Video Wall; Data Wall; Media Wall
Video walls easy to be found in control rooms, stadiums, and other large public venues such as airports where patrons are expected to observe the display at long distances. Video walls can also benefit smaller venues when patrons may view the screens both up close and at a distance, and respectively necessitating both high pixel density and large size. One from many example of video wall "good-use" is said located in the main lobby of the Lafayette Library and Learning Center. The 100 inch video wall has size large enough for distant passerby to view photos, while also providing information about upcoming events to nearby observer.
Apart from video wall, we may have heard about Data Wall and Media Wall as well, both –due to its shape and function-- can also be referred as video wall. In fact, any large electronic display of an image or images being displayed in a presentation format can referred to as video wall.
A video wall is typically multiple display devices are tiled together as close as possible in a matrix to create a single logical screen, and by using special Video Processor devices, an image is scaled across the logical screen, but it also can be multiple images spread out over the logical screen, or a combination of both if the case is picture in picture. These are all for the individual display devices physical boundaries.
The individual display devices can be anything from 4” diagonal (the smallest) direct view LCD screens to 120” (very large) front or rear projection devices depending on the ultimate size of video wall being created by the matrix. LED video walls usually use individual discrete light emitting diodes from 5mm each to create each pixel.
Reason for creating large logical displays in such fashion is the possibility to assemble a single logical display area that is brighter, larger, higher resolution and has inherent redundancy unlike any other method of image display. Since the human brain has the ability through your eyes to see and comprehend multiple changing messages through images, everything that happens in real time by scanning each image in some rotation. For this reason, video walls can uniquely present many pieces of information to multiple people at the same time in the same place.
As equally important as the devices that make up the video wall itself are the electronics that drive the video wall, which is called Video Processor. The task of Video Processor is to take all the source images to be viewed, convert them to a common format, size and place them across the video wall matrix. In the case of Video Processor, video processing often employs video filters where the input and output signals are video files or video streams. The techniques are commonly use in every devices involving screen and pictures including television, VCRs, DVDs, or video scalers. In short, Video Processor holds important position in creating a video wall.
Which display to use in order to build a matrix of displays in order to create large video wall? There are two different display technologies for creating video wall: video wall rear projection cubes or Direct View LCD/Plasma screens.
DIRECT VIEW LCD OR PLASMA VIDEO WALLS
It seems to be more logical and saves money to just go down to the local home electronics reseller and buy inexpensive LCD displays to create a large display matrix and hang them on the wall...a video wall will be done in a flash of time...but it’s not so fast. The method actually has some side effects:
- Direct view LCDs/Plasma video walls each have a border or bezel around each one and when you tile these together to create an array, there will be gaps in the overall image. It is what the industry referred to as mullions and transoms, it is fine for windows in a building but causes problems when viewing images on a video wall. You will find it as a distorted information and hard to look at. Although Video Processors that drive these walls can compensate for the width of the mullions, you would also losing data in the gap of the mullion. It may be acceptable for some images, but not for numerical data or mapping functions.
- Consumer grade LCD and plasma video walls are made, sold and discontinued from production in a very short life cycles, generally between 1 year and 3 months. Because of a cost and competitive marketplace that demands manufacturers to constantly churning the product mix to ave the latest being offered. Manufactures know that for most consumers, it will cost less to buy a new unit, than fix the old one. So even with long warranties, there is a stipulation that if the failed item is not repairable, consumers have an option to replace with as similar item. But it is a different case when it comes to LCD video walls in a tightly spaced array because inevitably the replacement unit will not be the same physical size nor have the same optical characteristics, which means the video walls’ colors won’t match. The repairment of LCD video walls will require replacement of the entire array when even only 1 unit fails which means can wipe out one’s savings instead of using the Video Wall Cubes technology.
- It is known that human eye is extremely critical of very small color temperature, brightness and hue difference between closely spaced displays placed in this fashion. Because direct view of LCD video walls were never made for this application they generally don’t have the necessary color and geometry adjustment in them to match the neighboring display greatly.
- LCD video walls could suffer from some form of TIR or temporary image retention with static images. The term for this may varies but it is a function of the technology and manufactures exclude this as a failure, but you may not need to worry so much, it is visible but not necessarily permanent.
- If a unit fails, do not assume a repair can be done easily. That won’t be happen for video walls. Video walls are made to be repaired at a service facility not at the customers’ site. This brings up how we should pack the video wall to be shipped for repair? It is not as simple as put it in a box and send it right away considering its size, shape and fragility. Manufacturers usually provides specialized shipping packaging and difficult to obtain as most of it is made overseas.
- The weight of an array of direct view display devices in video walls is more than most commercial building walls are able to support safely. For example, a 4x3 array of 57” LCD with mounting hardware would weigh approximately 1620 Lbs. Most commercial building walls are not meant to have this kind of weight being cantilevered off of them and if the wall were to fail it could be dangerously lethal.
- All issues above don't generally arise when these devices are used for their intended design application which is for occasional television use. LCD displays are not designed and don't function well when being used in a group as a video wall array. Yes there are "Commercial" versions of LCD's available which can help to mitigate some of its weakness above, but they will not work optimal and will cost many times what the consumer counterparts do.
VIDEO WALL CUBE DEVICES
Although Rear Projection Video Wall Cubes cost more but they are designed and purposefully built for such address and function that cannot be met by LCD plasma video walls. Field service ability is a part of the overall design and can easily be performed in the field by dealer or end user personnels. Spare parts also made available for time horizons in the 7 year range and can even be longer. In general the Video Wall Cubes systems are made for incorporation into an overall installation design that will stay good for many years to come.
There are two types Video Wall Cubes, one is short arc lamp illuminated Video Wall Cubes and the other is LED illuminated Video Wall Cubes. Using LED illumination Video Wall Cubes is admittedly can reduces the cost for lamp purchase, but the brightness will fade over the life of the LED Video Wall Cubes illumination module. The LED Video Wall Cubes have only been available from mid 2010, but the Video Wall Cubes long term reliability and cost can lasts long.
NARROW MULLION LCD VIDEO WALLS
The display was first introduced in early 2010. Narrow Mullion LCD is a commercial grade direct view video walls with purpose for use on video wall matrices creation. The video wall is a hybrid between typical LCD video walls and Video Wall Cubes. Video Processor in Narrow Mullion video walls has the same mechanism as the one in the LCD video walls. although the Narrow Mullion Video Walls are not as small as a cube can provides, the video walls are small enough for some application. The video wall can be an attractive solution but also suffers number of problems including for long term support and longevity.
(Date: 20 June 2013; Frida)