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:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/da...tal_radios.htm
http://www.digitalradiotech.co.uk/mp...rs_1GB-5GB.htm
http://www.digitalradiotech.co.uk/mp...e_capacity.htm

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


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 difficulty is that doesn't necessarily lead to your conclusion. The
spectral components present in any time frame may extend across a wider
range, and be more unform in size. But if the *number* of components that
are resolved in the time frame are sigificantly less, then the 'weeding'
process may lose less info. Impossible to assess this without much more
specific info than simply observing a tendency for the components that are
present to have similar levels, etc.

Hence I think the point you make is certainly an important one, but it may
not establish the conclusion you draw without more specific evidence. Not
saying you are wrong. Just saying 'dunno', but 'not proven' simply from
what you have said.



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.

OK. The interesting part here seems to me to be that the matissa may be
down to just a few bits.

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...

That is certainly possible. Also quite possible that I am imagining it, or
it stems from something else in the chain...

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.

Can't really comment on what may be 'fair' here. Just have an interest in
when the system may show audible problems. Since I don't listen much to
R1/2 (and never on DAB) I can't pass any comment on them one way or the
other.

FWIW in terms of *video* I have certainly seen very 'odd' effects at times
on BBCTV4 via DTTV. e.g. I have DVD+R's of one prom where the 'live' sic
broadcast has a picture that 'stutters' throughout a large part of the
broadcast, but where the late-night repeat is fine. I assume this was
variable rate statmux stealing bitrate from BBCTV4 during the evening to
give to some other station(s), but a higher rate being available after
midnight for the repeat. Would not surprise me if similar 'audio' crudities
turned up on DAB at times. But as I say, I have no direct experience of
that so can only surmise. The effect I think I've heard on DTTV R3 seems to
occur on some occasions and not others even when the music is similar.

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:


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 difficulty is that doesn't necessarily lead to your conclusion.


Common sense dictates that it does.


The spectral components present in any time frame may extend across a
wider range, and be more unform in size. But if the *number* of
components that are resolved in the time frame are sigificantly less,
then the 'weeding' process may lose less info. Impossible to assess
this without much more specific info than simply observing a tendency
for the components that are present to have similar levels, etc.

Hence I think the point you make is certainly an important one, but
it may not establish the conclusion you draw without more specific
evidence.


What I've heard over the last 3 years tell me that I'm right.


Not saying you are wrong. Just saying 'dunno', but 'not
proven' simply from what you have said.


I cannot prove this with absolute certainty, but it's beyond reasonable
doubt IMO.


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.

OK. The interesting part here seems to me to be that the matissa may
be down to just a few bits.


Yes, less bits are assigned to higher frequencies because we're less
sensitive, apparently. Having said that, it's the top-end that is the
biggest problem, IMO.


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...

That is certainly possible. Also quite possible that I am imagining
it, or it stems from something else in the chain...

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.

Can't really comment on what may be 'fair' here. Just have an
interest in when the system may show audible problems. Since I don't
listen much to R1/2 (and never on DAB) I can't pass any comment on
them one way or the other.


Well I can, and they sound ****e, and it is unfair that they sound ****e
while R3 uses a 50% higher bit rate. Only a fascist would disagree.


FWIW in terms of *video* I have certainly seen very 'odd' effects at
times on BBCTV4 via DTTV. e.g. I have DVD+R's of one prom where the
'live' sic broadcast has a picture that 'stutters' throughout a
large part of the broadcast, but where the late-night repeat is fine.
I assume this was variable rate statmux stealing bitrate from BBCTV4


Probably. The BBC never alter the stat-mux bit rate allocations, which
is incredibly lazy, IMO.


during the evening to give to some other station(s), but a higher
rate being available after midnight for the repeat. Would not
surprise me if similar 'audio' crudities turned up on DAB at times.


I thought you were talking about video?



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

Find the cheapest Freeview, DAB & MP3 Player Prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/da...tal_radios.htm
http://www.digitalradiotech.co.uk/mp...rs_1GB-5GB.htm
http://www.digitalradiotech.co.uk/mp...e_capacity.htm

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


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 difficulty is that doesn't necessarily lead to your conclusion.


Common sense dictates that it does.

I'm afraid that would only be so if the 'common sense' does not take into
acount the distinctions I was outlining. :-) Hence it would be like the
'common sense' that sometimes causes people to say all kinds of things
which may turn out to be incorrect. I am wary of conclusions "dictated" by
"common sense" as this often turns out to be a poor guide.


