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What about using the CI slot on a digital TV?
It’s not very practical. A French company called Neotion has made modules that can convert H.264 to MPEG 2 in a CAM (Common Access Module) but the use of DVB-T2 means you’d need almost a whole set-top box in the CAM. Controlling a CAM through your TV’s menus isn’t very straightforward, and may not be possible without an upgrade to the TV’s firmware anyway, as most sets only expect to use the CAM for encrypted channels. Some older sets will only have an SD MPEG 2 decoder, so still wouldn’t be able to show H.264 HD pictures this way.

Why not use the same standard as everywhere else?
To make HD practical on terrestrial television, using H.264 is essential, unless lots of other channels are turned off to make room. Lots of existing sets made for the European market would work if we used H.264 with DVB-T, but even more wouldn’t, as they lack any HD tuner or decoder at all – only some sets made in the last couple of years would cope, so many people would need to upgrade anyway.

With DVB-T2 providing much more bandwidth, in the longer term it’s likely that a change to that standard would happen anyway. Launching HD now, and then using the new transmission technology later would force many people to upgrade twice in a short time, once for H.264 and then again for DVB-T2. By linking the two upgrades together, the intention is to ensure that once you do buy into Freeview HD, you won’t have to upgrade again for a long time as we should have the most technically advanced terrestrial TV system in the world.

What’s so special about DVB-T2?
DVB-T2 can provide more capacity for programmes than DVB-T. Tests suggest around 60 per cent more capacity for the same robustness of signal. With DVB-T, it’s often been a much harsher trade-off, for example with the main BBC multiplex being more robust, but carrying fewer channels than the ITV/Channel 4 one, and some multiplexes being more susceptible to interference.

You can read up on the maths behind T2 here (PDF).

Does this mean my existing equipment is obsolete?
No. Only one of the six multiplexes - the digital TV transmission frequencies, essentially - in the UK is converting to DVB-T2. All the others will continue broadcasting DVB-T with MPEG 2 pictures for the foreseeable future. You will be able to continue watching the existing Freeview channels, and you only need to invest in new equipment if you want to watch HD services.

Will more channels move to the new technologies in future?
It’s possible, and during the downtime of the HD channels, they may sublet capacity to other channels, perhaps SD ones using H.264 video. But we’d consider it very unlikely that all the current DVB-T/MPEG 2 transmissions will cease much before the 2020s - the BBC won’t be in a rush to disenfranchise viewers, and the operators of the commercial multiplexes won’t switch over until they can convince their customers (the channels they carry) that they won’t lose out on audiences by switching to DVB-T2/H.264. Yes, in the long term, all the multiplexes will probably move to DVB-T2 and H.264, even for SD. But like we said, don’t expect it any time soon. ®

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