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Programmers Intro to OCAP
Frank Sandoval
PurposeThe OpenCable Applications Platform (OCAP) is the software environment standard
developed by the North American cable TV industry to enable interactive applications to
run on cable. This paper is meant to provide an introduction to the OCAP platform to the
programming community. Programmers provide the content that is delivered over the
cable network, and include television networks, movie studios, advertisers, and
independent developers. OCAP provides the means for programmers to extend their
current service offerings with software services.
BackgroundAlong with the transition to digital signaling on cable networks comes the possibility of
providing interactive services to subscribers. A prime example of an interactive service is
an Electronic Program Guide (EPG). This software application parses program data
broadcast on the network and provides a User Interface (UI) that lets subscribers navigate
the channel lineup, with helpful features like search, favorites, and so on. Digital
networks also provide the opportunity for programmers to deliver interactive services
bundled with their other service offerings.
Over the last few years several companies have developed platforms that enable
interactive services, and each of the two primary network equipment suppliers have
provided settop box solutions. Although it has been technically feasible for network
operators to host programmer applications, the market has suffered in part due to a lack
of standards. Without a standard and ubiquitous software environment content providers
are faced with a platform choice, and no single platform has captured a critical mass of
deployment. Programmers have been reluctant to develop services that run on only a
subset of networks, or in a subset of the homes within a network.
OCAP is the cable industrys answer to the platform problem. By transitioning to a single
software environment, both network operators and programmers can enjoy the benefits of
deploying a single set of application files to any OCAP enabled device attached to the
network. As MSOs purchase OCAP devices, and as Consumer Electronics Manufacturers
(CEMs) supply retail channels, the cable industry expects to see adoption of OCAP
devices become widespread over the next few years.
Note that OCAP was developed by cable operators primarily in order to allow them to
deploy their own interactive services across the widest possible footprint of devices on
their networks. OCAP also has features that facilitate the deployment of services
originating with programming content. Programmers can leverage the platform to
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enhance their own service offerings, and perhaps evolve new businesses around these
new services.
Programmer Services
The concept of interactive television (iTV) has been around for a while, and polarizedcamps of true-believers and nay-sayers have developed. For those who are curious about
the possibilities, OCAP removes some of the barriers that have made even the exploration
of the medium difficult, much less the successful launching of products. Encouraging
news comes from Britain, where the BskyB satellite network has launched quite a
number of very popular interactive services. Media industry leaders such as John Malone
and Rupert Murdoch have made substantial investments in iTV recently, showing their
endorsement of the concept.
It is important for the cable industry to get feedback from the programmer community on
the vision of iTV. In order to ensure that the OCAP platform supports your needs, and to
anticipate infrastructure requirements, we want your input. Some of the servicepossibilities that have been identified so far are:
targeted ads
one-click purchases
programmer specific guides ( a mini-EPG embedded in the master EPG)
polling (voting in reality TV or game shows)
display configuration (overlay sports stats or choose camera angles)
Of course the range of possibilities is limited only by the imagination of developers and
the fashions of the marketplace. For each of the items listed above, there are specifictechnical details that must be worked out in order to ensure that the expectations of both
programmers and network operators can be met.
OCAP SpecificsOCAP is a software specification that provides a layer of abstraction between
applications and the underlying device. This layer is sometimes called middleware, and
it allows the same program files to run on a number of different types of devices. The key
to the platform is Java technology, which provides the write once, run anywhere
capability. This is a crucial feature for MSOs, because as the CEMs develop new anddifferent devices that connect to the network, the exact same EPG application must run
identically on all of them. This same feature will allow programmers to develop an
application in the lab, and deploy it unchanged to a national audience.
OCAP defines a set of Java Application Programming Interfaces (APIs). These are Java
classes that applications use to manipulate the underlying device. A metaphor used in the
software community is that APIs are sort of like the steering wheel, brake pedal, and
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accelerator in a car. Every driver has the same set of controls, which work for every
brand of car.
The OCAP APIs are a combination of software packages that have been independently
developed by CableLabs, Sun Microsystems, DAVIC, HAVi, and MHP. The latter three
are standards developed to serve similar needs in different markets. OCAP heavily reliesupon the MHP spec, which was developed by a consortium of manufacturers and
broadcasters for the European market. CableLabs is currently working with ATSC to
ensure that the ATSC DASE specification and OCAP are compatible.
Along with the APIs, OCAP defines certain other requirements, such as the network
signaling needed to launch applications, the rules for displaying graphics on the display,
and so on. The specification attempts to provide a minimum definition of the platform, in
order to provide the maximum flexibility to implementers. An OCAP implementation is a
combination of hardware and software, it is a device that has the OCAP software running
on it.
There are some requirements placed on the types of devices that may have OCAP. The
most significant requirement is that the device supports a removable cable conditional
access device, the so-called Point of Deployment (POD) device. To enable cable
networks to support multiple tiers of service, certain content is encrypted and only
decrypted in the homes of those who have higher tier subscriptions. Since different
networks have different encryption schemes, the network operator provides the POD,
which can plug into any device. In this way, the device doesnt have to worry about
which encryption scheme is used on the network it happens to get attached to.
As with many other standards, an important element in its successful adoption is to run a
series of conformance tests on devices that claim to implement the standard. CableLabs
will run tests and certify products before they can be attached to a network. This will
ensure that your applications will run predictably on every device in the field.
Currently, there are two versions of OCAP. OCAP 1.0 defines the Java environment, and
work on conformance tests and by implementers is well under way. OCAP 2.0 builds
upon 1.0 and adds an HTML based environment. There is currently little activity in
developing OCAP 2.0. It is expected that other versions of OCAP will be developed, as
business requirements are identified that can be addressed by further extensions to the
basic platform.
Programmer applications in OCAPTo deploy an interactive service on an OCAP system, one must first build the application
in Java. Several tools developers can provide simulation environments that facilitate
building and testing applications. Dont let Java intimidate you, there shouldnt be any
barriers to rapidly developing any application that you design. The application and the
data files that it accesses are packaged into an Object Carousel (OC) format. The Object
Carousel is an extension of the MPEG-2 transport environment that exposes a file system
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to the device at the other end of the network. Add to this an Application Information
Table (AIT) which tells the receiver that there is an application present, and where to find
it. This collection of files is then multiplexed into your A/V transport streams. Again,
there are tools that already exists that manage the low-level bit munging.
When the receiver tunes to the transport stream that contains your application, the OCAPsystem reads the AIT and launches your application. If the receiver tunes away from your
service, your application is terminated. This type of application is called a service
bound application in OCAP, as its tied to a particular service.
OCAP also supports so-called unbound applications that are generally meant to be
persistent installed applications, like an EPG, that transcend programming services. It is
conceivable for programmers to integrate their offerings with an MSOs unbound services,
or otherwise gain extended access to network services, through bi-lateral agreements with
individual operators.
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