Dan Warne29 May 2009, 11:23 PM
MASSIVE SUPERGUIDE | Digital Radio officially goes live today. Here's our massive guide on how CD quality audio over the air works.
Digital radio was launched with much hooplah this week -- or to be precise, launched in Sydney. Turns out the other major capital cities have had it for a few months now -- who'd have known?
Now that Sydney, Melbourne, Brisbane, Adelaide and Perth have DAB+ digital radio blitzing its way through the airwaves, retailers finally have the green light to start selling digital radios full-steam ahead, rather than just having the odd display model that nobody in the shop quite knows how to use and can't be tuned in to anything.
But first… what is DAB+ digital radio?
Digital radio is to radio what digital TV is to TV -- at the most basic level, it's the same thing at much higher quality. You can forget the hiss, buzz and crosstalk of analogue radio, as well as the muffled sound of AM radio stations. With digital radio, you get somewhere between optimal FM and CD quality sound.
We hesitate at calling it "CD quality" because if you listen to it with headphones, it sounds more like an 128Kbit/s MP3 -- on some songs you do hear the audio compression artefacts. But it's much better than listening to analogue FM, and it's a vast improvement on muffled old AM radio.
Naturally, because it's digital, a range of different sound problems can occur -- just like suboptimal digital TV reception, you can get unpleasant squealy audio glitches or sound dropping in and out like a GSM mobile phone with bad reception. However, many digital radios come with a big extendable antenna (about twice as long as an average FM radio) that gives them better reception.
Digital radio is about more than just nicer quality sound though -- it has some other major benefits, the most important of which is that there's no longer the need to remember frequencies of your favourite stations. The DAB+ radio system hides frequencies from you -- DAB+ radios auto-tune a list of stations and you simply scroll down a list of stations ordered alphabetically and select the one you want. (Let's hope this doesn't have the unfortunate effect of encouraging unscrupulous radio broadcasters to start moving towards station names like AAA Aardvark.)
You can also receive a lot more channels than on a regular radio. Each broadcaster gets a 128Kbit slice of spectrum allocated to them, however, most are slicing that up into smaller chunks in order to broadcast multiple stations. For example, the Triple M network got 128Kbit/s, but is actually broadcasting two stations using 48Kbit/s each, and using the remaining 32Kbit/s data transmission to go along with the channels.
The 48Kbit/s sound quality really is quite incredible -- especially if you think how crap music on your PC would sound if it was encoded at 48Kbit/s, rather than 192 or 256Kbit/s. While DAB radio marketing executives are at pains to point out that they don't claim it's CD quality, it's very satisfying to listen to. Although you can occasionally hear the sound compression, the lack of analogue hiss, interference and so on tricks the mind into thinking it's listening to a CD or iPod.
The remaining 32Kbit/s of bandwidth is used for data transmission, and when you're listening to the audio, your digital radio displays album cover art, song name, weather/traffic information for your area, web addresses for the music you're listening to, program name, and so on. Of course, not all digital radios will have a colour screen capable of displaying cover art.
The DAB signal also broadcasts the time, so your clock radio will never again lose the time because the power had a temporary outage. Hallelujah. And yes, there are already DAB clock radios on sale... here's pictorial proof:
Many digital radios will also let you pause the radio and restart it, just like a TV PVR. You might be thinking, "yeah right, I bet that's built into the specification, but we'll never see it in an affordable radio…" but I can tell you that I am listening as I write this article to a digital radio with pause/resume function capable of buffering 15 minutes of sound, that only costs $249.
Wait, $249 sounds expensive…
Yes, digital radio is, for now, a lot more expensive than standard AM/FM radios. The reason is that AM/FM radios are really pretty simple devices -- the circuits required to pick up and amplify AM/FM signals are very basic. Digital radios, on the other hand, are small computers, decoding an AAC audio stream, displayig images and text on the screen, using digital signal processors to automatically correct signal corruption on the fly, and so on.
That said, digital TV receivers started out expensively too, and now you can buy them at Woolworths for $49 -- though not necessarily a good brand with a well thought-out feature-set.
If you're a lover of AM talk radio, digital radio may well be worth the money for you, because instead of the muffled sound of AM, you can get the kind of sound quality -- and better -- than FM radio stations have had for ages. The downside is that ABC Radio (arguably the only worthwhile talk radio on the air) isn't yet broadcasting -- they'll switch on their stations a month from now, in June.
Will we see digital radio built into MP3 players?
The answer is: hopefully, but it depends. The USA has chosen a different digital radio format from the rest of the world -- HD Radio -- and it's totally incompatible with DAB radio. Since most devices get designed for the US market and its 306 million potential customers, it might take a while for electronics makers to address the rest of the world with DAB built into digital music players.
The new Zune HD that Microsoft has announced (hissing cats, garlic, stakes and silver bullets and horseshoe over the door of the APC offices) has HD Radio built in, which shows that it can obviously be done, but the radio bit will on work in the United States thanks to their arse-about choice of broadcasting technology.
