Over extended?

Integration and installation of audiovisual systems could be defined as the art of combining disparate components into a single and cohesive whole; the more successful and efficient integrators possessing an above average ability to identify and apply the most suitable component for each element in a large and complex system. Steve Montgomery reports on the technology that glues these systems together.

One area that has been a concern for a number of years and has presented multiple solutions is that of AV extenders: the technology to transmit AV signals over longer than normal distances. Sounds simple, but as the world of AV migrates from analogue to digital, the range of image and sound formats mushroom and legacy systems and wiring have to be accommodated, the range of technology required and offered increases almost exponentially. AV extenders are distinct from, and incompatible with networked AV where video and audio signals are converted to packetised (IP) based formats for transmission over existing IP networks. These IP networks require compressed signals which inevitably results in some loss of image and sound quality. Lossless AV signals at full bandwidth require their own dedicated interconnections and the use of complex switchers, routers and distribution amplifiers to build complete systems. As a consequence a whole range of products, including AV extenders has been developed by specialist manufacturers to deliver specific functionality with which AV integrators can build entertainment, signage and information systems.

Several years after the introduction of digital transmission in the form of DVI, computers still operate to a large extent with analogue connections to displays. Consequently many installations that use computers as the source device, which includes the majority of digital signage systems, still utilise analogue interconnections. Peter Gallagher, Marketing Manager of Magenta Research: “The bulk of the overall extension business continues to be driven by analogue due to ease of distribution, reliability and cost effectiveness. While digital transmission is bound to become more common in the long term, there all still present-day hurdles to overcome such as copy protection and cost . Obviously, Magenta is positioning itself to address the digital market. Within the analogue product range we have a series of extenders based on distance, including the new XR 2000 receiver. When combined with Octet, an 8 channel transmitter, WUXGA video, stereo audio and display-addressable control signals are distributed within a 2,000-foot (610 meter) radius from the source, with no repeaters or booster units. The combination of up to five cascaded Octet transmitters and up to twelve daisy-chained receivers off of each output allows hundreds of displays to be driven from a single VGA port and controlled from a single EIA-232 communications (COM) port. This is representative of Magenta’s cost-effective “building block” approach to signal distribution and is an ideal cost effective solution for digital signage applications.”

Gefen also still considers the analogue market as a significant sector and one that is in a state of flux, also cites the digital signage market as a driving factor. Hagai Gefen, CEO: “We have products that combine the old and the new, allowing the best digital source and display technologies to be connected over installations that were originally designed for analogue systems. So for example, HDMI can be transmitted over existing five wire component cabling using our HDMI over RGB Extender, designed as a ‘dongle’ replacement for existing component solutions where projectors or displays are extended using RGBH&V cable terminated with BNC. The system employs Gennum's ActiveConnect technology and is capable of transmitting high
definition audio/video up to 50 meters making it well suited for most home installations today. This extender supports HDMI at 1080p resolutions and offers complete HDCP-compliance and operates with plug and play ease.” Gefen have announced the development of a version that will operate over coaxial cable, which will be ideally suited to old RF based TV systems. Hagai Gefen: “This will allow the transmission of HDMI over 100 feet with the bidirectional data flow multiplexed over the video information. We have met the criteria for the HDCP Approved Retransmission Technology so it is completely compliant and is similar to the technology used in our wireless HDMI extenders.”

Similarly, a large proportion of Kramer’s business is still in the traditional analogue domain, with digital solutions as alternative. Nick Mawer, Kramer’s Marketing Manager: “There is still a massive interest in analogue distribution. For full bandwidth transmission in adverse environments, for example in rental and staging traditional five wire component (RGBHV) is often preferred; cables are robust and less easily damaged than fibre or Cat5. One of the problems associated with analogue over Cat 5 is the skew between the colour pairs which causes colour halos around images. We have solved this with the introduction of skew free Cat5 cable that eliminates the problem. VGA over Cat5 is also very popular, not all digital signage is IP based and this is an obvious choice for that type of application. We can transmit HDMI over twin Cat5 cables with distances of up to 60 metres at full 1080P resolution. With a fibre and Cat5 combination this can be extended up to 1000 metres. We can also transmit HDMI 1.3 over coax using at three times the distance of copper transmission cables using Gennum’s ActiveConnect.”

