Evaluation standard for small-pitch LED screens by government purchasers

A qualified small-pitch LED display that can stand the test must have undergone strict relevant tests before leaving the factory. Only in this way, after it is officially delivered to customers, can it guarantee a long period of normal operation and good display effect, and reduce the failure rate. Let’s take a look at the evaluation standards and methods of government purchasers for small-pitch LED displays

1. Test methods and conditions for small-pitch LED displays

(1) Equipment: 1 Blu-ray high-definition player with 1080P (1920×1080 full frame) resolution; 1 high-performance computer with 1080P HDMI output; 1 video signal splitter with 1-to-4 component component output.

(2) Standard video sources, pictures, etc. for testing: blue light source disk; professional test video Hi-Definition Reference (select multiple scenes); DisplayX, SJ/T 11281-2007 “Light Emitting Diode (LED) Display Screen Test Method” standard Test software; computer-generated 1080P standard color scale, full-color gradient, gray scale and pictures from the Internet, pictures intercepted or generated by the above two items, etc., night scene pictures of highway bridges.

(3) Test method: Before the official evaluation, each manufacturer is allowed to conduct on-site debugging for its own LED\large screen (due to the limited size of the site, it is recommended to test the resolution 720P or 1080P line of the splicing screen) to achieve the best results of their respective products. best effect. Beginning at the specified time, a review team will be composed of a number of experts with rich experience in image transmission, video display, and led screen visuals large-screen hardware to evaluate the actual application effect.

2. Evaluation requirements for small-pitch LED displays

(1) Grayscale image test

①Grayscale and color scale tests have always been an important indicator reference for large screens such as DLP/plasma/LCD/LED or spliced large screens, and are used to evaluate the gray scale transition capabilities of large screen splicing and controllers (if any), and Black and white conversion capability, etc. The more obvious the contrast, the stronger the ability of the display system to process the color picture.

The bidirectional grayscale signal is used to test the at least 16 grayscale levels that the system should display. If each level can be distinguished, 3 points will be awarded; if there is less resolution, 1 point will be reduced, and the lowest point for this item is 0 points.

25 + 2 levels of gray scale images must be able to distinguish the darkest 3 gray levels A, B, C and the brightest 3 gray levels U, V, W on the screen at the same time. A, B, and C must have layers and cannot look black; similarly, U, V, W must also have layers and cannot look white. If there is any color/color cast in the large-screen image during playback, points should be deducted. If there is no color difference (black and white impurity and other colors), add 2 points. If there is color cast, deduct 1 to 2 points as appropriate.

②Comprehensive test of sharpness and gray scale. This scene is used to comprehensively test the line count, gray scale, geometric distortion and other performance of the entire system. Under 1080P (1920×1080), each gray level and number of lines should be clearly identifiable, and the black and white purity of the gray scale can also be tested. 1 point is deducted for one question; minimum 1 point.

③Grayscale real scene map. The more black and white levels are displayed, the better the gray scale processing capability of the system can be reflected. Minimum 2 points, maximum 5 points.

(2) Color picture test

①Comprehensive test of the dark part of color pictures. This scene is a night scene, which focuses on the changes in the strength of color light and shade and halo, and is used to test the system’s color, grayscale, and detail display and other performance. The boat on the left under the bridge and the top halo above the main tower and the cables on the bridge deck can be clearly distinguished, scoring 4 points. If there is a problem, 1-2 points will be deducted depending on the severity. If there is no problem in distinguishing light and dark changes in other details, add 1 point.

②Highlight detail test: A test of detail restoration ability based on bright white. The scene is a dining table and dressing table with relatively high brightness. The main test is the restoration ability of the white part of the system under high light and the dynamic range of grayscale. The details of the texture of the window curtain, cloth, brush and other objects should be completely preserved. All items are met, 5 points. If there is any non-compliance, 0.5 points will be deducted for each item, and a maximum of 2 points can be deducted in total.

