video on demand (VoD)
Video-on-demand(VoD) is an interactive multimedia service that allows videos to be accessed individually. Video-on-demand is a form of streaming video, but is more broadly defined by the development of the vlogosphere. On the one hand, it is about retrieving videos from a stationary video server operated by a streaming service, which can be a media library; on the other hand, in the context of the vlogosphere, it is about video downloads from the Web, vodcasting.
In classic video-on-demand, a service provider operates a video server on which several hundred video films can be accessed simultaneously, which can be called up by the user at any time. Use can be free of charge or subject to a charge and is calculated on the basis of the number of video films viewed.
Video-on-demand uses an individual, broadband forward channel for transmission and a narrowband return channel for communication with the server. The channels are made available exclusively for the duration of use.
Among VoD services, a distinction is made between PC-based web video portals and TV-based VoD. TV-based video-on-demand achieves the quality of analog television and is transmitted using the MPEG-2 and MPEG-4 compression algorithms. PC-based VoD has a much lower quality and is particularly suitable for transmitting video clips or short reports.