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Distributing TV Using CAT5e (3/10/2006)

By Steven Hopkins, Unicam

Traditionally, an RF distribution system has been used to transmit TV around the house, but this will not be adequate or of high-enough quality for the new HD formats. We are in a period of change, and there is currently no sure way to install any system that will be future-proof and be able to do all that may be demanded tomorrow. What is sure and probable however, is that Cat5 wiring will play an important part in TV distribution around the home.

The USA and Japan have been enjoying 1080i and 720p HD content, on tape, off air, by cable and satellite, for some time now. They also have HD-DVD and Blu-ray - one of which already supports 1080p, and the other, no doubt, is soon to follow.

HDTV in the UK at present, is represented by Sky, who is transmitting 1080i and 720p HD content for sports and movies. The BBC is trialling HDTV via Sky and Freesat, with a limited trial in London on Freeview. HD-DVD and Blu-ray are being promised by the end of the year.

HD content for Europe is at 1080i and 720p, at a refresh rate of 50Hz. For the bulk of this content, the pressure will be to output using HDMI. HD-DVD and Blu-ray are going to use HDMI, as will PlayStation 3, and virtually all sources will have some form of copy protection.

Whilst both the hardware manufacturers and the content providers want to go 100% digital as soon as possible, there are many displays installed and in the supply chain, that are not capable of accepting an HDMI signal. Hence Sky has backtracked and put component output on its SkyHD+ first-generation boxes to aid adoption by customers, and Universal Home Studios Video has said that it will delay ICT (Image Constraint Token) - a software flag for deterring piracy that down-samples the output of the consumer's HD-DVD player to 540 lines of vertical resolution when outputting to an analogue monitor.

The pros and cons of HDMI

Introduced around three years ago, HDMI was seen both as an easier way to connect video and audio to a display, and to protect copyrighted material thanks to the HDCP (High Definition Content Protection) that is used for signals travelling over HDMI.

Whilst HDMI seemingly has a number of plus points, its introduction has been far from trouble-free, with many instances, even now, of incompatibilities between displays and input devices. We have also seen specification changes to HDMI, starting with 1.1, moving to 1.2 and the soon-to-be-released 1.3, and although they are backwardly compatible to some extent, both devices will need to be 1.3 if they are to support the latest Dolby and DTS high-definition sound formats.

One thing is for sure; with its 15m distance limitation, HDMI is not the way to distribute HD to multiple displays around a house. There are however, some DVI and HDMI extenders on the market that are able to transmit the signals up to around 50m or more. These take the form of Cat5e cable or glass fibre devices, and tend to be single-distribution systems rather than matrix ones. Furthermore, due to the way HDCP display and input devices must handshake, it is essential to check whether the extender supports HDCP at all!

The advantages of Cat5e

Cat5, or the one that we all should be using, Cat5e, cable is a conduit for now and the future, and the only clear option for TV distribution. Cat5e is the cable of choice for modern-day installers, and is already used for residential computer networks, lighting control, telephony etc. Cat5e cable is a transmission medium favoured for local installations that need high bandwidth and high resolution without any existing network infrastructure. It provides these advantages at a considerably lower cost than fibre optic cable, and supports realtime multimedia transfer through inexpensive, low-density, twisted-pair cabling.

While Cat6 and Cat6e are also becoming popular, Cat7 and Cat8 are yet to be embraced by the domestic custom installer, and both are yet to become an official specification.

Table showing the differences in category cable

In certain ways, Cat5e video distribution combines the best aspects of fibre optic and network technologies. Like fibre optic cable, Cat5e requires no special software or display-side CPUs, and is completely hardware-based and network-independent. Only transmitter and receiving units are required. This network independence means that Cat5e cable allows high-performance, real-time transmission of high-resolution multimedia without slowdowns.

While Cat5e covers shorter distances than fibre optic cable (typically 100-300m/300-1000ft), Cat5e costs considerably less, making it a leading option for combination solutions which overcome its distance limitations. In addition, Cat5e technology can be used in point-to-multi-point applications, allowing the broadcast of media content from one central source to hundreds of display stations. As a result, Cat5e technology alone can be an ideal solution.

