» posted on Wednesday, February 6th, 2013 at 11:39 by Nigel
Ofcom’s promise of more HD is a stalking horse for a second DTT switch
On the Ofcom website today is a set of documents about award of the 600MHz spectrum, with a request that stakeholders notify Ofcom of their intention to apply. The headline news from this, which you’ll probably see elsewhere, is that the proposals will provide two more HD multiplexes on Freeview, with coverage of up to 66% of the population.
Think of it as doing something a bit like the original HD trials and early roll-out, using additional bits of spectrum where available, to give some more channels to people in certain parts of the country.
All well and good, and lots more HD will be appreciated by many people. But don’t get too excited, because a read through the document reveals that this is very likely about something else entirely – a ‘secondary switchover’ that will leave many people with equipment that won’t be much use at all.
Picking apart the proposal
The summary of the proposal makes it clear that this is an interim use of the space – which may be needed for existing services from as early as the end of 2018. Licences will run at least until the end of 2018, but that could still mean only five years of a service, if it were to start at the beginning of next year.
It’s mentioned in the proposal that there could be up to ten HD channels provided in the space, if DVB-T2 and MPEG4 (the technologies currently used on Freeview HD) were used, using two multiplexes – though the space will be awarded as a single lot. At least one stream will be visible to consumers within 12 months of the award of a licence, reaching 10% coverage, with 50% within two years.
That could be superficially appealing to, say, Sky; space to offer ten HD channels, covering a big chunk of the population. But in fact, with only a five year guarantee, it’s likely not enough for anyone to make a good return, especially when with NOW TV they have another way of getting paid for content in front of people, without expensive transmitters.
The real clue is in the phrase
the new services in the 600 MHz band using DVB-T2 and MPEG4 could encourage consumer take-up of receiver equipment which makes use of these more efficient technologies
And that’s what this is really all about. The longer term sell off of the UHF bands to satisfy the needs of mobile operators means that the space available for Freeview will be squeezed tremendously as time goes on; and some experts believe that there simply won’t be the space to provide all the existing services in the amount of spectrum that’s available, when things are shifted to 600MHz.
T2 to the rescue
One way of conserving spectrum is by using what’s called a ‘Single Frequency Network’, where all the transmitters in an area use the same channel, rather than the situation now where to provide coverage across the south of England, for example, there are transmitters on the Isle of Wight, Midhurst that both send out the same programmes, but need different frequencies to do so. Digital TV is supposed to make it possible to just use the same frequency, and leave the receiver to sort it all out, but for very technical reasons, that simply won’t work well in the UK using the first generation of terrestrial receivers, or DVB-T.
That problem is largely fixed in DVB-T2, which is used by the Freeview HD mux in the UK, and allows for very large areas with a single frequency network, which can be much more efficient. Add in the fact that T2 is more efficient anyway – about 50% more capacity than the older version – and you’re some way to solving the bandwidth squeeze.
When Freeview HD launched, it used T2, and also the more efficient MPEG4/AVC (H.264) video codec. The two don’t have to be used together, but it made sense to switch to both at the same time, for even greater efficiency. And while at the moment, the combination is used exclusively for high definition channels in the UK, it doesn’t have to be. You can transmit an SD channel using T2 and H.264 if you want – but no one does that right now, because older SD only receivers won’t be able to pick it up (though of course, some of the IP TV channels on Freeview do use it in SD, just not via broadcast).
Long term, the only way to keep the level of service we have on Freeview, with the decreasing amount of spectrum, is likely to be to move all the channels to T2 and H.264, and to use more single frequency networks (which, of course, will mean some more aerial readjustments for many).
But before that can happen, there need to be many more homes with equipment that will be able to receive it. While the current bundle of HD channels is nice to have, it doesn’t really represent a startling reason for everyone to decide to upgrade their set top box or buy a new TV set.
Make more HD content available, even if only for a short while, and perhaps you can create the conditions where people will decide it’s worth investing in equipment to watch whatever it is.
On that topic, my suspicion is HD versions of more of the main channels, frankly; very likely a pair of muxes operated by the BBC, with space given to other PSBs. Who’s got the money to launch an expensive temporary commercial operation that will only last five years, just at the start of another recession?
So, I think we can expect to see a BBC-backed mux providing HD versions of existing channels, with perhaps a bit of new stuff in the mix, but not much. And the real reason this is happening is not just about bringing more HD into your home. It’s about making sure your technology is up to date, so that a wholesale switch to DVB-T2 and H.264 can happen in time to ensure that most people don’t have their Freeview service drastically reduced when mobile phone networks take up the freed parts of the spectrum.
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