catalogue
Introduction to XviD
The importance of XviD
filename extension
Size of XviD file
XviD movie and television resources
The birth process of XviD technology
History of XviD version
Rich and colorful technical features
launch
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Introduction to XviD
XviD is the most commonly used video codec in the world at present, and it is the first truly open source code, which was released through GPL negotiation. In the comparison of many codecs, XviD performs very well and is one of the best and most common codecs.
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The importance of XviD
In recent five years, XviD has been the most popular video encoder in the world. It is estimated that at least 90% movies and TV series on BT(BitTorrent) and eMule are suppressed by XviD. However, the situation in China is somewhat special, because film and television publishers in China like to use RMVB format.
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filename extension
The file extension of XviD can be AVI, MKV, MP4, etc. It should be noted that the encoding format of this video cannot be viewed only from the extension. For example, a movie is on. Avi format, but the actual video coding format can be DV code, XviD ID or other formats. The audio coding format can be PCM, AC3 or MP3.
MP4 and MKV formats are more advanced than AVI and support more functions, such as subtitles. The subtitles of AVI video need another SRT file. At present, most foreign film and television resources are in AVI format.
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Size of XviD file
Most video resources on the Internet use fixed bit rate (CBR), so the file size is very stable and will not change because of different publishers.
1. One episode is 43 minutes, and the file size is about 350MB. According to the calculation of 22 episodes per season, a season of American TV series needs 7.5 GB of hard disk space.
2. One episode is 22 minutes, and the file size is about 175MB.
3. The size of the movie file is determined by the length of the movie.
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XviD movie and television resources
The specific meaning of the file names of European and American TV dramas released by foreign TV drama production groups
Drama name, number of S seasons, number of E episodes, episode name (not marked partially), signal acquisition source, audio coding (not marked by default MP3), and video coding-production group.
For example:
Prison. Break. Season 2 0 1. Manhunt.HR.HDTV.AC3.5. 1。 XviD dimension
The title of the play is Prison Break
Second season
Number of group e -E0 1
Collection Name-Chasing
Signal acquisition source -HDTV
Audio coding -AC3.5. 1
Video coding -XviD
Production Team-Dimension
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The birth process of XviD technology
Before 1998, the only MPEG-4 encoder available on PC was developed by Microsoft, including the serial coding cores of Ms. MPEG-4 V 1, Ms. MPEG-4 V2 and Ms. MPEG-4 V3. The first two of them can be used to make AVI files, and they have been used as the default components of Windows. However, the coding quality of V 1 and V2 is not very good, and the picture quality has improved significantly until MPEG4-4 Lady V3. However, Microsoft decided to encapsulate the video coding core of MS MPEG4 V3 in Windows Media streaming technology, which is called ASF format and can no longer be used in AVI format. ASF format certainly has some advantages, but it is too closed to edit, which annoys fearless movie hackers. Soon, a team modified Microsoft's MS MPEG4 V3, lifted the restriction that it could not be used in AVI format, and opened some of its compression parameters. Thus, the MPEG4-4 encoder DivX, which we are familiar with today, was born. -)3. 1 1。
DivX is widely popular and has become the standard of DVDRip. The problem is that its basic technology is illegally stolen from Microsoft, and it can only be circulated underground, not on the table. It can't be commercialized on a large scale, and it can't produce hardware players. In this case, some engineers who are proficient in video coding (including the original developers of DivX 3. 1 1) set up a company called DivX Networks Inc, hereinafter referred to as DXN. DXN initiated an open source project, Mayo Project, with the goal of developing a new set of open source MPEG4 4 coding software. In particular, the Open DivX codec, which fully conforms to the ISO MPEG4 standard, attracted the participation of many software experts, and soon developed the prototype of the Open DivX codec, and then developed the encoder Encore 2 with higher performance and so on. During this period, the main coding work was completed by DXN people, and many technical problems were solved with the help of open source association.
Just when everything seemed to be going well, the fun began. Of course, Project Mayo is open source, but it is not based on GPL (General Public License, a common protocol used in open source projects to guarantee the right to freely use and modify software), but on LGPL (Lesser GPL), which is a public license just like GPL. The biggest difference from GPL is that it allows private ownership. )。 DXN participated in the design of the license agreement. In July of 200 1 year, when Encore 2 was basically formed and almost ready for production, DXN established a DIVX website, closed the original code and released their own DivX 4. DivX 4 is based on Encore 2 in Open DivX, but it uses the brand of divx, which is unexpected. Because DXN is no longer involved, the Mayo Project comes to a standstill, and the original code of Encore 2 is also deleted from the server by DXN. After a heated debate, DXN certainly admitted that Encore 2 was legal and open, but still refused to put it back on the server. In this way, the open source community was seriously smashed.
