1, MPEG- 1, MPEG-2 and MPEG-4.

MPEG- 1 is widely used to make VCDs and download some video clips, among which VCDs are the most-almost all VCDs are compressed in Mpge- 1 format (the file is *. Dat format). The compression algorithm of MPEG- 1 can compress a movie (original video file) with the length of 120 minutes to the size of 1.2 GB.

MPEG-2 is suitable for DVD production (the file format is *. Vob format), as well as some HDTV high-definition TV broadcasts) and some demanding video editing processing. Using the compression algorithm of MPEG-2, the size of a 120-minute movie (original video file) is about 4GB to 8GB. Of course, its picture quality index is incomparable with MPEG- 1.

MPEG-4 is a new compression algorithm. The ASF format file using this algorithm can make a movie (original video file) with a length of 120 minutes "slim down" to about 300MB. Because it is small and easy to spread, it has become one of the main ways to watch online. In addition, the source file can be compressed to about 600MB by using DivX format, but its image quality is much higher than ASF.

2.AVI format

AVI is a format widely used by TV stations and film and television companies. Its most direct advantages are good compatibility, convenient call and good picture quality, so it is often said to DVD. But its disadvantage is also obvious: large volume. It is precisely because of this that we have seen the birth of MPEG- 1 and MPEG-4. The AVI file size of a 2-hour image is almost the same as that of MPEG-2, but this is only for the standard resolution: the resolution of AVI can be adjusted at will according to different application requirements. The larger the window, the larger the data volume of the file. Reducing the resolution can greatly reduce its size, but the image quality is inevitably damaged. When the file size is similar to MPEG-2 format, the video quality of AVI format is relatively poor, but the requirements for computer configuration are not high. People usually record videos in AVI format first, and then convert them into other formats.

3.RM format

This is the great contribution of Real Company to the multimedia world and the promotion of online movies. Its birth also makes streaming files known to more people. This kind of file can be played immediately. This way of "broadcasting while transmitting" avoids the disadvantage that users have to wait for the whole file to be downloaded from the Internet before they can watch it, so it is especially suitable for watching movies online. RM is mainly used for real-time transmission of compressed video on low-speed networks, and also has the characteristics of small size and clarity. The size of RM file depends entirely on the compression ratio chosen when making it, which is why sometimes we see that the image of 1 hour is only 200MB, while others are 500MB.

4.ASF and WMV formats

Video files with suffix *. Asf and *. Wmv is born for RM and is the core of WindowsMedia. Their * * * feature is that they use MPEG-4 compression algorithm, so the compression rate and image quality are very good (just worse than VCD and better than RM format). Like most video formats, the picture quality is inversely proportional to the file size. In other words, the better the image quality, the larger the file; On the contrary, the smaller the file, the worse the image quality. When making ASF files, it is recommended to adopt a resolution of 320×240 and a frame rate of 30 frames per second, which can give consideration to both clarity and file size. At this time, the 2-hour image is about 1gb.

5.MOV format

Of all the video formats, MOV format is probably the least known. Maybe you have heard of QuickTime, which plays files in MOV format. Today, when PC almost dominates the world, the MOV format transplanted from Apple is naturally excluded. It has the technical characteristics of cross-platform and small storage space requirements. The MOV format file with lossy compression method has a slightly better picture effect than AVI format. So far, it has four versions, of which version 4.0 has the best compression ratio.