BBC has increased Radio 3 back to 192 kbps

5th October 2006

Something that I almost forgot to report on because of the news that the old DAB system is effectively dead is that the BBC has climbed down over its reduction of Radio 3's bit rate to 160 kbps to allow the freed-up 32 kbps to be used to provide a 24/7 looping trail for Radio 5 Sports Extra to allow those people that couldn't figure out where Radio 5 Sports Extra had gone to when it wasn't actually transmitting to find it — the poor loves.

However, despite Radio 3 having its bit rate increased back to 192 kbps on DAB, Radio 3 still sounds a lot better on FM.

One negative side-effect of the change is that Radio 4 has to be reduced to mono in the evenings when Radio 5 Sports Extra is carrying commentary, and Radio 3 still has to be reduced to 160 kbps in the daytimes when R5 Sports Extra is transmitting.

One obvious question (apart from the fact that it makes you wonder what planet the BBC decision-makers were on in the first place) that this climb-down raises is: why is it acceptable that Radio 1, Radio 2, 6 Music and 1Xtra are all transmitted at 128 kbps when Radio 3 is transmitted at 192 kbps? There is no scientific or engineering reason that necessitates Radio 3 to transmit at a higher bit rate, so it is simple BBC hypocrisy and preferential treatment towards Radio 3.

I'm not against Radio 3 using 192 kbps in any way — I am in favour of high audio quality wherever possible. What the BBC should obviously do is provide its radio stations at high audio quality on one of the digital TV platforms where they have an enormous amount of bandwidth at their disposal. For example, on digital satellite the BBC has 231,000 kbps of capacity, whereas on DAB it only has 1,184 kbps of capacity. It is therefore clear that the BBC could perfectly easily provide its radio stations at high quality, but it chooses not to — and this includes Radio 3, because as I mentioned above, Radio 3 still sounds better on FM than it does on DAB.

The German public service broadcaster ARD transmits its 55 stereo radio stations on digital satellite at 320 kbps, whereas the highest bit rate the BBC uses for any of its radio stations on any digital platform is far more meagre 192 kbps. The only conclusion I can come to is that the BBC wants everybody to buy DAB, and everybody that wants good audio quality can go take a running jump. It's great to see the BBC, whose staff we pay for, whose bandwidth we pay for, whose transmitters we pay for etc, takes these decisions that are obviously against the interests of the people who pay for it.

On the subject of scientific / engineering issues, Radio 3 fans usually try to justify Radio 3's higher bit rate by saying that the dynamic range on Radio 3 is wider, and therefore it needs more bits to encode the information. However, the MP2 audio codec used on DAB represents audio samples using a crude floating-point number system (technical bit: the scale factors act as the exponent, and the subband samples themselves act as the mantissa), and the dynamic range covered is much wider than any audio Radio 3 throws at it, and the number of bits used to encode the scale factors is constant, so dynamic range is actually independent of bit rate. Therefore, the argument that radio stations that have a wider dynamic range requirie a higher bit rate is incorrect.

In fact, having a wider dynamic range is actually beneficial for perceptual audio encoding — because the way audio codecs work by masking nearby frequencies means that audio with a flatter spectrum, such as the spectra of audio that has had its dynamic range compressed, is more difficult to compress, because there is a lower probability that nearby frequencies will be masked by larger neighbouring frequencies. Hence, having a wider dynamic range, and hence a less flat spectra, means that there is more opportunity to find inaudible frequencies, and thus the remaining frequencies can be encoded more accurately for a given bit rate. Therefore, having a wider dynamic range makes the audio easier to encode, and thus actually requires a lower rather than higher bit rate!

And a quick listen to any rock track with loud electric guitars playing shows that the BBC's decision to use 192 kbps for Radio 3 whilst keeping the other music stations at 128 kbps was certainly not made to provide equal audio quality on all stations, because rock music sounds abysmal on DAB at 128 kbps, whereas Radio 3 doesn't sound bad — although it doesn't sound particularly good either.