Smart-e 4K-RX9000 User Manual - What Is Hdbaset
4K-9000 USER MANUAL V1.1
© 2018 Smart-e (UK) Ltd
www.smart-e.co.uk
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7
WHAT IS HDBASET
The shift to digital content began in earnest in 2002 when development commenced on the HDMI 1.0
standard, up to this point content had been delivered through a variety of analogue methods and connectors.
The aim was to create a new standard suitable for all foreseeable high-resolution and high-bandwidth video
needs. Since this time HDMI has grown to become the standard video connector interface. In very recent times
competition to HDMI has been seen due to data rates exceeding that designed for HDMI standards, the advent
of display port and thunderbolt 3 has enabled higher resolutions for niche applications, however HDMI is still
the most common interface for domestic and commercial installs alike.
The advent of HDMI did present a challenge to AV distribution. Since the late 80s and early 90s, AV distribution
had been perfected to send any analogue content possible over long distances and over a variety of
transmission mediums. Initially AV distribution manufacturers saw the only answer was to convert HDMI in to
an analogue format and then send the information as they always did. This led to a variety of issues, HDMI was
designed to digitally protect content which was near impossible to comply with when sending an analogue
signal, HDMI sources relied on EDID reading of the attached screen which was very difficult to incorporate
existing analogue designs and it removed a number of the conveniences of HDMI such as CEC control and the
Hot Plug Detect mechanisms.
In 2010 Valens developed what has gone on to become the leading standard for extending HD video with their
HDBaseT standard and chipsets. HDBaseT enables the transmission of 10.2 Gbps of uncompressed UHD
video data over 100m of Cat5e/6 cable. As well as video the transmission can also be used for audio, control,
data and power, this provided the AV distribution industry with the perfect tool to replicate the functionality
they enjoyed in the analogue world but also to remove some of the headaches with variable image quality and
EDID which can now be passed from the screen to the distribution point.
HDBaseT has been adopted by nearly all AV manufacturers, HDBaseT is commonly found as an input directly
accessible on high-end screens and projectors removing the need for any additional hardware at the screen
location. This convenience does come with some draw backs, previously in the analogue world it was
commonplace to be able to extend a HD VGA signal at up to 300m, with HDBaseT the maximum range in long
reach mode is 150m, retrospectively replacing these analogue installs would therefore require daisy-chaining
back-to-back HDBaseT systems. Another drawback is the large amounts of data flowing through the
transmission medium leaves the system more vulnerable to EMI, in the analogue world this would have
displayed itself as a distorted signal and an installer could then work through various fixes to see the changes
this has on the image, with HDBaseT high levels of EMI on a sub-standard transmission medium will often result
in no signal being displayed leaving the installer with not much guidance as to where the problem may lie.
The only viable alternative for extending HDMI over large distances is the use of HDMI over network extenders,
commonly referred to as streaming products. These devices use Ethernet protocol to extend HDMI. One
benefit of streaming products is no direct physical connection need exist between a transmit and receive
device, if both are on the same network any receive device can be pointed at any transmit device. Another
benefit is their low cost, compared with HDBaseT extenders a streaming solution can be up to a quarter of the
price. A major drawback with a streaming solution is with video quality. HDBaseT is an uncompressed method
of transmission, streamers will typically use H.264 encoding, this is a compression method and will hence
cause a in quality for the resulting image seen by the client. H.264 encoding is only effective on images up to
1080p in resolution, this compares with HDBaseT ability to send UHD signals. Another downside is the
overhead on network resources. Streaming devices require access to a centralised network to communicate
between the various transmit and receive devices. Each 1080p stream to a receive device in best case
scenario would need a bandwidth allocation of 5Mbps, the solution employed would either need to allow for
this overhead on an existing network or employ a whole new network dedicated to the streaming solution.
As discussed in section 6 of this manual the problems of EMI in digital transmission can be overcome or at
least mitigated against with the use of high quality cabling, in the case of HDBaseT, CAT6a U/FTP cable. To
enable the transmission of such large amounts of data HDBaseT uses a modulation scheme, broadly known
as Pulse Amplitude Modulation (PAM). PAM works by dividing a plane in to a 2
X
number of voltage levels. PAM
therefore has several encoding methods PAM-3 (x=1), PAM-5 (x=2), PAM-8 (x=3) and PAM-16 (x=4). PAM-3
and PAM-5 use the 0V level as an additional encoding level. PAM-16 is the modulation scheme used for
HDBaseT, the higher the PAM technique used the greater the bandwidth. Firstly, to understand how PAM
works let us look at PAM-5, the modulation technique used for 1Gb Ethernet.