The spectral components present in any time frame may extend across a
wider range, and be more unform in size. But if the *number* of
components that are resolved in the time frame are sigificantly less,
then the 'weeding' process may lose less info. Impossible to assess
this without much more specific info than simply observing a tendency
for the components that are present to have similar levels, etc.

Hence I think the point you make is certainly an important one, but it
may not establish the conclusion you draw without more specific
evidence.


What I've heard over the last 3 years tell me that I'm right.

Or rather, leads you to *believe* you are right. :-)

Not saying you are wrong. Just saying 'dunno', but 'not proven' simply
from what you have said.


I cannot prove this with absolute certainty, but it's beyond reasonable
doubt IMO.

I note your opinion, but am trying to distinguish between opinions and
matters of fact.




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

Can't really comment on what may be 'fair' here. Just have an interest
in when the system may show audible problems. Since I don't listen
much to R1/2 (and never on DAB) I can't pass any comment on them one
way or the other.


Well I can, and they sound ****e, and it is unfair that they sound ****e
while R3 uses a 50% higher bit rate. Only a fascist would disagree.

Your comment seem to be in the spirit of the 'Ken Livingstone' school of
scientific discussion. :-)

FWIW in terms of *video* I have certainly seen very 'odd' effects at
times on BBCTV4 via DTTV. e.g. I have DVD+R's of one prom where the
'live' sic broadcast has a picture that 'stutters' throughout a
large part of the broadcast, but where the late-night repeat is fine.
I assume this was variable rate statmux stealing bitrate from BBCTV4


Probably. The BBC never alter the stat-mux bit rate allocations, which
is incredibly lazy, IMO.


during the evening to give to some other station(s), but a higher rate
being available after midnight for the repeat. Would not surprise me
if similar 'audio' crudities turned up on DAB at times.


I thought you were talking about video?

Depends what comments I made that you are referring to. I have made some
comments about the sound of R3 on 'Freeview'. I have made some comments
about the sound of BBCTV4 on Freeview. I have also made a comment about
the *video* on BBCTV4 on Freeview. How these may be related, though, I am
unsure. Only generalisation is that they all involve data-reduction
'compression' systems to communicate the information.

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:


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 difficulty is that doesn't necessarily lead to your conclusion.
The spectral components present in any time frame may extend across a
wider range, and be more unform in size. But if the *number* of
components that are resolved in the time frame are sigificantly less,
then the 'weeding' process may lose less info. Impossible to assess
this without much more specific info than simply observing a tendency
for the components that are present to have similar levels, etc.

Hence I think the point you make is certainly an important one, but
it may not establish the conclusion you draw without more specific
evidence. Not saying you are wrong. Just saying 'dunno', but 'not
proven' simply from what you have said.


An interesting experiment is to encode some CD material into VBR MP3 at
a given quality level. That way the MP3 encoder chooses what bit rate to
use to achieve the given level of quality on a frame-by-frame basis.

If you want to compare results with me then do the following:

* download Lame v3.90.3:

http://www.hydrogenaudio.org/forums/...howtopic=28123

* I use RazorLame as a front-end GUI, which you can find he

http://www.dors.de/razorlame/download.php

* overwrite lame.exe in the RazorLame folder with lame.exe that you
downloaded with Lame v3.90.3 above

* then in Lame Options in RazorLame use the VBR presets on he

http://www.hydrogenaudio.org/forums/...howtopic=28124

--alt-preset standard
--alt-preset- extreme

Do this by going to the Expert tab, entering one of the above into the
Custom options edit box and tick Only use custom options.

Theoretically, the higher the average bit rate the more difficult that
piece of music is to encode to a given level of quality.


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

Find the cheapest Freeview, DAB & MP3 Player Prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/da...tal_radios.htm
http://www.digitalradiotech.co.uk/mp...rs_1GB-5GB.htm
http://www.digitalradiotech.co.uk/mp...e_capacity.htm

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


Hence I think the point you make is certainly an important one, but it
may not establish the conclusion you draw without more specific
evidence. Not saying you are wrong. Just saying 'dunno', but 'not
proven' simply from what you have said.


An interesting experiment is to encode some CD material into VBR MP3 at
a given quality level. That way the MP3 encoder chooses what bit rate to
use to achieve the given level of quality on a frame-by-frame basis.

If you want to compare results with me then do the following:

Erm... what OS, etc, are you assuming I am using? :-)

* download Lame v3.90.3:

[snip]


You would need to direct me at a version that runs under RO on an
ARM-core CPU and which can be verified to act identically to the
one you use. However even if that were done and I had the time
to try it...


