"If you need to reprint, please indicate: https://blog.csdn.net/qq_29350001/Article/details/78225725 The last article mainly said H.264, then let's take a look at other codec standards. See: Current mainstream digital video compression decoding standards See: Summary of video coding standards and comparison Be See: an Explanation of Video Compression Techniques JPEG
Be JPEG, Joint Photography Group is established in 1987, established in 1987, was established in 1987 in 1988 in 1988 in 1988. (Joint Bi-Level Image Experts Group, is now associated with ISO / IEC JTC1 / SC29 WG1 (ITU-T sg8), which is dedicated to still images. "STILL images) compression. JPEG has developed three image standards. The first is directly called JPEG standard, official name is called "Digital Compression and Coding of Continuous-Tone Still images), officially passed in 1992. The second standard for JPEG development is JPEG-LS (ISO / IEC 14495, 1999). JPEG-LS is still a still image lossless encoding, which can provide close to loss compression compression ratio. The latest standard of JPEG is JPEG 2000 (ISO / IEC 15444, equally ITU-T number T.800), formed a draft working in March 1999, and became a formal standard (first part) at the end of 2000. According to the Target of the JPEG expert group, this standard will not only improve the compression quality of the image, especially when the low-rate rate is low, and will also get many new functions, including progressive transmission based on image quality, visual sensing and resolution. , The random access and processing, open structure, and downward compatibility of the code stream. The JPEG standard develops four working modes: (1) sequence-based DCT (SEQUENTIAL DCT-BASED) mode, is composed of three steps of DCT (discrete cosine transform) coefficients, quantization, and entropy encoding. From left to right, scan the signal from top to bottom, encoding each image. (2) The progressive DCT-based DCT-based mode is the same as the key step in generating DCT coefficients and quantizations is the same as the basic order codec. The main difference is that each image component encodes multiple scans instead of only one scan. Each continued scan is improved, until the image quality established by the quantization table is reached. (3) Lossless mode, independent of DCT processing, is used to define a means of achieving lossless continuous tone compression. The predictor combines the sampling area and predicts the adjacent system area based on the sampling area. The predicted area is predicted against the complete lossless sampling of each region, and this difference is performed by the HUFFMAN encoding method or the arithmetic entropy encoding method, and the compression ratio of the better quality can usually reach the compression ratio of 2: 1. (4) Hierachical mode, hierarchical mode provides a means of achieving a variety of resolutions. The resolution of the image encoding at the horizontal or vertical direction is twice the resolution in the horizontal or vertical direction. The data it transmits includes the supported minimum resolution image, and the difference information of adjacent images of adjacent images required to decode to reset to the original full resolution image. The average compression ratio of the JPEG algorithm is 15: 1. A block effect will occur when the compression ratio is greater than 50 times. JPEG's performance, the ratio of quality and bit rate is quite superior, especially its low complexity, and long use time, it is a profound impact. The basic JPEG encoding method (also most common) is the order encoding. First, the image is divided into a pixel block of 8x8, and the raster scanning mode from the top to right is sorted from the top to right. DCT is calculated at 8x8 pixel blocks, and then quantifies 64 DCT coefficients with a uniform quantization table. The uniform quantization table is derived by the experiment of psychological hearing (Lohscheller H., A Subjectively Adapted Image Communication System, IEEE TRANS. On Communications COM-32 (12): 1316-1322, 1984). This uniform scalar quantization table is provided as an optional portion of the JPEG standard. After quantify the DCT factor, the coefficients in the block will be sorted by "z", and the resulting bitstream line sequence encodes the intermediate symbol sequence, and then these symbols are encoded for transmission or storage through HUFFMAN.