The open DivX can't be used in practice, but DivX 4 (and the subsequent charging version DivX 5) has become private property. Many people's wisdom and labor to break Microsoft's monopoly only helped DXN make a fortune. Of course, this result is unacceptable. Therefore, the whole organization of 0dayz rejected DivX4/5 of DXN company forever, and the survivors of the original Open DivX development team gradually regrouped their development strength and developed XviD ID on the basis of the last Open DivX version.
It has been nearly 1 year since the rest of the robbery. It inherits and develops Open DivX Encore 2, and its performance has been greatly improved. It is considered as the fastest MPEG4-4 codec in the world. XviD rewrote all the code, and used the past experience for reference to publish it according to GPL (note that it is not LGPL now, so it is illegal for anyone to use it as a product without opening the source code). However, due to the patent problems of MPEG-4, XviD can only imitate LAME's practice and only serve as a research exchange on how to realize ISO MPEG-4 standard. Only the source code is provided on the website. If you want to use it, you must compile the source code yourself or download the compiled and operational version from a third-party website.
I think when some guys like Gaj started Open DivX, it was like a decent open source project at first, and many people were attracted to develop and test it together. Until later, those guys showed their true colors overnight, took all the results of Open DivX, turned it into a closed source code DivX4, and then further became the current charging DivX 5. Originally good Open DivX was forced to abort, but it also contributed to the birth, development and growth of XviD today. Now XviD can be said to surpass DivX 5 and challenge the new generation of MPEG4 application battlefield with better quality and stronger functions.
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History of XviD version
February 2002 17 first edition, first published.
1.0 On February 28th, 2002, a lot of modifications and more accurate explanations were made.
1.1March 2, 2002 The analysis clarified many concepts.
1.2 On March 4th, 2002, quantization matrix was added, quant was removed, and smoothing technology was adopted.
1.3 Detailed explanation of XviD Directshow filter of Nic on March 8th, 2002.
1.3+On July 23rd, 2002, the supplementary contents were revised according to the XVID encoding and decoding of Nic.
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Rich and colorful technical features
DivX and XviD set key pictures from time to time to improve the poor quality of dynamic pictures caused by the original fixed-time key pictures, while the two-pass compression mode makes the picture quality smoother. Basically, there is little difference between the two coding effects, but XviD saves more capacity in terms of file size with the same picture quality. For a movie of 1.5 hours, most of the DivX codes are two CDs, while most of the XviD codes only need one CD!
The version of DivX jumped from 2, 3 and 4 to 5. It was originally used by netizens for non-profit, and later it came from DivX and began to be used as commercial software. Some of them left to develop a non-profit decoding program, which is XViD ID. Maybe that's why you want to write DivX backwards! )
Not only the qualification of XviD ID itself is a typical textbook of open source society, but also its new technical features are genuine and childlike. For the second generation MPEG4-4 video coding core, the design of various algorithms of XviD ID is representative and advanced.
Multiple coding modes
In addition to the original single-valued fixed stream compression (1 CBR), XviD also provides dynamic stream compression including single quality mode, single quantization mode and two two-pass dynamic stream compression modes including external control and internal control. XviD is obviously the video coding with the most optional modes in MPEG4-4 coding core on PC at present.
Especially in the two-pass dynamic code stream compression mode, by detecting the motion amplitude of the picture, the quantization amplitude of the picture is allocated in an optimal way, so that the video film full of moving elements can achieve the best balance in space occupation and image quality. However, the single quantization mode of dynamic bitstream compression can generate dynamic bitstream video files with controllable picture details at a high speed at one time, and obtain stable picture detail quality at the expense of less compression time, which is an excellent function that simple DivX 3. 1 1 does not have.
Quantization mode and range control
Quantization, simply speaking, is the assimilation and blurring degree of details by temporally or spatially adjacent picture units during coding, which is the most basic control factor for picture quality. XviD not only provides standard MPEG quantization method, but also provides h263 quantization method which is more suitable for low bit stream compression. And XviD can also dynamically determine the picture quantization mode of a scene according to the comprehensive analysis of the picture information in the process of two operations, which can really be said to be considered for the balance of space and picture quality in the spread of online media files, and the design is thoughtful.
In addition to the selection of quantization mode, XviD also provides powerful quantization amplitude range control in the compression process. Users can choose the quantization amplitude range allowed by compression. For example, if the quantization upper limit is set, the situation that the quality of the outgoing line image may decrease significantly can be avoided.
Motion detection and curve balance
After motion detection is carried out frame by frame, and the motion detection results of the whole segment are analyzed, the quantization amplitude of each frame is redistributed through curve balance, so as to realize that more space, higher bit stream and lower quantization amplitude can be allocated for the moving picture with high bit stream to keep the details of the picture; For static images that do not contain much motion information, the allocation budget is reduced. This practice of using good steel on the blade is the core content of XviD as the second generation MPEG4-4 coding.
