Articles and whitepapers
Distributing TV Using CAT5e (3/10/2006)
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
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,
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
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
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.