Cablevision was the first to launch an HD video-on-demand tier with the BitPack-HD.
As American consumers’ appetite for HD programs continues to grow, stimulated by a significant reduction in digital HDTV set prices, broadcasters and multichannel system operators (MSO) are experimenting with a variety of distribution platforms and technologies to satisfy demand and help business grow.
With more HD sports and entertainment channels debuting in the United States all the time (there are currently about 30 HD channels available), cable and satellite TV operators have quickly begun to build out their infrastructures with sophisticated encoding systems that help operations engineers automatically manage and control the available channel bandwidth. The better the encoding system, the more digital channels operators can squeeze into new subscription TV services.
Launching HDVOD
Cablevision Systems, based in Bethpage, NY, has installed about one million digital set-top boxes to date, with roughly 25,000 able to receive and display HDTV signals. Last fall it became the first cable MSO to launch an HD video-on-demand (HDVOD) tier offering a collection of major motion pictures, independent films and IMAX titles for $6.95 each.
Facilitating the new pay-per-view service, Cablevision is using the Digital Vision BitPack-HD pre-mastering workstation. It’s an HDTV offline signal encoding system that creates 1080i format digital files from D-5 videotape and 35mm film masters. The workstation also can generate 480i and 576i SD streams.
The cable company distributes these HDVOD titles with specialized encryption software that allows thousands of customers to individually rent the titles at their leisure and view them for a 24-hour period. While watching the programs, viewers have the full array of VTR-like functions — fast-forward, rewind and pause — at their fingertips.
Encoder hardware The encoder is used for video file compression, which is critical for conserving channel capacity and maintaining a HDVOD business. The system is used for digital cinema, archiving and DVD applications, and it supports future HD DVD formats.
The hardware behind BitPack-HD is based on a proprietary MPEG-2 compression engine. This provides picture quality and the flexibility to adjust bit rates as necessary. Also included with the workstation computer are integrated machine control functions that enable cable operators to perform automatic frame-accurate encoding and real-time playback. With an intuitive Windows NT user interface, the encoder enables comprehensive project management (using integrated EDLs), bit-rate encoding control and quality-of-service (QoS) monitoring via thumbnail pictures.
At Cablevision’s headend facility in Bethpage, engineers can take a D-5 master tape and use the worksstation system’s sophisticated compression algorithms to reduce the size of the resulting audio and video data files. The result is two separate streams (one for SD and one for HD) that are distributed through several SeaChange VOD servers.
Looking ahead
The cable company currently transmits 1080i HD programs with a data transfer rate of about 14Mb/s, which produces an HD picture. However, this rate can be changed during different parts of the program as new services are added or as special live events (such as sports) require. The BitPack-HD system is completely upgradeable. Users can purchase the SD version to get their digital program service off the ground, then migrate to HD channel programming with a software and hardware exchange.
Cablevision operates two BitPack-SD systems and upgraded one to HD operation via a hardware-board swap to feed the new HDVOD service.
Though Cablevision was the first to launch an HDVOD tier, now many other operators are following suit. Using the Digital Vision BitPack-HD workstation, HDTV programming can be quickly developed into a profitable business.
Michael Grotticelli regularly reports on the broadcast industry.
