Introduction to LED display grayscale knowledge

1. Grayscale

Grayscale is also called color scale or grayscale, which refers to the degree of brightness . For digital display technology, grayscale is the determining factor of the number of displayed colors. Generally speaking, the higher the grayscale, the richer the displayed colors, the more delicate the picture, and the easier it is to show rich details. The grayscale level mainly depends on the number of bits of the A/D conversion of the system. Of course, the system's video processing chip, memory and transmission system must provide support for the corresponding number of bits. At present, domestic LED display screens mainly use 8-bit processing systems, that is, 256 (28) levels of grayscale. Simply put, there are 256 brightness changes from black to white. Using the three primary colors of RGB, 256×256×256=16777216 colors can be formed. This is commonly referred to as 16 trillion colors. International brand display screens mainly use 10-bit processing systems, that is, 1024 levels of grayscale, and the three primary colors of RGB can form 1.07 billion colors. Although grayscale is the determining factor of the number of colors, it does not mean that the larger the better. First of all, the resolution of the human eye is limited. Secondly, the increase in the number of system processing bits will involve changes in various aspects of the system video processing, storage, transmission, scanning, etc., which will increase costs dramatically and reduce the cost performance. Generally speaking, civilian or commercial products can use 8-bit systems, and broadcast products can use 10-bit systems.

2. Grayscale Nonlinear Transformation

Grayscale nonlinear transformation refers to transforming grayscale data according to empirical data or some arithmetic nonlinear relationship and then providing it to the display screen for display. Since LED is a linear device, it is different from the nonlinear display characteristics of traditional displays. In order to make the LED display effect conform to the traditional data source without losing the grayscale level, the nonlinear transformation of grayscale data is generally performed in the back stage of the LED display system, and the number of bits of data after the transformation will increase (to ensure that the grayscale data is not lost). At present, some domestic control system suppliers’ so-called 4096-level grayscale or 16384-level grayscale or higher refers to the size of the grayscale space after nonlinear transformation. The 4096-level uses the nonlinear transformation technology from 8-bit source to 12-bit space, and the 16384-level uses the nonlinear transformation technology from 8-bit to 16-bit. The space after nonlinear transformation from 8-bit source is definitely larger than that of 8-bit source. Generally, it is at least 10 bits. Like grayscale, this parameter is not the larger the better, and generally 12 bits can do enough transformation.