Applications and Advances in Video on Demand
Video on Demand (VOD) has been actively pursued for the past several years. VOD would accomplish three distinct purposes in terms of community service. These include interactive distance learning, video conferencing, and entertainment. While it is the first two, video conferencing and interactive distance learning, which would serve to the best advantage in terms of education and business; it is the last, entertainment which has the most appeal to the largest number of people. The application of video on demand in terms of education and business is currently being utilized in remote learning programs and company training programs around the nation.
Video on demand can take many forms. In the simplest of forms it is a series of Video Cassette Recorders (VCR) located in a control station which are networked to either homes, classrooms, motel rooms, etc. The customer simply calls in their order and a technician retrieves the tape and plays it over the centrally located VCR. This setup and slightly more complex ones which operate under similar procedures, with customers ordering only individual programs, are referred to as one-way multicast (Shenoda). Video on demand is particularly adapted to "narrowcasting" the ability of the networks to economically present specialized television programming even for small audiences (O'Brien).
Video on Demand is supported by two major systems and transport standards: Telecommunication Union-Telephony (ITU-T) Recommendation H.320 Audiovisual Systems specifications and related standards and Motion Picture Experts Group (MPEG) systems and standards (Shenoda). Both ITU-T and MPEG were developed with the purpose of supporting compression and encoding of video and audio signals (Shenoda). They were also developed to those signals with data/graphics and control signals as well as others and to transport those through the networks which are already in existence today (Shenoda).
It is the H.320 specification which is most applicable for narrowband time-division multiplexed (TDM) networks (Shenoda). MPEG on the other hand is more suited to broadband packet-oriented networks and it is these networks which maintain end-to-end quality of service (Shenoda). A third type of specification is motion JPEG but this specification, while it is useful in high-quality video such as that utilized in studio program presentation, is of less general interest due to the high amount of bandwidth it consumes (Shenoda).
An underlying physical layer and an overlying H.221 framing standard is recommended for ITU-T H.320 (Shenoda). Shenoda also reveals that:
"Above framing reside H.230 control signals, the G.7xx suite of digitized-audio protocols, and the H.261 codec standard for digitized video. Data or other information can be multiplexed with video and audio using the H.221 framing standard.
H.320 specifies the system reference configuration and...