On Wednesday 2 December, at a small gathering in its Media Village in west London, the BBC launched, with all the modesty and quiet pride we've come to expect from the corporation. After a brief explanation of what was involved, we finally got to see some of the early hardware and the live service as it was going out. No-one can really watch these channels yet, though, because no compatible hardware exists, since is so new.
The event was kept reasonably low-key because it's only a technical launch at the moment. The BBC is waiting until hardware becomes available next year before it starts pushing the service. Expect to see plenty of promotional content in March, though, because that's when everything is going to start gearing up to make sure people know they can watch the World Cup in high definition. Also, Ofcom has made it clear that it expects Channel 4 to make itself available in HD on Freeview, so expect to see much more HD in general soon.
We also found out that the service will be using statistical multiplexing to ensure that all the channels get bandwidth when they need it, but aren't wasting it when they don't. To give an example of this: if ITV is showing football, and BBC HD is showing a programme with little or no motion, then the football will be given much more bandwidth than the BBC programme. The bit rates range from 3Mbps to 17Mbps. In reality, though, you're very unlikely to see any channel go as low as 3Mbps. On the audio side of things, where possible, the BBC will transmit Dolby Digital 5.1 at 320kbps. If surround sound isn't practical or necessary, the channel will use stereo audio at 128kbps, AAC.
We also got a chance to ask Ofcom about the analogue spectrum. Our concern is that, when the UK is all digital, the space used for analogue TV will be sold to the highest bidder. Greg Bensberg, principal adviser for broadcasting at Ofcom, didn't do much to reassure us. He said that the market would decide who needed the space, and it wasn't Ofcom's job to legislate on spectrum use. It seems, therefore, that, as we expected, the spectrum will be deployed to whatever industry can stump up the most cash.
After the main briefing, we got a chance to sit down and chat with Graham Plumb, Phil Layton and Andrew Cotton, who have been crucial in the development of BBC HD on all platforms. We asked about the recentand all denied that picture quality has dropped in real terms. The 40 per cent data-rate reduction shouldn't be visible to anyone, and people posting screenshots have, apparently, discovered that there were problems in the way they captured images. The R&D bods at the BBC have spent a great deal of time comparing the two versions of the channel, and they are certain that the new encoding hardware is delivering the same quality as the old equipment, but at a much lower bit rate.
We also asked why the BBC was using 1,440x1,080 pixels instead of 1,920x1,080. The answer was, quite simply, that a good percentage of HD acquisition is done at this resolution. It's the format of choice for both HDCAM and DVCPRO HD. It's also much more efficient, especially if you're using interlacing, where each field doesn't have the full horizontal resolution anyway. Anamorphic compression has been in use on digital TV since it was launched -- it's also the way DVDs store widescreen movies.
We were slightly concerned that the expectation is that multiplex B will eventually contain five HD channels. Four, at around 10Mbps each, is one thing, but adding more will surely reduce the quality to unbearable levels. We were assured that, by the time this happens, it's likely that the encoder efficiency will have been increased again, although we were told that another reduction of 40 per cent wouldn't be possible.
We also wanted to know who would be managing the multiplex that these channels reside on. The BBC owns that space, so we questioned if that meant the BBC would get more bandwidth than the other channels. That's not the case -- the encoder makes all the decisions about what channel gets what bandwidth at what time. Of course, if everyone shows a football match at the same time, or confetti spraying about, then we could see picture quality on all channels suffer. In reality, though, it's very unlikely that this will be a problem.
We also asked about the receiving equipment itself. The BBC doesn't have anything to do with the hardware, but using the Freeview HD logo means you have to conform to certain standards. For example, the electronic programme guide must now be Freeview-branded -- a minor issue but one that adds at least a modicum of consistency to all hardware. You must also have an Ethernet jack, and, although our chat didn't yield information about whenwould come to Freeview HD, the platform uses the same technology as freesat HD, so it's reasonable to conclude it won't be far off.
Freeview HD boxes must also output at 1080p50. This is to ensure that the TV doesn't need to adjust itself, which also means no ugly blank screens between each programme, as you might have seen on channels that transmit 4:3 and switch to 16:9 for adverts. The user interface for the box will be available in 1080p too, which makes for a pleasing look and feel. The downside of this is that you'll be forced to use the upscaling hardware in the Freeview HD box, and we wonder if that will be of the same high quality as the one in mid- to high-end TVs.
We're thoroughly excited by this service. The BBC is hoping to get sample equipment out to us soon so we can test it in full, but HD on Freeview has arrived. That's a technical feat if ever we saw one, and a very exciting moment in broadcasting history too.