Technology Review writes about how IP-TV works:
IPTV converts a television signal into small packets of computer data like any other form of online traffic such as e-mail, a Web page or the Internet phone service known as VoIP, or Voice over Internet Protocol — making it easier to integrate the various services on a TV screen.
Using the home’s high-speed Internet connection in both directions, a channel selection is transmitted from the set-top box to a local facility, which sends back only the packets of video and audio for the desired channel. The packets are reassembled into programming by software in the set-top box.
A conventional analog or digital cable signal uses far more bandwidth. Every single channel is sent all the way to the set-top box at all times. Each channel requires a separate stream, and there’s only so much room on the wire.
That’s why IPTV addresses a more pressing need for SBC, which is replacing its major copper phone cables with speedy optical fiber. SBC is not, however, replacing the local lines to every home, as Verizon is.
The stock examples of an IPTV future include caller ID, e-mail and voice mail on the television; programming a digital video recorder via cell phone; pulling up data during a sports match to see how an athlete’s record; and watching a show from multiple camera angles.
At a minimum, both SBC and Verizon expect to offer an interactive program guide that might enable viewers to watch a sample clip, program a digital video recorder, pull up information about the actors and director or search for other shows on a related topic or from the same genre.
SBC has indicated it may offer other interactive features from the outset such as the ability to program one’s home digital video recorder over the Internet.