Freeview audio quality compared to DAB.

According to Commercial Radio Australia, "DAB+ implements AAC+ as the audio
compression codec, a far more modern technology which is an extension of
the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what a
lot of people think it is . What usually screws it is the amount of
digital transcoding and overdone processing long before it gets to the
listeners radio!...


quality audio can be
compressed into as little as 64 kilobits per second,

Quality eh?, what a variable that is;!...

compared with around
160kbps for the earlier DAB standard."


--
Tony Sayer

"tony sayer" wrote in message
...
According to Commercial Radio Australia, "DAB+ implements AAC+ as the
audio
compression codec, a far more modern technology which is an extension of
the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what a
lot of people think it is .

Is there any fundamental limit to FM quality?

Bill

In article , Bill Wright wrote:
According to Commercial Radio Australia, "DAB+ implements AAC+ as the*
audio
compression codec, a far more modern technology which is an extension of
the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what a
lot of people think it is .

Is there any fundamental limit to FM quality?

Well, theoretically it needs infinite bandwidth to carry all the sidebands
in order to form a perfect replica of the original modulating signal.

But then, digital systems theoretically need infinite sampling frequency and
an infinite number of bits in each sample to do the same.

So I guess it always boils down to practical limits based on human
perception, and the question then becomes "Whose perception?", and "Under
what conditions?", followed by "Who decides?"

Rod.

"Bill Wright" wrote in
:


"tony sayer" wrote in message
...
According to Commercial Radio Australia, "DAB+ implements AAC+ as the
audio
compression codec, a far more modern technology which is an extension of
the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what a
lot of people think it is .

Is there any fundamental limit to FM quality?

Bill



There is a 15KHz lowpass filter applied to the audio on FM so that audio
does not cause interference with the 19KHz stereo pilot tone. When I was
younger, I used to easily hear the 19KHz tone on a mono radio set.

Peter

PeterW wrote:
Mizter T wrote in
ups.com:

On 6 Aug, 17:13, "DAB sounds worse than FM" [email protected] wrote:

(snip)

The BBC at least will provide higher quality on DAB+.


If and when that happens.

There are absolutely no concrete proposals, let alone plans, to
transfer over to DAB+ by either the BBC or the commercial
broadcasters.

Bear in mind that there are now 5 million DAB sets out in the wild,
the vast majority of which can't be upgraded to DAB+, and no
broadcasters - having encouraged listeners to convert to DAB
receivers - are going to be keen on alienating those with this
equipment. No amount of wishful thinking will change that.

It's a shame because the DAB+ technology would certainly appear to be
preferable. We are however where we are.


The big problem with DAB is that MP2 is an old and not very good
codec and needs at least 192kbps to be subjectively like MP3 at
128kbps or AAC+ at about 96kbps. This corresponds to "near-CD
quality". However, Ofcom's perceived wisdom that "more is better"
applied it to channels rather than bandwidth resulting in lots of
horrible sounding stations on DAB.


Indeed.


Analogue compression (companding) is a separate issue and is
[over]used on all broadcasts except I think on BBC Radio 3.

According to Commercial Radio Australia, "DAB+ implements AAC+ as the
audio compression codec, a far more modern technology which is an
extension of the MPEG4 Advanced Audio Codec. 'Better-than-FM' quality
audio can be compressed into as little as 64 kilobits per second,
compared with around 160kbps for the earlier DAB standard."


I don't go along with that, to be honest, because I think it would require a
significantly higher AAC/AAC+ bit rate to match FM-quality.


See http://www.digitalradiotech.co.uk/bi...vs_quality.htm for
subjective compression graphs describing how annoying the perceived
digital compression is.

MP2 at 128kbps is described as "annoying" (96kbps is "very annoying")
MP3 at 128kbps is "slightly annoying"
AAC at 128kbps is "not annoying" (96 kbps is "slightly annoying")

Unfortunately the vast majority of UK DAB is therefore "annoying"
with the exception of Classic FM (annoying/slightly annoying) and BBC
R3 (slightly annoying). A good FM signal is not annoying.

The Estonians introduced DAB at 320kbps which sounds like a good
idea. Pity the UK didn't.

Freeview and Digital satellite has the advantage of a bit more
available bandwidth and therefore the MP2 compression can be less
than on DAB.


Yep - it's just a shame that the BBC is intent on not making the most of the
bit rate levels in use or increasing the bit rates, especially on satellite
where there's masses of bandwidth available - the BBC has 231 Mbps of
capacity on satellite, of which the radio stations only consume 0.7%, so
they could easily increase the bit rates of the stereo stations to 224 kbps
ot 256 kbps if they wanted to, but they just don't want to.


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

In article , Roderick Stewart
wrote:
In article , Bill Wright wrote:
According to Commercial Radio Australia, "DAB+ implements AAC+ as
the audio
compression codec, a far more modern technology which is an
extension of the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what
a lot of people think it is .

Is there any fundamental limit to FM quality?

Well, theoretically it needs infinite bandwidth to carry all the
sidebands in order to form a perfect replica of the original modulating
signal.

ahem ...for reasons quite distinct from those that arise in what you went
on to write about, below... :-)

But then, digital systems theoretically need infinite sampling frequency
and an infinite number of bits in each sample to do the same.

Pardon?

