Video on demand (VOD) is a programming system which allows users to select and watch/listen to video or audio content such as movies and TV shows whenever they choose, rather than at a scheduled broadcast time, the method that prevailed with over-the-air programming during the 20th century. IPTV technology is commonly used to bring VOD to televisions and personal computers.
VOD streaming, whereby a user selects a video program and it begins to play immediately on the television set, or
downloading to a digital video recorder (DVR) rented or purchased from the provider, or downloading onto a PC or to a portable device, for viewing in the future.
Internet television, using the Internet, is an increasingly popular form of video on demand. VOD can also be accessed via desktop client applications such as the Apple iTunes online content store.
Some airlines offer VOD as in-flight entertainment to passengers through individually controlled video screens embedded in seatback or armrests or offered via portable media players. Some video on demand services, such as Netflix, use a subscription model that requires users to pay a monthly fee to access a bundled set of content, which is mainly movies and TV shows. Other services use an advertising-based model, where access is free.
Downloading and streaming video on demand systems provide the user with all of the features of Portable media players and DVD players. Some VOD systems that store and stream programs from hard disk drives use a memorybuffer to allow the user to fast forward and rewind digital videos. It is possible to put video servers on local area networks, in which case they can provide very rapid response to users. Cable companies have reeled out their own versions of video on demand services through apps, allowing for TV access anywhere where there is a device that is internet compatible. In addition to cable services launching apps that offer on demand video, they have combined it with offering live streaming services as well. The recent launches of apps from cable companies usually have the phrases "go" or "watch" are attempts to compete with Subscription Video on Demand (SVOD) services since they lack having live news, sports, etc. 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 Video Head-End Office (VHO).