XviD provides the accuracy of multipole motion detection, including half-pixel interpolation technology, which marks motion vectors in blocks of 16x 16 pixels; And that motion vector is record in an 8x8 pixel block for double analysis.
Dynamic key frame distance
Dynamic key frame spacing is another technique for XviD to achieve the maximum balance between space and picture. We know that in video compression, not all picture information is recorded in every frame. In fact, only the key frames record the complete picture information, and the subsequent P frames only record the difference between the previous frame and the next frame. If the picture changes greatly between key frames, it will waste valuable space on P frames. By recording the changed frames in key frames, the space required for P frames can be saved, because there is no change in subsequent frames. Therefore, changing the position of key frames according to shot switching and motion amplitude will have a multiplier effect on improving the image quality under video compression.
Psychological visual brightness correction
In addition to the basic MPEG4 4 coding, XviD ID provides many additional functions. Among them, the typical one is psychological vision brightness correction. This function can improve the compression efficiency by removing the brightness signal and brightness difference that cannot be distinguished by the naked eye. Unfortunately, although this design is very creative, it will lead to a decline in the quality of the picture visible to the naked eye in the current practical application, and it is expected to be improved in future versions.
Casting options
Another thoughtful design is the "cast list option" specially designed for movies. This function can set a very low bit stream in some user-specified paragraphs (such as the cast list of a movie) that do not need to keep details. Even if the feature stream is compressed to less than 10%, it can save a lot of space and the design is very intimate.
External custom control
In addition to the internal curve distribution control method provided by XivD, XviD also provides an external open interface. Users are allowed to skip the encoding analysis core of XVI ID, use external analysis tools provided by third parties, such as Gordian Knot, to generate allocated control files, and then return XVI ID for final double operation compression. This method extends the usability of XviD ID and the degree of user control, because software like Gordian Knot can even control the quantization amplitude and the quota of code stream allocation per frame by users, which can provide more possibilities for advanced applications.
Motion vector accelerated coding
XviD also has a design specially developed to improve coding efficiency, which is to record the motion vector information of the next picture into a log file. Then, the information in the file is directly read during double operation compression, which saves the repeated operation of motion vector information and greatly improves the coding speed.
Image optimization decoding
XivD is not only powerful in coding, but also has many new achievements in decoding and picture optimization. For example, "horizontal breakout (Y)" can soften the brightness mosaic in the horizontal direction; "Horizontal Breakthrough (C)" can soften horizontal color mosaic; "Dering (y)" can soften annular bright spots; "Deing (c)" can soften the annular chromaticity spots; "Mosquito" can reduce the mosquito-like noise in the picture. Moreover, these screen optimization methods of XviD ID are optional, so as long as you turn off a few unnecessary options, you can play on a low-end PC.
Framework under development
Another striking technological development in XviD ID is B-frame. As we know, I frame is a key frame, and P frame only stores the difference between the key frame and the previously decompressed picture. The principle of B-frame is the same as that of P-frame, but in addition to the decompressed pictures of the first three frames, it will also refer to the picture information of the next frame. Therefore, the image extracted from frame B is better than the image extracted from frame P. ..
The previous MPEG4-4 coding core only used I frames and P frames to store pictures. If B-frame technology can be used on this basis, the image quality and compression ratio will naturally go up a storey still higher. At present, XviD has provided developers with the XviD coding core of the B-frame experimental version. It is believed that in the near future, XviD will give full play to the advantages of MPEG4-4 coding and become the leader of online video recording format.
A little knowledge about the origin of DivX
The technology called DivX was created by 27-year-old French audio-visual enthusiast Rota and a computer hacker Gej.
It turns out that these two guys didn't invent the technology used by DivX. They're just pirates. With the popularity of Windows, Microsoft developed MPEG-4 technology, which can compress the video file size to a very small size. Rhoda and Kiel rewrote the program, but renamed it DivX and put it on the Internet for anyone to download.
Microsoft claims that it will investigate all the people and enterprises that promote the development of DivX. But Rhoda is making every effort to apply for the legalization of their DivX. DivX was invented from Windows, but it didn't use any Microsoft technology. Moreover, he also held a meeting with some American technicians and financial personnel to form a new company ProjectMayo, and fully promoted DivX.
In fact, DivX is another way to save video DVD, which can only be done by DeCSS program (note). Because the DVD itself has the anti-copy mark, so the DVD can't be copied to the computer casually, but DeCSS can decode it, so you can copy the movie compressed into DivX. In response to this practice, major filmmakers immediately took action to stop the outflow and spread of DeCSS, but it was too late. DeCSS is already in Yahoo! You can find it on Google.
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How to play XviD video
For most users, as long as Storm Video or K-Lite codec package is installed, the XviD video can be played smoothly. In fact, most of these playback software are decoded by ffdshow, so when playing video, the icon of ffdshow will appear in the Windows taskbar.