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Showing Multicast Streaming TV

As standard, a NTB has a TV Capture. However, this implies bringing a TV coax cable to the NTB. This can be a wiring hassle - especially for collections of NTBs on a single site. A solution is to deliver the TV signals as a set of Multicast streams via the LAN infrastructure itself.

A typical TV Multicast stream will require 8 Mbits per second - each. Multicast streaming works well but some older Network infrastructures will be over-stressed by Multicast streams. Always check with the Networking folks. See below.

How Streaming Works

Streaming Transmit Servers take in the TV data in either Analogue or Digital form. They output Multicast IP packets.

The NTB has the ability (as of software version 4.3 - Q1 2006) to receive and decode an IP multicast stream (a streaming Client) , placing the TV image into a Zone on the NTB's output along with other information in other Zones.

The intervening network's Switches and Routers are required to forward the Multicast IP packets from the Transmitting Servers to any client (including the NTBs and indeed other PCs fitted with streaming client software). Modern (acquired within the last 4 years) networking products (multi-port Switches and Routers) can handle Multicasting. They are clever enough to figure out which outbound ports require the Multicast stream and only forward the packets to them. Older Switches tend to send an incoming Multicast packet to ALL outbound ports. This can lead to network flooding. Network Managers are rightfully cautious about Multicasting.

Types of Streaming Server

There are at least 3 possible classes of Multicast Streaming Server devices:

Analogue TV Encoders. Analogue TV in (say from a Camera in Composite form) to IP Multicast out. These devices typically deal with one input Analogue TV channel and produce one MPEG Encoded Multicast stream out. They vary in in the efficiency of the encoding. Typical price is 1,000 for a single unit.
DVB-T 'Re-Broadcasters'. These devices take in a Digital Terrestrial TV (DVB-T) stream from an aerial (which is already in MPEG format), and output an IP Multicast stream. Hence the phrase 're-broadcaster'. The DVB-T standard provides multiple TV streams within one frequency band - called a multiplex. A re-broadcaster with a single TV Capture can collect around 5 TV channels from a single multiplex and multicast them all onto a network. Devices exist in the market with multiple Tuners. A 2 Tuner version (approx 10 TV channels) costs around 3000. A 6 tuner version costs around 7000. The number of tuners required depends on the number of TV channels and whether they are conveniently located within a small set of multiplexes. A 6 tuner version will normally cover all TV channels on UK Digital Terrestrial TV. 2 Tuners will often get all channels required for commercial use. To be safe, ask the end user for a list of the TV channels he might require and choose accordingly.
DVB-S. As DVB-T but for free-to-air Satellite delivered TV.

Beware, there may be copyright issues involved in 're-broadcasting' material onto a LAN.