How does Freeview radio compare with DAB/FM?

"Roderick Stewart" wrote in message
.myzen.co.uk...

Hmm. It seems that for every expert opinion there's an equal and opposite
expert opinion. Clearly, they can't both be right.

As I'm sure you'll already have realised, Lesurf and Dabsworthless are a pair of
quacks.
They're both trying desperately to sound like real experts because, having
failed in life, it's the only way they can make themselves feel special.
Normally the impostor relies upon a gullible and uninformed audience in order to
flourish.
If he meets a real expert, the impostor is promptly crushed and his metaphorical
corpse swept aside.
If he meets a fellow impostor, however, it results in the kind of long-winded
nonsensical arguments we see in this thread.
You might as well watch two little Siberian hamsters fighting it out, as waste
your time reading this trash - it'd have the same educational value.

"DAB sounds worse than FM" wrote in message
...

Basically, the vast, vast majority of noise that's added is due to
quantisation - assuming that you count samples that simply aren't encoded
at all because the psychoacoustic model deems them to be imperceptible as
being due to quantisation, and I think it's fair to describe that as
quantisation noise.

So I think calling the difference signal "quantisation noise" is a fair
description of the signal's contents.

Thank you for that. It clearly boils down to two different phenomena being
called "quantisation noise". The original use of the term represented the
inaccuracies introduced at the A/D state, and this term is still in use.

The second use of the term is as used by DABSWTFM. He uses it to refer to
distortion introduced into the signal by the compression process, which
involves quantisation the amplitude of certain frequencies in the frequency
domain.

OK, fair enough.

My argument remains: we now have two entirely different meanings of
"quantisation noise". Their causes are different, and their acoustic
effects are different.

Even though I've read the references given by DABSWTFM, it still isn't clear
to me that the second usage of "quantisation noise" is in wide use. Many of
the papers describe how MPx quantisation in the frequency domain allows for
compression, and which introduces distortion when the signal is
reconstructed. But I still haven't seen that end result called
"quantisation noise".

However, I'm sure that DABSWTFM could search around and find us a paper
which does just that.

Personally I'd like to see two separate names for the two types of
quantisation noise.

SteveT

jamie powell wrote:
"Roderick Stewart" wrote in
message .myzen.co.uk...

Hmm. It seems that for every expert opinion there's an equal and opposite
expert opinion. Clearly, they can't both be right.

As I'm sure you'll already have realised, Lesurf and Dabsworthless are a
pair of quacks.
They're both trying desperately to sound like real experts because, having
failed in life, it's the only way they can make themselves feel special.
Normally the impostor relies upon a gullible and uninformed audience in
order to flourish.
If he meets a real expert, the impostor is promptly crushed and his
metaphorical corpse swept aside.


Funny that, it sounds very much like your visits to alt.radio.digital where
you either try to lecture me or David Robinson on a subject you know naff
all about.


If he meets a fellow impostor, however, it results in the kind of
long-winded nonsensical arguments we see in this thread.
You might as well watch two little Siberian hamsters fighting it out, as
waste your time reading this trash - it'd have the same educational value.

--
Steve - www.digitalradiotech.co.uk - digital radio news & info

The BBC's "justification" of digital radio switchover is based on lies

In article ,
jamie powell wrote:
As I'm sure you'll already have realised, Lesurf and Dabsworthless are a
pair of quacks.
[snip]

Was the term '******' invented with you in mind?

--
*Bills travel through the mail at twice the speed of cheques *

Dave Plowman London SW
To e-mail, change noise into sound.

"DAB sounds worse than FM" wrote in message
...
jamie powell wrote:
"Roderick Stewart" wrote in
message .myzen.co.uk...

Hmm. It seems that for every expert opinion there's an equal and opposite
expert opinion. Clearly, they can't both be right.

As I'm sure you'll already have realised, Lesurf and Dabsworthless are a
pair of quacks.
They're both trying desperately to sound like real experts because, having
failed in life, it's the only way they can make themselves feel special.
Normally the impostor relies upon a gullible and uninformed audience in
order to flourish.
If he meets a real expert, the impostor is promptly crushed and his
metaphorical corpse swept aside.

