OCAP,OCAPRI,Tru2Way,MHP,ETV,Java TV,CDC

OCAP is a specification developed by cablelabs and public facing brand name is Tru2way.Before going to Tru2 way i have to discuss on MHP(Multimedia Home Platform).

MHP is a specification developed by DVB(digital video broadcasting) which is extensively used in Europe and some parts of Asia.The first origin for Tv applications is started by DVB.The Television that support these applications is known as interactive Television.These Applications are supported by Digital TV's(which implements digital signaling).

The applications developed are installed on set-top boxes.The set-top boxes of north america are different from rest of the world.Cable Labs started working on Interactive applications(Firstly started by DVB) which gave rise to OCAP(OpenCable Application Platform ).This spec is branded as Tru2Way.

OCAP can be shown as a stack for easy view.


Applications

----------------------------

OCAP API


JavaTv JFM MHP


CDC/FP/PBP

-------------------------------------

JVM



By now we can get an idea from the application perspective that OCAP is a collection of API's.

OCAP is based on MHP.It uses some of the elements in MHP.The first OCAP Spec is based on MHP version 1.0.0.Later on DVB released another specification Called Globally Executable MHP(GEM) to make it easier to use elements of MHP by other specifications.Later on OCAP is based on GEM.

Java TV describes set of concepts required for Dtv such as acessing serviece information,selecting new services and loading files form corousel.It is done in way that it is not tied to Dtv standards.JavaTv describes many of the concepts required for DTv platform.there are some elements missing.So,JavaTv is more a component rather than a middle ware software itself.OCAP uses JavaTv concepts for accessing service information,selecting new services and loading files form corousel etc.

JFM(Java Media Framework) ,an API for rendering Video and other Media.

CDC(Connected Device Configuration) It forms the base of a Java technology stack. It is intended for devices such as television set-top boxes, automobile computers, and other midsized computers.

FP(Foundation Profile) and Personal Basis Profile (PBP) round out CDC with additional APIs, including APIs for user interface and graphics.

OCAP RI(OpenCable Application Platform Reference Implementation) is the implementation for OCAP.The applications can be developed using OCAPRI.

In order to start with OCAP we have to go through some of technical terms.

• Bound application: An application that is tied to a service in order to operate. When the user selects another service, then (in most cases) the application is terminated.
• Unbound application: An application that is not tied to a specific channel and can run independent of any service. Unlike bound applications, an unbound application continues to run after the user navigates to other services.
• MPEG-2 transport stream: The binary stream of data that delivers the audio, video, and interactive content to Tru2way-enabled devices (TVs, set-top boxes, and so on). The transport stream originates from the cable operator and terminates at the cable installation.
  
• Return channel: A separate bidirectional data connection between the Tru2way-enabled device and the cable operator. All Tru2way-enabled devices include a cable modem that enables the device to have a high-bandwidth connection back to the cable operator.
  
• Service: Conceptually, a service is a TV channel. However, a service is actually an integrated collection of audio, video, and program data that's presented together.
  
  

The main feature of these apps are two way communication between User and cable operator.

ETV is another specification in TV app dev.It aims at maximum set-top boxes.

The main differences between Tru2Way and Etv are
ETv applications are supported by legacy set-top boxes,where as Tru2Way applications don't.But the present Set-top boxes support Tru2Way apps and Etv applications may not provide user interactivity.
Tru2Way is having Superset functionality of Etv.So,the applications which are developed in Etv can be completely developed using Tru2Way.
For Bound applications Etv is best and for Unbound Applications tru2way is best.

Both have common "Write once deploy any where" concept.

ATSC have recently announced the Advanced Common Application Platform (ACAP). This is supposed to be a common basis for all interactive TV systems in the US, be they cable, satellite or terrestrial. This is also based on GEM, and adds some elements from OCAP that are appropriate for the US market.

Here are some references:

http://developers.sun.com/mobility/ocap/articles/intro/

http://www.interactivetvweb.org/tutorials/javatv

http://www.ibm.com/developerworks/java/library/j-ocap1/index.html?ca=drs-

http://www.ibm.com/developerworks/java/library/j-ocap3/index.html?ca=drs-

http://www.ibm.com/developerworks/java/library/j-ocap2/index.html?ca=drs-