This format is a big one in the video camp, and it is also the most common video format we usually see. There are many derived formats, including video files with suffixes of mpg, mpe, mpa, m 15, m 1v, mp2, etc. , all from this family. MPEG format includes three parts: MPEG video, MPEG audio and MPEG system (video and audio synchronization). MP3(MPEG-3) audio file is a typical application of MPEG audio. Video includes 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 (which will be introduced next) 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. This algorithm is said to be a coding technology prohibited from export in the United States. In addition, the source file can be compressed to about 600MB by using DivX format, but its image quality is much higher than ASF. Because of its high efficiency, there are rumors that the US government prohibits the export of this technology.
By the way, I also want to introduce the DivX format. The most incisive word to summarize DivX format is: DVD killer. DivX video coding technology can be said to be born for DVD and developed to break the shackles of ASF. As mentioned above, it uses MPEG-4 algorithm, so only two VCDs are needed to compress a DVD! This not only means that you can get almost the same video quality without buying DVD-ROM, but also has low requirements for the machine to play this code: as long as the CPU is above 300 MHz, 64MB of memory and 4MB of graphics card (I believe most machines meet the requirements now), it can play smoothly.
In addition, it is worth mentioning that MPEG- 1 and MPEG-2 have their own special resolution standards when they are made into VCD and DVD respectively. The resolution of MPEG- 1 compressed image is 352×240 when using NTSC format, 352×288 when using PAL format, and DVD is used. If you plan to make CDs for DVD/VCD players, you need to pay special attention to the formats used by various video recorders when making video files.
Timetable:
Format mpeg-1mpeg-2 mpeg-4 mpeg-4+divx
2 hours standard quality image 1.2GB 4-8GB 300MB 600MB
2.AVI format
AVI is not as complicated as MPEG, and it has existed since WIN3. 1. 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.
Stream format
1.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 in real time, that is, some video files are downloaded from the server to form a video stream buffer and then played in real time, and at the same time, the download is continued to prepare for the next play. 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.
2.ASF and WMV formats
Video files with *. Asf and *. Wmv came into being with the suffix RM, which is also 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.
3.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.