Funny that, it sounds very much like your visits to alt.radio.digital where
you either try to lecture me or David Robinson on a subject you know naff all
about.

The real lives impostors leave behind are almost uniformly intolerable and
oppressive. The impostor is an escapologist, then, as much as an adventurer.
Endlessly creative and reasonably intelligent, impostors recognise the
limitations of the hand life has dealt them.
They cannot change the world into which they are born as losers, so they change
themselves, this time - crucially - by awarding themselves a sporting chance.
If they are prepared to break one of society's great tabboos - to lie so
convincingly and consistently that they begin to believe the lies themselves -
the doors of opportunity, which seemed so firmly shut against them, might one
day spring open.
For the impostor, this strategy is entirely logical.

In article , Paul S
PAULatSONIFEXdotCOdotUK wrote:

"Jim Lesurf" wrote in message
...


BTW you and others might care to try an experiment of the kind I've
done a few times recently. This is to take a source LPCM file and
generate a copy via an encode-decode cycle. Then generate a new LPCM
file that just consists of the sample-by-sample differences between
this and the original. *And listen to the resulting difference file.*

Depending on the details of the source and the encode-decode you may
be surprised or intrigued by what you hear. In various cases it
doesn't sound either just like (random) noise or distortion in any
traditional sense. Quite interesting to compare it with the source by
ear. :-)


Given the way that audio is removed that is masked by nearby higher
amplitude content, I would expect to hear some garbled/muffled portions
of the original content. I guess it depends on how hard the encoder is
driven and the quality of the psycho-acoustic masking algorithms.

It also depends on the degree to which the encoder uses two different
methods to reduce the amount of data.

One is the method the two Steves have been discussing. This is the
'requantisation' of some spectral components which can lead to what Steve G
seems to call "quantisation noise" IIUC.

The other is that some frequency components may be removed completely from
the spectra if the 'judgement rules' decide they can be ignored entirely.
This isn't like the above because no requantised spectra values are put in
the encoded data to represent these 'removed' components. This part of the
process hence differs significantly from the above.

Signal engineers will be familiar with behaviour that gets described with
terms like "Gibbs oscillations". e.g if you limit the bandwidth of a
squarewave with time symmetric filters you get 'ringing' with peaks at the
'edges' of the squarewave that make the waveform extend to peaks beyond the
level of the 'top' of the squarewave. This is an example of the way
filtering and reducing the bandwidth can alter the shape of the waveform.

As a result if an encoder removes some components entirely it behaves like
a complicated filter that then alters the shape of the remaining waveform
This is nominally an entirely linear effect, and in principle the same
change could be made by an analogue filter if you could make one that
happened to 'notch out' the same components.

To make clearer the effect of the requantisation of other spectral
components you can make use of a simpler situation. Think of a large
waveform and imagine slightly altering its overall amplitude. e.g. take
digital waveform that extends over a range of sample values of, say, +/-
10,000 and alter its amplitude by, say, 0.05 dB.

If I just pressed the right buttons on my hand calculator in the right
order that would change the amplitude of the waveform by around 500. If you
then subtracted this from the original you'd get 'difference values' of up
to around 500. Hence when you plotted difference values you'd actually get
a smaller version of the orginal, but if you hadn't twigged what was
happening you might interpret is as some other kind of 'error' or 'noise'
giving difference values in the hundreds. Which can look scary unless you
know what actually happened. :-)

BTW That kind of problem bedevilled people like Hafler and PJW who tried
to use a nulling method to analyse amplifier distortions. Slight
alterations in the gain or frequency response of the two paths gave
'errors' that might be taken as 'distortion'. But the behaviour was linear
and could easily be small enough to be inaudible in normal use.

In the case of complicated encoders, this kind of 'error in gain' value may
be happening for many spectral components at a time, and then it changes as
you go from one time-chunk to the next. So the effect is more like
complicated variations in the overall frequency response as time passes.
However as you can see from the above example, with a loud (large
amplitude) input signal you only need tiny 'gain errors' to produce
'differences' that may have values in the hundreds or more.

The phase can also be wiggled about by this process as it will be affected
by the 'overlaps' used for the 'real' transforms used for various lossy
encoders. All depends on the details.

