XviD and DivX
In 2002, in the rules of TDX2002, in addition to the old DivX3. 1 1 code, a second recognized code, the XivD code in the title of this article, was added. As an online high-quality audio-visual organization that publishes thousands of latest movies on the Internet every year, the rules they follow are of decisive significance to the entire MPEG-4 coding application market. In TDX2002, XviD is called Di: XviD is a non-commercial equivalent version inherited from DivX3. 1 1. So what exactly is XviD? What kind of video compression skills does it have? What you may not know is that XviD is something that will never appear. ...
The birth of several twists and turns
Four years ago, the only MPEG-4 encoder available on PC was developed by Microsoft, including serial coding cores of MS MPEG4V 1, MS MPEG4V2 and MS MPEG4V3. 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 MS MPEG4V3. However, Microsoft decided to seal the video encoding kernel of MS MPEG4V3 in Windows Media streaming technology, which is also known as ASF file, and can no longer be used for AVI files. Although ASF files have some advantages, they are too closed to edit, which annoys fearless movie hackers. Soon, a team modified Microsoft's MS MPEG4V3, lifted the restriction that it can't be used for AVI files, and opened some of its compression parameters, so the MPEG4 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 programmers who are proficient in video coding (including the original developers of DivX 3. 1 1) set up a company called DivXNetworks Inc, hereinafter referred to as DXN. DXN initiated an open source project ProjectMayo, with the goal of developing a brand-new open source MPEG4 4 coding software. In particular, OpenDivX codec, which fully conforms to ISO MPEG4 standard, attracted many software experts to participate, and soon developed OpenDivX encoder and decoder prototypes, and then developed a higher-performance encoder Encore 2 and so on. During this period, the main coding work was done by DXN people, and many technical problems were helped by the Open Source Association.
Just when everything seemed to be going well, the fun began. Although ProjectMayo is open source, it is not based on GPL (General Public License, a common protocol used in open source projects to ensure the free use and modification of software or source code). DXN participated in the design of the license agreement. In July, 200 1 year, when Encore 2 was basically formed and almost ready for production, DXN established a DIVX.COM website, closed the source code and released their own DivX 4. The foundation of DivX 4 is Encore 2 in OpenDivX, but it can be said that the brand of DivX was unexpectedly cut by everyone. Because DXN is no longer involved, ProjectMayo is stuck, and the source code of Encore2 is also removed from the server by DXN. After a heated debate, DXN admitted that Encore 2 was legal and open, but still refused to put it back on the server. In this way, the open source society has been severely lashed.
OpenDivX can't be actually used yet, but DivX 4 (and the subsequent charging version-DivX 5) and so on have become private property. Many people's wisdom and labor to break Microsoft's monopoly only helped DXN make a fortune, and this result is certainly unacceptable. Therefore, the whole 0dayz organization rejected DivX4\5 of DXN company forever, and the survivors of the original OpenDivX development team gradually regrouped their development strength and developed XviD on the basis of the last OpenDivX version.
It has been nearly 1 year since the XviD of the survivors. It inherits and develops OpenDIVX 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 open source). However, due to the patent problems of MPEG-4, XviD can only imitate LAME's practice 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 guys like Gaj started to do OpenDivX, it was like a decent open source project from the beginning, which attracted many people to develop tests together. Until later, those guys showed their true colors overnight, took all the results of OpenDivX, turned it into a closed-source DivX4, and then further became the current charging DivX5. OpenDivX 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.
Rich and colorful technical features
Not only the appearance of XviD 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 kernel, 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 selectable modes in MPEG4-4 coding kernel 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. The quantization mode of dynamic bitstream compression can generate dynamic bitstream video files with controllable picture details at one time at high speed, and obtain stable picture detail quality at the expense of less compression time, which is an excellent function that simple DivX3. 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.
XviD also provides powerful quantization amplitude range control during compression. Users can choose the quantization amplitude range allowed by compression. For example, if the upper limit of quantization is set, the possible sharp decline of image quality can be avoided.
Motion detection (motion search) and curve balanced distribution (curve)
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, and the motion vector is marked by 16x 16 pixel blocks; And that motion vector is record in an 8x8 pixel block for double analysis.
Dynamic key frame interval (I-frame interval)
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 well-thought-out design is the "cast list option" specially used for movies. This function can be set as a very low bit stream in some user-specified paragraphs (such as the cast list of movies) that do not need to keep details. Even if it is compressed to less than 10%, it can save a lot of space and is very thoughtful.
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 kernel 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 remarkable technological development in XviD ID is B-frame. We know that I frame is the key frame, and P frame is between the key frames, and only the differences from the previously decompressed pictures are stored. The principle of B frame is the same as that of P frame, except that it refers to the previously decompressed picture and the picture information of the next frame. Therefore, the picture extracted from B frame is better than that extracted from P frame.
The previous MPEG4-4 coding core only used I and P frames to store pictures. If we can use B-frame technology on this basis, we can naturally improve the image quality and compression ratio. At present, XviD has provided developers with an experimental version of XviD coding kernel for B frames. 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.
How to treat DVDrip in XviD format
There is little difference between DVDrip in XviD format and DVDrip in XviD format when playing. Please note the following two points:
1. Install ffdshow. After installation, you can decode any MPEG-4 code, and there are many picture optimization functions.
2. install ZoomPlayer. At present, many new DVDrip audio parts support multi-channel modes such as Chinese-Cantonese, Chinese-English and Chinese-Japanese. It is very troublesome to adjust channels when playing with MediaPlayer, and ZoomPlayer can easily switch channels. ZoomPlayer is a green playback software, which has the unique functions of eliminating overscan and optimizing zoom screen. In addition to supporting full screen and playlist, it also supports panel replacement (panels can be customized, see defaultSKIN.skn in the skin directory for details), and it also includes easy-to-use control bar, control bar with background color to test the brightness of display, and the function of testing the brightness of display with background color. When playing ASF, WMV and other files, it can drag the time bar (without repair) and support DVD playback. DirectX support is required, and the minimum must not be lower than DX8.
Recently, in many DVDrip communities, subtitle groups have cooperated with each other to produce subtitles, and the translation and localization of DVDrip have appeared. Recently, the "Ghost King" widely circulated on the Internet is the subtitle produced by the Comic Club of colleges and universities.
References:
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