At present, there are many kinds of graphics cards, which can be roughly divided into five categories according to their functions: 1. Video conversion card or video signal converter (encoder or encoder box). Convert VGA signal into NTSC or VHS signal of TV, usually this signal also has VGA signal output, which can be used to send VGA signal of portable computer or notebook computer to general VGA screen. If this converter is used to convert VGA or TV signals, it is usually used for education, training, briefing, demonstration and so on. Whether the planner in the company gives a demonstration, a school teacher or a company training lecturer, or even business personnel and application engineers, they have the opportunity to train and demonstrate with computers in the classroom, demonstration room or conference room. If you can use this device to move the contents displayed on the computer screen to the big screen TV, the effect is very good. In view of the practicality of the built-in video converter card and the external video converter, the external converter does not need to use the expansion slot inside the computer, which saves the trouble of plugging and unplugging the interface card and disassembling the computer shell. 2. TV tuner. Simply put, with this card, you can choose TV channels on your computer. Usually, this channel selection card has no channel selection buttons or buttons like TV, but uses software to let users select channels with buttons or mouse on the screen of PC. This kind of channel selection animation often has a sound output interface for the user to connect the speaker with speaker or the sound input port of sound card. Otherwise, the TV programs on the computer will have to be "silent" forever. Generally speaking, the hardware part of the TV channel selection card is the channel selection circuit, and the additional functions such as whether there is a dual-tone system and how many channels can be preset are all controlled by software. 3. Still image capture card or frame grabber. When we work in a multimedia environment, we may need to capture scenes from TV programs, videos or cameras. We can capture pictures through this static image capture device, and the obtained pictures can be put in a disk file for later editing or demonstration. Because the image captured by this image capture device is a single picture, it is called "static"; Moreover, because the image it obtains is a discontinuous picture, it does not obtain sound signals at the same time. The only difference between a still image capture card and a capture device is that the former is built-in and the latter is external. Just like other computer peripherals; Built-in needs to occupy a group of computer expansion slots, which is easy to cause accidental damage when disassembling the computer chassis; External devices only need extra power (usually DC power). The applicable occasions of still image capture equipment include: image database management, desktop typesetting, image processing, demonstration, briefing, education and training, etc. 4. Dynamic image acquisition card. Different from the static image acquisition card, the dynamic image acquisition card collects continuous image signals, and this kind of graphics card usually has the output and input ports of sound signals, and the collected results are continuous images and synchronous sounds. The collected continuous images and accompanying sounds can be stored in an audio and video file with an extension. AVI file format AVI. Dynamic image acquisition card can also be roughly divided into two levels: image window card and image compression/playback card. Image window card is a low-priced product in this kind of high-priced graphics card. It can specify a "window" for continuous images from TV, video tape or camera, and capture continuous images in the window. This is the origin of the name of the image window card. Some people may think, why not just grab a continuous image of the whole screen? Why do you want to specify a window? The so-called continuous image is actually composed of many still pictures, so a half-minute image may be composed of hundreds of still pictures. If the resolution of a full-color picture is 1024×768, you must use1024× 768× 24 bit = 22 MB disk space to store the picture. If there are 900 pictures in half a minute, it will not be considered. In order to make the capture of dynamic images feasible, two improvements must be made: first, image data are compressed by software or hardware, and these data also need to be decompressed when playing; Secondly, the captured image should not be too large, that is, users can obtain a certain size of continuous images in the form of windows. As for the methods of compression and decompression, the lower-priced dynamic image acquisition cards all use software, so they can't capture too large a picture, otherwise the dynamic images we see on the screen will become "slow-motion" dynamic images. 5. Image compression/playback card. The compression/decompression methods used are all hardware, so the speed is much faster, and there is no need to limit the size of the captured picture through the window. Although the price is not low, this kind of graphics card is suitable for professional demonstration, demonstration and program production, as well as amateurs. Some manufacturers separate image compression from playing cards. The image compression card is responsible for capturing dynamic images and compressing them by hardware, while the graphics card decompresses the compressed video files by hardware. Due to the maturity of hardware compression technology, we have the ability to store two hours of video programs on a CD. As long as we have a playing card, we can also play programs on the computer that can only be played by optical disc players with optical drives.