Views: 0 Author: Site Editor Publish Time: 2020-01-06 Origin: Site
The typical 4k TV system model is the most popular production layer of the TV center. It includes the most important acquisition, editing and broadcasting links in the production process. The program signal distribution layer is below, according to the needs of the lower distribution layer. Generate different types of compression encoded streams. The distribution layer is responsible for transmitting the compressed encoded stream to the user terminal. The lowermost user terminal decodes the received compressed encoded stream and sends the decoded baseband signal to the 4K display terminal. This is the whole link of the 4k TV system. The key technologies are introduced below.
From the process of collecting to the presentation of the user terminal, after a series of processes such as camera recording, recording uploading, non-linear editing, transcoding synthesis, broadcast, compression, transmission, reception decoding, display, etc., the program signal pattern has changed several times. During the testing process, the baseband image format should be focused on, so that the baseband image format of each processing step meets the design requirements.
Quadrature sampling: The number of pixel quantization bits is 10 bits or 12 bits.
Scanning method: With the development of hardware computing power and the improvement of display technology, new coding algorithms with higher compression efficiency have emerged, such as HEVC/H.265. The 4k TV system can occupy higher data bandwidth, in order to reduce the screen flash. With progressive scanning, the pixel addressing in the row is from left to right, and the row addressing in the frame is from top to bottom.
The aspect ratio is the basic parameter of the image format, and in the image format conversion process, the image conversion between different aspect ratios is prone to image distortion. The pixel shape recommended by the 4k TV system is square (1:1), and the image width is The model ratio is 16:9.
Program production and exchange signal formats: The signals of the 4k TV system are represented in multiple ways. If the goal is to ensure the highest image quality, the RGB signal format can be used; if the goal is to reproduce the brightness to the greatest extent accurately or to improve coding efficiency.
In the conversion process of analog and digital signals, there are two cases where nonlinear coding is required. One is to improve coding efficiency, and the other is to compensate for the optical-to-electrical conversion distortion of the camera and display. Therefore, in camera and display testing, pay attention to the setting of the nonlinear compensation switch to avoid test errors caused by improper settings.
The 4k TV system recommends a 22.2-channel audio system. The higher-definition TV system is much more complicated. The following aspects should be considered in the test:
1. Check that the channel configuration of each processing step is correct .
2. Check that the audio compression encoding format of each processing step is correct.
3. Check the audio channel characteristics to avoid excessive phase difference between channels, poor channel amplitude and frequency characteristics, distortion, and abnormal insertion gain.
Compression coding mode: The 4k TV baseband signal has a high code rate, and needs to be compressed before transmission and storage. The commonly used compression coding algorithm is HEVC/H.265. When testing the coding link, attention should be paid to the compliance of the encoded data format, and the image quality damage caused by the encoding process is evaluated by the main and objective image quality evaluation methods.
The heat dissipation of display can be achieved by fan heatsink, aluminum heatsink fins, heat pipe heat sink and so on.
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