Be MPEG-1 is the first video and audio loss compression standard developed by MPEG organization. The video compression algorithm is done in 1990. At the end of 1992, MPEG-1 was officially approved to become an international standard. MPEG-1 is a video and audio compressed format customized for CD disc media. A 70-minute CD disc transmission rate is approximately 1.4 Mbps. MPEG-1 uses a block mode of motion compensation, discrete chord transform (DCT), quantization, etc., and optimized for 1.2 Mbps transmission rate. MPEG-1 will then be used as a core technology by VIDEO CD. The output quality of MPEG-1 is approximately the traditional video recorder VCR, the signal quality is comparable, which may be the reason why VIDEO CD is not successful in developed countries. Application: MPEG-1 has been the main compression standard of VCD, is the mainstream of real-time video compression, can be applied to devices of different bandwidth, such as CD-ROM, VIDEO-CD, CD-I. Compared with M-JPEG technology, there is significant improvement in real-time compression, data volume, and processing speed. MPEG1 can meet up to 16 or more 25 frames / second compression speed, at a definition of 500kbit / s compressed stream and 352 pixels × 288 rows, only 2K per frame size. If you look at the VCD to Super VCD to DVD, MPEG1's 352 × 288 format, MPEG2 can have 576 × 352, 704 × 576, etc., which are used to store synchronous and color sports video signals on CDROM, which is designed to achieve VCR. (Animal Tape Recorder Video Cassette Recorder; VCR) Quality, its video compression ratio is 26: 1. MPEG1 allows images to compress one/38 on the spatial shaft, and compressed up to 1/5 of the data smaller on the time axis. After the MPEG1 compressed data transmission rate is 1.5Mbps, the compressed source input format SIF (Source INPUT FORMAT), the resolution is 352 pixels × 288 rows (PAL system), the luminance signal is 360 × 240, chromaticity signal The resolution is 180 × 120, 30 frames per second. MPEG1 has a quantity of 4: 1: 1 for the color difference. MPEG1, MPEG2 is a partial screen that passes a different action. In implementation, MPEG1 can be done by means of an existing decoding chip, rather than excessive relying on the host's CPU as M-JPEG. Hardware compression can save computer resources and reduce system costs than software compression. But there are also many shortcomings. First, the compression ratio is not large enough, in the case of multiple monitoring, the disk space required by the recording is too large. Especially when the DVR host exceeds 8 roads, in order to save a month of storage, 10 80G hard drives are usually required, or more, the hard disk investment is large, and the hard disk failure and maintenance caused by the hard disk. Second, the image clarity is not high enough. Since the MPEG1 maximum sharpness is only 352 x 288, with other factors such as capacity, simulation of digital quantization loss, the playback clarity is not high, which is also the main problem of market reactions. Third, there must be certain requirements for the bandwidth of the transmission image, not suitable for network transmission, especially remote multi-channel video transmission, which is unable to achieve remote multi-channel video transmission. Fourth, the number of record frames of MPEG1 is fixed to 25 frames per second, and the frame cannot be lost, and the flexibility is used. From the currently widely used compressed chip, there is also a lack of effective regulatory means, such as keyframe settings, sampling area settings, etc., resulting in not suitable in the field of security monitoring, and cost. Overall, M-JPEG and MPEG1 have been mainstream technology in the DVR market due to technology, but the fatal weakness of both is that the hard disk costs, and cannot meet the needs of security and real-time recording. Features random access, flexible frame rate, variable image size, define I-frame, P-frame, and B-frame, motion compensation can span multiple frames, half pixel precision motion vector, quantization matrix, GOF structure, SLICE structure, technical details, input video format. Maximum number of parameters / line: 720 Maximum number of lines / shadow: 576 Maximum picture / second: 30 Maximum macro block / photo: 396 maximum macro block / second: 9900 maximum element rate: 1.86MBPS maximum decoded buffer size: 376832bit.Be MPEG-2 Technical Introduction MPEG-2 is set in 1994, the design goal is an image quality of advanced industrial standards and a higher transmission rate. MPEG-2 The transmission rate can be provided between 3-10 Mbits / SC, which can reach 720x486 under NTSC system, and MPEG-2 can also provide and provide broadcast-level video and CD level sound quality. The audio coding of MPEG-2 can be provided with two surround channels, as well as an aggravated bass channel, and up to 7 parties (DVD can have 8 language dubbing reasons). Since MPEG-2 is ingenious during design, most MPEG-2 decoders can also play data in MPEG-1 format, such as VCD. Be
