John Phillips wrote:
In article , DAB sounds
worse than FM wrote:
John Phillips wrote:
In article , DAB sounds
worse than FM wrote:
Don Pearce wrote:
Does *anybody* listen to that other crap? Low bit rate is the
least of their problems.

Yes, see:

http://www.rajar.co.uk/INDEX2.CFM?menuid=9

Well, no. This researches "reach"

Did you actually look at the page? RAJAR researches more than just
"reach"; they also survey the number of hours that people listen, and
from this calculate the total number of hours that people listen and
the % share of listening. And it's these parameters that should
worry any Radio 3 fanatic who is trying to justify why Radio 3 is
provided with a 50% higher bit rate than Radio 1, Radio 2, 6 Music
and 1Xtra on DAB.

I did indeed read the RAJAR pages (well the ones that showed and
explained the figures - I don't have semi-infinite amounts of time).
The RAJAR research, as I said, does not address the listening issues
which had been brought to my attention by a manufacturer of current
broadcast kit (used by BBC and others).


Here's your original claim (brackets deleted):

"There is research which differentiates between those who actually
listen and those who merely have the station on in the background. He
says the results are quite different"

For there to be more people actually listening to Radio 3 than people
actually listening to Radios 1 or 2 then there would have to be 19 times
as many people actually listening to Radio 3, and that is obviously not
going to be the case.


He has reported a number of
separate listening issues which inform his designs for kit and the
parameters set by broadcasters.

Which bit of this do you not understand?:
snip

Well, I am a little disappointed that you repeat the same points as
before and resort to the ad homienem. That is a fairly well trodden
path for network news (and I suppose I should have expected it rather
than hoping for better) but unfortunately it creates more heat than
light.


Well, I've argued this issue over and over, and have yet to be convinced
in the slightest that Radio 3 should have a 50% higher bit rate than
Radios 1 & 2. Given the following reason, I really do not have a clue
how you can actually argue that Radio 3 should have a far higher bit
rate than Radios 1 or 2:

* for a given level of audio quality, music on Radios 1 is as good as
certain to require a higher bit rate than Radio 3, and music on Radio 2
is very likely to require a higher bit rate than Radio 3;

And if you're going to fall back on the "Radio 3 listeners actually
listen" argument, then that is a number of listeners issue -- the exact
thing that you hate so much.


Your point of view seems a little narrow


Mine are narrow? The only supporting argument for Radio 3 using a 50%
higher bit rate is really "Radio 3 is just more deserving than Radios 1
& 2".



--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

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In article ,
DAB sounds worse than FM wrote:
Well, I've argued this issue over and over, and have yet to be convinced
in the slightest that Radio 3 should have a 50% higher bit rate than
Radios 1 & 2. Given the following reason, I really do not have a clue
how you can actually argue that Radio 3 should have a far higher bit
rate than Radios 1 or 2:

Clue. Look at the dynamic range of the samples on your website. R1&2 -
about 3 dB. R3 - about 25.

--
*Why is a boxing ring square?

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

Dave Plowman (News) wrote:
In article ,
DAB sounds worse than FM wrote:
Well, I've argued this issue over and over, and have yet to be
convinced in the slightest that Radio 3 should have a 50% higher bit
rate than Radios 1 & 2. Given the following reason, I really do not
have a clue how you can actually argue that Radio 3 should have a
far higher bit rate than Radios 1 or 2:

Clue. Look at the dynamic range of the samples on your website. R1&2 -
about 3 dB. R3 - about 25.


Exactly! It is the narrow dynamic range that makes R1 and R2 more
difficult to encode than R3.

I bet that's confused ya!


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

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http://www.digitalradiotech.co.uk/mp...e_capacity.htm

In article , DAB sounds worse than
FM wrote:
Dave Plowman (News) wrote:
In article , DAB sounds worse
than FM wrote:
Well, I've argued this issue over and over, and have yet to be
convinced in the slightest that Radio 3 should have a 50% higher bit
rate than Radios 1 & 2. Given the following reason, I really do not
have a clue how you can actually argue that Radio 3 should have a far
higher bit rate than Radios 1 or 2:

Clue. Look at the dynamic range of the samples on your website. R1&2 -
about 3 dB. R3 - about 25.


Exactly! It is the narrow dynamic range that makes R1 and R2 more
difficult to encode than R3.

I bet that's confused ya!

It has certainly puzzled me. Can you explain your reasoning and define what
you mean by "more difficult"?

