Video Format Identification Guide
The AVI format whose full name is "Audio Video Interleaved" is very familiar to peoples. This format is widely used in daily life, and its video quality is superior, while there are also many defects such as its large size, which takes too much hard-disk to store.
In 1992, Microsoft corporation developed the AVI video format, which is known by people with Windows3.1. Namely "Audio Video Interleaved", the AVI file interleaves video and audio data and play them together. One of the advantage of AVI file is it can be used and played in different platforms. In another hand, to achieve the good quality, its file size is too large. Even worse, there are many different compression standards so that some AVI files can not be played if the system does not contain a proper codec. In order to play a AVI, sometimes, you have to download newer codec updates and that is very inconvenient.
The full name of MPEG is ?Moving Picture Expert Group?, which is an international compression standard designed for moving images. MPEG algorithms compress data to form small bits that can be easily transmitted and then decompressed. Redundancy between subsequent images and previous images is removed while most similar parts are preserved to cut down the file size. Its compression rate can reach 50:1 and it is a video standard of good compatible. Currently, MPEG includes three compression standards: MPEG-1, MPEG-2 and MPEG-4. Additional, MPEG-7 and MPEG-21 are being developed.
MPEG-4 (MP4) is a moving picture compression standard which is used for Internet, broadcast, and on storage media. Relative to MPEG-2, MPEG-4 provides improved quality at a small size. Not only can it be used in narrow bandwidth but also in wide bandwidth. Currently, the most compression technology of MPEG4 are DivX and XviD. Videos processed by DivX or XviD lose a little quality but the size will be reduced greatly. It provides users a convenient way to store a movie in a common CD-Rom disc, while the quality is better than VCD obviously.
RM format developed by RealNetworks Corporation is a video format for stream media. It includes RealAudio, RealVideo and RealFlash. To transmit and play real-time video files in narrow-bandwidth Internet, Real Media adopts distinct compress rate according to the bandwidth. RealVideo is used to transmit video data. Except being played as a normal video file, it also can be used together with RealServer. RealEncoder converts real-time video to RealMedia Format, which is broadcasted by RealServer. You can enjoy the video when you are downloading it. Not like many other video format, it is not necessary for RM format to download the whole video file before it can be played.
Currently, many websites provide RealVideo files. You can use RealPlayer or RealOne Player to play videos compressed by RealMedia technology. Another important feature of the format is video files can be played without downloading, if you use RealPlayer or RealOne Player.
As the heir of RM format, RMVB format is developed based on RM format. The advantage is RMVB format abandons Average Bit Rate and use Variable Bit Rate to compress video data. By Variable Bit Rate technology, quality of video files is greatly improved while file size of them is acceptable.
DivX developed by DivX, Inc. is a popular new video compression technology, which enables users to create and play high-quality videos in a fast and convenient way. For its outstanding quality, the DivX codec is one of the most popular MPEG-4 based codec. It integrates MPEG-4 and MP3 technology, namely it adopts DivX technology to compress DVD video data, while MP3 or AC3 is used to compress Audio. The quality is so superb that there is only a little disparity between DivX videos and DVDs. Another remarkable advantage is compared to DVDs, DivX videos provide the same image quality at only 1/10 the size. Especially, it is suitable for movie downloads. In a word, this video format is very popular and liked by many movie fans.