Be At the same time, since the excellent performance performance of MPEG-2 can be applied to HDTV, the MPEG-3 intended for HDTV design, it has been abandoned yet. (MPEG-3 requires transmission rates between 20 Mbits / SEC-40MBITS / SC, but this will make the screen slightly distorted). In addition to the designated standards for DVD, MPEG-2 can also be used to provide broadcast, cable TV, cable network, and satellite live broadcast (DirectBroadcastsatellite). Digital video. Another feature of MPEG-2 is that it can provide a wide range of variable compression ratio to accommodate different picture quality, storage capacity, and bandwidth requirements. For end users, due to existing TV resolution restrictions, the high-definition screen quality (such as DVD screen) is not obvious on TV, and it is its audio characteristic (such as aggravating bass, more Sound channel, etc.) more compelling. The encoded image of MPEG-2 is divided into three categories, called I frame, P frame, and B frame, respectively. The I frame image uses an intra coding method, ie, only the spatial correlation within the single frame image, and does not utilize time dependencies. The P frame and the B frame image uses a frame encoding method to simultaneously utilize space and time correlation. The P frame image only uses forward time prediction, which can improve compression efficiency and image quality. In the P frame image, the portion of the intra-encoded portion may be included, that is, each macroblock in the P frame may be forward prediction, or an intra code. The B frame image adopts two-way time prediction, which can greatly improve the compression multiple. The coded code stream of the hierarchy MPEG-2 is divided into six levels. In order to better represent the encoded data, the MPEG-2 uses the syntax to specify a hierarchical structure. It is divided into six layers, from bottom to bottom: image sequence layer, image group (GOP), image, macroblock, macroblock, block.
Be MPEG-4
Be MPEG-4 has become a common format MPEG4, which MPEG4, has been published in November 1998. The international standard MPEG4 that is expected to be put into use in January 1999 is not only for video, audio coding, more focus on multimedia system, but also more interactive. And flexibility. The experts of the MPEG expert group are working hard for MPEG-4. MPEG-4 standards are mainly used in Video Phone, Video Email and Electronic News (Electronic News), and its transmission rate requires low, between 4800-64000BITS / SEC, resolution It is 176x144. MPEG-4 utilizes very narrow bandwidth, compacts, and transmits data by frame reconstruction, to obtain optimal image quality at least with minimal data. I. MPEG-4 Introduction Compared with MPEG-1 and MPEG-2, MPEG-4 features that it is more suitable for interactive AV services and remote monitoring. MPEG-4 is the first dynamic image criterion that makes you passively become active (no longer just viewing, allowing you to add interactive), which is its comprehensive characteristics. From the root cause, MPEG-4 attempts to dissolve natural objects with artificial objects (visual effects). The design goals of MPEG-4 have wider adaptability and more flexible scalability. MPEG is a MOVING PICTURES EXPERTS Group. It is an English abbreviation of "Dynamic Image Expert Group", which was established in 1988, which is committed to the standardization of motor image and its sound control, originally planned to develop MPEG1, MPEG2, MPEG3 and MPEG4 four versions for requirements for different bandwidth and digital image quality. Currently, MPEG1 technology is widely used in VCD, and MPEG2 standards are used for broadcast television and DVD. MPEG3 was originallyThe coding and compression standard developed by HDTV, but MPEG3 can only be died of MPEG3 due to the excellent performance performance of MPEG2. The protagonist we have to talk about today - MPEG4 officially became an international standard in early 1999. It is a solution suitable for low transmission rate applications. MPEG4 more focuses on interactive and flexibility of multimedia systems compared to MPEG1 and MPEG2. Second, MPEG-4 goals (1), multimedia communication at low bit rate; (2), is a synthesis of multimedia communication in multiple industries. According to this goal, MPEG4 introduces Audio / Visual Objects, making more interactions possible. MPEG-4 is the latest MPEG standard to be developed for real-time tone / video signals on international internet or mobile communication devices (such as mobile phones), MPEG4 uses Object based method to decompress, compression than indicators are far better than the above In the case, the compressed multiple is 450 times (more than 800 times the still image), and the resolution input can range from 320 × 240 to 1280 × 