Introduction

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IPTV stands for Internet Protocol TV. Is the service of digital television transmission over broadband systems using Internet protocols.

There are several schemes of operation in IPTV, the two most important are:

- Live broadcasting. It's similar to conventional television scheme, the broadcast center retransmits a scheduled programming. At any time the client connects to the broadcast center and displays what is broadcasting at that moment.

- Broadcast Video on Demand or VOD. The broadcasting server stores a certain amount video, the client chooses one and the server broadcast it to the client.

In both schemes the video is usually compressed in MPEG-2 or H264, wrapped in a container specially designed for video transmision over unreliable networks known as MPEG-TS and send to the client.

In the case of live broadcasting, video is usually sent using UDP multicast.

For VOD is often used RTSP protocol, which introduces commands that the client can give to the server, such as: Output, Pause or Terminate the session. This protocol used at a lower layer the RTP protocol to retransmit the video.

Live broadcasting using XFrame.

XFrame system is a continuity system. It's responsible of broadcasting the video manually or automatically. It supports the most extended professional video formats (DV25, DV50, MJPEG, H263, H264, MPEG I FRAME, etc. ..) combined with the most extended professional audio formats (MP2, MP3, WAV). It has a complete set of tools for transcoding, editing, titling, mix, catalog, send and receive video and audio as well.

XFrame has been adapted to be used in the live broadcast scenario. Usually the output of a XFrame System is a digital signal (SDI, HDMI, etc..) or an analog one (component, composite video, s-video) in SDTV (PAL and NTSC) and HDTV (720p - 1080i). For its use as a data source in IPTV an additional output was added, a data stream with the video compressed in H264 and the audio compressed in AAC-LC. This data flow is wrapped in MPEG-TS and sent to the IP/multicast group indicated. It uses the UDP protocol for transmission. This will enable the use of XFrame as an IPTV broadcasting center, using the state of the art techniques in real-time compression.

This data stream can be received by IPTV hardware decoders (STB or Set Top Boxes), making it suitable for any signal distribution over IP: headers TV, local TV channels, Hotels, Hospitals, airports, etc..
It can also be received by computers for re-broadcast or local display.
The flow can also feed a MPEG-TS multiplexer, which can also receives input streams from other systems. Et combine them, and the output is another MPEG-TS data stream with information grouped by video and audio channels, this flow is used to feed the DVB-T decoders, in this case the coding is MPEG-2.