It isn't clear to me what value the process you suggest would have w.r.t
the issues we were discussing in terms of the differences between what
the BBC do for R1/2 and R3. If you wish to support your argument for
that then I'd assume you need to do so in terms of the specifics of
the BBC signals and waveforms. The snag being that to do so you ideally
may need access to the originals before they were level compressed
and data reduced.

AIUI your point was based on argueing that the R1/R2 typical signals
have a more unform and flatter spectrum. My point was that it may
also depend on the number of spectral components, not just the
uniformity and range of those present. Without access to the BBC
original waveforms and their level compression, etc, how would
my attempting to use Lame establish this?

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


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 difficulty is that doesn't necessarily lead to your conclusion.


Common sense dictates that it does.

I'm afraid that would only be so if the 'common sense' does not take
into acount the distinctions I was outlining. :-) Hence it would be
like the 'common sense' that sometimes causes people to say all kinds
of things which may turn out to be incorrect. I am wary of
conclusions "dictated" by "common sense" as this often turns out to
be a poor guide.


I couldn't give a flying fk whether you're wary of such conclusions or
if you're madly in love with them.


The spectral components present in any time frame may extend across
a wider range, and be more unform in size. But if the *number* of
components that are resolved in the time frame are sigificantly
less, then the 'weeding' process may lose less info. Impossible to
assess this without much more specific info than simply observing a
tendency for the components that are present to have similar
levels, etc.

Hence I think the point you make is certainly an important one, but
it may not establish the conclusion you draw without more specific
evidence.


What I've heard over the last 3 years tell me that I'm right.

Or rather, leads you to *believe* you are right. :-)


Absolutely it does.


Not saying you are wrong. Just saying 'dunno', but 'not proven'
simply from what you have said.


I cannot prove this with absolute certainty, but it's beyond
reasonable doubt IMO.

I note your opinion, but am trying to distinguish between opinions and
matters of fact.


The fact that I cannot prove this does not mean that I am just going to
drop this view; which just happens to be exactly what you would like me
to do.


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

Can't really comment on what may be 'fair' here. Just have an
interest in when the system may show audible problems. Since I
don't listen much to R1/2 (and never on DAB) I can't pass any
comment on them one way or the other.


Well I can, and they sound ****e, and it is unfair that they sound
****e while R3 uses a 50% higher bit rate. Only a fascist would
disagree.

Your comment seem to be in the spirit of the 'Ken Livingstone' school
of scientific discussion. :-)


Suits me.


FWIW in terms of *video* I have certainly seen very 'odd' effects at
times on BBCTV4 via DTTV. e.g. I have DVD+R's of one prom where the
'live' sic broadcast has a picture that 'stutters' throughout a
large part of the broadcast, but where the late-night repeat is
fine. I assume this was variable rate statmux stealing bitrate from
BBCTV4


Probably. The BBC never alter the stat-mux bit rate allocations,
which is incredibly lazy, IMO.


during the evening to give to some other station(s), but a higher
rate being available after midnight for the repeat. Would not
surprise me if similar 'audio' crudities turned up on DAB at times.


I thought you were talking about video?

Depends what comments I made that you are referring to.


Correct me if I'm wrong, but all of this seemed to be to do with
TV/video:

"FWIW in terms of video I have certainly seen very 'odd' effects at
times
on BBCTV4 via DTTV. e.g. I have DVD+R's of one prom where the 'live'
sic
broadcast has a picture that 'stutters' throughout a large part of the
broadcast, but where the late-night repeat is fine. I assume this was
variable rate statmux stealing bitrate from BBCTV4 during the evening to
give to some other station(s), but a higher rate being available after
midnight for the repeat."


I have made
some comments about the sound of R3 on 'Freeview'. I have made some
comments about the sound of BBCTV4 on Freeview. I have also made a
comment about the *video* on BBCTV4 on Freeview. How these may be
related, though, I am unsure.


Well, you were the bloody one making all the various points, so if you
don't know what point you were trying to make then how the bloody hell
should I know?


Only generalisation is that they all
involve data-reduction 'compression' systems to communicate the
information.


Give the man a Nobel prize.

BTW, you seem to be entering pedant mode, again. If at all possible,
please don't enter said mode again. TIA.


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

Find the cheapest Freeview, DAB & MP3 Player Prices:
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http://www.digitalradiotech.co.uk/mp...e_capacity.htm

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


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 difficulty is that doesn't necessarily lead to your conclusion.


