Building BBCi on Freesat

Published on 4 December 2007 in , , , , , , , ,

I don’t know what anyone else thought, but when I read that bit of the Freesat FAQ about interactive content on Freesat, I thought that the author was being just a little cagey – that they weren’t really telling me much.

I suspect that’s just me though, mainly because I was the author of that little segment and I had to write it without saying too much. With good reason I might add – when I was asked to concoct something for that little blurb, I was quite aware that there were just some parts of BBCi which we don’t know when they will launch on Freesat, and you don’t want expectations to be built up, which might not be met.

One of the joys of working in interactive television is that every platform works in a slightly different way. Even down to the basic code each one is written in – on the Sky box, you write applications in OpenTV, whilst Virgin Media’s applications use the HTML derived Liberate language which would be so much better if the version in use wasn’t based on HTML 3.2…

Meanwhile over on digital terrestrial television – aka Freeview – it’s something different again, where applications are written using MHEG-5. That’s just the start of the differences between the platforms…

The result of this is that our techies need to build everything three times – one per platform. To make things a little easier, there’s some common standards behind the scenes – the data that comes out of the content management systems is generally pretty much the same for each platform, and then transformed automatically into something platform specific. However there’s still code for each platform.

And so Freesat enters the mix which is our fourth platform.

For interactive content, Freesat’s using MHEG 5 just like DTT. Although it is actually a newer version than what DTT currently uses, it’s backwards compatable. That means when our techical team have been building work for Freesat, it’s quite possible to simply lift elements of the code from our Freeview service and use it on Freesat. This ability to recycle code is quite useful and means that work can be done faster than if it was all being built from scratch.

Of course not everything is recycled – in the BBC applications used to be written in any number of technologies. Much of the DTT backend is written in Perl, however the department has recently been moving to Java, so Freesat’s backend is being built in that too. We’ve also been introducing a lot more automated testing – something which wasn’t done in the past – but of course, that means writing the tests as well. This takes time, although the benefits going forward will be absolutely huge, and will help reduce the number of bugs and errors that make it on screen. At the same time the team are also making optimisations and improvements to take into account the oppertunities available in the MHEG version available on Freesat.

Then there’s the differences in playout enviroment.

Freesat will be using the same satellites as Sky use, and the same video will be used on both. The BBC has more video on satellite than it does via the old aerial method, because there’s more space.

The playout differences especially cause problems for the scheduled, video based applications – like Test The Nation or the various Sport Multiscreen services. The Freeview versions of these have completely different editorial propositions to their satellite counterparts because on satellite we have seven different video options, whilst Freeview only gets two. This means it’s simply not possible to re-use the Freeview applications straight away on Freesat – some will get away with just minor changes, whilst others will need ground up re-writes.

To do everything is a huge job – and certainly not all possible for the launch date in Spring 2008. Instead we’re taking a phased approach – currently we’re building the foundations of the text service, whilst the team building the new sports service (known internally as “My Sport Now”) are building the Freesat version alongside versions for the other three platforms.

Whilst the aim is to have the Freesat service able to do anything the others can (and maybe a bit more), the exact dates aren’t known yet – we don’t even have proper set top boxes to work with yet! Everthing is being built using a set of “reference recievers” – specially built equipment which should work in the same way as a proper Freesat box. But it’s not the same as testing on something that’s actually going to be in peoples homes.

That said, I’m pretty confident it will all turn out okay in the end. Just don’t mind if I don’t tell you when that final end will be! The launch will be spring. But it doesn’t end there.


  • Francis says:

    “Everthing is being built using a set of “reference recievers” ”
    <insert garbled sounds here: rough translation “yeah, ‘cos that has worked lots”>

  • David says:

    Is there a publicly available document describing the MHEG that will be used on Freesat similar to the UK profile 1.06 for DTT?

  • Andrew Bowden says:

    Nothing that’s publicly available, that I know of. I’m sure it will be in due course.