Robert Freeman's whole Media, Business and Technology thing. Sorted.

CBBC wants to extend hours. Where’s the bandwidth?

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Head of CBBC (and a former boss of the author) Richard Deverell wants to increase CBBC’s transmission up to 10pm. There’s a very good technical reason why CBBC stops just before 7pm: it shares the same space in the terrestrial multiplex (Freeview) with BBC Three. When one stops the other can start.

This is because at the launch of digital TV, the BBC had one multiplex (called multiplex A) and had to fit all of its channels into it. At the time Greg Dyke saw this as a natural constraint to the BBC’s services.

Have at look at this Melvyn Bragg piece, dug out from the Observer. He quotes the former DG :

We have to limit our ambitions. It is as if Disraeli had said to Queen Victoria: ‘Let’s not bother with India, the Empire’s too big already.’

However since then, interactive TV has blossomed and more space was needed for ‘red button’ multiscreens for news and sport, as well as extra editions of programmes.

But on the collapse of ITV Digital, the BBC was handed another multiplex (B), which has now been filled with other TV channels and radio stations, in fact it’s also expanded into the so-called ‘commercial’ multiplexes A and D. Here you can see exactly what is running on all these multiplexes.

Satellite bandwidth is still available, but the BBC clearly cannot say goodbye to universal service, so that means having to find extra space on the DTT multiplex. And that either means knocking something else off, or squeezing the bitrates down as it has already done to the detriment of with DAB Radio.

In my opinion DTT bandwidths are already squeezed as low as they can go, without compromising the quality of the picture. DVD bandwidth is probably the benchmark for the public, and DVDs can run at a healthy 6-9 Mbits per second. DTT bandwidths can be less than half that.

The folks at DigitalSpy have been working out how this change might be accomodated.

Personally I cannot wait for the day when broadcasters only have to send a programme once. It is then recorded locally by your TV. Then they just transmit control metadata which creates a linear channel by playing the first-run stuff live, and anything repeated comes off the local recording. That would end all our bandwidth issues at a stroke!

… And don’t get me started on MPEG-4 compression!


Written by Robert

21 November, 2006 at 7:23 pm

Posted in Media, Technology

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