96 kbps stereo stations proposed for local DAB

In case you were in any doubt about how pathetic the DAB system is, Now Digital, the GCap Media-owned multiplex operating company, wants to leave you in no doubt whatsoever, because it is proposing to use 96 kbps stereo for three music stations on its application for the Gloucestershire local DAB multiplex (page 49 of the pdf) -- the stations that would use 96 kbps stereo if GCap is awarded the licence would be Gold, Chill and 'Dance' (the latter is just a placeholder name for whichever "dance" station would end up broadcasting on the multiplex).

However, GCap's proposal is to use the 'low sampling frequency' (LSF) mode for these 96 kbps stereo stations, and this is perfectly within Ofcom's rules, because broadcasters have been allowed to use 96 kbps stereo LSF since the late 1990s when the regulations were first written by the Radio Authority -- it's just that no-one has stooped as low as this before.

Low Sampling Frequency

LSF mode means that the sampling frequency for the audio is just 24 kHz instead of the 48 kHz sampling frequency that is used for the vast majority of DAB stations, and the sampling theorem for digital signals requires that the sampling frequency must be at least twice that of the bandwidth of the signal being sampled, and in practice the highest audio frequency that LSF mode can handle is 11.25 kHz. 

In comparison, human hearing goes up to around the 20 kHz level (although the bandwidth of human hearing narrows with age), and FM and typical DAB stations have audio going up to about 15 kHz - 15.5 kHz, so stations using LSF mode basically have the top-end of the audio chopped off completely, so they will sound very dull.

What a ridiculous system DAB is

It is absolutely ridiculous that in the 21st century we have a proposal for music stations using 96 kbps MP2 for stereo and using a sampling frequency that cuts the top-end of the audio off altogether. Then again, there are so many music stations being broadcast in mono on DAB that nothing surprises me about this prehistoric digital radio system any longer, and nor does Ofcom's toothless regulation of DAB surprise me either, as they have shown that they could not care less about what consumers want just so long as the commercial radio groups get what they want.

The sooner the ridiculous DAB system is switched off altogether the sooner we can put this sorry chapter of broadcasting behind us.

It's not just GCap either

The other application for the Gloucestershire local DAB multiplex is from the newly-formed Muxco DAB multiplex operator, and it is proposing to use 112 kbps for some of the stereo stations included in its application -- until a month or so ago, the minimum bit rate level used for stereo stations on DAB was 128 kbps, and that provides audio quality that is far below that provided on FM, so 112 kbps provides even lower quality still.

Channel 4 Radio sticking with 112 kbps for stereo stations

I've been informed that despite capacity being freed up on the forthcoming national DAB multiplex due to the DAB-IP mobile TV service closing (space was reserved for mobile TV channels to launch on the new multiplex using the DAB-IP system), Channel 4, which won the licence for the new national multplex, has decided to stick with using a pathetically low 112 kbps for the stereo stations on its multiplex. This unfortunately suggests that, like the rest of the radio industry, Channel 4 Radio couldn't care less about the sound quality of its stations or the stations it will carry on its multiplex. I suppose that could have been expected, as the people in charge of Channel 4 Radio are ex-Capital Radio Group people, but there was the possibility that moving to a public service broadcaster might have allowed them to acquire some ethics on the way.