Video on demand

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Video on demand (VOD) systems allow users to select and watch video content over a network as part of an interactive television system. VOD systems either "stream" content, allowing viewing in real time, or "download" it in which the program is brought in its entirety to a set-top box before viewing starts. The latter is more appropriately termed "store and forward". The majority of cable and telco based VOD systems use the streaming approach, whereby a user buys or selects a movie or television program and it begins to play on the television set almost instantaneously.

Download and streaming video on demand systems provide the user with a large subset of VCR functionality including pause, fast forward, fast rewind, slow forward, slow rewind, jump to previous/future frame etc. These functions are usually referred to as "trick modes". For disk-based streaming systems which store and stream programs from hard disk drive, trick modes require additional processing and storage on the part of the server, because separate files for fast forward and rewind must be stored. Memory-based VOD streaming systems have the advantage of being able to perform trick modes directly from RAM, which requires no additional storage or CPU cycles on the part of the processor.

It is possible to put video servers on LANs, in which case they can provide very rapid response to users. Streaming video servers can also serve a wider community via a WAN, in which case the responsiveness may be reduced. Download VOD services are practical to homes equipped with cable modems or DSL connections. Servers for traditional cable and telco VOD services are usually placed at the cable head-end serving a particular market as well as cable hubs in larger markets. In the telco world, they are placed in either the central office, or a newly created location called a VHO or "Video Head-End Office".

The first commercial VOD service was launched in Hong Kong around 1990. The technology was not mature, Video CDs were much cheaper, and pay TV was not common in Hong Kong. Hong Kong Telecom lost a large amount of money and the service was acquired by Pacific Century Cyberworks in 2000, who subsequently discontinued it.

VOD services were first offered in Hawaii by Oceanic Cable, January 2000, but are now available in all parts of the United States. Streaming VOD systems are available from cable providers (in tandem with cable modem technology) who use the large downstream bandwidth present on cable systems to deliver movies and television shows to end users, who can typically pause, fast-forward, and rewind VOD movies due to the low latency and random-access nature of cable technology. The large distribution of a single signal makes streaming VOD impractical for most satellite TV systems; however, EchoStar recently announced a plan to offer video on demand programming to PVR-owning subscribers of its DISH Network satellite TV service. After the programs are automatically recorded on a user's PVR, he or she can watch, play, pause, and seek at their convenience. VOD is also quite common in more expensive hotels. VOD systems that store and provide a user interface for content downloaded directly from the Internet are widely available.

In 1999, HomeChoice became the first UK company to launch VOD services, but were restricted to London. After attracting 40,000 customers, they were bought by Tiscali in 2006. Cable TV providers Telewest and NTL (now Virgin Media) launched their VOD services in the United Kingdom in 2005 in attempt to snatch subscribers from the country's leading pay TV distributor BSkyB whose satellite-based network is unable to offer such a service. BSkyB responded by launching Sky by broadband, which was later renamed Sky Anytime on PC. The service went live on 2 January 2006. The Sky Anytime on PC uses a legal peer-to-peer approach, based on Kontiki technology, to provide very high capacity multi-point downloads of the video content. Instead of the video content all being downloaded from Sky's servers, the content comes from mulitple users of the system who have already downloaded the same content. Other UK TV broadcasters have implemented their own versions of the same technology, such as the BBC's iPlayer, which has been in the trial stage since 2005, and Channel 4's 4OD (4 On Demand) which launched in late 2006.

VOD services are available in many other parts of the world as well. The ANYTIME service provides VOD to cable providers in Taiwan and to TransACT Communications in Australia. TransACT also operates its own VOD services including sports and adult content. The ReelTime service provides both VOD (Download to Rent) and Download to Own (burn to own DVD, PC and Portable device) services nationally throughout Australia, and offers full feature length Hollywood and independent movies and TV episodes. ReelTime also announced that its X18+ rated adult site, in cooperation with PlayboyTV and other Adult providers, will be available end of February 2007, known as www.XStreem.tv

It is possible to implement VOD using methods such as bandwidth skimming, which can deliver O(log n) scaling as the number of users increase.

Recently, VOD has been utilized in advertising, as Comcast Spotlight has begun offering on-demand commercials. These are up to 10 minute features on a particular business or event, available to consumers whenever they are looking for more information instead of the business or event trying to generalize information for the entire viewing public^[1].

Four major vendors supply server systems for cable and telco VOD, including Motorola On-Demand Solutions (formerly Broadbus Technologies, Inc.), SeaChange International, Concurrent Computer Corporation and C-COR. Collectively, these vendors represent more than 80% of the world-wide cable and telco server deplyoments.

1 Near video on demand
2 Push video on demand
3 See also
- 3.1 Video on demand providers

[edit] Near video on demand

Near video on demand (NVOD) is a pay-per-view consumer video technique used by multi-channel broadcasters using high-bandwidth distribution mechanisms such as satellite and cable television. Multiple copies of a program are broadcast at short time intervals (typically 10–20 minutes) providing convenience for viewers, who can watch the program without needing to tune in at a scheduled point in time. This form is bandwidth intensive and is generally provided only by large operators with a great deal of redundant capacity.

[edit] Push video on demand

Push video on demand is a technique used by a number of broadcaster on systems that lack the interactivity to provide true video on demand, to simulate a true video on demand system. A push video-on-demand system features a Personal Video Recorder that automatically records a selection of programming, often transmitted in spare capacity over-night, for the user. The user can then watch the downloaded programming at a time of their choosing. As content occupies space on the PVR hard-drive, downloaded content is usually deleted after a week to make way for new programmes. The limited space on a typical PVR hard-drive means that the flexibility and selection of programmes available on such systems is much more restricted than true video on demand systems.

Examples of push Video on demand services include the UK based Top Up TV Anytime and the forthcoming Sky Anytime TV service for BSkyB's digital satellite service Sky Digital.