DAB Performance of different makes?

Jim Lesurf wrote:

Once you've sent me the info I'll reply to the rest of your post.

Don't worry. I think I can live happily enough without it. :-)

TBH I suspect that those reading this thread can make up their own
minds about which of us they would be inclined to agree with w.r.t
what we have been discussing, and about you snipping most of what I
wrote above.
So I am happy for people to draw their own conclusions...


Okay, I publicly apologise for the way I acted in trying to get you to
send me the information. I admit that what I did was wrong, and the only
reason I did it was that I'd already requested the information from you
and hadn't got a reply, but you had written a long post on this thread
and I felt you were ignoring my request.

I apologise, and I can do no more than that.


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

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

On Fri, 28 Oct 2005 10:06:13 +0100, Jim Lesurf
wrote:

Does anyone else think that what I have been saying was unclear and
"ambiguously worded"?

No, it was perfectly clear.

--
Alan White
Twenty-eight miles NW of Glasgow, overlooking Loch Goil and Loch Long in Argyll, Scotland.
Web cam and weather:- http://www.windycroft.gt-britain.co....her/kabcam.htm
Some walks and treks:- http://www.windycroft.gt-britain.co.uk/walks/

Alan White wrote:
On Fri, 28 Oct 2005 10:06:13 +0100, Jim Lesurf
wrote:

Does anyone else think that what I have been saying was unclear and
"ambiguously worded"?

No, it was perfectly clear.


Hahahahahhahahahahahahahahahahhahahahahhahaha.


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

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

On Fri, 28 Oct 2005 11:45:23 GMT, DAB sounds worse than FM wrote:
Nobody Here wrote:
On Fri, 28 Oct 2005 10:10:32 +0100, Jim Lesurf wrote:
In article ,
Nobody Here wrote:
DAB sounds worse than FM wrote:

Actually, I emailed you yesterday with a request for some
information that's important to something I'm currently doing. So,
if I'm going to provide you with a load of information then I
think it's only fair that you provide me with the information that
you've said you've already got and that I need.

Once you've sent me the info I'll reply to the rest of your post.

Wow, another example of absolutely unbelievable arrogance. You
really do understand how to get the best from people, don't you?

Apparently so. :-) Indeed I was so impressed when I read the above
that I deleted the email I had just written to send to Steve
regarding the questions he'd asked me.

LOL. I bet that happens a lot :-)


I have already put you in my killfile twice. If you try to circumvent my
killfile filter again I *will* send an abuse report to .

Go on then.

--
Nobby

In article , Peter Bunclark wrote:
Well since you mention it... I've always been disappointed by the
appearance of the pitch on digital transmission of football matches.
The smeared-together greens are, in my subjective opinion, the
single worst digital artifact.

Not to mention the entire picture going blocky on slow fades, or any
lighting change that effectively requires every pixel to change value
simultaneously. These situations represent extremely low frequency
components in the analogue domain, so you might expect them to be
easily handled by any transmission system, but they make a sudden large
demand on bit rate in the digital domain, so any system that uses lossy
bit rate reduction can't cope with it at all.

Not that I would go back to fuzzy,
speckled, narrow-vision.
I'm hoping that HD will give us our grass back.

It seems doubtful unless the bit rates are also raised. It isn't the
fundamental resolution of the image that smears the grass, because
normal unadulterated standard-definition television easily has enough
pixels to show it properly. It's just the digital processing that
throws the information away.

Rod.

Jim Lesurf wrote:

Ah! OK. So the intensity/volume your reactions is due to a worry that
someone might be daring to even imply that others might not accept
everything you say. :-)

Since you have now said the above I can reconfirm that you are
jumping to the wrong conclusion, and misunderstanding what I have
been saying.


I do *now* accept what you were asking. I do still think your wording of
the particular paragraph was ambiguous, so we'll have to agree to
disagree and leave it at that.


See below for more details...

There will always be bit errors, and different DAB modules will
perform differently.

