By fully embracing DVB through support for its Service Information (SI) elements, the RDK (Reference Design Kit) has completed a journey that began around 2008, as an internal Comcast project to facilitate IP migration and shorten the two year development cycle of set top boxes.
RDK has now become an existential threat to traditional set top vendors, isolated as redundant middlemen by the RDK pre-integrated middleware, connecting operators with the underlying SoC makers. RDK first of all opened up to other MSOs as Time Warner and then Liberty Global joined the party, followed as licensees by CE vendors, SoC makers, software developers, system integrators and TV service providers, now numbering around 200.
The threat to set top vendors was implicit from the start with Comcast’s stated ambition of working directly with SoC manufacturers to get the RDK up and running on their platforms before building a box around that chip. That has previously been the job of set top makers, but Comcast had got fed up with the long cycle of development this entailed, which it saw as a growing liability in competition with more nimble IPTV and especially emerging OTT operators.
The MSOs, especially in the US, came to see the big global Internet players, Apple, Google, Amazon and increasingly Netflix, as their future major competitors on a worldwide scale. To some extent there was a sense of “we are all in it together.” It was not so surprising then when RDK as a whole opened up to other sectors, especially satellite, during 2013, even though it appeared to benefit direct competitors. This was also motivated by the desire to make RDK the standard worldwide platform for broadcast to IP migration, benefiting from economies of scale.
As Steve Heeb, President and General Manager at RDK Management said at the time, “It was a very big decision for RDK Management and some of the folks involved, to open it up to anyone, but they decided that in order for this platform to work it needs worldwide scale and the project has to be bigger than the traditional cable industry.”
Against this background it was surprising that RDK Management has taken this long to fully embrace DVB, given that this dominates in Europe and has also gained widespread adoption in some other major markets, including, Russia, Australia and just about all of Asia with the notable exception of China.
But many of these regions are in the throes of migration from one to two way networks, or are still just one way as in the case of satellite. RDK until now could do nothing for such operators since it relied on a return path, with no reliable way of delivering vital in-band data, required for tables of contents, EPGs, teletext, subtitles and other services associated with TV channels.
In a DVB service, whether this is satellite, cable or terrestrial, this data is delivered via the SI (Service Information), effectively a table of contents binding all the components of a Transport Stream, into a coherent service, enabling navigation and search. These components are known as Elementary Streams, each comprising just one element output from an encoder, such as the video, audio or closed caption associated with a particular channel.
Without support for SI, RDK could not guarantee accurate delivery of the required data for contents and the EPG, which would result in errors. In various real cases, set tops have been found to retune from their default frequency in search of a new Transport Stream, but after discovering there is no such stream, they wait perhaps 30 seconds and then time out. After this they return to the default frequency, reacquire the transport stream and then attempt to retune again.
The SI defines two types of table, firstly taking the PSI (Program Specific Information) defined by MPEG, which binds all the elements of a single Transport Stream (TS) together. Then come the DVB-specific SI tables unifying all services and Transport Streams, to yield a full multichannel package of services under a single EPG. The PSI lists all the services found in a given TS, identifies all the Elemental Steams contained in it and controls content scrambling through a CAT (Conditional Access Table) associating one or more CA systems with their EMM (Entitlement Management Message) stream and any other extra data that may be required.
The SI tables provide tuning information for negotiating between different transport streams, which are allowed to come from different delivery mechanisms altogether, such as satellite and terrestrial. Also important here is the Bouquet Association Table, which allows services to be presented to users as though they were all on the same transport stream. Taken together then these two can enable DVB hybrids. Then there is the Service Description Table, giving name and optionally other related information, such as language codes and country availability, but most important of all is the Event Information Table (EIT), since this underpins the database serving the EPG and is the means of communicating program information.
For DVB compliance it is mandatory to provide information on both the running and next programs. Then there is the option of providing an EIT schedule looking further ahead, which can, if required, cover multiple channels. EIT information includes things like program title, start time, duration, description and parental rating. It is also possible to classify programs through “content descriptors”, organized into two hierarchical layers. The top layer specifies 10 broad program categories, such as movie/drama, news/current affairs, show/game show, but within each of these are 7 to 18 sub-categories, which for movies say could include actors, director or genre.
DVB-SI is currently the most widely implemented TV metadata standard in the world, but has yet to be deployed to its full potential, because only the minimum mandatory information is usually specified. Full use is not made of tools, such as the content descriptors, with information often only available on the present and following program, rather than for several days ahead and multiple channels. As a result many viewers are not watching programs that they might otherwise have chosen, or may not even know of their existence, which is one reason many current EPGs are still so poor. That may all change after RDK’s embrace of DVB-SI, which may also suggest a lifeline for beleaguered set top makers. To survive they will most likely have to retreat to the cloud, but they can at least become expert in configuration of DVB-SI themselves and help operators deliver a better UI.