What is the principle of compressing video?

Principle of video compression: Video compression can effectively send and store digital video files by reducing and removing redundant video data. In the process of compression, it is necessary to apply compression algorithm to compress the source video and generate compressed files for transmission and storage. If you want to play compressed files, you need to apply the opposite decompression algorithm to restore the video, and the restored video content is almost identical to the original source video content. The time required to compress, send, decompress and display files is called delay. Under the same processing capacity, the more advanced the compression algorithm, the longer the delay. Video codec (encoder/decoder) refers to two cooperative compression-decompression algorithms. Video codecs using different standards are usually incompatible with each other; In other words, video content compressed by one standard cannot be decompressed by another standard. For example, MPEG-4Part2 decoder cannot work with H.264 encoder. This is because one algorithm can't correctly decode the output signal of another algorithm, but we can use many different algorithms in the same software or hardware to support the compression of files with many formats. Because different video compression standards will adopt different methods to reduce the amount of data, the compression results are different in terms of code rate, quality and delay. In addition, because the designers of encoders may choose to use different tool sets defined by a certain standard, even among encoders using the same compression standard, their compression results may be different. However, as long as the output signal of the encoder meets the standard format and the requirements of the decoder, different implementations can be adopted. This is very advantageous because different implementations can achieve different goals and meet different budget requirements. For the non-real-time professional software encoder used to manage the storage of optical media, it should be able to provide higher quality encoded video than the real-time hardware encoder integrated in the handheld device used for video conferencing. Therefore, even the specified standard cannot guarantee to provide the specified bit rate or quality. Moreover, if the implementation is not determined in advance, a standard cannot be correctly compared with other standards, or even compared with other implementations of the same standard. Unlike an encoder, a decoder must implement all the necessary parts of a standard in order to decode a bitstream conforming to the standard. This is because the standard clearly stipulates how the compression algorithm should restore every bit of compressed video.