Video on Demand

mGenXTechno Tags: video, demand, video on demand, load, distribution, server

Pay-per-view (PPV) services could be considered a primitive form of distributing media on demand. This requires the subscriber to sign-up for an account and thus enabling him access the service. The subscriber is being charged for installation and a periodic rental. This scheme is different from pure broadcast in the sense that it provides the subscriber the control to receive according to his subscription.
Quasi Video-on-Demand (Q-VoD) services, takes selective subscription a little more ahead by multicasting media content amongst a group of users who share a common set of interests. To access media content that is not available in a particular group a subscriber belongs to, he can switch between groups. Near video-on-demand (N-VoD) services simulate media access control functions like forward and reverse in discrete time intervals. This capability is usually facilitated by providing multiple channels with the same media content, skewed in time.
All these concepts collate to the introduction of a True Video on Demand system. To provide control to the subscriber, a True Video-on-demand system requires a feedback mechanism installed at the subscriber device that aids the Video-on Demand service engine control the rate of data transfer over the network. Thus depending on the network bandwidth the service provider, signals the underlying encoding engine to manipulate the media encoding bit rate so that media can be delivered to the subscriber trading off between the quality or the request-response latency.
The Challenges
1. Load distribution on server: To support multiple connection requests from user, and facilitate minimum response time.
2. Media content management: This includes high storage space, effective content management, replication strategy etc.
3. Adapt to dynamic network bandwidth: As the client-server link may not always be consistent, one needs to manage the content corresponding to network change and still maintain quality of the media.
4. Decide on Buffer/Cache: To facilitate user with better quality and high-response time, the system may have to decide upon the buffer size and cache.
5. Rate control: For adapting to network, the system may need to vary the transport and encoding rates.
6. Scalability and cost effectiveness.
7. To provide reliability and availability
In addition to these parameters, such a set-up needs to be highly fault-tolerant and fairly scalable to ensure subscriber satisfaction. Several architectures are proposed in this regard which address the above mentioned issues by employing expensive hardware infrastructure.