| BBC DRM trial in Devon22nd May 2007 The BBC is carrying out a trial of the new Digital Radio Mondiale (DRM) system in the Devon area. The trial signal is being transmitted on MW, and the channel bandwidth is only 10 kHz, which means that the bit rate used for the audio is only approximately 23 kbps. And although DRM is using the ultra-efficient AAC+ audio codec, when they're using a bit rate as ridiculously low as 23 kbps, it is inevitable that the audio quality would be very poor, and as the following sample that someone sent me shows, it does sound awful in practice as well: As the audio quality is so low, you have to ask why on earth they're using a bit rate as low as 23 kbps. It would be possible to increase the bit rate (by increasing the error correction coding code rate), albeit that this would require the transmitter powers to be increased, but as it stands, I fail to see what the point of using DRM at all if all they're going to provide is radio stations at abysmal audio quality. And the BBC is not the only broadcaster using these low bit rate levels on DRM, because I was provided with a Morphy Richards DRM/DAB radio a couple of months ago, and all of the radio stations I could receive (Deutsche Welle, BBC World Service and RTL France were the only ones normally available -- and even they were unavailable for hours on end) were using bit rates in the 18 - 21 kbps range. Furthermore, there is a DRM trial in the 26 MHz band currently taking place in London, and they even have 20 kHz channels where TWO radio stations are sharing the channel. Doubling the channel bandwidth allows the bit rate to be doubled, so this would obviously allow the awful audio quality to be vastly improved, and yet they actually have two radio stations sharing the channel so BOTH stations will sound very poor. What is it with digital radio? Why do broadcasters think it is acceptable to broadcast such very poor audio quality in the 21st century? I'd have thought that they'd have learnt their lesson from the DAB debacle, but obviously they haven't... Note, however, that I'm referring to the DRM system, and not the
extension of DRM, called DRM+. DRM+ will use 50 kHz channel
bandwidths, so each such channel can carry about 100 kbps. That's
enough to carry a radio station at pretty high quality, although maybe
the UK disease of providing ultra-low and completely insufficient bit
rates will hit DRM+ as well, and insted of carrying one channel maybe
they'll carry four stations, with all of them at very poor quality.
Ridiculous.
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