|
A video wall is a special multi-monitor setup that consists of multiple computer monitors, video projectors, or television sets tiled together contiguously or overlapped in order to form one large screen. Typical display technologies include LCD panels, Direct View LED arrays, blended projection screens, Laser Phosphor Displays, and rear projection cubes. Screens specifically designed for use in video walls usually have narrow bezels in order to minimize mullion, the gap between active display areas, and are built with long-term serviceability in mind. Such screens often contain the hardware necessary to stack similar screens together, along with connections to daisy chain power, video, and command signals between screens. A command signal may, for example, power all screens in the video wall on or off, or calibrate the brightness of a single screen after bulb replacement. Reasons for using a video wall instead of a single large screen can include the ability to customize tile layouts, greater screen area per unit cost, and greater pixel density per unit cost, due to the economics of manufacturing single screens which are unusual in shape, size, or resolution. Video walls are sometimes found in control rooms, stadiums, and other large public venues. Examples include the video wall in Oakland International Airport's baggage claim, where patrons are expected to observe the display at long distances, and the 100 screen video wall at McCarran International Airport, which serves as an advertising platform for the 40 million passengers passing through airport annually.〔(【引用サイトリンク】title=Las Vegas Airport 100 Screen Video Wall )〕 Video walls can also benefit smaller venues when patrons may view the screens both up close and at a distance, respectively necessitating both high pixel density and large size. For example, the 100-inch video wall located in the main lobby of the Lafayette Library and Learning Center has enough size for the distant passerby to view photos while also providing the nearby observer enough resolution to read about upcoming events. Simple video walls can be driven from multi-monitor video cards, however more complex arrangements may require specialized video processors, specifically designed to manage and drive large video walls.〔 Software-based video wall technology that uses ordinary PCs, displays and networking equipment can also be used for video wall deployments. The largest video wall as of 2013 is located at the backstretch of the Charlotte Motor Speedway motorsport track. Developed by Panasonic, it measures 200 by 80 feet (61 by 24 m) and uses LED technology. The Texas Motor Speedway will install in 2014 an even larger screen, measuring 218 by 125 feet (66 by 38 m).〔(World’s largest HD video board to be built at Texas Motor Speedway ) - NBC Sports, 23 September 2013〕 Video walls are not limited to a single purpose but are now being used in dozens of different applications. The global video wall market is expected to double by 2020 as technology continues to advance. ==Video wall controller== Video wall controller (sometimes called “processor”) is a device that splits a single image it 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 operating system. The advantage of using 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 (typically arranged in a linear matrix, e.g., 2x2, 4x4, etc.). 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 resolution of input signal. It is also not possible to display multiple inputs in 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 (e.g. Datapath Limited, Matrox Graphics, Jupiter Systems). Video wall controllers typically support bezel correction to correct for any bezel with LED displays or overlap the images to blend edges with projectors. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Video wall」の詳細全文を読む スポンサード リンク
|