Signal distribution goes the distance with KVM

KVM is still an outsider in the AV world, yet the technology can be a huge assistance in proAV installations, especially in high-end/complex AV projects. Paul Milligan outlines the benefits.

As analogue video is phased out in favour of high quality high definition video, many organisations are taking the opportunity to restructure IT and AV installations to better suit their specific industrial and corporate workflows and practices. 

KVM (kyboard, video and mouse) technology is rapidly emerging as a tool that enhances and facilitates this evolution.  KVM extender devices allow people to operate computers and computer-based equipment at a distance, using screens and keyboards at their desks, even though the base units are located tens, or even hundreds, of metres away; with no degradation in video quality or delay in interactive response.

Basic extenders work in pairs, connecting a single operator workstation to a computer on a point-to-point basis and these have delivered reliable service for many years.  The next logical step is to add a KVM matrix switch to which all devices and operator workstations are connected.  By simple keyboard command or by means of a third party GUI any operator can access any computer. 

This setup delivers a wide range of benefits, not least of which is increased productivity and cost-savings.  Convenience, security, reliability and system management are all greatly enhanced. KVM technology has become an essential element in the most successful and productive businesses across many fields; from air traffic management to broadcasting and music editing through to utility control rooms and military installations.


This technology is now finding widespread application in the proAV field, particularly as more attention is paid to ensuring security of content and networks and as the highest available video resolutions is a prerequisite in most AV installations.  Many AV installations border on true broadcast quality, and often feed content to broadcast streams.  Typically at large public events in stadiums and halls where the same content is generated and used on internal signage and screens and fed to outside broadcast vehicles for TV transmission.

There are two distinct types of KVM systems, each are suited to different applications and have a separate set of features: KVM-over-IP and direct KVM.  In KVM-over-IP systems, content and control data is packetized and distributed to users over the in-house IP network at the same time as the network is used for other corporate functions.  Direct KVM makes use of a dedicated copper or fibre cabling network which is exclusively used for the KVM system. 

Other technologies can provide similar functionality.  The reasons that high-performance KVM technology is adopted in high-end ProAV lie in the quality of transmission, interactive response, operational flexibility and security.  John Halksworth, senior product manager, Adder Technology  explains some differences:  “HDBaseT is a technology that was originally based on a 10Gbp/s Ethernet connection, but this has now been levelled to provide uncompressed HD video over proprietary cable.  However, this is not a flexible KVM solution, as it is far too costly and complicated to use for switching and just isn’t flexible enough for many businesses.

“Video-over-IP covers a range of codecs that are designed for video signals, and while they’re good for simply watching video content, they’re not accurate or of sufficient quality. For example, in displaying accurate straight lines and computer-generated lettering on a display; which makes it unsuited to CAD design work.  It’s a high latency technology; control of computers results in a lot of lag, creating a very unpleasant user experience.”

It is the user experience that counts.  “KVM systems, in which users interact directly with the source device must be absolutely latency-free, both in forward video and audio transmission as well as the control backchannel,” explains Jochen Bauer, marketing director of Guntermann & Drunck.  “It is essential that video performance in professional systems is of the highest level, especially when images need to be pixel-perfect, which means that the quality and performance of compression algorithms is paramount.  With the ever-increasing increase in video resolution and frame rates this is even more challenging to system integrators.

KVM extenders enable remote interaction on interactive screens at the Parlamentarium visitor centre (2)

“Selection of the type of system for a specific task depends on the requirements and infrastructure of the application environment, each has advantages and disadvantages.  Direct KVM makes use of the full bandwidth of the dedicated connection between the source computer and the user over a secure network, but it has limited bridging distance of around 150 metres for copper, although fibre allows greater extension distances. 

"KVM-over-IP shares an existing network to offer infinite distance capability but suffers from problems associated with bandwidth bottlenecks including loss of image quality, delay in transmission and response and reliability and security issues that are associated with the network infrastructure.  A hybrid solution of the two types offers the best of both worlds: quality within the system and external access, so is suited to installations in which different levels of reliability versus flexibility levels are required by the user, or set of users.”