(As a sidenote, despite our sarcasm, there are actually some advantages to the HD Radio adopted by the US, the main one of which is that it's broadcast as part of the analogue signal, so if the digital side of things drops out, the radio seamlessly switches to playing the analogue radio station instead -- good for cars in the transition period where digital radio coverage is expanded out across the analogue reception area. However, it also has major downsides such as lower digital sound quality on AM stations, whereas Australia's DAB+ standard no longer has the concept of AM and FM -- all stations are just DAB+.)
Pocket DAB radios (e.g. dedicated units, rather than media players with DAB built in) are expected to hit the market next year, with manufacturers already working on them.
What about the car?
Of course, a huge amount of time people listen to the radio is in the car while they're on the move. According to Austereo spokesman Jaime Chaux, it's somewhere around 30 — 35 per cent. So cars are a very, very important target market for digital radio.
However, the development of digital radios for cars is a bit behind home radios -- the problem is that many cars made in the last 5-10 years have dashboard-integrated radios that can't be swapped for an after-market slot-in radio, even if a DAB one was available. As a result, the first DAB car radios are ones that can be plugged into the auxiliary output of an existing head unit, or retransmitted via FM to a standard car stereo.
The PURE Highway, pictured below, is one such model, and only costs $299, which will be a more approachable price for most people than the cost of a whole new head unit, and it means if people upgraded their car recently for iPod or Bluetooth connectivity, they won't have to pay to replace that all over again with a DAB-capable head-unit -- they can just just use the add-on unit.
That said, DAB head-units, and integrated DAB+ radios from car manufacturers will no doubt be coming; they're just not on the market yet.
Annoyingly, because the US uses HD Radio rather than DAB+, there are heaps of American head units with HD Radio built-in, but none using DAB+. There are also a few DAB head units available around the world, but before you contemplate buying one from overseas, read the next bit…!
France is blazing a trail in digital radio in the car -- it has mandated that all radios sold must be digital by 2012, and by 2013 all cars must be digital radio capable too. Unfortunately, they've gone with yet another different digital radio standard, T-DMB, so while there will no doubt be plenty of T-DMB car head units, it won't necessarily help the DAB+ head unit situation.
What's the difference between DAB and DAB+?
Yikes, it turns out that little "+" means a heck of a lot. The two standards are completely incompatible.
DAB is an earlier version of digital radio technology that used MPEG2 audio, which is a relatively old and inefficient compression technology (the same one used on DVDs). It requires 256Kbit/s of bandwidth to provide CD quality, and it's not very resilient to signal interference.
Australia ran transmission trials of DAB, but has opted for a newer standard which has since been developed, called DAB+, which broadcasts sound in AAC+ (similar to the default AAC audio CODEC used in iTunes) which is part of the MPEG-4 family. That's why broadcasters can squish such good sound quality into 48Kbit/s. In fact, 48Kbit/s encoded with AAC+ gets a rating of "excellent" on the MUSHRA listening scale -- a controlled listening test -- whereas MP3 at the same bit rate is considered "poor" -- and MPEG-2 is even worse than that.
DAB+ also uses "Reed Solomon" encoding which means even if there are small transmission errors, the radio can auto-correct the audio stream. Reed Solomon encoding is used in CDs, DVDs and BluRay discs to correct data lost to scratches, in ADSL broadband and in your hot-rod PC's RAID-6 array.
Because of the completely different audio encoding format, DAB radios cannot tune and play DAB+ transmissions and vice versa -- so don't be tempted to buy a cheap DAB radio off the net.
Since it's digital streaming, can you listen to internet radio stations too?
No, no, no… digital radio comes over the air like digital TV; internet radio comes over an internet connection. That said, since they're both digital streaming media, there will be lots of DAB+ radios that can tune into internet radios via WiFi was well. But of course, they'll be more expensive, and internet radio will suck as much as it always does when the internet connection at home (or at the radio station) gets busy with something else.
So who's making digital radios?
Electronics makers that have so far announced or released DAB+ digital radios include Arcam (from $1899), Sangean (from $239), Bush (from $149), PURE (from $199), Revo, Roberts (from $299), Yamaha (from $599), Grundig from $249. No doubt, all the major electronics brands are readying their models too.
We'll bring you reviews of these radios soon. So far, we've been playing with a PURE One Classic ($249) which is an impressive listening experience. The smallish mono speaker in it doesn't really do the sound quality it's pumping out justice, though -- plugging in a pair of Bose headphones really gives an indication of how good the listening experience is. Normally, using a radio near the MacBook Pro this article is being written on results in intolerably strong static inference, but with the digital radio, there is no hint of interference.
The Classic One also has an iPod connector so you can use it as an iPod speaker (though you need to get the accessory iPod dock to go with it) and a battery bay that can double as an automatic internal battery charger if you buy the accessory rechargeable battery pack.