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An interactive video information service system is implemented
to study the feasibility of providing interactive video
services over the existing telephone subscriber lines. Thisim
plementation applies the ADSL (asymmetric digital subscriber
lines) technology to enhance the traditional copper twisted
pair wires to simultaneously provide a one-way high bit rate
channel of 1.544Mbps, a bidirectional control channel of
9.6Kbps and the original POTS (plain old telephone system)
line. Applying the MPEG technology, the supplier's audio and
video information density (Megabit per second) is compressed to
1.5Mbps. Audio and video information of this density can be
reconstructed with a quality comparable to VHS. The ADSL
transmission technology and the MPEG compression technology
together make providing interactive video service over the
existing telephone subscriber lines feasible. In the
implemented system, a FDDI network is used as the video server
backbone of the central office. All video servers and the
network manager are connected over the FDDI network and thus
compose a video server system capable of providing 32 sets of
program to 450 subscribers. The implemented system provides all
control functions of VCR such as PLAY, FAST FORWARD, FAST
BACKWORD, PAUSE and SLOW PLAY; in addition, the display area
can be proportoinally readjusted. While pausing and forwarding,
the advantage of digital signal processing renders a better
video quality than the traditional analog VCR.
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