas become lost when something
becomes commonplace.

Who knows what would come from digital voice. But I remember 30 years ago
one local ham being interested in it, not to the extent of putting
something on the air, but as information from the computer world started
flowing in, the potential started being there. YOu can't resist new
things and say "they have no use", you have to embrace the new and see
what can be done with it. Maybe not as initially seen, but maybe it fits
in somewhere else.

Amateur radio has never done much with envelope elimination and
restoration (was that what it was called? I now forget). It's in one of
the sideband books, and Karl Meinzer of AMSAT fame wrote about it in QST
about 1970. Break the SSB signal into two components, so you can multiply
it up to a higher frequency, then modulate the output stage. If you have
an efficient modulator, you can do away with linear amplifiers (which is
why it was in that SSB book). I gather he used the scheme in at least one
of the amateur satellites after Oscar 6.

But what happens in the digital age? Can you generate the two streems, in
essence but not so simple an FM component and an AM component, without
needing to generate SSB and then extract the two streams? I don't know,
but so much digital processing is being done now, it may be something to
look into. With solid state devices and class D amplifiers, modulating
high level class C amplifiers can't be as much trouble as in the old days.
Maybe it amounts to nothing, but maybe it overall becomes more efficient,
if it can be done.

Maybe there's no value to digital voice, except that in the process of
learnign about it, and implementing it, one can learn something. Maybe
something merely new to the person learning, but maybe something
completely new. No advances are made without learning, the learning
triggers new advances.

Michael

On 2/24/2015 7:12 PM, Jerry Stuckle wrote:
On 2/24/2015 7:03 PM, rickman wrote:
On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message
...
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers?

Perhaps it is cynicism from the manufacturers who introduce such
things
as they see their traditional highly-priced corner of the market
being wiped away by SDR technologies?

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the
1970s
and 1980s digital transmissions used a much greater bandwidth than
their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.
A UK standard 625 line PAL video transmission would have used a
bandwidth of over 400MHz!
Times have changed and left me behind, but I've still got me beer
so who
cares?

But you forget compression. For instance, unless there is a scene
change, the vast majority of a television picture does not change from
frame to frame. Even if the camera moves, the picture shifts but
doesn't change all that much. Why waste all of that bandwidth
resending
information the receiver already has?

And voice isn't continuous; it has lots of pauses. Some are very
noticeable, while others are so short we don't consciously hear them,
but they are there.

And once you've compressed everything you can out of the original
signal, you can do bit compression, similar to zipping a file for
sending.

There are lots of ways to compress a signal before sending it
digitally.
About the only one which can't be compressed is pure white noise -
which, of course, is only a concept (nothing is "pure").

I think that depends on what you mean by "pure". Sounds very
non-technical to me. Even noise can be compressed since if it is truly
noise, you don't need to send the data, just send the one bit that says
there is no signal, just noise. lol


Pure white noise is a random distribution of signal across the entire
spectrum, with an equal distribution of frequencies over time. Like a
pure resistor or capacitor, it doesn't exist. But the noise IS the
signal. To recreate the noise, you have to sample the signal and
transmit it. However, since it is completely random, by definition no
compression is possible.

Why does it not "exist"? That is not at all clear. You don't
understand compression. Compression is a means of removing the part of
a signal that is unimportant and sending only the part that is
important. In most cases of "pure" noise, you can just send a statement
that the signal is "noise" without caring about the exact voltages over
time. So, yes, even noise can be compressed depending on your
requirements.


Pure white noise is a concept only. There is no perfect white noise
source, just as there is no pure resistor or capacitor.

And yes, I do understand compression. One of the things it depends on
is predictability and repeatability of the incoming signal. That does
not exist with white noise. The fact you don't understand that pure
white noise is only a concept and cannot exist in the real world shows
your lack of understanding.

This is not very productive. You make an assertion and the fact that I
don't agree means I am wrong. Ok, you have an idea in your mind and
can't explain it. I get that. The fact that you don't have a white
noise source in your lab doesn't mean it doesn't exist other than in the
same way that 100.1 doesn't exist. No one has ever made anything that
was *exactly* 100.1.

This is a pointless abstraction so I won't continue to debate it.


Some compression algorithms (i.e. mp3) remove what they consider is
"unimportant". However, the result after decompressing is a poor
recreation of the original signal.

That is a value judgement which most would disagree with not to mention
that your example is not valid. MP3 does not *remove* anything from the
signal. It is a form of compression that simply can't reproduce the
signal exactly. The use of the term "poor" is your value judgement.
Most people would say an MP3 audio sounds very much like the original.


But for perfect recreation, nothing is "unimportant". Voice/video
compression is no different than file compression on a computer. Can
you imaging what would happen if your favorite program was not perfectly
recreated?


A friend worked in sonar where the data was collected on ships and
transmitted via satellite to shore for signal processing rather than
doing any compression on the data and sending the useful info. As the
signal was nearly all "noise" trying to do any compression on it, even
the aspects that weren't "pure" white noise, would potentially have
masked the signals. Sonar is all about pulling the signal out of the
noise.


You mean the signal can't be compressed? No way. Any non-random signal
can be compressed to some extent. How much depends on the signal and
the amount of processing power required to compress it. However, in
your example, the processing power to compress the signal would probably
have been greater than that required to process the original signal. So
if there wasn't enough power to process the signal on the ship, there
wouldn't be enough power to compress the near-white noise signal, either.

You really like your all encompassing assumptions. No, all signals can
not be compressed, even non-noise signals can't be compressed if the
signal is not appropriate for the compressor. This is really a very
large topic and I think you are used to dealing with the special cases
without understanding the general case.


Which is just the opposite of what you claimed above. Please make up
your mind.

This is the sort of stuff that makes discussions with you unenjoyable.
You clearly don't understand compression or you would understand this
statement. Compression maps a combination of bits into a smaller number
of bits. By the counting theorem it is impossible for any compression
algorithm to compress all possible input sets. Whether it can be
compressed depends on a match between the input bits and the compression
algorithm. Even white noise (which can exist if you define "white
noise" adequately) can be compressed by the appropriate algorithm. That
algorithm won't compress much else though.


Try visiting comp.compression and offering them your opinions. There
are many there who are happy to explain the details to you.


I understand the details, thank you. Much better than you do,
obviously. But that's not surprising, either.

Ok, you have reverted into snarky mode. I'm done.

--

Rick