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Unformatted text preview: thout leaving the comfort of
their homes, and interact with the programs via VCR-like functions, such as fastforward and rewind. In essence, it implements a virtual video-rental shop from
which customers can borrow and view the videos of their choice at their own
convenient time. The rental shop being virtual provides 24 hours service.
Interactive TV is implemented by using a Video-on-Demand (VoD) system and
the facilities offered are often referred to as movie-on-demand, news-on-demand,
sports-on-demand, education-on-demand, etc. depending on which ones of these
are supported by the system.
The main components of a VoD system are as follows (see Figure 19.8):
Video server. A video server consists of massive storage and media
controllers. It stores a large number of digitized videos and serves simultaneous video requests to the same or different videos on demand. The storage media
usually consist of magnetic disks, optical disks, and magnetic tape and are usually
organized hierarchically for cost effectiveness. Under this configuration, popular
videos are stored in the disks. Less popular ones are stored in tape devices with
terabyte capacity and retrieved as necessary to the disk drive for processing. The
basic functions supported by video servers include request handling, random
access, and user interactions.
2. Transport network. The transport network delivers video programs from the
video server to the customers. The network must have a very high data rate and
satisfy the real-time delivery constraints of video traffic.
3. Set-top box. A set-top box along with the television monitor and the infrared
controller (i.e., remote control), serves as the bridge between the subscribers and
With on-screen images and cursor-like devices, viewers are
connected to the video server and can browse the video selections and interact
with the services via VCR-like functions. The major functions of the set-top box
include receiving the incoming video streams; demodulating, demultiplexing, and
decoding the si...
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This document was uploaded on 04/07/2014.
- Spring '14