What bandwidth are you assuming the input signal to be sampled, has?

What dynamic range are you assuming the input signal has?

If your answer to both these questions is "infinite" then you aren't
talking about any real-world signals. If your answer is in terms of finite
values, then the required sampling rate and bit-depth are also finite. This
follows from basic Information Theory.

So your comment is only "theoretically" correct for signals which are
"theoretical". The real world can be kinder. ;- But this assumes, of
course, that those sampling the signal know what they are doing. Given what
crops up pun on some CDs I am not certain of that in every case.

So I guess it always boils down to practical limits based on human
perception, and the question then becomes "Whose perception?", and
"Under what conditions?", followed by "Who decides?"

Indeed.

What isn't clear from the above is what relationship there may be between
"quality" for FM and the effects of transmission bandwidth limitation. The
effect doesn't only depend on the frequency and amplitude of the audio
components. It also depends on if the audio has L-R components. (Ignoring
any multipath or tuner imperfections.) You can work out the distortion
levels for various test waveforms, but with music the situation is harder
to evaluate. As you say, "whose perception?"...

R3 FM traditionally tended to avoid this by keeping down the modulation
levels. However modern 'popular' stations generally seem to have a dynamic
range from 'very loud' to 'very loud' so may not do so... Hard to tell what
the FM "quality" is in such cases if they are also playing CDs that were
clipped or otherwise heavily limited before being sold.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.audiomisc.co.uk/index.html
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html

In article , Bill Wright
wrote:

"tony sayer" wrote in message
...
According to Commercial Radio Australia, "DAB+ implements AAC+ as the
audio
compression codec, a far more modern technology which is an extension
of the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what a
lot of people think it is .

Is there any fundamental limit to FM quality?

In theory or practice?

Jim Lesurf's site has plenty of info.

http://www.st-and.demon.co.uk/

--
*On the other hand, you have different fingers*

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

In article , Dave Plowman (News)
wrote:
In article , Bill Wright
wrote:

"tony sayer" wrote in message
...
According to Commercial Radio Australia, "DAB+ implements AAC+ as
the audio
compression codec, a far more modern technology which is an
extension of the MPEG4 Advanced Audio Codec. 'Better-than-FM'

Wonder how it makes it better?. FM properly done is better than what
a lot of people think it is .

Is there any fundamental limit to FM quality?

In theory or practice?

Jim Lesurf's site has plenty of info.

http://www.st-and.demon.co.uk/

Better to use http://www.audiomisc.co.uk/ these days as I am in the process
of moving hosting of audio material from demon. This means newer material
has been only appearing recently on the audiomisc site and the demon one
will vanish in due course.

Unless you had the uni 'Scots Guide' site in mind. However although that
deals with the basis of FM theory it doesn't go on to consider the real
effects of finite TX bandwidth as I judged that to be beyond what was
needed in a general introductory undergrad course. Generalised FM theory
can be a bit of a brain-teaser at times. :-)

FWIW The recent 'Hi Fi News' article on the effects of finite bandwidth on
FM stereo won't appear on the website for a few months. This is because I
tend to allow six months or more after magazine publication before putting
up a web version of an article.

However you might find

http://www.st-and.demon.co.uk/temp/fmspectra.html

of interest.

That is a temporary page I did recently during a discussion with Tony Sayer
about this issue. It shows the transmitted spectra for a few examples of
audio waveforms. In particular it illustrates how high frequency, high
level *difference* (L-R) modulation tend to spread over a much wider RF
bandwidth than mono components. The result being that they may run into the
bandwidth restrictions for broadcasting. Filtering the RF for transmission
(or filtering in the RX) will then lead to distortion. This is a
consequence of the way a 38kHz subcarrier was 'shoehorned' into FM to add
'stereo'.

The HFN article quantifies this for some specific examples of modulation,
etc, and gives a plot of how we can expect the level of distortion to rise
with audio level for a specific case. I'll put a version up in due course,
but there are a few other articles on other topics 'in the queue' in front
of it at present. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.audiomisc.co.uk/index.html
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html

On Thu, 09 Aug 2007 20:48:10 GMT, "DAB sounds worse than FM"
[email protected] wrote:

Zathras wrote:
On Thu, 09 Aug 2007 09:57:41 GMT, "DAB sounds worse than FM"
[email protected] wrote:

There's a simple way to avoid me bleating on about how excellent I
am, and that's to not try to belittle me in the way that you did.

*You* supplied the material with your idiotic and offensive
generalisation that smoking ban supporters are Nazis. You did your own
belittling..


Clearly you have an extremely short memory. Here's what you wrote:

"DAB was a failure out of the box (nothing to do with you).
When the public didn't buy into it (nothing to do with you), it was
only a matter of time until manufacturers lost interest (nothing to do
with you) and then forced the issue.

The powers that be would have ignored you (if they ever heard of you)."

Hello..testing testing..anybody in there....? If my memory is
short..yours is shorter. Go back to where I entered this thread and
check out your bragging, over-long, response to that point. Note how
*I* didn't ask for *any* information about your alleged DAB
contribution but, somehow, got it anyway!

In any case, going round in debating circles like this is quite dull,
if you want to go on and on about how brilliant you are and
substandard or Fascist anybody else is, feel free to take it to Email.

--
Z