What is IPTV?

IPTV (Internet Protocol television) is the delivery of programming by video stream encoded as a series of IP packets. IPTV is distributed by a service provider and can be free or fee-based and can deliver either live TV or stored video. It can be bundled with other Internet Protocol services, including VoIP and high-speed Internet access.
In traditional television delivery, all programming is broadcast simultaneously. The available program signals flow downstream and the viewer selects which program he wants to watch by changing the channel.
IPTV, by contrast, sends only one program at a time. Content remains on the service provider's network and only the program the customer selects is sent to the home. When a viewer changes the channel, a new stream is transmitted from the provider's server directly to the viewer. Like cable TV, IPTV requires a set-top box.
IPTV primarily uses multicasting with Internet Group Management Protocol (IGMP) version 2 for live television broadcasts and Real Time Streaming Protocol for on-demand programs. Compatible video compression standards include H.264, Windows Media Video 9 and VC1,DivX, XviD, Ogg Theora and the MPEG-2 and -4.
IPTV competes with another delivery model known, somewhat confusingly, as iTV (Internet TV). In the iTV delivery model, content is typically distributed through a website.