All posts by Trevor Harris
Below are all of Trevor Harris's postings, with the most recent are at the bottom of the page.
@Mark
DAB+ does not give only a slight improvment in error correction. DAB uses unequal error protection using convolutional error correction coding. This means that different parts of the DAB signal have different levels of correction. The part of the stream which contains the audio information has the lowest level of correction. The overal level of correction is very weak compared to DAB+.
I don't know where you got the 2% figure but that certainly not my experience. In fact DAB is famous for the burbling sound it can produce under non ideal conditions. DAB+ gives a much sharper cutoff with weak signals.
For a good comparision of DAB and DAB+ see
DAB vs DAB+
Although DAB+ is much better than DAB it still cannot replace FM. The BBC could be charged with misselling DAB. Infact they had to pull some of thier adverts where they claimed that DAB was CD quality.
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@brianist
Your second point is correct. However, the "market" has spoken: the public like choice over audio quality.
Not true. When Ofcom did thier public consultation on lowering bitrates there was overwhelming opposition. Ever since the public have been voting with thier wallets and not buying grotty DAB radios.Talk of the FM switchoff is to scare people into going to DAB.
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There are some internet stations transmitting FLAC. The only problem is the high bitrates but it is possible over 3G in a good area. With 4G even better. I use FLAC for archiving.
The best audio source is Blu-ray LPCM up to 24bit,192khz sampling frequency, 8 channels, 27.648 mb/s. Now thats what I call quality.
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Ok found some figures for Ofcoms own survey
What do you see as the main advantage of listening to Digital Radio? (Spontaneous)
Better sound quality 63%
Extra Stations 21%
Which of these do you think would be particular benifit to you? (Prompted)
Better sound quality 57%
Extra stations 36%
There are other surveys which gave similar results.
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The survey was with "All analogue radio listeners who know alot / a little about digital radio" and was carried out for Ofcom by Mori.
@PJH
"The general public haven't a clue about what sound quality means with regard to DAB Trevor. "
I find that a very insulting comment. They may not appreciate the technical details but they can appreciate the difference between poor and good quality sound. Infact most audio quality testing is done with non experts and is found to be consistant with the expert opinion.
Infact in a subsequent consultation the public were opposed to the bitrate lowering and it was only the broadcasters who wanted it. Reading the report it becomes clear that the main motive was financial. Ofcom also stated that they did not believe that most broadcasters would lower the bitrate but they were proved wrong.
It is quite clear that Ofcom was not acting in the public interest.
@MikeB
They might be buying DAB radio but it does not mean they are listening to DAB. I have an Internet/FM/DAB radio but I certainly do not listen to DAB awfull noises.
You are right about internet listening but the point is that the BBC has waisted hundreds of millions on a legacy radio system which is not fit for purpose. Rather like the £100 million they waisted on thier computer project or the £250 million overspend on Broadcasting House.
All this is not the main issue here in any case it is the proposed national shutdown when 50% of listeners are still using FM. That is insanity.
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A decent digital radio costs about £150. I have a Roberts Stream 205 which by no means what I call a quality radio. It's of no value to quote low prices for cheap dab radios as you can get a Sony AM/FM radio for £8 from Amazon.
@PJH
Roberts probably don't support DAB+ because of the extra licence fee thay would have to pay.
The fact is the share of listening on DAB is still only a pathetic 23.9%. This is after years of massive advertising campains.
If people want to listen to DAB fine but FM should not be switched off to satisfy such a small proportion of listeners.
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The BBC has been trialing DRM+ in Scotland.
Results of the DRM+ High Power Field Trial in the United Kingdom - Publications - BBC R&D
DRM+ stations can be fitted between existing FM stations in the VHF Band 2. The big advantage is that car radios and (houses) can use existing aerials. The BBC could fit all thier stations in the FM band.
I think is is very unlikely that the BBC would spend the money on this trial if it did not consider DRM+ to be a possible future system.
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I was very carefull in saying that the BBC may be considering DRM and DRM+. Clearly the BBC will want to get national FM turned off before adopting DRM+. if only to justify thier waist of money. As I have said before I do not believe that the BBC will ever be able switch off FM with DAB.
Lindsay Cornell is a principal Systems Architect at the BBC. He is Chairman of the World DMB and DRM Technical Committees. So the BBC is very involved in DRM development. The BBC world service already uses DRM.
DRM+ is certainly far superior to DAB and FM and so is a candidate to replace FM. Infact it can be used in band 3 and so could replace DAB as well. It would make more sense to switch DAB to DRM+ rather than DAB+.
France is trialing DRM+ at the moment. As to wether it will become a major player in Europe is difficult to predict.
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@Mark
Still they are trialing DRM+
Digital Radio Europe 2013: French Riviera DRM+ To Be Presented
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Tuesday 17 September 2013 4:15PM
I understand the some radios sold in the UK have had DAB+ disabled in order to save on licence fees. I suppose it may be possible to upgrade with firmware but it is likely to be chargable. I have seen reports that some UK radios which are ment to support DAB+ have been found not to work in Europe.
Better quality sound is not the only reason for using DAB+ it is the far superior error correction which gives more consistant coverage. In any case the broadcasters are more likely to lower the bit rates even more with DAB+.
The adoption of DAB is the biggest technical mistake the BBC has ever made.
Although DAB+ is much better it is still only suitable for national networks.