③ Face detail sharpness test. This scene is a close-up static picture of a girl and flowers, reflecting the fidelity of the large-screen stitching system to various details such as skin color and spots on the face and the authenticity of the skin color. The total score is 5 points, if the facial details are not clear, 0.5 points will be deducted. If the facial color is impure, 1 point will be deducted

④ Color reproduction test. Mainly test the uniformity of color and the purity of white. It is very important to restore the various ingredients and fruit colors in the kitchen, the pure white crystals on the tray and the barrel of the colored pencil, the wood grain part, the grassland, and the cloud layer. If the white is impure, 1-3 points will be deducted depending on the purity of the color cast. The full score is 5 point


⑤ Color saturation and detail test. The fluff at the edge of the ball of wool should be clearly visible, as should the grain of the spool and the padding. 5 points out of 5. If the fluff is not clear, 1 point will be deducted; if the texture of the spool is not clear, 1 point will be deducted; if the texture of the doily is not clear, 1 point will be deduct


(3) Dynamic scene t


Waves and Reefs (ROCK&WAVE, Blu-ray video source: 00014.m2ts). This scene is a reef scene, which is used to test the image quality of the device against a static background containing a lot of small movements, especially the white balance and detail resolution. In addition, the Fog (water mist) produced by the waves at the 20-27s playback place should be clearly distinguished. 5 points for a full score, if the level of waves and reefs is not clear, 0.1 to 1 point will be deducted as appropriate. If the FOG is not clearly displayed, 0.5 to 2 points will be deducted as appropria


① Light and dark detail test (Tokyo Night, Blu-ray video source: 00019.m2ts). This scene is a moving image of the Tokyo night scene, which is mainly divided into 4 scenes: the tower illuminated by lights; the Christmas tree embedded with lights; the night scene of the bridge and both sides; the night scene around the Ferris wheel. The main test system is the color reproduction ability and the dynamic range of light and dark contrast during dynamic video playback. The mesh details in high-brightness neon lights, Christmas tree details, dark details on both sides of the bridge, bright parts of the Ferris wheel and dark details of the street should be completely preserved. The minimum score is 2 points, and the maximum score is 5 points (if the details and levels of each item are unclear, 0.1 to 1 point will be deducted as appropria


②Black and white contrast test (Black&White, Blu-ray video source: 00020.m2ts). It mainly tests the edge resolution ability of black and white scenes and black and white dressed people. The highest score is 5 points, and the black background and the edge of the black clothes can be clearly distinguished, and the score is 3 points. If the white background and the edge of the white clothes can be clearly distinguished, 2 points will be awarded. If the edge of the same color is unclear, 1 to 2 points will be deducted as appropri


③Color expressiveness: accessories (Accessory, blue light test source: 00021. m2ts). The main scenes are flowers and accessories (necklaces, gloves, feather accessories, etc.), mainly testing the permeability of colors and the texture of items. In addition, the display of the tiny fluttering details of feathers is also very important. The highest score is 5 points, if the level of the flower is not enough, 1 point will be deducted; if the feather details are not clear, 1 point will be deducted; if the color is not transparent, 1 point will be deduc


④ Dark detail test (Black Image Blu-ray test source: 00027.m2ts). The more black and white levels are displayed, the better the system’s ability to handle dark details, and the higher the number of gray levels that can be displayed and restored. If the black level is clearly distinguished, the full score is 10 points; if the level of the black part is insufficient, 2 to 6 points will be deducted as appropr


The rest of the tests will not be described in de


(4) Professional software testing (DisplayX se


①Pure color: Black, RGB, P (purple), Y, C (cyan), White. Black and white and 6 solid colors are displayed, and the overall color is uneven, with a total deduction of 0 to 1 point, compared with the same period last year. If there is a bad pixel, 2 to 3 points will be deducted depending on the number of bad pixels, compared with the same period last year. Maximum 5 po


②Color and gray scale: Gradient test (no polarization). The R/G/B three-color signal with chromaticity gradient from left to right and the Y/Purple/Cyan after the two colors are mixed are used to test the chromaticity and grayscale changes of the system. The gradient has no sense of step, that is, the smoother the transition, the higher the grayscale level of the system. The gradient of each color is transparent, and there are no faults and vertical steps, the full score for this item is 5 points. Different colors are graded according to the degree of severity, and 1-3 points will be deducted compared with the same period last


③Full color gradient. Full chromatogram gradient and no polarization change, the brighter and more transparent the color, the better. If there are more steps in each color, the less ideal, the corresponding points shall be deducted during the evaluation; the closer the display of each color is to the vertical, it proves the gray scale of each color The more synchronized the changes, the better. Gradient and transparent, without faults and vertical steps, this item is 4 points. If there is no uneven color change during the gradient, another 1 point will be awarded for this item. Depending on the severity of color faults, 1 to 3 points will be deducted compared with the same period last year.


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