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Meet the Green Button! New Developments on Freeview+ and Freeview+HD: Trailer Booking

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Ant Miller Ant Miller | 09:00 UK time, Friday, 6 August 2010

Dr Nick Yeadon of the Digital Service Development team has written us this post giving a facinating overview to the recent development and deployment of a new feature on the Freeview platform:

A feature that all new Freeview+HD recorders are required to support is "Trailer Booking", also known as Green Button. This new feature allows broadcasters to send metadata about a trailer in-time with on-screen trailers. The metadata tells the recorder what is being trailed so the viewer can book a programme to be recorded when the green 'Book Me' icon pops-up. No need to go searching through the EPG for it.

The BBC has been broadcasting this service on BBC1,2,3,4 and the HD channel since the end of May, although on BBC1 and 2 is only available in England at the moment. We are currently assessing the challenges of rolling it out on BBC 1 and 2 in Northern Ireland, Scotland and Wales.

This new feature relies on a DVB table called the Related Content Table (RCT). This table changes dynamically as the broadcast content changes. We are using this table to transmit two kinds of links: links to programmes and links to whole series. We can transmit multiple concurrent links as the trail requires. So these links tell a recorder that we are currently broadcasting a trailer for a particular programme, for multiple programmes or for one or more series, and thus allows the viewer to decide which to book for recording. The specifications allow the broadcaster to transmit their own icon for the initial viewer alert (e.g. 'Book Me') or to use a 'default icon' already embedded in the recorder. We can also transmit a message with each link suggesting why they the viewer might like to record the programme or series.

The mechanism builds on the existing features of Freeview+ recorders that the BBC already supports such as series linking, repeat identification and recommendations.  

The whole system is reliant on an identifier called the Content Reference ID (CRID). This allows the identification of a programme rather than a timeslot in the schedule. It also allows the abstract identification of a series. This concept has been around for some years and comes from a set of specifications defined by the TV-Anytime Forum but the BBC was the first to broadcast these ids over-air with the launch of Freeview Playback (now Freeview+). This separation of programme from schedule means we can promote a programme or series long before it appears in the schedule - so the viewer can book programmes and series based on those 'coming soon' trailers.

R&D have been fundamental to this complex project, which involved different BBC departments ("Marketing, Communications & Audiences (MC&A)", Future Media & Technology, and Distribution) and our technology and metadata suppliers - we had to make the business processes work to support this and to get the right systems in place to produce the correct information at the right time. We've worked with recorder manufacturers, through the Digital TV Group (DTG), as they add this feature into their new products.

Behind the launch of this feature by the BBC are many years of investigation by R&D. We initially contributed to the DVB standard (Carriage of TV-Anytime over DVB networks, ETSI 102 323) which determines the interchange between the broadcaster and receiver. Through the DTG D-Book process we profiled how the DVB tool kit would be used in the UK and defined how the recorder could and should use the information signalled by the broadcaster. This aspect required significant discussion with receiver manufacturers because although the TV-Anytime standard (TS 102 822-3-1) specifies different types of linkages (in the 'HowRelated' classification scheme) how the types should be used, e.g. what a receiver should do with a link type called 'IsTrailerOf', needed to be defined locally (i.e. in the UK). Throughout all this we had built an end-to-end test and development chain in our lab, and even built some prototype/test receivers to make sure we had the signalling right.

Within the BBC itself we helped MC&A integrate the correct processes to support the new signalling. We had worked with MC&A before to enable trailer booking on the Sky platform. This mainly meant enabling the correct linkages in the information sent to Sky by our metadata distributor. For Freeview we needed to source extra identifiers and metadata from within the BBC and our metadata provider in order to provide such things as the promotional text with each link, and help commission a brand new system to generate this signalling.

There were other interesting technical challenges in this project: Trailer booking relies on the in-built 'native' software of the recorder to book programmes to be recorded rather than any kind of MHEG application - trailer booking does not use MHEG. One of the reasons for this approach is that each recorder has it own way of presenting a booking to the viewer, and so trailer booking needed to be a familiar user experience. However, it is quite unusual for a broadcaster initiated action to cause something to pop-up on the native user interface - most of the time it is viewer initiated, e.g. changing channel, pressing the info button, selecting the guide (obviously broadcaster initiated pop-ups happen all the time in the MHEG application domain). Many MHEG applications run in a 'sandbox', in that the recorder can't easily tell in how the user is interacting with the MHEG application, e.g. whether the application is in full-screen mode or just an icon is showing. Also, some receiver software cannot display native graphics and MHEG graphics simultaneously. The problem this gives is that it would be an annoying user experience if the recorder put up a green 'book me' icon over an MHEG application or, even worse, tore down the MHEG application, while it is being used by a viewer, in order to put up a green icon. To solve this problem R&D and the recorder manufacturers came up with a way for MHEG and trailer booking to co-exist, whereby the MHEG application has the ultimate control of when green button icons are permitted. So, when the user starts to use MHEG, the MHEG application can choose to suppress trailer booking pop-ups.  When we were reviewing this idea we built this into our prototype receiver to check this feature would behave as expected.

