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After a Decade, Digital Radio Still an Also-Ran In UK
beschra writes "Digital Audio Broadcast (DAB) was developed as early as 1981. After launching in the UK 10 years ago, only 24% of listeners listen on DAB. The article credits a good part of the delay to the fact that the technology was largely developed under the Europe-wide Eureka 147 research project. How does government vs. commercial development help or hinder acceptance of new technology? From the article: '"If Nokia develops something, they'll be bringing out the handsets before you know it," [analyst Grant Goddard says]. "Because DAB was a pan-European development, you had to have agreement from all sides before you could do anything. That meant progress was extremely slow." But this alone did not account for the hold-up. The sheer complexity of introducing and regulating the system was also a major factor, Mr. Goddard adds."'
I think reception is a major DAB killer. I live in London, and still can't get a usable DAB signal. The 24% of the country listening on DAB are probably pretty much the 24% who can receive DAB. DAB is a looking like a failed technology at the moment. I use internet radio at home, and there's no real alternative to FM in my car.
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Depends. A clean FM signal is actually pretty good quality, but a clean FM signal is pretty rare. DAB uses 128Kb/s MP2, which is terrible quality. DAB+ uses 64Kb/s AAC+, which is good enough that cheap speakers are going to be the cause of poor quality in a lot of circumstances, but still not actually good. 128KB/s AAC would definitely be better than FM in most cases, but this doesn't seem to be an option for DAB.
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DAB is around 30% efficient in transmission, whereas FM is about 90%.
Please define "efficiency in transmission".
DAB is already transmitted at far greater power than FM, yet we still have trouble with reception on receivers.
You really need some documentation for that statement. In Denmark the important FM transmitters are 60kW (a few are 100kW), whereas the main DAB transmitters are 2kW. Coverage is only marginally worse with DAB.
It's a technology that needs to die before it really takes off.
I don't disagree, but don't make it worse than it actually is. FM is obsolete even as an analog technology (radio amateurs can do better quality in less bandwidth even without going digital). Let us just hope that we replace FM with something sane.
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There IS a case for what DAB gives you - more radio stations - but that is not a thing specific to DAB. The real problems with the roll-out of DAB stack up as follows:
1) DAB was promoted as being superior to FM in terms of quality, but then the broadcasters started to tinker with bitrates on order to squeeze as many stations into the available bandwidth, even transmitting some music stations in mono, so that the quality was clearly inferior to FM. This has created a big credibility issue for DAB because the quality angle is still pushed towards an audience that has evidence to the contrary.
2) DAB reception is patchy in many areas, especially indoors. This may be mitigated when (if?) analogue is switched off and DAB transmissions get more power, but at the moment, for example, I can only receive about 50% of the available stations on my DAB kitchen radio - and if the weather is bad the error rate rockets so all I get is a burble.
3) DAB reception on public transport, especially trains, is crap. Well-paid city commuters would snap up a decent, working gadget but only AM and FM work well on the move.
4) The original DAB radios were expensive and also butt-ugly, looking like 'Practical Wireless' projects from the 70s. Many were also mono, with only one speaker - you paid extra for an add-on. These wooden-boxed radios appealed to early adopters and the curious, but the general public were not so enthusiastic. Recent designs are more sensible.
5) Portable DAB sets - especially the shirt-pocket sized ones - really really eat batteries. I'm lucky to get 4-6 hours out of a pair of good quality alkaline AAA cells. In fact, I have just ordered some 1300mAh AAA rechargeables because the cost to feed the radio with normal cells is stupid - you could easily spend more on cells in 3 weeks than the cost of the radio.
6) Getting a DAB radio for a car at a sensible price is pretty much impossible - and those who have them don't seem to be impressed with the reception and performance.
7) The technical spec for DAB is out of date already, but to replace it would mean admitting that the original design was not well thought out AND would force all current adopters to scrap their current kit; and no-one wants to be the one to announce that.
8) Many people take their own music with them and can pick and choose what they want to listen to. Why swap this for something that sounds worse and doesn't play what you want?
9) The number of mobile phones with DAB receivers is (I believe) 1 - and it's only available on one mobile network (Virgin). Having a mobile phone with DAB would give the service a *bit* of credibility, but would probably screw up battery life.
