a use for uk dvb-t +1 channels

After reading about the BBC HD trial, I was idly wondering what the UK DVB-T channel line up might look like in the post-analogue days (2012, at the current estimate) and trying to decide how much HD content there might be (or how many more shopping and +1 channels[1] could expand to fill the space and so force people onto pay platforms for HD content. Not that I’d accuse any other operators of using up DVB-T spectrum as a loss leader in order to force customers to buy better quality[2] from their other arm).

I googled around a bit and found an interesting but unrelated list of channel numbers to analogue video and audio frequencies as well as the digital centre frequency. A bit later I found an introductory FAQ where Q10 tries to explain why some channels might come through fine, and others drop out or are just not available.

Ben managed to find the real gem, though, over at Wikiedia where the multiplexes are listed with the actual data bit rate and not just the bandwidth (they’re all 8MHz of course, to fit into the UK channel plan). Now it makes much more sense when it’s shown that the ‘dodgiest’ channels when it comes to being able to watch them over the neighbours’ petrol lawnmower generated interference are all QAM64 encoded (five, C4, E4) but down the bottom there’s E4+1, sitting on a QAM16 multiplex. Why ? I haven’t a clue. If I were Channel 4 I’d have bumped C4 to the QAM16 and relegated the E4 pair to the others, but then I’ve long suspected that being sensible is the worst thing to put at the top of a business plan.

So if you have a PVR or other timeshifting device for DVB-T (I think that the EyeTV software is well worth a look too) then plump for E4+1 instead of E4 for all of the first run US imports and you ought to get a more reliable signal, and possibly less MPEG artefacts too.

[1] For non-UK readers, channels that have identical content to another bearing the same name, but the content is broadcast 1 hour later
[2] Measured in bit-rate, pixel count or some other tangible metric: actual programming is not included

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