Yes! That is the kind of thing I have been asking about - with the
aim of identifing the *actual* differences between *specific* RXs in
various specific situations. For the reasons I have (twice) explained.


The output BER is the all-important parameter, and two receivers which
have an identical BER should provide effectively identical output audio
quality (assuming, say, that the audio is routed via S/PDIF to the same
DAC).

However, even with an identical output BER (the BER after the Viterbi
decoder) there may be very slight differences between the performance of
different DAB chipsets/modules. The possible differences could be caused
by different implementations of the Viterbi algorithm such that the
distribution of uncorrectable errors over the different parts of the
audio frame are different.

I'll explain what I mean by that:

DAB uses UEP (unequal error protection) where different parts of the
audio frame are protected with different error correction code rates:
the audio frame header uses a low code rate for high protection, whereas
the audio samples themselves use a higher code rate and thus offer lower
protection.

Therefore, if different chipsets/modules have implemented the Viterbi
algorithm differently (e.g by using a different constraint length) then
it is possible that the different chipsets/modules output a slightly
different distritution of uncorrectable errors over the different parts
of the audio frame, but still have the same overall output BER.

Personally, I think it's unlikely that it is very unlikely that this
would be significant, because the different code rate levels offer
markedly different protection levels to the different parts of the audio
frame, so I would say it is extremely likely that the distribution of
errors over the different protection levels will be the same.

Different receivers will have different RF performance, but this is --
or should be -- pretty irrelevant if the output BERs are equivalent, for
the reason I've just given.

You would expect the MP2 audio decoders would all pass the strict
conformance requirements, but there probably will be very, very slight
differences in the output PCM audio bitstream produced even for the same
input data stream (but due to the strict conformance requirements I
don't think this should be significant to the output audio quality).


But if the BER is low, then the differences in the AUDIO bitstream
coming out of the decoder will be slight.

That may be the case. Since you say the above can you direct me to
some measurement on the RXs currently on sale that examine the
outputs and show that they are either identical (i.e. same series of
output samples) or very similar? What you say above sounds quite
plausible, but I have been asking for evidence. Can you please direct
me to some?


No, I can't direct you to any evidence.

There's 2 chipset/module design companies: Radioscape and
Frontier-Silicon, and they account for probably 95% or more of all DAB
receivers sold in the UK. They may use different RF front ends, but my
impression is that receivers usually install full modules provided by
these companies. Having said that, from reading people's experiences,
there does seem variability of reception quality for things like DAB
personal radios, so there may be some model-specific stuff as well.


Bear in mind that someone who wishes to use, or starts using, a DAB
RX may well have read various statements about DAB, and about digital
systems more generally. These sometimes include the *misleading* ones
which the BBC have been guilty of making at times. They also include
comments by you, me, and various others. They also include comments
meant more generally like "digital either works or it doesn't".

Thus they may - in some reception situations with some RXs - be
puzzled to find the results may be variable, and may be *worse* than
they have been
led to expect. In some cases a change of RX *might* have a noticable
effect on this.


Absolutely! ;-)


However (third time) the reason I am interested in this is to try and
find reliable info on what variability in performance there may be in
RXs - both when RF reception is poor (in various ways) and when it is
good. However to assess this, as an engineer/academic, I like to find
measured and checkable data.


I don't think you'll find any, to be honest.


Thus I have been asking for it. Hence I
also welcome what you wrote above as it seems you may have some
information on this point. I have
not been asking (or arguing) about the audible effects produced by
the choice of bitrates.


Okay.


I hope it is now as clear to you what I have been saying/meaning.


It is *now*, yes. But I maintain that your original wording was
ambiguous, and we'll have to agree to disagree on that.

Different DAB receivers will have different performance. I think that
for the same output BER there wouldn't be any perceptible differences in
the audio quality, as I explained above. But there will be differences
in the way some or all of the different digital receiver parts are
implemented, such as:

* different ADC sampling rates and world-length
* different choice of IF (which determines the ADC sampling "mode", i.e.
undersampling, oversampling)
* different FIR filter lengths, hence attenuation specs
* different downconverter implementation
* different time and frequency synchronisation algorithm implementations
(very important to performance)
* different FFT implementation. i.e. different world-length
* different world-length at different stages in the receiver
* different Viterbi algorithm implementation

There's a lot of scope for variability in the things above.

