Video wall controller (sometimes called “processor”) is a device that splits a single image into parts to be displayed on individual screens. Video wall controllers can be divided into groups:
- Hardware-based controllers.
- Software-based PC & video-card controllers.
Hardware-based controllers are electronic devices built for specific purpose. They usually are built on array of video processing chipsets and do not have an operating system. The advantage of using a hardware video wall controller is high performance and reliability. Disadvantages include high cost and the lack of flexibility.
The most simple example of video wall controller is single input multiple outputs scaler. It accepts one video input and splits the image into parts corresponding to displays in the video wall.
Most of professional video wall displays also have built-in controller (sometimes called an integrated video matrix processor or splitter). This matrix splitter allows to “stretch” the image from a single video input across all the displays within the whole video wall .These types of displays typically have loop-through output (usually DVI) that allows installers to daisy-chain all displays and feed them with the same input. Typically setup is done via the remote control and the on-screen display. It is fairly simple method to build a video wall but it has some disadvantages. First of all, it is impossible to use full pixel resolution of the video wall because the resolution cannot be bigger than the resolution of the input signal. It is also not possible to display multiple inputs at the same time.
Software-based PC & video-card controllers is a computer running an operating system (e.g., Windows, Linux, Mac) in a PC or server equipped with special multiple-output graphic cards and optionally with video capture input cards. These video wall controllers are often built on industrial-grade chassis due to the reliability requirements of control rooms and situational centers. Though this approach is typically more expensive, the advantage of a software-based video wall controller vs the hardware splitter is that it can launch applications like maps, VoIP client (to display IP cameras), SCADA clients, Digital Signage software that can directly utilize the full resolution of the video wall.
That is why software-based controllers are widely used in control rooms and high-end Digital Signage. The performance of the software controller depends on both the quality of graphic cards and management software. There are a number of multi-head (multiple output) graphic cards commercially available. Most of general purpose multi-output cards manufactured by AMD (Eyefinity technology), NVidia (Mosaic technology) support up to 6-12 genlocked outputs.General purpose cards also do not have optimizations for displaying multiple video streams from capture cards.
To achieve larger number of displays or high video input performance one needs to use specialized graphic cards .Video wall controllers typically support bezel correction (outside frame of monitor) to correct for any bezel with LED displays or overlap the images to blend edges with projectors.