1024, which is more than ten times the same quality MPEG1 and MJEPG. MPEG4 uses "Layer" mode, it is possible to intelligently select the different image, and it can be separately compressed according to the image content, the object (character, object, background) is separated separately, so that the map file capacity is significantly reduced. And to accelerate the transmission / video transmission, not only greatly increased the compression ratio, but also makes the function and accuracy of the image detection more fully. In the network transmission, the code flow rate of MPEG4 can be set, and the sharpness can also be made in a certain range, so that the user is different from the different requirements of the video time, the number of transmission, and the sharpness of the clarity. It greatly improves the adaptability and flexibility of the system. Dynamic frame testing technology can also be used, and the dynamic is fast recorded, and slowly appear when it is static, thereby reducing the average amount of data, saving storage space. Moreover, when transmitting a bit error or packet loss, the MPEG4 has a small impact and can recover quickly. MPEG4's application prospect will be very broad. Its appearance will have a large driving effect on the following: Digital TV, dynamic image, web (WWW), real-time multimedia monitoring, mobile multimedia communication under low bit rate, in content storage and retrieval multimedia system, Internet / Video streams on intranet, visual games, virtual conferences based on facial expressions, interactive multimedia applications on DVD, computer network-based visual cooperation laboratory scene applications, playback TVs, etc. Of course, in addition to MPEG 4, there are more advanced next versions MPEG 7, exactly, MPEG-7 is not a compression encoding method, but a multimedia content description interface. Following MPEG4, the contradiction to be solved is the management and quick search of the increasing image, sound information. MPEG 7 is a solution for this contradiction. MPEG7 strives to quickly and efficiently search for different types of multimedia materials required by the user. This program is expected to be finalized and announced in early 2001. According to the experience of MPEG-4, MPEG-7 is at least two years to enter the actual application phase. Third, Multimedia Video Code Motion Image Expert Group MPEG officially announced the first release of MPEG-4 (ISO / IEC14496) standard in February 1999. At the end of the same year, the MPEG-4 second edition was also sure, the MPEG4 multimedia coded satellite TV digital set-top box and was officially become an international standard in early 2000. MPEG-4 is very different from MPEG-1 and MPEG-2. MPEG-4 is not just a specific compression algorithm, which is an international standard for integration and compression technology such as digital TV, interactive drawing application (audio and video synthesis), interactive multimedia (WWW, data acquisition and dispersion). MPEG-4 standard integrates numerous multimedia applications in a complete framework to provide standard algorithms and tools for multimedia communications and application environments, thus establishing a general purpose use of multimedia transmission, storage, search and other applications. Unified data format. The MPEG-4 coding concept is that the most significant difference between the MPEG-4 standard with the previous criteria is that it is a video audio that is divided into a number in time and space when encoding. Objects, after encoding, then transferred to the receiving end, and then decodes different objects, thereby combining the required video and audio. This makes it easy for us to adopt different encoding methods and representations for different objects, and it is conducive to the fusion between different data types, and this can also be convenient to implement the operation and editing of various objects. For example, we can put a cartoon character in a real scene, or put the live-action in a virtual studio, you can also interact in the Internet, according to your own needs, select a variety of video audio and Graphic text object. The general framework of the MPEG-4 system is: representation of natural or synthetic audiovisual content; management of audiovisual content data streams, such as multi-point, synchronization, buffering management, etc .; support for flexibility and different parts of the system. 