Digital systems using DVI and HDMI utilise bi-directional handshaking in the form of interrogation and response communication between the AV source and display. This often presents a problem to designers of longer range transmission systems. Normal analogue video can be transmitted using a variety of level changing or shifting, reclocking and format translation technologies. With digital systems, the status information has to be transmitted as well. Opticis has developed another method, which they refer to as ‘virtual EDID. Kwon Do Hyun: “Our new M1-201CA fibre extender offers up to 500 meters distribution at WUXGA resolution. The four channels that constitute optical data: red, green, blue and clock are multiplexed and de-multiplexed through a multi-mode CWDM optical module. We have a special program in the transmitter module that automatically stores the EDID information and communicates with the source device. This self-EDID programming feature makes the installation of M1-201CA more easy and flexile at any variable resolution display systems.” Digital transmission excels in installation s that need to be installed and left alone. With analogue interfaces to plasma and LCD displays it is often necessary to adjust the pixel phase regularly to maintain optimum picture quality, a process that is unnecessary with DVI and HDMI interconnection.

Extron provides an extensive range of ‘glue’ components for AV systems including a comprehensive range of video extenders for analogue and digital signals over Cat5 and fibre. Mike Andrews, Extron’s Director of Marketing Communications: “Products like our Fox 500 fibre extenders deliver pixel for pixel transmission of very high resolution computer video or HD video over single or multimode fibre at very long distances, even up to 30 Km if required. Twisted pair products have application in all sorts of fields, ranging from point-to-point transmission to a single display up to complex installations where multiple signals are sent to arrays of displays. Using Extron twisted pair extenders in concert with twisted pair distribution amplifiers or matrix switchers affords AV system designers great flexibility to create elegant signal routing solutions. Typical applications include corporate training facilities, themed entertainment environments, movie theatres and schools. Another area where twisted pair excels is in retrofit in protected architectural buildings. Adding AV systems to beautifully decorated country houses, churches and stately homes requires the minimum amount of modification and thin twisted pair cables are more easily concealed than larger ones.”


Another manufacturer involved in the design of AV processing, switching and extender products is TVOne, whose range of high level video processors has been hugely successful throughout the world. The recently introduced 1T-DA-631HDMI extender is claimed to be the only product on the market with integral DDC correction that restores the HDMI v1.3 signal at the end of long cable runs, just prior to the input to the display. Steven Mattingly, Managing Director: “The 1T-DA-631 is the first of its kind to offer DDC Correction ensuring that the HDMI signal stays true to the original form. It has a maximum distance of 40 meters from the source to the Equalizer input and up to 5 meters from the output to the display when using Z-Plus grade HDMI cables. All signal components present within the encoded signal are maintained, including Stereo or 7.1 Audio and HDCP encryption.”

Avocent however has bucked the trend slightly by producing the new ECMS4000 extender. This provides the ability to extend a pair of DVI signals, together with USB over a Gigabit network. Matt Nelson, Marketing Director explains: “Full resolution DVI signals are transmitted digitally over a single pair of wires within a Cat5 or Cat6 cable, with no colour skew problems.” A second product line is a wireless point to multipoint, and multipoint to multipoint transmitter receiver pair. Matt Nelson: “The MPX1500R receiver announced at the start of the year is shortly to be augmented by the MPX1500T. These are reduced size and cost multipoint extenders for the data and video markets. Together they will provide the ability to deliver multiple VGA or 1080i/720p HDTV at up to 1000 feet wirelessly. In addition, they can deliver serial control, allowing a remote devices to be switched on and off and controlled via its serial input over a distance.”

With an abundance of signal formats covering both analogue and digital spectra at different rates and resolutions for both video and computer audiovisual systems, it is inevitable that there will be a similar range of transmission products. The trick is in selecting the correct format to use for any specific installation or application and then choosing the appropriate product to suit that selection. It is certain that for any choice, an AV extender will be available of sufficient quality and performance to achieve the desired effect.

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