DAB discussions on BBC Radio 4

"Roderick Stewart" wrote in message
...
On Wed, 25 Dec 2013 08:55:11 +0000 (UTC), Tweed
wrote:

What really surprises me is how much better the car receiver appears to be
than the various DAB radios I have in the house. If the latter performed
as
well as the former there would be a lot less complaints about poor
reception and bubbling mud.

It shouldn't surprise you, as the reason is perfectly plain. try
running a car engine in your living room while listening to your
hi-fi, and see if you can hear any bubbling mud.

Bill's Rolls-Royce is totally silent.
--
JohnT

In article
, Tweed
wrote:


The audio quality argument needs to move on - as I've said, Internet
delivery of high quality streams is the way to go for static domestic
installations.

True as that may be for those who have an internet connection that can cope
with it, I am reluctant to accept the argument whilst we in Scotland
continue to be denied the same sound radio quality for the same periods for
R1-4 as the rest of the UK.

Radio delivery, being something that comes via a finite
resource, will always have the audio quality pinned back to the bare
minimum regardless of the encoding mechanism.
It didn't happen with FM
because there wasn't an easy way of doing this.

It didn't happen with BBC FM because the engineers worked steadily for
decades to keep on improving the audio quality! If you were right they'd
have left it with the mono quality we got from GPO landlines and mono from
the start.

The key distinction was that back then the engineers were driving the
system forward and had an interest in improving quality as well as
coverage. Now the suits and accountants rule and they just want the minimum
spend for the maximum dumbest audience.

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

In article , Roderick Stewart
wrote:
On Tue, 24 Dec 2013 18:54:44 -0000, "Robin" wrote:

Leaving aside issues which would be of interest to only a very small
fraction of few listeners, what if any technical details are necessary
to deal with issues such as audio quality, coverage, compatibility with
other states, cost and power consumption?

Bit rate.

Higher means fewer stations with better sound quality.

Lower means more stations with inferior sound quality.

Sound quality is not the same thing as reception. A digital signal with
a low bit rate can be received perfectly reliably throughout the service
area and still sound rubbish.

Lack of technical info also allows people to be confused about DAB and
DAB+. Also fall prey to arguments of the kind that appeared again in the
programme where an answer blurs different systems to make misleading
claims. e.g. being told how many countries have adopted 'digital radio'
without saying how many are DAB rather than DAB+. Ditto for similar
assertions in the past about how many in the UK use 'digital' radio - thus
conflating the internet and freeview with DAB to justify a decision about
DAB versus FM.

It might also be worth mentioning that when the service was started it
did have a higher bit rate and the sound quality was praised by those
who care about it, and after the bit rate and the quality were
subsequently reduced to squeeze in lots of extra stations, some of those
stations have been closed down through lack of interest.

Indeed. Another point people can't appreciate without careful technical
explanation is that encoders can improve, even using the same basic codec.
So sound quality could have *improved* at the same bitrate and using the
same RXs *if* this had been what the engineers were allowed to get on with.

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

"Scott" wrote in message
...
On Wed, 25 Dec 2013 09:11:19 +0000, Roderick Stewart
wrote:

On Tue, 24 Dec 2013 18:54:44 -0000, "Robin"
wrote:

Leaving aside issues which would be of interest to only a
very small
fraction of few listeners, what if any technical details
are necessary
to deal with issues such as audio quality, coverage,
compatibility with
other states, cost and power consumption?

Bit rate.

Higher means fewer stations with better sound quality.

Lower means more stations with inferior sound quality.

Sound quality is not the same thing as reception. A
digital signal
with a low bit rate can be received perfectly reliably
throughout the
service area and still sound rubbish.

It might also be worth mentioning that when the service
was started it
did have a higher bit rate and the sound quality was
praised by those
who care about it, and after the bit rate and the quality
were
subsequently reduced to squeeze in lots of extra stations,
some of
those stations have been closed down through lack of
interest.

I know I have raised this before, but surely the space
occupied by DAB
must be a very small part of Band III (compared to the
nation's
independent televiision service). Is it five DAB
multiplexes per TV
channel? I still can't see why they cannot find some
space (through
efficiencies by another user, for example) to provide a
second BBC
multiplex which would allow all the bitrates to be doubled
and keep
everyone happy (except possibly that doubling R3 would
exceed the
maximum for many receivers).


Actually four DABs per mux, that's why they are A-D
suffixed.

UK DAB (i.e. mp2) can actually work up to 320K - as was
tried in Germany - but you get very few stations then... UK
DAB was never intended to work above 192K (which is what
BBCR3 uses even now during the day) so most non-car radios
are software limited at 192K. Cars however have to work
anywhere so will work at any data rate.

mp3 at 128K (as used by most stereo stations) would sound
significantly better than mp2 does now: aac or aac+ as will
be used on DAB+ will give near CD quality (certainly no
really noticable difference other than on a hi-fi system) at
128K.