FWIW I have no experience of DAB. But with freeview the times I (think!) I
may have noticed problems with R3 are mostly when the sound levels are
quite low. e.g. Strings playing very quietly. i.e. at levels well below
what I hear on R2.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:
Dave Plowman (News) wrote:
In article , DAB sounds
worse than FM wrote:
Well, I've argued this issue over and over, and have yet to be
convinced in the slightest that Radio 3 should have a 50% higher
bit rate than Radios 1 & 2. Given the following reason, I really
do not have a clue how you can actually argue that Radio 3 should
have a far higher bit rate than Radios 1 or 2:

Clue. Look at the dynamic range of the samples on your website.
R1&2 - about 3 dB. R3 - about 25.


Exactly! It is the narrow dynamic range that makes R1 and R2 more
difficult to encode than R3.

I bet that's confused ya!

It has certainly puzzled me. Can you explain your reasoning and
define what you mean by "more difficult"?


The noise to mask ratio (NMR - noise (error) energy to energy under
masking curve for each subband) gives a measure of coding head-room, and
you want it to be as low as possible (i.e. noise as far below the
masking threshold as possible). Because Radios 1 & 2 and all the pop
stations have audio processing applied then the spectrum tends to be
wide and flat, which tends to result in aa lot of remaining frequency
components after the psychoacoustic model has produced the masking
curves to throw away the inaudible subbands. The same is not true for
classical music, because its spectrum isn't as flat, and on average less
frequency components remain after masking. Therefore, for a given bit
rate, there are more bits per post-masking frequency component for Radio
3 than for Radios 1 & 2, thus the NMR is superior (lower) for Radio 3,
because the noise energy is the quantisation noise, which decreases as
the bits per frequency component encoded increases.


FWIW I have no experience of DAB. But with freeview the times I
(think!) I may have noticed problems with R3 are mostly when the
sound levels are quite low. e.g. Strings playing very quietly. i.e.
at levels well below what I hear on R2.


Dynamic range and sound level for MPEG-encoded audio are irrelevant,
because the MPEG encoder changes the sample values to floating point.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
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Returning again to the original topic of the thread, I can report
that the BBC have confirmed that "there was a problem with some of
the coders on Radio 3 but we believe that all is now fixed".

Patrick Wallace
------------------------------------------------------------------

In article , Pat Wallace wrote:
Returning again to the original topic of the thread, I can report
that the BBC have confirmed that "there was a problem with some of
the coders on Radio 3 but we believe that all is now fixed".

Ah. Useful. That seems to explain the problem at least partially.

I was wondering about the possibility of a temporary rate reduction
(as postulated by another poster). However, from listening to R3/DAB
at a time when I knew the bandwidth had been reduced, I concluded that
the fault seemed to have a bigger impact.

--
John Phillips

In article , DAB sounds worse than
FM wrote:
Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:


Exactly! It is the narrow dynamic range that makes R1 and R2 more
difficult to encode than R3.

I bet that's confused ya!

It has certainly puzzled me. Can you explain your reasoning and define
what you mean by "more difficult"?


The noise to mask ratio (NMR - noise (error) energy to energy under
masking curve for each subband) gives a measure of coding head-room, and
you want it to be as low as possible (i.e. noise as far below the
masking threshold as possible).

OK.

Because Radios 1 & 2 and all the pop stations have audio processing
applied then the spectrum tends to be wide and flat, which tends to
result in aa lot of remaining frequency components after the
psychoacoustic model has produced the masking curves to throw away the
inaudible subbands.

Is that the case in the timescales relevant for the data reduction 'frames'
(or whatever the correct term is)? I can see that R1/2 tend to use audio
'compression' (in the old sense) and this may work to flatten the medium
term power spectrum. However that does not in itself mean the spectrum is
'white' if it has a finite number of components. Nor does it necessarily
mean that each individual processed time-frame will have a near uniform
power spectral density. Do you have some data on this relevant to R1/2?


The same is not true for classical music, because its spectrum isn't as
flat, and on average less frequency components remain after masking.

As you can see above, I can see your general point and it seems logical.
However I'm not certain of your use of terms like 'flat' here. A signal
might only contain a few components of the same level, or it might give a
spectrum with a uniform spectral density, but these would be quite
different cases. Also a spectrum may be uniform when averaged over one time
interval, but not uniform over another. (Indeed, for music this seems
desirable if we don't just want to listen to white noise. :-) )


Therefore, for a given bit rate, there are more bits per post-masking
frequency component for Radio 3 than for Radios 1 & 2, thus the NMR is
superior (lower) for Radio 3, because the noise energy is the
quantisation noise, which decreases as the bits per frequency component
encoded increases.