Then there's the RF front-end performance.

So, yeah, different DAB modules/chipsets will perform differently wrt to
performance at different input signal strengths. I don't think you'll
find any measurements of this though. There's sensitivity values on the
Frontier-Silicon website, IIRC, and the Radioscape website might have
some similar information. But you want more detailed information, and
I've never seen any.



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

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

On Fri, 28 Oct 2005 12:18:35 GMT, "DAB sounds worse than FM"
wrote:

Alan White wrote:
On Fri, 28 Oct 2005 10:06:13 +0100, Jim Lesurf
wrote:

Does anyone else think that what I have been saying was unclear and
"ambiguously worded"?

No, it was perfectly clear.


Hahahahahhahahahahahahahahahahhahahahahhahaha.


That sounds like a jackass.

See:-

http://aviary.owls.com/kookaburra/kookaburra.html

HTH

--
Alan White
Twenty-eight miles NW of Glasgow, overlooking Loch Goil and Loch Long in Argyll, Scotland.
Web cam and weather:- http://www.windycroft.gt-britain.co....her/kabcam.htm
Some walks and treks:- http://www.windycroft.gt-britain.co.uk/walks/

Nobody Here wrote:
On Fri, 28 Oct 2005 11:45:23 GMT, DAB sounds worse than FM wrote:
Nobody Here wrote:
On Fri, 28 Oct 2005 10:10:32 +0100, Jim Lesurf wrote:
In article ,
Nobody Here wrote:
DAB sounds worse than FM wrote:

Actually, I emailed you yesterday with a request for some
information that's important to something I'm currently doing.
So, if I'm going to provide you with a load of information then I
think it's only fair that you provide me with the information
that you've said you've already got and that I need.

Once you've sent me the info I'll reply to the rest of your post.

Wow, another example of absolutely unbelievable arrogance. You
really do understand how to get the best from people, don't you?

Apparently so. :-) Indeed I was so impressed when I read the
above that I deleted the email I had just written to send to Steve
regarding the questions he'd asked me.

LOL. I bet that happens a lot :-)


I have already put you in my killfile twice. If you try to
circumvent my killfile filter again I *will* send an abuse report to
.

Go on then.


Actually, I did read your posts on Google Groups this morning to see
your reaction to being blocked, and I think it was Dave that said people
should just put someone in their killfile without telling them. I think
I'll do that with you from now on, because that way the only way you'd
know that your posts would be visible to me would be if you had just
changed your email address. If you want to be that sad, then be my
guest.

I'll just keep killfiling your new email addresses and ignoring your
posts. Eventually, you will get bored of your pathetic little game. And
make no mistake about it, it is pathetic.

You slag my behaviour off. You really need to look in the mirror, Mr
Perfect.


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

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

Geo wrote:
DAB sounds worse than FM wrote:

Look, I've put you in my killfile. Get the message.

That sounds like a good idea, after all you just spout the same
tedious crap over and over again, you've said it plenty times, you
don't like DAB, lucky you, but we've got the message.


I'm devastated that you don't like what I post about.


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

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

"Jim Lesurf" wrote in message
...
In article , DAB sounds worse
than FM wrote:
Jim Lesurf wrote:
[snip]


Since you have now said the above I can reconfirm that you are jumping
to the wrong conclusion, and misunderstanding what I have been saying.


As I said previously, I feel your original post was ambiguously worded,
so try and accept some responsibility for what you've written rather
than blaming me for mis-interpreting somethign that you've written which
WAS ambiguous. If that is okay with you?

I accept that is what you feel.

Does anyone else think that what I have been saying was unclear and
"ambiguously worded"? My impression thus far is that others have
understood
what I have written, but maybe I am wrong...


[snip]

No you're not wrong - all 3 explanations have been perfectly clear

--
Paul Schofield