Overview
One of the main ways to solve the contradiction between the large amount of data after digitalization of video and audio and the small capacity of digital storage media and communication networks is compression. To this end, the International Organization for Standardization had established video and audio encoding MPEG1 and MPEG2 in 1993 and 1995 respectively. When the MPEG1 and MPEG2 technologies were originally developed, the standards they defined were high-level media representations and structures. However, with the rapid development of computer software and network technologies, the disadvantages of MPEG1 and MPEG2 technologies were revealed: lower interactivity and flexibility. The volume of compressed multimedia files is too large to achieve real-time network propagation. Therefore, the new multimedia communication standard MPEG4 was developed.
definition
The so-called video encoding method refers to a method of converting a video format file into another video format file through a specific compression technique. The most important coding and decoding standards for video streaming are ITU H.261, H.263, M-JPEG for the Motion Still Picture Experts Group and the MPEG series standard for the ISO Motion Picture Experts Group, in addition to the Internet. Widely used are Real-Networks' Real Video, Microsoft's WMV, and Apple's Quick Time.
The basic principle of video coding
The basic principle of video coding Video image data has a strong correlation, that is to say there is a lot of redundant information. The redundant information can be divided into spatial redundancy information and time domain redundancy information. Compression technology is to remove the redundant information in the data (remove the correlation between the data). Compression technology includes intra-frame image data compression technology, inter-frame image data compression technology and entropy coding compression technology.
Video compression technology is a prerequisite for computers to process video. After digitizing the video signal, the data bandwidth is very high, usually above 20MB/sec, so it is difficult for the computer to save and process it. With compression techniques, the data bandwidth is usually reduced to 1-10 MB/s, so that the video signal can be stored in the computer and processed accordingly. Commonly used algorithms are developed by ISO, namely JPEG and MPEG algorithms. JPEG is a static image compression standard for continuous-tone color or grayscale images. It consists of two parts: one is distortion-free coding based on DPCM (spatial linear prediction) technology, and the other is based on DCT (Discrete Cosine Transform) and Huffman. The encoding has a distortion algorithm, the former has a small compression ratio, and the main application is the latter algorithm. The most commonly used in nonlinear editing is the MJPEG algorithm, MotionJPEG. It changes the video signal from 50 frames per second (PAL) to 25 frames per second and then compresses each frame at 25 frames per second using the JPEG algorithm. The Betacam image quality is usually achieved at a compression ratio of 3.5 to 5 times. The MPEG algorithm is a compression algorithm that is suitable for dynamic video. In addition to encoding a single image, it also uses related principles in the image sequence to remove redundancy, which can greatly improve the video compression ratio. The former MPEG-I is used in VCD programs, and MPEG-II is used in VOD and DVD programs.
Code Introduction
There are many audio and video coding schemes. The use of a hundred schools of thought is not too much to describe. The common types of audio and video coding are as follows:
MPEG series
(Developed by MPEG (Moving Picture Experts Group) under ISO [International Organization for Standardization]) Video encoding is mainly Mpeg 1 (it is used by VCD), Mpeg2 (DVD is used), and Mpeg4 (DVDRIP is all used Its variants, such as: divx, xvid, etc., Mpeg 4 AVC (orthodox); audio coding is mainly MPEG Audio Layer 1/2, MPEG Audio Layer 3 (famous mp3), MPEG-2 AAC, MPEG-4 AAC and so on. Note: DVD Audio does not use Mpeg.
H.26X series
(Conducted by the ITU [International Telecommunication Video Consortium], focusing on network transmissions, note that only video coding) includes H.261, H.262, H.263, H.263+, H.263++, and H.264 (ie, MPEG4 AVC- Crystallization of cooperation) etc.
One of the main ways to solve the contradiction between the large amount of data after digitalization of video and audio and the small capacity of digital storage media and communication networks is compression. To this end, the International Organization for Standardization had established video and audio encoding MPEG1 and MPEG2 in 1993 and 1995 respectively. When the MPEG1 and MPEG2 technologies were originally developed, the standards they defined were high-level media representations and structures. However, with the rapid development of computer software and network technologies, the disadvantages of MPEG1 and MPEG2 technologies were revealed: lower interactivity and flexibility. The volume of compressed multimedia files is too large to achieve real-time network propagation. Therefore, the new multimedia communication standard MPEG4 was developed.
definition
The so-called video encoding method refers to a method of converting a video format file into another video format file through a specific compression technique. The most important coding and decoding standards for video streaming are ITU H.261, H.263, M-JPEG for the Motion Still Picture Experts Group and the MPEG series standard for the ISO Motion Picture Experts Group, in addition to the Internet. Widely used are Real-Networks' Real Video, Microsoft's WMV, and Apple's Quick Time.
The basic principle of video coding
The basic principle of video coding Video image data has a strong correlation, that is to say there is a lot of redundant information. The redundant information can be divided into spatial redundancy information and time domain redundancy information. Compression technology is to remove the redundant information in the data (remove the correlation between the data). Compression technology includes intra-frame image data compression technology, inter-frame image data compression technology and entropy coding compression technology.
Video compression technology is a prerequisite for computers to process video. After digitizing the video signal, the data bandwidth is very high, usually above 20MB/sec, so it is difficult for the computer to save and process it. With compression techniques, the data bandwidth is usually reduced to 1-10 MB/s, so that the video signal can be stored in the computer and processed accordingly. Commonly used algorithms are developed by ISO, namely JPEG and MPEG algorithms. JPEG is a static image compression standard for continuous-tone color or grayscale images. It consists of two parts: one is distortion-free coding based on DPCM (spatial linear prediction) technology, and the other is based on DCT (Discrete Cosine Transform) and Huffman. The encoding has a distortion algorithm, the former has a small compression ratio, and the main application is the latter algorithm. The most commonly used in nonlinear editing is the MJPEG algorithm, MotionJPEG. It changes the video signal from 50 frames per second (PAL) to 25 frames per second and then compresses each frame at 25 frames per second using the JPEG algorithm. The Betacam image quality is usually achieved at a compression ratio of 3.5 to 5 times. The MPEG algorithm is a compression algorithm that is suitable for dynamic video. In addition to encoding a single image, it also uses related principles in the image sequence to remove redundancy, which can greatly improve the video compression ratio. The former MPEG-I is used in VCD programs, and MPEG-II is used in VOD and DVD programs.
Code Introduction
There are many audio and video coding schemes. The use of a hundred schools of thought is not too much to describe. The common types of audio and video coding are as follows:
MPEG series
(Developed by MPEG (Moving Picture Experts Group) under ISO [International Organization for Standardization]) Video encoding is mainly Mpeg 1 (it is used by VCD), Mpeg2 (DVD is used), and Mpeg4 (DVDRIP is all used Its variants, such as: divx, xvid, etc., Mpeg 4 AVC (orthodox); audio coding is mainly MPEG Audio Layer 1/2, MPEG Audio Layer 3 (famous mp3), MPEG-2 AAC, MPEG-4 AAC and so on. Note: DVD Audio does not use Mpeg.
H.26X series
(Conducted by the ITU [International Telecommunication Video Consortium], focusing on network transmissions, note that only video coding) includes H.261, H.262, H.263, H.263+, H.263++, and H.264 (ie, MPEG4 AVC- Crystallization of cooperation) etc.
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