"Fredxx" <(E-Mail Removed)> wrote in message
news:h1udcv$fgc$(E-Mail Removed)
> "Kráftéé" <kraftee@b&e-cottee.me.uk> wrote in message
> news:(E-Mail Removed)...
>> DAB sounds worse than FM wrote:
>>> "Alan" <(E-Mail Removed)> wrote in message
>>> news:(E-Mail Removed)
>>>> In message <(E-Mail Removed)>, DAB sounds worse
>>>> than
>>>> FM <(E-Mail Removed)> wrote
>>>>> There's a 10 Downing St petition to stop FM/AM being switched
>>>>> off:
>>>>>
>>>>> http://petitions.number10.gov.uk/AM-FM-Radio/
>>>>>
>>>>> Please sign. Thanks.
>>>>>
>>>>>
>>>>
>>>>
>>>> Why would anyone want to sign something that may prevent us
>>>> getting
>>>> hundreds of radio stations on DAB?
>>>
>>>
>>> What you say is wrong for the following reasons:
>>>
>>> * The Digital Britain report said that the FM band would be used
>>> for
>>> "ultra-local" FM stations once all of the bigger FM radio stations
>>> have been switched off. So FM actually isn't planned to be
>>> switched
>>> off, so the FM band couldn't be freed up for DAB anyway
>>>
>>> * DAB uses frequencies of around 200 MHz, whereas FM uses
>>> frequencies of around 100 MHz - i.e. DAB couldn't be transmitted
>>> in
>>> the FM band anyway
>
> DAB can be transmitted at any frequency, it doesn't have to be
> 200MHz. It's just what was available.
Yes, but DAB receivers can only receive signals that are transmitting
in Band III or L-band - and there are no multiplexes in L-band in the
UK.
> The bandwidth for DAB and FM aren't much different.
>
>>>
>>> * DAB won't be getting any more spectrum than it's already got,
>>> because DAB spectrum was all allocated to Europeam countries in
>>> 2006
>>> (there is one unused DAB channel at the moment that was going to
>>> be
>>> used for a 2nd national commercial multiplex which fell through
>>> when
>>> Channel 4 decided against entering radio last year, but I think
>>> that's just going to be pretty much wasted when they replan the
>>> spectrum)
>>>
>>> * Apart from in London, where I think the figure is around 55
>>> stations, people can typically receive about 35 radio stations on
>>> DAB. DAB could never carry hundreds of radio stations. DAB was
>>> designed in the 1980s. It is an incredibly inefficient system
>>> because the technologies it uses are so old.
>>>
>>> Some other things that you might like to bear in mind which it
>>> sounds like you're probably unaware of at the moment are that
>>>
>>> * DAB provides lower audio quality than FM, Internet radio and
>>> radio
>>> via digital TV
>>>
>>> * DAB's audio quality isn't going to get any better in future
>>> because the MP2 audio codec it uses is 20 years old so they've
>>> obviously been optimising it for years but it still sounds crap at
>>> the low bit rates that it's used at in the UK
>
> Agreed - DAB bit rates are embarrasingly low. I have no idea why
> MP2 was
> chosen.
They held listening tests in 1990 at Swedish Radio where they compared
a load of codecs and boiled it down to 2, which went on to become MP2
and MP3. They chose MP2 because - get this - MP2 provided higher
quality than MP3 at high bit rate levels - above 192 kbps basically.
Also, MP2 decoders have a lower computational complexity than MP3, and
MP2 allowed lower error correction coding with a computational
complexity as well. In 1990 when electronics were extremely slow and
expensive compared to today the difference in computational complexity
might have mattered, but it was a bad long term decision. And as for
the decision to go with MP2 because it provided higher quality than
MP3 at high bit rates that was an even worse decision. What they
should have done IMO was implement MP3, which was designed to be
backwardly compatible with MP2 anyway, then let the broadcasters
decide. What they did was cripple the whole system by adopting MP2 -
and the fools didn't even bother to upgrade the codec since even
though AAC was standardised in 1997, and development of it began in
1994. Basically, it's a textbook lesson of incompetence.
Apparently the BBC R&D dept were recommending AAC to be used in the
late 1990s, but the BBC execs obviously ignored them.
> Even DAB+ isn't compatible with old DAB. All in all, a complete
> mess!
It's definitely a complete mess - the fact that DAB+ had to be
designed just 3 years after the BBC had properly launched DAB in 2002
shows how incompetent the broadcasters were in choosing to go with DAB
without upgrading it first.
To be fair to them about DAB+ though, DAB+ was designed to solve DAB's
problems, so they added the AAC+ audio codec to make DAB more
efficient and added RS error correction coding to make receptino more
robust - but DAB receivers produced up to that point didn't support
AAC+ or RS coding, so they had to accept non-compatibility.
--
Steve -
www.savefm.org - stop the BBC bullies switching off FM
www.digitalradiotech.co.uk - digital radio news & info
"It is the sheer volume of online audio content available via
internet-connected devices which terrifies the UK radio industry. I
believe that broadband-delivered radio will explode in the years to
come, offering very local, unregulated content, as well as opening a
window to the radio stations of the world." - from the Myers Report
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