|LED screen key technical indicators-full color rental outdoor video wall led panel for screen displa|
The following is an explanation of the technical indicators:
1. Loss of control rate
The pixel loss rate refers to the proportion of the screen's smallest imaging unit (pixel) that is not working properly (out of control). There are two modes in which the pixel is out of control: one is the blind spot, that is, the blind spot, when it needs to be bright, it does not light, it is called the defect; the other is the constant bright spot, when it needs to be bright, it is always on. , called the constant bright spot. Generally, the composition of the pixel is 2R1G1B (2 red lights, 1 green light and 1 blue light, the same reason below), 1R1G1B, 2R1G, 3R6G, etc., and the loss of control is generally not in the same pixel. The red, green and blue lights are all out of control at the same time, but as long as one of the lights is out of control, the figure is considered to be out of control. For the sake of simplicity, the statistics and calculations of the uncontrolled pixels are respectively performed according to the respective primary colors of the P10 SMD LED screen (ie, red, green, and blue), and the maximum value thereof is taken as the pixel loss rate of the screen. The ratio of the number of uncontrolled pixels to the total number of full-screen pixels is called the "full-screen pixel out-of-control rate." In addition, in order to avoid the loss of control pixels concentrated in a certain area, that is, "area pixel out of control rate", that is, in the 100 × 100 pixel area, the ratio of the number of uncontrolled pixels and the total number of regional pixels (ie 10000).
2. Gray scale
The gray scale is also called the gradation or gray scale, which refers to the degree of brightness of the brightness. For digital display technology, grayscale is the determining factor in the number of colors displayed. In general, the higher the gray level, the richer the displayed color, the finer the picture, and the more detailed the details.
The grayscale level depends mainly on the number of A/D conversion bits of the system. Of course, the system's video processing chip, memory and transmission system must provide support for the corresponding number of bits. If the video LED screen uses an 8-bit processing system, that is, 256 (28) gray scale. A simple understanding is that there are 256 brightness variations from black to white. If RGB three primary colors are used, it can be composed of 256 × 256 × 256 = 16,777,216 colors, which is commonly referred to as 16 mega colors. The international brand screen mainly adopts a 10-bit processing system, that is, 1024 gray scales, and RGB three primary colors can constitute 1.07 billion colors. Although the gray scale is the determining factor determining the number of colors, it does not mean that the larger the limit, the better. Because the resolution of the human eye is limited first, the increase in the number of processing bits in the system will involve changes in the system video processing, storage, transmission, scanning, etc., and the cost will increase sharply, and the cost performance will decrease. In general, 8-bit systems can be used for civilian or commercial grade products, and 10-bit systems can be used for broadcast-grade products.
3. Chromatic aberration correction
Due to the difference in color coordinates, the color gamut of the TV video signal is different from the color gamut of the LED, which causes the color of the broadcasted TV program to be unreal. Therefore, the correction of the color coordinates is very important. The calculation of the correction conversion is complicated and difficult to complete with software. From the perspective of the products of various manufacturers, although everyone claims to have such a color correction function, I am afraid that color correction is not achieved.
The biggest difficulty of the full-color LED large screen is consistency, or the fault that is most easily perceived by the audience is that the consistency is not good. The screen appears to be a deep and shallow, commonly known as mosaic phenomenon, which is the most objectionable. There are many reasons for the poor consistency, including the choice of LED quality, drive circuit, structural design and construction. However, unless the dispersion of the light-emitting diodes used is too large, the problem of consistency is mainly a matter of design and construction. Perhaps the average person can watch the problematic LED outdoor billboards. Maybe they can't see the mosaic phenomenon at first. It may be light but not without. There will be some differences between the average person and the professional.
5. Brightness discrimination level
The brightness discrimination level refers to the brightness level between the blackest and the whitest images that the human eye can distinguish. The grayscale level of the screen mentioned above is very high, and can reach 256 or even 1024. However, since the human eye has limited sensitivity to brightness, these grayscale levels cannot be fully recognized. That is to say, many grayscale human eyes of adjacent levels may look the same. And the ability to distinguish the eyes is different for each person. For the screen, the level of human eye recognition is naturally as good as possible, because the displayed image is for everyone to see. The more brightness levels that the human eye can distinguish, the greater the color space of the screen and the greater the potential for displaying rich colors. The brightness discrimination level can be tested with a dedicated software. Generally, a screen with a level of 20 or higher is a good level.
6. Digital processing capability
To get good quality images, you must have a high quality video source. For the average big screen user, the best signal that can be obtained is the broadcast TV signal, DVD, VCD, etc. are only household level. Therefore, digital processing of the input signal and improvement of image quality are indispensable. In fact, everyone has the experience: when playing a selected program, the display effect is very satisfactory, but if it is a live broadcast of a TV program or a DVD movie, it is inevitable that there are various pictures and lenses, such as dark scenes such as night scenes or large The high-brightness and bright picture of the area, the effect will be greatly reduced. How can I have satisfactory results in various pictures and lenses? This depends on digital signal processing, such as digital comb filtering, filtering noise reduction, edge sharpening, telecontrol prediction and compensation, chromaticity correction, nonlinearity. Fix and so on. Especially worth mentioning is the scaling (SCALE) processing, which is a special problem of the LED large screen, which should be studied by the big screen industry. Since the large-screen pixels are always less than the video information source, the scaling problem is inevitable during playback, and the loss in sampling and reproduction and the resulting aliasing and defects may result in degradation of image quality. How to reduce and reduce losses requires digital signal processing techniques. Digital image processing technology has made great progress, and there are many achievements, such as the technical results in large-size TV or projection, which can be directly applied to large-screen displays. The processing power of the digital processing system is concentrated in the processing of the number of bits and the processing speed. The use of DSP or high-end FPGA is an inevitable trend.
7. Gray-scale nonlinear transformation
Gray-scale nonlinear transformation refers to transforming gray-scale data according to empirical data or some kind of arithmetic nonlinear relationship to the screen display. Since LEDs are linear devices, they have different nonlinear display characteristics from conventional displays. In order to enable the LED display effect to conform to the traditional data source without losing the gray level, generally the nonlinear transformation of the gray scale data will be performed in the latter stage of the LED display system, and the number of transformed data bits will increase (guarantee not to lose gray) Order data).
8. Reliability and longevity
Reliability is the life of the screen. Whether it's for corporate image or business model-based activities, LED screens are critical and reliable. Reliability metrics are expressed by mean time between failure (MTBF) and mean time to repair (MTTR). MTBF 10,000 hours is a very high indicator and is not necessarily needed. Many manufacturers have made great efforts to improve the reliability of the system, but what level has been achieved, and can not provide convincing information, which also caused us to find the difficulty of the LED screen, and caused the quality and price of the LED screen.