Until the early 80s, multiple image screens consisted of synchronized slide projectors banks. It was a very effective and artistic way to display multiple images on a single screen. But very expensive and cumbersome and required a lot of maintenance. The movement or virtual animation could be achieved using a large number of slides and intelligent programming, but it was not the same as video. However, this was the only way to achieve a large and dynamic image.
In the 80s, the video projection was in its infancy and was based on cathode ray tube (CRT) technology. The biggest challenge with the video projection at that time was brightness: a typical CRT projector could only reach between 600 and 800 lumens. This meant that the projected images were limited to about 4 meters wide and required a dark room.
Monitors and televisions also made use of CRT technology and were limited to 28 inches.
The introduction of videowall processor
In the mid-1980s, the first video wall processors were introduced in the audiovisual industry. They consisted of large equipment racks connected by meters of multi-core wires. Because they could only handle standard PAL or NTSC resolutions, they had very limited functionality, usually they handled only four simultaneous video inputs at the most.
However, they were able to include basic video effects and were able to freeze an image on the screen.
In 1985 there were no specially designed Video Wall monitors. In fact, the first Video Wall used modified tube TVs as displays. The televisions were modified to accept RGB video and installed in custom-designed sheet metal cabinets. These steel structures had three main purposes: they allowed stacking televisions, reducing the gap between one screen to another and providing electromagnetic shielding.
It was a technical challenge since they had to align the images, combine the brightness and color of the different screens and control the problem of the magnetic effect caused by the adjacent monitors. The system was very bulky and difficult to configure.
It was also a rather expensive solution.
The first Video Wall had two main problems: the low resolution and the blinking of large format images.
The resolution of the initial Video Wall was based on PAL or NTSC standards. Therefore, it had a maximum resolution of 625 TV lines throughout the image. This made it almost impossible to see any detail when it was enlarged on several screens.
The flickering was due to the low refresh rate of the image of only 25 frames per second.
The graphics processor
At the beginning of the 90s, the VGA standard was introduced in the Video Wall graphics processors. This new high resolution standard (which at that stage had only 640 x 480 pixels) opened a completely new market for Video Walls. The new applications included control rooms and monitoring facilities used for security systems or telephone networks.
One of the advantages of the graphics processor was the ability to display different resolutions and video standards, simultaneously, in the same system.
Then came SVGA, XGA and until the 4K of the latest generation Video Wall, the ones used by SB Service.
The CRT monitors gave way to the first flat screens of plasma and then LCD. In 2003, large flat LCD screens with
46 ” displays were launched. The main problem was the wide frame, since they were not yet specially designed monitors for the Video Wall. Their fragility also made them more suitable for fixed installations, than for the rental industry. In 2006, a thin bezel LCD screens of approximately 5 mm were presented, or in other words, one centimeter between images from one monitor to the next one.
These monitors frames have been improving being finer and finer until reaching the minimum of 1.8mm that we use today.
As far as image processing is concerned, today the most sophisticated processors are configured for the number of screens and the type of source of each system. They incorporate a scaler to configure the entire display, as well as an architecture of seamless switch operation so that we do not lose the signal even for a moment when making any type of switching between several screens or in the display in general.
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