There are Cat5e TV distribution systems on the market from companies such as Audio Authority, Endeleo, Smart-e and Scion, which have their strengths for particular applications. Some support composite video, which is not sufficient for HD, and while VGA (15-pin D-sub) can be used, it is not universal, leaving component video as by far the best for HD.

The Smart-e TV distribution system

The Endeleo TV distribution

While the above examples use a hub and end point boxes, Audio Authority systems differ slightly. For example, the 1166/1176 switcher and expander feed six wallplates over Cat5e cable (or Cat6), thus becoming a 6x6 matrix. The wallplates have connections for component video, digital and analogue audio, plus an IR pathway - similar functions to end-point boxes, but more conventional in appearance for the home.

The Audio Authority 1166/1176 Matrix with six wallplates and remote control

Multiple 1176s can be used to expand the network to up to 36 wallplates. The 1166 has both component and DVI video to feed to a high-definition TV for the main room. The DVI input (HDMI adapters may be used in many cases to convert DVI to HDMI or vice-versa) and component video signals are routed to the unit's main output, however a special circuit converts YPbPr signals to DVI-D, so both component video and DVI source signals are present on the DVI main output. No conversion takes place for DVI/HDCP signals - they are switched normally since the 1166 is HDCP compliant. Component video is then available on the wallplates.

The Audio Authority 9870 Series, is a low-cost, single-source, two-room unit, incorporating the key signal paths, YPbPr, analogue audio, and digital audio, plus an IR pathway for easy remote control of AV components. This is over two easy-to-install Cat5e cables, to the same wallplates as used in the 1166/1176 system. The Model 9871 Cat5 Driver distributes HDTV signals up to 1,000 feet from the source, with each driver feeding the two wallplates. Expanding capacity is as easy as adding more driver modules and wallplates.

The Audio Authority 9870 system

Distributed video over IP

We now live in a digital world. Through advancements in digital video compression, audio and video signals can now be carried over typical network circuits both on the LAN and across the WAN, and even over the Internet. Video over IP, or IP Streaming Video, are newer technologies that allow video signals to be captured, digitised, streamed and managed over IP networks.

IPTV has become the topic of conversation over recent years, and the future could lie with products like the Digital Media Projects HD Media Server (HDMS). The HDMS is a DVB-IP gateway which provides distributed video over IP. The unit will transmit over unlimited distances to unlimited end points with zero signal loss. It is HD ready and interoperable with existing IP infrastructure (broadband, email, voice-over-IP), and supports up to 200 channels.

The HDMS currently provides up to six multiplexes of live DVB-T, DVB-C and DVB-S channels. Pre-recorded content can be streamed from a playlist using the internal hard disk drive. Additionally, a live video signal can be encoded and broadcast alongside the chosen live DVB multiplexes, either by dedicated Cat5e wiring or often over existing network cabling. The HDMS feeds standard IP set-top boxes to provide all the connectivity required by modern AV equipment: composite, component, HDMI (HDCP compliant), analogue audio (stereo) and digital audio (S/PDIF).

An easy-to-use web-based management interface allows the chosen mix of digital TV, prerecorded video and audio channels to be changed as frequently as required. Key to the HDMS implementation is the infrastructure over which it runs. One of the biggest features is the ability to integrate into existing IP multicast-aware infrastructures without disruption to existing services.

Digital Media Projects HD Media Server

All of the above systems use Cat5 to network TV around the house. Where no Cat5 has been installed, or it is not possible to retrofit, there are products from Corinex and Netgear for example, that use mains wiring and RF coax to convert to the familiar RJ45 connector used by Cat5 installations, but I believe results can be inconsistent.

Similarly, the new 802.11n wireless technology, necessary for HD video streams, will not be available until 2007, and wireless can still be a problem in some installations. For the moment therefore, all that can be sure is that Cat5 will play an important part in TV distribution around the home.

Steven Hopkins is Audio Authority Sales for the Unicam Group, European distributors for Audio Authority Corp. of Lexington, Kentucky, offering a new line of high-definition signal distribution and control components for custom installation.

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