10) Here's the kicker: FM and AM 'just work' and very few have problems with the quality - there is no public tidal wave of protest demanding anything better and this leads to a sense that DAB is being pushed onto the public - which instantly gets people pissed off.
The current way forward for the broadcasters and politicians seems to be a defensive 'do nothing' while half-heartedly championing DAB, and no doubt there will be some form of mad scramble to do something half-assed when the analogue switch-off dates are imminent. There is an analogue trade-in promotion at the moment and it will be interesting to see what the take-up is.
Very recently, a Government source stated that the FM switch off would only happen when there was little demand for the service - which is a change from the previous 'rock solid' fixed date, but unless there is some serious push to improve DAB reception and produce a portable set with a sensible battery life, I fear we are going to bump along the 'do nothing' road for a long time.
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I used to work as a programmer at one of the few British DAB firms, which went bust not that long ago. What really annoys me is all the myths about DAB that are propagated by various journalists.
Myth 1. FM audio quality is better than DAB at 128kbits. This just isn't true and the only FM station with any quality at all is Radio 3, because the BBC pump massive amounts of power and engineering effort into the signal. The problem is that FM signal degradation creates white noise, which the human brain filters out without even noticing (especially in a speeding car). In contrast all digital audio has to suffer unpleasant squeaks and artefacts if the signal is corrupted. However, under truly equivalent conditions of power the DAB signal trounces the FM quality. Unfortunately, in practice the DAB signal is much nearer the noise floor because: linear broadband transmitters are way more expensive to run than constant power FM transmitters; because the thermal noise in the receiver is proportional to bandwidth and the DAB wavelength doesn't penetrate buildings all that well.
Myth 2. DAB is failing, because the MPEG2-Layer II codec is old and inefficient compared to MP3 and AAC. Truth is the DAB+ codec is horrible to listen to in practice and the old DAB one is much better for the job of sending over poor signal paths. The higher the compression ratio the longer the encoded audio frames get. With the 24ms audio frame of DAB, losing a frame simply causes the classic 'bubblng mud' sound and some frame repetition can be allowed to pad the gaps in a benign fashion. With AAC+ you get 120ms superframes, which equates to massive silent pauses and repetition sounds like Max Headroom. Certainly the DAB+ standard has reed-solomon to push it even nearer to Shannon's limit of SNR, but in truth most fading that causes problem is brief total signal loss, which long frames actually aggravate. This sort of signal loss happens a lot, because most people put there radios deep indoors and actually have a much worse signal reception than they realise. The end result is with DAB+ radios people start to think the software is on the blink due to the on-off nature of getting audio out of one as you move the aerial about and it is very hard to suss out a good reception spot for the antenna as there is no feedback on signal quality.
Myth 3. The low bitrate used in DAB is in some way due inefficient coding/transmission. This is simply due to short sighted commercial decisions and basically the broadcasters will always reduce the bitrate till users complain. The commercial networks clearly intend to reduce the 128kbits channels used for DAB to 32kbits and 24kbits when using AAC in DAB+ (see Australian DAB+ tender bids), by which point any quality gains from the codec have been thrown away.
The real reasons DAB is dying are:
1. All forms of broadcast are dying due to the rise of on-demand/interactive ways of listening to media. The moment decent MP3 players started to be sold, DAB radio sales were doomed. People mostly want to listen to their own choice of music and whilst news, chat and introducing new music are important most commercial stations just act as a jukebox that you can't control.TV and satellite are going the same way, but are partly saved by the fact that the mobile device form factor cannot provide a decent viewing experience. Decent internet connected smartphones are the final nail in the coffin for the classical broadcasting model and I do wonder who on earth is going to want the TV wavelengths when they are finally freed up.
2. Digital radio is hard to make portable and low powered. The power requirements for MP3 audio decode are tiny compared to those of capturing, sampling and DSP decoding an 8MHz/s signal to the point where you can start the equivalent of MP3 audio decode. FM can be decoded to an adequate signal with a few non-linear components and provide perfectly adequate audio. The aerial size for DAB is also awkwardly large and a proper dipole is essential for coping with the poor broadcast power used in the