Layer II + SBR

[JA Rowson]

I haven't heard much on the progress of SBR with DAB recently. I've pretty
much come to the conclusion that it won't be implemented as to do so would
require cutting the sound quality even further on none SBR enabled sets.
(yes it could get even worse!) Yet I could be wrong.... does anyone have any
more up to date info? For instance are there any sets that are capable of
decoding the SBR, for sale yet?

Cheers.

[David Robinson]

Post by JA Rowson
I haven't heard much on the progress of SBR with DAB recently. I've pretty
much come to the conclusion that it won't be implemented as to do so would
require cutting the sound quality even further on none SBR enabled sets.
(yes it could get even worse!) Yet I could be wrong.... does anyone have any
more up to date info? For instance are there any sets that are capable of
decoding the SBR, for sale yet?

I can't answer your question, but it's worth pointing out that another
possible development is "parametric stereo", where existing receivers
decode a standard mono signal, while new receivers use extra
information to re-build the full stereo version (or something like
it!).

I haven't heard this mentioned with respect to DAB yet, but it's
certainly a technology that's being deployed in modern low bitrate
codecs (e.g. some of the latest versions of AAC). I could imagine, for
example, 80kbps mono mp2 plus a 16kbps "helper" stream would deliver a
kind of stereo in 96kbps (total) that could easily beat the worst
128kbps which stations you can find on DAB today.

I can conceive of that being popular, because even more stations could
be crammed into a single multiplex. Only existing _stereo_ receivers
would become out of date, because all the mono evokes etc will carry
on as normal!

However, it's not an answer to the audio quality problems. Neither SBR
nor parametric stereo are designed to deliver transparently coded
audio - they're designed to "make the best" of low bitrates.

Cheers,
David.

[DAB sounds worse than FM]

Post by JA Rowson
I haven't heard much on the progress of SBR with DAB recently.

I've not seen it mentioned, either.

Post by JA Rowson
I've
pretty much come to the conclusion that it won't be implemented as to
do so would require cutting the sound quality even further on none
SBR enabled sets.

There's supposedly 500,000 DAB receivers sold already, and they expect
another 500,000 to be sold this year, so maybe they think it's already
too late? If so, then this would be the most recent in a long line of
terrible technology decisions regarding DAB.

Post by JA Rowson
(yes it could get even worse!)

As far as I was concerned, limited, short-term pain would allow plenty
of gain and whichever companies opposed SBR were wrong (I believe that
some WorldDAB Forum members were in favour, some were against).

Post by JA Rowson
Yet I could be
wrong.... does anyone have any more up to date info? For instance are
there any sets that are capable of decoding the SBR, for sale yet?

No.

[JA Rowson]

Post by DAB sounds worse than FM
As far as I was concerned, limited, short-term pain would allow plenty
of gain and whichever companies opposed SBR were wrong (I believe that
some WorldDAB Forum members were in favour, some were against).

Completely agree, and let us all not forget that over 400,000 FM sets were
rendered useless after World War II in the USA, due to the frequency
re-allocation. Now I'm sure that an FM radio set back then was a BIG
investment. Therefore in today's climate - although a million sets rendered
worse, is not a good thing for those million owners (or whatever it'll be by
the end of the year) - the FM system as we know it today is proof that a
system can be changed in the early stages and turn out to be successful long
term.

Will it change though? I guess probably not, there is far too much arrogance
and money tied up in the industry! :-(

Have a look at http://ieee.cincinnati.fuse.net/reiman/09_1994.html

Cheers,
John

[DAB sounds worse than FM]

Post by JA Rowson

Post by DAB sounds worse than FM
As far as I was concerned, limited, short-term pain would allow
plenty of gain and whichever companies opposed SBR were wrong (I
believe that some WorldDAB Forum members were in favour, some were
against).

Completely agree, and let us all not forget that over 400,000 FM sets
were rendered useless after World War II in the USA, due to the
frequency re-allocation. Now I'm sure that an FM radio set back then
was a BIG investment. Therefore in today's climate - although a
million sets rendered worse, is not a good thing for those million
owners (or whatever it'll be by the end of the year) - the FM system
as we know it today is proof that a system can be changed in the
early stages and turn out to be successful long term.

Absolutely, but I very much doubt it will change now, mainly because
they've now got a load of manufacturers on-board and producing kit, and
they'd no doubt set their lawyers into action to re-claim any changes,
although I'm not sure who they'd sue.

Post by JA Rowson
Will it change though? I guess probably not, there is far too much
arrogance and money tied up in the industry! :-(

Absolutely. That's all it is about these days. What is right from an
engineering perspective is virtually irrelevant. Here's a direct quote
from the head of BBC R&D (maybe the ex-head, but he was the head at the
time):

"6 stations per mux, but that's pushing it a bit"

The BBC now has 12 stations on its mux when R5 Sports Extra is on-air,
and 13 when R5 Sports Extra and R4 LW secondary service is on-air at the
same time as R5 Sports Extra. Clearly the views of the engineers that
developed DAB have been completely ignored, and the marketing and
accounting bods took over as soon as the engineers let go.

Post by JA Rowson
Have a look at http://ieee.cincinnati.fuse.net/reiman/09_1994.html

Very interesting, and a very accurate precedent, although times have
changed, and I think we both know that SBR won't be added now, because
engineers' opinions don't count any more.

It's interesting to compare DAB using the MP2 codec with DVB-H using the
HE AAC codec. I wrote this on my home page today:

"It's interesting to compare the combination of DVB-H using the HE AAC
codec with the DAB system which uses the MP2 codec. The best way to
compare these 2 systems is to compare how many digital radio stations
with the same level of audio quality they can fit into a given amount of
spectrum:

DVB-H allows a capacity of 11 Mbps in an 8 MHz channel, which gives a
spectral efficiency of 1.375 bits/s/Ha.

DAB allows a capacity of 1.15 Mbps in a 1.7 MHz channel, which gives a
spectral efficiency of 0.676 bits/s/Hz.

HE AAC at 64kbps (ignore the values in the article linked-to, they're
not correct) can provide an audio quality similar to 192 kbps MP2, so HE
AAC is 3 times as efficient as MP2.

Combining the above figures:

relative efficiency = (1.375 / 0.676) x 3 = 6.1

So, DVB-H using the HE AAC codec is 6.1 times as efficient as DAB using
the MP2 codec, which means that you could fit 6.1 times as many digital
radio stations into a given bandwidth using DVB-H as you can with DAB."

IMO it's not too late for the broadcasters to use DVB-H, and it could be
used on Band III. But I think one thing that would stop them from using
it is the egos of a lot of the decision-makers at the BBC, Ofcom, and
the commercial radio groups. If you looked at it dispassionately then
DVB-H just leaves DAB standing in terms of efficiency, which would
result in reductions in cost of transmitter hardware, cost of
transmission, cost of maintenance. But, as I said, the egos of those
that think they know best are in the way, and I'm sure we'll end up with
DAB providing lousy audio quality for decades to come.