Common sense dictates that it does.

I'm afraid that would only be so if the 'common sense' does not take
into acount the distinctions I was outlining. :-) Hence it would be
like the 'common sense' that sometimes causes people to say all kinds
of things which may turn out to be incorrect. I am wary of conclusions
"dictated" by "common sense" as this often turns out to be a poor
guide.


I couldn't give a flying fk whether you're wary of such conclusions or
if you're madly in love with them.

I am also not particularly concerned by you making such comments. :-)


[snip]


Not saying you are wrong. Just saying 'dunno', but 'not proven'
simply from what you have said.


I cannot prove this with absolute certainty, but it's beyond
reasonable doubt IMO.

I note your opinion, but am trying to distinguish between opinions and
matters of fact.


The fact that I cannot prove this does not mean that I am just going to
drop this view;

Fair enough. That's your prerogative. People believe all kinds of things.
Just as I and others are free to make our own decisions.

which just happens to be exactly what you would like me to do.

I'm afraid you are moving into the realms of imagination here... :-)

So far as I am concerned, you are free to believe whatever you wish.

What I was indicating was that to accept your view I would need suitable
evidence and explanations dealing with the relevant points. Up to you if
you choose to beleive something without providing such. Also up to you if
you don't care what view I adopt.

However by asking the questions I have, others can read what I have
written, see your responses, and make up their own minds as to the
reliability of your opinions. That seems fair enough to me. People can make
up their minds as they see fit on the basis of the evidence presented, and
assess your views in the light of your comments to/about me.

[snip]



during the evening to give to some other station(s), but a higher
rate being available after midnight for the repeat. Would not
surprise me if similar 'audio' crudities turned up on DAB at times.


I thought you were talking about video?

Depends what comments I made that you are referring to.


Correct me if I'm wrong, but all of this seemed to be to do with
TV/video:

"FWIW in terms of video I have certainly seen very 'odd' effects at
times on BBCTV4 via DTTV. e.g. I have DVD+R's of one prom where the
'live' sic broadcast has a picture that 'stutters' throughout a large
part of the broadcast, but where the late-night repeat is fine. I assume
this was variable rate statmux stealing bitrate from BBCTV4 during the
evening to give to some other station(s), but a higher rate being
available after midnight for the repeat."


I have made some comments about the sound of R3 on 'Freeview'. I have
made some comments about the sound of BBCTV4 on Freeview. I have also
made a comment about the *video* on BBCTV4 on Freeview. How these may
be related, though, I am unsure.


Well, you were the bloody one making all the various points, so if you
don't know what point you were trying to make then how the bloody hell
should I know?

Perhaps by reading the various postings I have made with more care? You
might then realise why your comment here is misdirected. :-)

Only generalisation is that they all involve data-reduction
'compression' systems to communicate the information.


Give the man a Nobel prize.

Don't bother with the medal. Just send me the cash that goes with it. 8-]

BTW, you seem to be entering pedant mode, again. If at all possible,
please don't enter said mode again. TIA.

Are you a member of a 'pedant mode' branch of the 'net police'? :-)

Sorry if you are offended by the way I ask questions and make points. If
you can deal with them in a reasoned way I'd be interested in your replies.
But if you can't answer, or dislike them, or my style of writing, then it
is open to you to ignore them and make no reply.

You may find, though, that if you do become employed in R&D areas of
engineering/science then what seems to you to be a 'pedant mode' on my part
is not only common in such areas, but an expected approach for the
necessary rigour. I'm afraid that having to justify/support your ideas with
evidence and reasoning that survives critical questioning is often
unavoidable in such areas of work.

TBH I feel you would find that people would find your views and arguments
more persuasive if you kept to engaging in a polite and reasoned
discussion. Switching to being abusive or dismissive or arrogant is, I
fear, unlikely to convince many people. Particularly those who have any
background in the relevant areas of engineering or science and who expect
well reasoned arguments based on reliable evidence.

You have said you have specific knowledge of these areas, and the main
point you made seemed a reasonable and interesting one to me. For all I
know it may be entirely justified. Therefore I am dissapointed that instead
of providing useful replies to my own comments/questions you switch to
being abusive/ dismissive. I was hoping for more informative replies as I
had expected you could provide the info I was asking for. It would be
interesting to know if your thesis *is* correct. However your replies here
simply show that you are convinced of this and offended that anyone doubt
the correctness of your opinions. But I still have no idea if you are
actually correct or not.

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