The compression algorithms used for KVM systems are key to performance of the video link
In a KVM system, the letter V – short for video – plays the most important role because it is the only component that is visible when transmitting and switching signals. The migration from analogue to digital image signals constituted a major challenge for KVM: higher resolutions require higher data rates. However, the bandwidth of cable infrastructures, especially when using CAT cables, is extremely limited. Here, signals cannot be transmitted without being compressed. For the benefit of their customers, Guntermann & Drunck (G&D) rely on their proprietary compression technology.
Why the letter V in KVM is so important
When using KVM technology, the main focus is on the video quality. KVM transmission stands and falls with the video signal because high resolutions and crystal clear images, without any loss or latency, are extremely important. However, increasing resolution also comes with great challenges. Without a doubt, one of these challenges is the high data rate required for 4K resolution with over 10 Gb/s, which in turn places enormous demands on the cabling infrastructure.
When it comes to data rate, keyboard and mouse signals play only a minor role although they form two thirds of the term KVM. The transfer of these two signals is very stable and not susceptible to faults. They need only an extremely small bandwidth when transmitting a wide variety of signals.
KVM and compression from one source
Although G&D have been approached by external development institutions regarding the development of a codec, they decided to develop their own compression algorithms to keep both their independence as well as the speed in their own hands. G&D have always been rejecting the development of external compression since they consider proprietary compression to be an important part of their intellectual property. The German manufacturers are aware of their obligations to their customers to deliver the best possible video quality even when dealing with market-related changes in graphics cards and monitors and even though this means having to invest many man-years of development.
For reasons of cost, the bandwidth of KVM matrix systems must be kept to a minimum – even when it comes to high resolutions. Due to the limited bandwidth of CAT transmission, the video signal has to be compressed in order to handle the large data volume while guaranteeing high-quality images. High-resolution video content can be transmitted only when compressed. Therefore, the compression developed by G&D uses a multistage process that supports maximum definition and a full colour depth at 24 bits.
Compressed or uncompressed – that’s the question
G&D’s customers are not restricted to pick only one solution. The German manufacturers offer KVM solutions that compress video signals for transmission and therefore support cost-effective cable infrastructures. But their portfolio also includes extenders covering the full range to transmit video resolutions up to 4K. The DL-Vision system, for example, transmits the full bandwidth via two fibre pairs without using any compression, lossless at 24-bit colour depth even over distances of several kilometres – provided the system uses optical fibres, the cable medium of choice when it comes to transmitting digital video information.
Ready for the future
The KVM environment is constantly evolving with new graphics cards (output signal) and displays (input signal). G&D are able to react fast to these changes without the relying on external suppliers. Experience has shown that internal development is often faster to market than the collaboration with third parties. In addition, the future generation of KVM components can profit significantly from the interplay between hardware and software. In such a rounded system, customers benefit from G&D standards such as:
- Higher image quality;
- On-screen display;
- Faster switching through harmonised matrix end devices - even for different video formats at input and output side;
- CrossDisplay —Switching to use the mouse to switch between channels;
- Positive hand-eye coordination;
- Lip sync, which is especially important for the broadcast industry.
In many ways, G&D’s compression is the key to current and future KVM products. Being able to rely on an in-house codec also means the protection of investments for G&D customers: on the one hand for maintaining existing installations, on the other hand with regard to the compatibility of future investments.
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