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Bionic Buffalo Tech Note #116: Supporting Pegasus/ISA Services in MHP and OCAP Environments
Bionic Buffalo Tech Note #116 
Supporting Pegasus/ISA Services in MHP and OCAP Environments 
last revised Tuesday 2004.06.15 
©2004 Bionic Buffalo Corporation. All Rights Reserved.
Tatanka and TOAD are trademarks of Bionic Buffalo Corporation
OCAP is a public specification defining middleware software for digital cable television set-top boxes
and other digital devices to be deployed by cable operators in North America. MHP is another public
specification (upon which OCAP is partly based), used primarily in Europe, defining a viewer
terminal, its associated peripherals and the in-home digital network. One of the most significant
features of both environments is the portability of software applications in each: compliant MHP
applications should run on any MHP platform with little or no modification, and compliant OCAP
applications should run on any OCAP platform with little or no modification. 
Pegasus and ISA are proprietary specifications describing certain protocols used to deliver some cable
services in portions of the North American market. A programming environment (including an API) is
defined for servers, but not for set-top boxes. The ISA specification defines portions of the server
environment, while the Pegasus specifications define the protocols. Although clients aren't meant to
comply with ISA (the server specification), understanding ISA is necessary for client design as part of
the overall system context. 
OCAP and MHP do not incorporate the Pegasus and ISA protocols. However, there is a large installed
base of Pegasus and ISA compatible equipment, and during the transition to OCAP it is desirable that
newer OCAP boxes support the legacy Pegasus/ISA protocols in a way that is transparent to compliant
OCAP applications. This Tech Note describes the approach taken by Bionic Buffalo to achieve that
This discussion does not include considerations involved in moving Pegasus applications to OCAP
environments (porting), or in running Pegasus applications alongside OCAP applications (which
simply requires dual APIs). 
Note regarding trademarks and acronyms: “OCAP” is an acronym for “OpenCable
Platform Specification”. “OpenCable” is a trademark of Cable Television Laboratories, Inc. “MHP” is
an acronym for “Multimedia Home Platform”, and is one of the specifications in the “Digital Video
Broadcasting” (DVB) family of specifications. “MHP” and “DVB” are trademarks of the DVB Project.
The Pegasus and ISA (Interactive Services Architecture) specifications are owned and published by
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