Sunday, 20 March 2011


IPTV covers both live TV (multicasting) as well as stored video (Video-on-Demand, or VoD). The playback of IPTV requires either a personal computer or a set-top-box connected to a TV. Video content is typically compressed using either a MPEG-2 or a MPEG-4 codec and then sent in an MPEG transport stream delivered via IP Multicast in case of live TV or via IP Unicast in case of video on demand. IP multicast is a method in which information can be sent to multiple computers at the same time. H.264 (MPEG-4) codec is increasingly used to replace the older MPEG-2 codec.

In standards-based IPTV systems, the primary underlying protocols used are:

    * Live IPTV uses IGMP version 2 or IGMP version 3 for IPv4 for connecting to a multicast stream (TV channel) and for changing from one multicast stream to another (TV channel change). IGMP operates within LAN's or VLAN's so other protocols, such as Protocol Independent Multicast (PIM), are used to route IPTV multicast streams from one LAN segment to another.

    * VOD uses UDP or RTP protocols for channel streams and control is done using the control protocol RTSP (Real Time Streaming Protocol).

    * NPVR (network personal video recorder), like VOD, uses UDP or RTP for IPTV streams, and the RTSP control protocol for end-user control communications.

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