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Flight Arrivals and Weather

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Farah Fahmy Farah Fahmy | 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  
CBeebies BBC Two Northern Ireland BBC Red Button 5  
BBC Three   BBC Red Button 6  
BBC One Northern Ireland   BBC Red Button 7  
Transponder 5 Transponder 6 Transponder 7  
BBC One West Midlands BBC One West England BBC News  
BBC One North West BBC One South East BBC Parliament  
BBC One E. Yorkshire & Lincolnshire BBC One South England BBC Alba  
BBC One Yorkshire & N.Midlands BBC One South West Various video loops (e.g. News Multiscreen)  
BBC One East Midlands BBC One North East & Cumbria    
BBC One East England BBC One Oxford    

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

Comments

  • 1. At 11:26pm on 20 Mar 2009, Peter wrote:

    Ah, so it was as I thought after all!

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  • 2. At 11:09am on 21 Mar 2009, Briantist wrote:

    Just wondered from reading the above, are the two data caroucels "equating to about 2Mbit/second and the other at about 6Mbit/second" - is this service using the "opportunisitic data" (ie, the spare bandwidth from the result of the MPEG2 picture encoding) or is the data part pre-reserved in the multiplex?

    Secondly, how about, for those poor people without access to the internet, it would be great more of the BBC News content (longer news stories, blogs etc) could be shoved into the Tier 2 area.

    It would be great for people who can't afford Internet access at home, or are somewhere where it cannot be accesses to have access to deeper information for current news stores, BBC blogs and so on, even if it did mean Ceefax-style waiting for the longer content.

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  • 3. At 12:14pm on 21 Mar 2009, Brekkie wrote:

    Having not had Sky I always assumed we got an inferior, more basic, service on Freeview - but recently when I got my hands on a Sky remote for a few days when staying elsewhere I was surprised to discover that's simply not the case.

    Yes, Freeview can't match Sky in terms of number of interactive streams, but in the functionality and speed of the text services the service is far superior. Although thanks to your blog I now understand why, I found it very annoying being forced to watch the chosen screen just to browse the text, being so used to doing it while watching the channel, and also the lengthy delay in accessing any interactive service in the first place, especially as, unlike Freeview, it's not waiting a few seconds for it load, it's waiting even longer with a blank screen waiting for it to load. I'm guessing due to the transponder issue the situation is similar on Freesat too then.

    So perhaps this is an area where when it comes to the BBC at least Freeview actually comes out on top.

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  • 4. At 4:00pm on 22 Mar 2009, Bill Taylor wrote:

    Thank you for the information.

    I have an ongoing battle with BBC Engineering about what I perceive as a correlation between significantly poorer Standard Definition Picture quality on BBC SD channels when you are being over-clever with the use of the red-button facility to provide parallel video streams (not the TeleText like normal service).

    While my educated guess has been lack of available bandwidth and BBC choosing quantity over picture quality my protestations through the various communication channels available have not been successful with the usual response being for me to check with Sky as they are responsible for the broadcast! This is in spite of me stating that I see the problem on Sky, Freeview and FreeSat!

    Ok it may not be bandwidth, but something is causing it! Are there any other digital limitations in the BBC infrastructure that are causing this compromise having to be made?

    Please do not compromise on picture quality.

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  • 5. At 4:03pm on 22 Mar 2009, Bill Taylor wrote:

    How come my comment #4 is being moderated when the blog states all posts are reactively moderated? I am not a new member!

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  • 6. At 10:16am on 23 Mar 2009, Andrew Bowden wrote:

    Briantist - it's pre-reserved bandwidth. As to what we put in there, it's a balancing act between speed and content provision, however it's something that's regularly being reviewed.

    Bill-Taylor - the reason you're being moderated is because all your posts are moderated initially when you post to a blog or a message board for the first time. It's a standard procedure - indeed I was moderated myself despite the fact that I have the password to this blog and (technically) could write whatever I want, whenever I want! After a few comments, you'll be removed from the pre-moderation queue.

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  • 7. At 6:55pm on 24 Aug 2009, scraphaul wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 8. At 04:46am on 17 Sep 2009, funlol1 wrote:

    This comment was removed because the moderators found it broke the House Rules.

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