Date:25/10/2007 URL: http://www.thehindu.com/thehindu/seta/2007/10/25/stories/2007102550021500.htm Sci Tech
Internet Protocol TV: an alternative to cable TV, DTH Internet Protocol television facilitates real time access and dynamic streaming Services offered in broadcast, on demand modes The backbone network must carry many channels Present day customers may be happy if they are offered their favourite TV channels in the drawing room through a telephone cable which is already giving many other services like internet browsing, voice call etc. It has become a reality now. Internet Protocol TV by the telephone service provider on the land line is an alternative to cable TV and DTH. Enhancing quality Advanced compression techniques like H.264 or MPEG-4 or Windows Media VC1 are used in IPTV to enhance the quality in delivery and more importantly to pump in high capacity in a smaller bandwidth home access links. IPTV is almost similar to cable TV service, differentiated only on the payment part as we need to pay only for viewing time, but also in providing versatility in service. IPTV facilitates real time access and dynamic streaming. Services are offered in two different modes - broadcast mode and on demand mode. In broadcast mode, Electronic Programme Guide (EPG ) enables the required TV channel to be selected for viewing and account processing is done for charging on the basis of 'pay per view' concept. On demand type offers include interactive video on demand, time shifted TV channel viewing, music downloads, music on demand, games on demand and interactive gaming. The functional components for the operation of IPTV include: content sources; service nodes; IP networks or backbone network; access network v. customers' premises equipment (CPE ); client server software. Set top box (STB) is an intelligent device loaded with client software used to deliver IP based contents to the end user either for streaming of TV channels or for web based browsing. Picture-in-picture STB is a programmable device and it supports Video Codec, MPEG-2, MPEG-4 and Audio Codec. It also supports unicast, multicast and simultaneous streaming of two channels to be shown as picture-in-picture. The IPTV backbone network is required to be of high capacity to carry a number of SDTV channels, HDTV channels VOD channels and games on demand channels. As one SDTV requires roughly 4 MB and HDTV 20 MB, just for 100 SDTV channels and 20 HDTV channels bandwidth required is 800 MB. In the case of subscriber home access link it has been found that 18 MB bandwidth is enough to cater for 2 SDTV or 1 HDTV besides 2 MB for voice and internet browsing. Copper loops of up to 3,000 feet length and one ADSL 2+ link provide the bandwidth. The TV signals received by dish antenna are fed to the Integrated Receiver Decoder (IRD), which converts the RF signals into digital form and its output in MPEG-2 format is sent to a splitter, which distributes the digital stream through to an encoder. Compressed video The encoder output is compressed video using MPEG-4 format. The output is then fed to DSLAM equipment in the telephone exchanges. The MPEG-4 stream in the form of multicast group continuously flows into the BRAS. BRAS is a continuously generating general membership query to all hosts. As soon as a viewer starts his STB and selects a particular channel, the STB generates a request for a particular channel to BRAS (broadband remote access server) and places a membership report to BRAS. BRAS will place that specific host in a multicast group, and start forwarding the replicated copies of the stream to that specific host. Cost-effective, efficient Sun Microsystems India and Tech Mahendra entered into partnership for roll out of cost-effective and efficient IPTV services in India and Asia-pacific region. Bharti Airtel's test runs have been successful and opening of service is expected this year. BSNL is launching IPTV services in Chennai, Hyderabad and Bangalore soon. A. GANESAN Former DGM, BSNL Chennai To unsubscribe send a message to [EMAIL PROTECTED] with the subject unsubscribe. To change your subscription to digest mode or make any other changes, please visit the list home page at http://accessindia.org.in/mailman/listinfo/accessindia_accessindia.org.in
