Flight Arrivals and Weather
Post categories: Sky, Under the bonnet
| 10:00 UK time, Friday, 20 March 2009
Last week, a viewer made the following query: "When I access the flight arrivals screen, the picture changes from that which was on television to a rolling weather forecast. Why is this? Why would I want to know about the weather?"
This happens when using BBC Red Button on Sky, and there is actually a technical reason behind these seemingly unconnected pieces of content. But before I get into that let me explain how our channels, extra video content and text allocation are set up for the Red Button service on digital satellite.
The BBC makes use of seven transponders to broadcast its channel and text service on satellite. Transponders are collections of channels, which are broadcast together in one bundle. BBC One is scattered across transponders 1-6 due to its regional variations as bandwidth restrictions mean that we can't broadcast all of these on one transponder. BBC Two Scotland is broadcast on transponder 2, whilst BBC Three and BBC Four are both on transponder 1 (see table below).
| BBC channels on digital satellite | |||
|---|---|---|---|
| Transponder 1 | Transponder 2 | Transponder 3 | Transponder 4 |
| BBC One London | BBC One Wales | BBC Red Button 1 | BBC One Cambridge |
| BBC Two England | BBC Two Wales | BBC Red Button 2 | BBC One Channel Islands |
| BBC Four | BBC One Scotland | BBC Red Button 3 | BBC HD |
| CBBC | BBC Two Scotland | BBC Red Button 4 | Â |
| CBeebies | BBC Two Northern Ireland | BBC Red Button 5 | Â |
| BBC Three | Â | BBC Red Button 6 | Â |
| BBC One Northern Ireland | Â | BBC Red Button 7 | Â |
| Transponder 5 | Transponder 6 | Transponder 7 | Â |
| BBC One West Midlands | BBC One West England | BBC News | Â |
| BBC One North West | BBC One South East | BBC Parliament | Â |
| BBC One E. Yorkshire & Lincolnshire | BBC One South England | BBC Alba | Â |
| BBC One Yorkshire & N.Midlands | BBC One South West | Various video loops (e.g. News Multiscreen) | Â |
| BBC One East Midlands | BBC One North East & Cumbria | Â | Â |
| BBC One East England | BBC One Oxford | Â | Â |
Alongside the channel broadcast, the BBC also has some bandwidth allocated for the Red Button service on all of these transponders, and here is where it all gets more complicated.
The BBC has two sets of bandwidth allocation for broadcasting BBC Red Button text content, one equating to about 2Mbit/second and the other at about 6Mbit/second. The 2Mbit/second allocation ("Tier 1") accompanies all BBC channels, whilst the 6Mbit/second allocation ("Tier 2") accompanies the BBC's Red Button video such as the News Multiscreen and Children's content.
This means that viewers are able to look at the text service whilst watching a BBC channel. However, the text service isn't the only thing that is broadcast using this allocation - the application that frames the text service and makes everything work also uses this.
We know that it's important for viewers to be able to check certain pieces of information like the news headlines quickly, and whilst watching BBC programmes like Breakfast, so we've prioritised some of our content and included them alongside BBC channels.
Unfortunately we can't include all of the text service in Tier 1, and we also have to balance the need to make this content available against the need to make the content available quickly. Otherwise, if all the Red Button text content was available alongside BBC channels viewers would have to wait for a long time - a minute, for instance - to load the service to check the day's headlines.
Enter Tier 2. Here, as mentioned previously, we have up to 6Mbit/second of bandwidth for the text and application. Therefore, this is where we put all the content that we know is bandwidth-hungry like share prices, and you guessed it, Flight Arrivals.
When we decided to include Flight Arrivals in the Red Button service, there was a debate about where we should place this content for our service on satellite. Should we place it on Tier 1, thus giving viewers the ability to check this content whilst watching a BBC channel? Against that, we knew that we would be adding over 140 extra pages to the service, and this would affect the service's loading time.
In the end, we opted to have Flight Arrivals added to Tier 2. This however presented us with another problem. Flight Arrivals content would be presented across the entire screen, but it would need to be categorised into regions and airports, and this must be displayed using existing menus - yet all our menus on Tier 2 require a quarter-screen video to be shown alongside them (see previous screenshot).
Due to the way the Red Button service is structured, our choices for the quarter-screen video accompaniment for Flight Arrivals are limited to the non-channel video content that we carry. In practical terms, this means choosing a piece of video content within the News Multiscreen service. In the end it was decided that it made the most sense to display the weather news video alongside Flight Arrivals; viewers could listen to weather audio whilst looking at Flight Arrivals information.
Farah Fahmy is a Development Producer working in the TV Platforms Group
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