Being able to deliver synchronised typed metadata, which is what trailer booking is an example of, is just the start. The specifications,  DTG tests and head-end are designed to allow future expandability. Now this data stream and supporting processes are in place there's much more we can add. For example, there's whole range of different link types available. So watch this space.

Look out for trailer booking on the new range of Freeview+HD PVRs - it's a standard feature.


  • Comment number 1.

    I could be wrong, but isn't the link type "IsTrailerOf" (rather than "IsATrailerOf")?

    Also, I haven't read the specs fully, but the RCT contains "the numerical value of the TermID field" - and TermIDs are hierarchical; does this mean that only the parent TermID is encoded (i.e., 0x01 = Trailer (1), HasTrailer (1.1), IsTrailerOf (1.2); 0x02 = GroupTrailer (2), HasGroupTrailer (2.1), IsGroupTrailerOf (2.2); etc.), with the "direction" of the reference being inferred by context, or is there a particular encoding scheme I've missed?

  • Comment number 2.

    Hi Mo,

    Thanks for your feedback. You raised a couple of points, so we'll deal with them both:

    1/. Sorry about that, a typo slipped through the edit process, so we've corrected it in the text.

    2/. We think you may be working off an old spec document. If you have version 01.03.01 of ETSI TS 102 323 from 2008 and take a look in section 10.4.3 the relevant changes should be pretty clear. In essence the Term ID was changed to take account of heirarchical classification schemes, and it's now the rank of the element within the scheme, if the scheme is flattened.

    My thanks to David Waring of our DSD team for clearing that one up. (He stars in a forthcoming short film looking at research in the North Lab)

  • Comment number 3.

    Thanks Ant (and pass them on to David!)

    I was indeed looking at an outdated version of the spec. I don't have 1.3.1, but I do have 1.3.1 (from January this year), which also contains the changes you've described, and it makes much more sense now.

  • Comment number 4.

    It seems to be the day for typos. I did, of course, mean that I have 1.4.1 from January this year.

  • Comment number 5.

    "Look out for trailer booking on the new range of Freeview+HD PVRs - it's a standard feature."

    Having used a Philips HDT8520 (lots of problems was returned) and now a Humax HDR-FOX T2, both HD+ PVRs, I was surprised to read this blog and learn the data has been around since May.

    We've not once seen a trailer booking option on the BBC (or another channel for that matter) using these PVRs. Should all trailers be giving a "trailer booking" option, or do the BBC use it selectively?

    What safeguards have been put in place to ensure the series ID used for trailer booking which can be issued a long while before it appears in the EPG keeps the same series ID throughout?

  • Comment number 6.

    Manufacturers sometimes prefer to see the signalling on-air before releasing product into the market and there may be a delay while they 'catch-up'. We are aware of at least two models which currently support trailer booking. Trailer booking is a mandatory feature of the Freeview+HD trademark licence and we are expecting manufacturers of Freeview+HD PVRs which don't already support trailer booking to download new software over the air to add this feature to their recorders. Other broadcasters now support this feature (Channel 4 has also started broadcasting trailer booking information on Channel 4, E4, More4 and Channel 4+1) so it will become a widely used feature.

    Not all trailers have associated trailer booking metadata but many do. The BBC currently transmits around 60 trailer booking 'spots' per day, covering our main campaigns.

    Regarding safeguarding series IDs: we require appropriate management of theses ids as an integral part of our metadata provider's business process.

  • Comment number 7.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 8.

    Can we just not have T.V for what it is suppose to be for and that is for watching programmes and not having logos all over the place asking us to press this and press that. the one reason I got rid of sky because I got fed up of press red for this, press red for that.

    It is bad enough with the BBc using dogs on their digital channels, never mind having press red stuck on the screen.

    When I watch the grand prix or any other sport on BBc, we get a big logo stuck on the right and side, telling us to press red. Thankfully, I can get rid of the press red on my T.v, by pressing the green button.

    I am not interested in interactive, I just want to watch what I pay for, I only just got my t.v licence and started to watch T.v again after nearly two years, makes me wonder why I bothered.

  • Comment number 9.

    So we need to press the yellow butten to remove the Press Red and Press Green box

  • Comment number 10.

    And Humax finally get around to implementing it on their Freeview+ boxes. Wizard.

  • Comment number 11.

    The new Green 'Book Me' button is an intolerable distraction.
    We expect BBC technicians to provide an acceptable service, not to experiment with half-baked gimmicks at our expense.
    This Green Button thing appears on current programs and not only on trailers as intended, it has not been publicly explained or effectively coordinated with recorder manufacturers and it creates universal irritation and anxiety.
    Why does management tolerate this incompetence ?
    There is no way to get rid of the thing fron the screen!


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