Digital Radio Announcement
October 14th, 2005 at 04:11pm
The federal minister for communications, Helen Coonan has made an announcement about digital radio. Apparently the major metropolitan areas will get it first, and will use something called the Eureka 147 system, and they will provide broadcasters with 128 kilo bits per second, which is half the recommended bandwidth for the Eureka system.
Now, I don’t know much about the Eureka system, but if the bit rates are in any way similar to those of MP3 compression then 128kbps stereo will be fine for speech and some music, but won’t be great for music. In my experience “on the fly” compression generally requires higher bandwidth than “post compression” as the latter can deal the audio file as a whole whilst the former has to compress as it goes, which I find usually provides worse audio quality than post compression. The point I am trying to make here is that 128kbps stereo might be fine with post compression, but it won’t provide the same quality for broadcast.
I have read that the UK is using Eureka at 128kbps and it sounds dreadful, but I can’t confirm that, so if anybody knows better then I would be glad to hear from you.
Also Digital Radio will coexist with analog radio for now, as there is no set “switch off” date for analog radio. The same can’t be said for digital and analog television, with 2008 being confirmed as the switch off date for analog television (in metro areas anyway) to free up the airwaves for digital radio.
There hasn’t really been any clear decision made for the regional areas, except that they will get digital radio soon, and as far as I know, Canberra is considered a regional area when it comes to television and radio. The regionals might not even use Eureka, Ms. Coonan announced that DRM may be used instead. I personally don’t understand why we would use two different radio systems, but such is government regulation.
Interestingly, Radio 2 moved on to odd parts of the radio dial hoping to be part of the digital radio saga, but they have missed out, and that can’t possibly help the already dwindling share price. According to radioinfo.com.au “Low power community stations, open narrowcasters and Section 40 off-band licencees will miss out on space in the first round of allocations, which will be planned by ACMA.”
radioinfo also reports that “VHF spectrum will be the preferred carrier medium, with L Band being considered for in-fill transmission and other future uses. Spectrum planning will begin immediately, but the Minister expects that legislation and a staggered technical roll out will mean that consumers may still have to wait up to 2 years before they will be able to enjoy a full range of digital radio services.”
This certainly marks a very exciting period for the future of radio in Australia, I can only hope that the regulators make the right decisions, otherwise we may be left with a substandard system, and fixing that could be very tricky.
Samuel
UPDATE: Upon further reading it has become apparent that Eureka uses MP2, which is going to be interesting to say the least. Also, stations will be allocated 256kbps worth of bandwidth, but will only be allowed to broadcast at 128kbps, the other half of the bandwidth will be reserved for extra features and services. I don’t like the sound of this at all.
Entry Filed under: Entertainment,General News,Samuel's Editorials,TV/Radio/Media
5 Comments
1. John B1_B5 | October 18th, 2005 at 10:47 am
That bit rate would be ok for AM , but not for FM .
2. Samuel | October 18th, 2005 at 2:53 pm
Well, sort of, it would be pretty good for talk radio, but music would suffer. The system is supposed to make digital the top quality, followed by FM and then AM. Instead it has FM as the top quality with AM and Digital being roughly equivalent. I’ll have a new post showing a comparison between 128k DAB and 256k DAB soon.
3. btomsett | October 18th, 2005 at 10:42 pm
Actually I have found that 128kbps is sufficient for most music programs, you need more when you have a very large dynamic range and spectral range (i.e. classical music). The new MP2 compression routines are very efficient and a lot of work has been done to improve the listeners experience. It is very difficult to hear the difference between 128kbps and 256kbps as an average user for normal content, you will however hear the difference for classical music, this is why my most classical programs use bit rates of 160kbps or 192kbps. Of course if you have a dedicated Hi-Fi room and the high end equipment and speaker/headphones and know what you are listening for you could hear a difference.
Another thing is that the standard audio quality measurements used for analogue radio do not apply to digital audio and they can be very misleading if used. Indeed all the expert groups today use blind “golden ear” testing.
Just to clear up some confusion the 256kbps is raw data bits, the 128kbps is the actual audio content(this includes some extra info already at a very low bit rate). The rest of the bits are actually used to ensure a robust signal that can recover from the inherent corruption of air.
Finally Eureka 147 (DAB) is used for VHF frequency range as there is more bandwidth available as it uses MP2. However Digital Radio Mondiale (DRM) uses the same frequency bands as AM (LW, MW, SW) and has the same spectral occupancy. Due to the inherent propogation differences at these low frequencies a different digital standard had to be used to ensure that acceptable reception was available. DRM uses AAC for audio compression and thus needs less bandwidth than DAB. The two standards are compatible and will appear in radios in much the same way FM and AM did previously. I advise taking a look at the radios demonstrated at IFA, Berlin in September 2005. At IFA many users could not tell the difference between DAB, DRM and FM. It is a common problem that people expect DAB audio to better than that of FM it is not, it has equivalent quality, it does however not suffer from the hiss and background noise that FM suffers from. It is worth noting that this is not the case for DRM and AM, the audio quality improvement is massive, and there is no hiss or background noise and they are only using bit rates of around 20kbps, although bit rates of upto 72kbps are available. Speech uses less typically 5-10kbps. You have to hear it to believe it.
4. Samuel | October 18th, 2005 at 11:01 pm
That is most interesting, thankyou for clearing that up btomsett. You state that “It is a common problem that people expect DAB audio to better than that of FM”. That is true, people do expect that, and the reason for that could be attributed to the fact that it is often marketed as being higher quality.
Out of interest, how do DRM and DAB stack up against each other? Which one provides better sound quality? And also, what kind of reception range can we expect from the various technologies? Obviously that last question depends on the transmission power, but how would it compare to current reception charateristics?
5. btomsett | October 20th, 2005 at 4:32 am
I have to admit that the marketing of DAB as “CD Quality” and later as “Near CD quality” was a disastrous move, not mention not really accurate as most commercial recivers achieve 15-16bit resolution while CD is 18-bit. DAB’s strength is that is has equivalent qulaity to FM (without the background hiss, FM+Dolby is really just filtering out the high frequency content so even though it has no hiss it sounds flatter), but DAB has upto 10 times the content so it is a quantity vs quality issue. The new generation of DAB radios also support Electoronic programme guides similar to those use for SAT-TV, they also allow timed record etc and this is an improvment over FM!
Comparing the audio quality of DAB and DRM is like comparing FM and AM to some degree. Considering its limited bit rate DRM does suprisingly well, under ambient conditions (i.e. listening in your car or in your home) they are very similar, certainly most users will not be able to hear the difference. This is mainly due to the new technology used by DRM, this makes use of Spectral Band Replication (SBR) also known as AACPlus, this allows the encoding of frequency bands upto 15kHz even at bit rates as low as 20kbps. It is this that makes for such an unbelievable audio experience 😉 The sound quality is dependent on the bit rate and what format DRM is using. DRM has has speech codec CELP and HVXC that allow for speech at very low bit rates