KVM systems offer benefits to users and can enable computer-based production, control and other systems to be constructed that would be impossible, or extremely difficult without them.  For example in control rooms where there is insufficient space to locate all the necessary computer base units.  In the AV sector, KVM systems bring advantages to theatres, museums and airports and other locations in which flexibility of connection, interactivity and operator comfort is essential.  In education small KVM switches are often used to interconnect students with application computers and to allow lecturers to select and present individual devices onto large screens. 

“Modern digital extension and switching technology emphasise the movement away from a single user-to-computer model toward freely scalable matrices,” points out Daniel Prax, EMEA marketing communications manager of Black Box.  “Providing a quieter workplace and removing excess heat from the area through the placement of computers in low-dust, climate controlled equipment rooms without sacrificing video quality, picture resolution or real-time switching of peripherals.  Server maintenance, software updates and network administration become centralised so making it easier and less time-consuming and costly to support computers.”

The sharing of computers amongst users means that capital equipment and software costs can be reduced.  Computers and software applications can be provided to meet the overall requirement and shared between users rather than individually equipping each user with full set.  This often results in substantial, saving, particularly as high-end processes demand powerful dedicated computers.  Multiple screens and computers can be operated by a single keyboard and mouse on the desk, reducing clutter and operator confusion.  The mouse simply scrolls across the screens, automatically activating the relevant computer.

“In the broadcast industry editing tools that require dedicated computers and software are regularly shared between users; editors are constantly switching between tasks and require only intermittent use of specific tools, so simply connect to the specific source they need from their own desktop workstation,” explains Mark Hempel, head of product management for IHSE.  “At the same time, they benefit from being able to move between edit suites and are not tied to a specific room to undertake a particular task, which means that they, and the facility, are more efficiently employed.  This philosophy is exactly the same in other sectors.  In auto design centres for example, highly specific CAD processes can be accessed simply and easily as designers need; allowing them to change location and tasks and operate more efficiently.”

An important benefit offered by KVM switches lies in the security they offer.  “Locating computer and other source equipment in a safe and secure room prevents physical access to the content stored on it.  USB ports, hard drives and external network connections cannot be accessed, so data cannot be removed without authorisation.  Without an entry point, it is harder for viruses to be maliciously inserted,” says Hempel.  “Direct KVM systems use proprietary compression algorithms to transmit data over dedicated cabling, making it harder to electronically access and make use of those signals and consequently much more secure.  KVM extenders and switches are available that are Tempest approved; which means that they meet some of the most stringent security requirements in the world.”

Cross-conversion of signals through the KVM switch is also an inherent and useful feature. “Legacy computers with VGA outputs can be connected to the latest 4K DisplayPort monitors simply, using the internal signal conversion and upscaling of the switch system, which is a major advantage to integrators and means that organisations do not have to replace old equipment just because the desktop monitors have changed,” says Hempel.

KVM-over-IP solutions are maturing alongside the expansion in IP bandwidth.  “As the investment in IP and high capacity bandwidth continues to grow, so does the performance, reliability and potential of IP-based KVM,” points out Halksworth.  “IP-based high-performance KVM offers a level of control and management that is attractive to users, who can clearly see every node in the system, and gives them the freedom to manage the network on a granular level.  Users can tailor permissions, access, video quality, bandwidth and restriction of USB devices throughout this entire network.”

There are few, if any, limitations on the type of signal that can be transmitted. Frame rates of modern digital KVM systems have been designed for high performance while carrying high-resolution, full-motion video.  A frame rate of 50 fps or greater is required to support smooth mouse or tablet tracking.  Video compression is typically the main contributor to end-to-end delay.  Currently, these delays are typically 48ms round trip. This starts to become noticeable for the user once it reaches the range of 70-80ms, making the latency performance of a typical KVM system well below this threshold.

“Gesture and facial recognition is usually handled through sensors connected to a source like a mobile device or server,” says Prax.  “These devices provide a standardized interface and in some cases it is already possible to combine them with KVM.  VR is emerging and will eventually find its way into many professional areas like surgery, human machine interaction and media.  In many of those areas there are great benefits emerging from the combination of KVM and this technology: wherever there is a need to separate and remotely place sources from interactive devices and displays, signals will have to be extended either through a wired/wireless network or the Internet.”

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