The result can be that when you listen to the 'difference' then in some
cases you can hear what sounds quite recognisably as you described. A
'garbled' version of the source, including contributions at both freqencies
that were totally removed by encoding, and a portion of what was
requantised due to the slightly altered 'gains' at various frequencies.

Personally, as I have explained, I'd be reluctant to describe all the above
simply as 'noise' or 'distortion'. To me that seems to use terms familiar
in other contexts for a quite different sort of behaviour and end result.
Can easily lead to confusion. :-)


Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Jim Lesurf" wrote in message
...

Personally, as I have explained, I'd be reluctant to describe all the
above
simply as 'noise' or 'distortion'.

Or even more specifically, "quantisation noise".

To me that seems to use terms familiar
in other contexts for a quite different sort of behaviour and end result.
Can easily lead to confusion. :-)

Yes, that's what I think, too.

SteveT

Steve Thackery wrote:
"DAB sounds worse than FM" wrote in message
...

Basically, the vast, vast majority of noise that's added is due to
quantisation - assuming that you count samples that simply aren't encoded
at all because the psychoacoustic model deems them to be imperceptible as
being due to quantisation, and I think it's fair to describe that as
quantisation noise.

So I think calling the difference signal "quantisation noise" is a fair
description of the signal's contents.

Thank you for that. It clearly boils down to two different phenomena
being called "quantisation noise". The original use of the term
represented the inaccuracies introduced at the A/D state, and this term
is still in use.
The second use of the term is as used by DABSWTFM. He uses it to refer to
distortion introduced into the signal by the compression process, which
involves quantisation the amplitude of certain frequencies in the
frequency domain.


.... or samples in the time domain if compression takes place in the time
domain, such as for MP2. Also, there's always quantisation noise added to
the


OK, fair enough.

My argument remains: we now have two entirely different meanings of
"quantisation noise". Their causes are different, and their acoustic
effects are different.


Correct.


Even though I've read the references given by DABSWTFM, it still isn't
clear to me that the second usage of "quantisation noise" is in wide use.


I disagree.


Many of the papers describe how MPx quantisation in the frequency domain
allows for compression, and which introduces distortion when the signal is
reconstructed. But I still haven't seen that end result called
"quantisation noise".


But have you seen it described as anything? The difference signal isn't a
very useful signal - to use an analogy it's like the waste product from a
manufacturing process that's just discarded.


However, I'm sure that DABSWTFM could search around and find us a paper
which does just that.

Personally I'd like to see two separate names for the two types of
quantisation noise.


I would actually expect research papers and books to refer to the difference
signal as the "residual", because that's a common term used to describe
difference or error signals in DSP and in audio coding. But I'm happy with
my use of the term "quantisation noise" to describe that signal due to the
fact that the vast majority of the "error" is due to re-quantisation. But I
don't think it's a very important issue to be honest, because the signal is
so rarely used.

Anyway, I think enough has been said about this signal, so I'll duck out
here - I'm sure Jim'll have enough for say for two people anyway.


--
Steve - www.digitalradiotech.co.uk - digital radio news & info

The BBC's "justification" of digital radio switchover is based on lies

Steve Thackery wrote:
"Jim Lesurf" wrote in message
...

Personally, as I have explained, I'd be reluctant to describe all the
above
simply as 'noise' or 'distortion'.

Or even more specifically, "quantisation noise".

To me that seems to use terms familiar
in other contexts for a quite different sort of behaviour and end result.
Can easily lead to confusion. :-)

Yes, that's what I think, too.


I disagree.


--
Steve - www.digitalradiotech.co.uk - digital radio news & info

The BBC's "justification" of digital radio switchover is based on lies

On Tuesday, April 13th, 2010 at 17:13:33 +0100, Jamie Robert Powell plagiarized:

The real lives impostors leave behind are almost uniformly intolerable
and oppressive. The impostor is an escapologist, then, as much as an
adventurer.

....

You failed to attribute this to SARAH BURTON whose words you lifted from
the article at

http://www.thefreelibrary.COM/THE+GREAT+PRETENDERS;+Starting+today,+a+fascinatin g+new+series+that...-a0109625536