"Jim Lesurf" wrote in message
...
In article , Serge Auckland
wrote:


At the time DAB was first put into service, and even within the first
year when take-up of receivers was exceedingly small, they had an
opportunity to change to MP3, but chose not to. Also, the choice of 48k
sampling was a mistake with hindsight, as sampling at a lower rate would
create less data, and therefore there is less data to reduce, with a
better sounding result.

I think we need to distinguish between data and information here. :-)

Absolutely right, and choosing a lower sample rate would create less data
whilst losing very little if any information.

My impression/understanding is that the actual amount of information
content for most music tends, statistically, to be relatively low once you
go above around 10-15kHz. One that basis I am not sure that dropping from
a
48ks/s to 32ks/s rate would have much effect on the amount of actual
spectral *information* to remove/keep.

This information has come from former friends and colleagues at the BBC.
Apparantly a significant contribution to data above 10-15kHz comes from
broadband noise. With a sample rate of 48k, a fair amount of data is created
just by coding noise. That's one of the reasons why the audio bandwidth is
being restricted before the MPEG coding process, so there's more data
available for coding what's considered important.


My understanding at present is that the BBC tend to use 48ks/s as their
standard rate for music recordings/broadcasts, etc. (At least for radio.)
On that basis it may make sense to avoid any unnecessary rate conversions
if they can.

Partly correct: The BBC have started a programme to replace all their on-air
studios with digital mixers. 44.1kHz sampling is used in all their radio
studios for the very good reason that music comes off CD (either directly,
or from a hard-disk playout system) and pre-recorded programmes come into
the BBC on CDR, thus also 44.1k sampled. Live microphone feeds are converted
at 44.1k and the final network output is converted only once to 48k for
DAB/DSat/DDTV distribution. BBC engineers are very keen to avoid multiple
sample-rate conversions.

Television studios and news studios(for both radio and TV) sample at 48k, as
in this case, there are fewer pre-recorded contributions at 44.1, so the TV
programme audio and news provide their output at 48k. This has created the
need for dual 44.1/48k routing, distibution and monitoring infrastructure
within Broadcasting House in London and in the main regional centres.


Sampling at 32kHz would have resulted in the same bandwidth as FM, and
have improved the DAB audio quality to match or even exceed FM.

Can you provide any actual evidence to support the above? It is an
interesting hypothesis, but I have no data on it, and am not at all sure
it
is correct. so I'd be interested to see any work that sheds light on it.

As mentioned above, this information was gleaned as part of my previous work
with the BBC and as the UK distributor for Orban processors. There is a
great deal of information on processing for DAB on Orban's web site
www.orban.com


However, we mustn't lose sight of the fact that in the UK, DAB has been
a success, driven by all the new services that are available on DAB
only. In the rest of Europe, DAB has been struggling, even has failed,
as they kept the quality up, but then didn't have the capacity for new
services. Joe Public can't see the benefit of DAB just to received the
same services as on FM, so receiver sales have been lamentable. No
receivers, no possibility of additional revenue.

As I understand it, in France DAB is ready for a resurgence, but only
after Broadcasters have seen the success of the UK model, lots of new
services at, for the public at least, acceptable quality.

I have mixed feelings about the above. :-)

Me too, but as far as I know, DAB has only been successful in the UK so far
where it has provided many additional servics, and has pretty much failed
elsewhere, especially where there have been no additional services. In
France, the overseas market I am most familiar with, all commercial
broadcasters either did not go to DAB or withdrew, when they found that
receiver sales were nil, and that the public wasn't interested in having DAB
to receive the same stuff they could get on FM. They are now looking to
relaunch DAB with additional digital-only services.


Happy New Year

S.