Network this! (Part II): DPI, simulcast, switched broadcast top apps as cable migrates to IP.(Internet Protocol)

Last month's article (see CED August 2005, p. 28) discussed the benefits and the challenges of transporting video/audio payloads over IP networks. IP transport breaks certain assumptions about end-to-end consistency of a video payload, creating excessive jitter and data loss that causes a reduction in video quality. The optimum solution to the challenges created by IP is the use of intelligent "payload-aware" devices placed at the edge of the network.

Payload-aware devices understand specific constraints placed on the compressed video bitstream by MPEG encoding devices. The payload-aware device "smooths out" the bitstream to avoid buffer overflows or underflows at the decoder. By doing so, more advanced video applications can be inserted into the bitstream.

Intelligence within the payload-aware device enables it to overcome the challenges created by IP transport and further manipulate or modify the bitstream through Digital Program Insertion (DPI) and other video applications, all while maintaining consistent picture quality. The intelligence, or "processing engine," that powers improved functionality and advanced applications over an IP network is the duo of buffer management and rate-shaping.

In the conclusion of this two-part article, we present a more detailed study of core applications that ride on top of the rate shaping/buffer management engine. The core applications that have garnered the most recent interest are: DPI, digital simulcast, switched broadcast and Digital Motion Graphics Overlay (DMGO). Each of these applications can be deployed regionally and distributed across the network.

DPI: Money in your pocket

The Cable Advertising Bureau predicts that local cable advertising will generate nearly $5 billion in 2005. Cable operators can't ignore the financial rewards available from local advertising.

DPI is the vehicle for inserting advertising into a network feed at the regional or local level. While DPI standards provide the ability to insert any kind of local program into a compressed digital video stream, its most visible application today is ad insertion.

Ad insertion wasn't always done digitally. At one time, programmers added analog cue tones to the program, creating a relatively simple system that had limitations and problems inherent to analog video. With the advent of digital video, operators first replaced the analog tape machine with a …