We can but hope.......


--
Woody

harrogate three at ntlworld dot com

In article ,
Roderick Stewart wrote:
On Wed, 25 Dec 2013 08:55:11 +0000 (UTC), Tweed
wrote:

What really surprises me is how much better the car receiver appears to
be than the various DAB radios I have in the house. If the latter
performed as well as the former there would be a lot less complaints
about poor reception and bubbling mud.

It shouldn't surprise you, as the reason is perfectly plain. try running
a car engine in your living room while listening to your hi-fi, and see
if you can hear any bubbling mud.

The audio system in my car is rather superior to the average portable
radio. And capable of producing more level above ambient noise.

--
*I'm not your type. I'm not inflatable.

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

In article , JohnT
wrote:

Bill's Rolls-Royce is totally silent.

So's mine. Maybe that's why I can never find it...

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

In article , Woody
wrote:


UK DAB (i.e. mp2) can actually work up to 320K - as was tried in
Germany - but you get very few stations then... UK DAB was never
intended to work above 192K

I'd thought the pre-service tests narrowed down onto using 256k as
standard. And that 256k was what was used initially by the BBC before they
started stuffing a quart into a pint pot. In essence this matches their use
of 256k as standard for Freeview TV - until now in Scotland.

(which is what BBCR3 uses even now during the day) so most non-car
radios are software limited at 192K.

Interested to know where that info comes from.

mp3 at 128K (as used by most stereo stations) would sound significantly
better than mp2 does now: aac or aac+ as will be used on DAB+ will give
near CD quality (certainly no really noticable difference other than on
a hi-fi system) at 128K.

Erm "Near CD quality" is one of those vague terms that is easily misused.
The BBC R3 iplayer stream now uses 320k aac as the default.

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

On Wed, 25 Dec 2013 08:55:11 +0000 (UTC), Tweed
wrote:

The audio quality argument needs to move on - as I've said, Internet
delivery of high quality streams is the way to go for static domestic
installations.

Would you like to define 'high quality' because I'm afraid that a lot of
people have either forgotten or don't know what that is.

--
Alan White
Mozilla Firefox and Forte Agent.
By Loch Long, twenty-eight miles NW of Glasgow, Scotland.
Webcam and weather:- http://windycroft.co.uk/weather

On Wed, 25 Dec 2013 12:21:02 +0000 (GMT), Jim Lesurf
wrote:

I'd thought the pre-service tests narrowed down onto using 256k as
standard. And that 256k was what was used initially by the BBC before they
started stuffing a quart into a pint pot.

I thought that too, in fact I'm sure of it.

--
Alan White
Mozilla Firefox and Forte Agent.
By Loch Long, twenty-eight miles NW of Glasgow, Scotland.
Webcam and weather:- http://windycroft.co.uk/weather

In article , Alan
wrote:
On Wed, 25 Dec 2013 12:21:02 +0000 (GMT), Jim Lesurf
wrote:

I'd thought the pre-service tests narrowed down onto using 256k as
standard. And that 256k was what was used initially by the BBC before
they started stuffing a quart into a pint pot.

I thought that too, in fact I'm sure of it.

In addition, at the time the BBC 'experimented' with lowering the R3 DAB
rate below 192k they did this off the back of buying new encoders. Alas,
they introduced these around the start of the 'proms' one year generating a
storm of protests due to the fall in quality. At the time the increase in
artifacts was obvious. *However*...

A point that some forget and many others simply don't know is that the same
codec and bitrate can deliver a range of sound quality levels. Depends on
the skill and care of the *encoding* details - e.g. the 'judgement rules'
used to thin down and re-quantise the components in the transform output
and when to hop various settings.

Talking to one or two engineers at the time, their view was that the
drastic fall in quality was largely due to them not having had time to
experiment and adopt the best settings for their new encoders. And during
the next few weeks, the quality did improve for the given rates as they
learned what worked best for material typical of R3 rather than general
pop/speech which were the assumptions behind the 'standard as delivered'
settings.

They'd switched to the new encoders in the hope of *improving* sound
quality, but were caught out circumstances.

So this is far more complex than simplistic "DAB+ is better than DAB" and
"256k is better than 192k". Many such statements may have truth, but only a
part of a larger set of factors. Alas, suits and accountants simply then
assume this means they can squeeze more into the pot without giving the
engineers a chance to explain the problems. As duly showed up when the
above happened! The results undermine confidence as well as quality.

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