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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.