FWIW I have no experience of DAB. But with freeview the times I
(think!) I may have noticed problems with R3 are mostly when the sound
levels are quite low. e.g. Strings playing very quietly. i.e. at
levels well below what I hear on R2.


Dynamic range and sound level for MPEG-encoded audio are irrelevant,
because the MPEG encoder changes the sample values to floating point.

Is it the case that all MP2/3's encode the spectra as floating point
values? If so, what is the precision?

The point pun you make here is interesting as I have been wondering if
some of the artefacts I think I've noticed at low level may be due to
rounding or precision/quantisation errors and have been wondering if this
is due to the *receiver* using too low a level of precision.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:
Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:


Exactly! It is the narrow dynamic range that makes R1 and R2 more
difficult to encode than R3.

I bet that's confused ya!

It has certainly puzzled me. Can you explain your reasoning and
define what you mean by "more difficult"?


The noise to mask ratio (NMR - noise (error) energy to energy under
masking curve for each subband) gives a measure of coding head-room,
and you want it to be as low as possible (i.e. noise as far below the
masking threshold as possible).

OK.

Because Radios 1 & 2 and all the pop stations have audio processing
applied then the spectrum tends to be wide and flat, which tends to
result in aa lot of remaining frequency components after the
psychoacoustic model has produced the masking curves to throw away
the inaudible subbands.

Is that the case in the timescales relevant for the data reduction
'frames' (or whatever the correct term is)? I can see that R1/2 tend
to use audio 'compression' (in the old sense) and this may work to
flatten the medium term power spectrum. However that does not in
itself mean the spectrum is 'white' if it has a finite number of
components. Nor does it necessarily mean that each individual
processed time-frame will have a near uniform power spectral density.
Do you have some data on this relevant to R1/2?


No data; I've just looked at a lot of spectra. I know it's not white,
but it's a hell of a lot flatter and broader for R1/2 than R3. R3 tends
to tail-off quickly, whereas R1/2 tails-off significantly slower and for
the vast majority of the time it goes right the way up to the brickwall
filter.


The same is not true for classical music, because its spectrum isn't
as flat, and on average less frequency components remain after
masking.

As you can see above, I can see your general point and it seems
logical. However I'm not certain of your use of terms like 'flat'
here. A signal might only contain a few components of the same level,
or it might give a spectrum with a uniform spectral density, but
these would be quite different cases. Also a spectrum may be uniform
when averaged over one time interval, but not uniform over another.
(Indeed, for music this seems desirable if we don't just want to
listen to white noise. :-) )


I agree that it's not flat, but it is a hell of a lot flatter than for
R3.


Therefore, for a given bit rate, there are more bits per post-masking
frequency component for Radio 3 than for Radios 1 & 2, thus the NMR
is superior (lower) for Radio 3, because the noise energy is the
quantisation noise, which decreases as the bits per frequency
component encoded increases.


FWIW I have no experience of DAB. But with freeview the times I
(think!) I may have noticed problems with R3 are mostly when the
sound levels are quite low. e.g. Strings playing very quietly. i.e.
at levels well below what I hear on R2.


Dynamic range and sound level for MPEG-encoded audio are irrelevant,
because the MPEG encoder changes the sample values to floating point.

Is it the case that all MP2/3's encode the spectra as floating point
values? If so, what is the precision?


MPEG Layer I/II use 6 exponent bits (referred to as a scale factor)
which covers -118 dB to +6dB in 2dB steps and between 2 and 15 bits for
the mantissa, depending on subband and masking curve level.


The point pun you make here is interesting as I have been wondering
if some of the artefacts I think I've noticed at low level may be due
to rounding or precision/quantisation errors and have been wondering
if this is due to the *receiver* using too low a level of precision.


I think it's far more likely that you're hearing an MPEG artefact...

IME, the tracks that fair the worst on digital radio are loud electric
guitar tracks. Even within the same track the audio quality can vary
from being very good to absolutely abysmal. This can happen when the
loud electric guitar pauses and you've just got a vocal, and then the
electric guitar starts again and it is simply attrocious. This is, and
always will be, caused simply by insufficient bit rate. If VBR (variable
bit rate) and statistical multiplexing across the multiplex (as used on
digital TV) could be used then this suituation could be drastically
improved, but we can't use either, so when a track that is difficult to
encode is on then Radio 1 listeners in particular just have to suffer so
that the Radio 3 listeners don't. So, the next time you think you hear a
slight MPEG artefact, just consider that Radio 1 listeners have to put
up with most tracks consist of audio + MPEG artefacts throughout the
track.

If you can justify that to yourself as being fair then the only
conclusion I can come to is that you're extremely selfish.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
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