4. Advantages of MPEG-4 (1) Content-based interactive MPEG-4 provides content-based multimedia data access tools such as index, hyperlink, upload, download, delete, etc. With these tools, users can easily obtain their own content related to the object from the multimedia database, and provide content and bitstream editing capabilities, which can be applied to interactive family shopping, fade in fade out digitization Effect, etc. MPEG-4 provides an efficient natural or synthetic multimedia data encoding method. It can combine natural scenes or objects to become synthetic multimedia data. (2) Efficient compression MPEG-4 is based on higher coding efficiency. Compared to the other standards that have been formed, it is based on higher visual hearing quality than the other standards, which makes the video on the low bandwidth channel, and the audio is possible. At the same time, MPEG-4 can also encode data streams at the same time. The multi-view or multi-channel data stream of a scene can be efficient and synchronously into the final data stream. This can be used in virtual 3D games, three-dimensional movies, flight simulation exercises. (3) Universal accessibility MPEG-4 provides robustness of an error-breaking environment to ensure that it is in many wireless and wired networks and storage media, in addition, MPEG-4 also supports content-based segmentation That is, the content, quality, complexity is divided into many small pieces to meet the different needs of different users, support transport channels and receiving ends with different bandwidth, different storage capacity. These features will undoubtedly accelerate the development of multimedia applications, the applications from which they benefit are: Internet multimedia applications; radio television; interactive video games; real-time visual communication; interactive storage media applications; studio technology and TV post-production; Animation technology virtual conference; multimedia mail; multimedia applications under mobile communication conditions; remote video surveillance; remote database business through ATM networks, etc. (4) MPEG4 technical features MPEG1, MPEG2 technology At the time, the standards of their positioning were high-level media representations and structures, but with the rapid development of computer software and network technology, the drawback of MPEG1.MPEG2 technology was displayed: The interactivity and low flexibility, the compressed multimedia file is too large, and it is difficult to achieve real-time communication of the network. The standard of MPEG4 technology is to encode content in motion images. The specific encoding object is an audio and video in the image, and the term is called "AV object", while consecutive AV objects are combined together to form an AV scene. Therefore, the MPEG4 standard is based on the encoding, storage, transmission, and combination of the AV object, high efficiency, tissue, storage, and transmission AV objects are the basic content of the MPEG4 standard. In video coding, MPEG4 supports encoding of natural and synthetic visual objects. (The synthetic visual object includes 2D, 3D animation and human face expression animation, etc.). On the audio coding, MPEG4 can be audio encoding with natural sound objects such as voice, music, etc., with a set of natural sound objects such as voice, music, and synthetic sound objects with echo, spatial orientation. Since MPEG4 only processes a difference between the image frame and the frame, the same element is given, thus greatly reduces the volume of the synthetic multimedia file. The most significant feature of the audio and video file of MPEG4 technology is that the compression ratio is high and the imaging is clear. In general, an hour's image can be compressed into data about 350m, and a high definition DVD movie can be compressed into two or even A 650M CD CD is stored. For the vast "civilian" computer users, this means that you don't need to purchase DVD-ROM to enjoy a high quality image of approximate DVD quality. Moreover, MPEG4 encoding technology, the requirements for machine hardware configuration are very low, 300MHz or more CPU, 64M memory and a 8M memory card can be smooth. In terms of playing software, it requires very loose, you only need to install a 500K MPEG4 encoded driver, use the media player comes with Windows to play smoothly. V. MPEG-4 Applications (1) Applying for Internet Vision Audio Broadcast Due to the increase in the number of Internet users, the audience of traditional TV broadcasts gradually decreases, and it is the decrease in advertising revenue, so now fixed TV broadcasts will eventually Turning to TCP / IP-based Internet broadcasting, the viewer's viewing method is also converted to an online video on demand by a simple remote control. The concept of video on demand is not to download the program to the hard drive, then play, but streaming video, click to watch, playback. Now the Internet is played in the Internet: Real Networks's Real Media, Microsoft's Windows Media, Apple's QuickTime, which is not compatible with each other, it is possible to cause trouble in the media stream, and MPEG -4 Provide a range of standard tools for Internet video applications to make viewing audio code streams. Therefore, in the Internet playback audio adopts MPEG-4, it should be said to be a secure choice. (2) Applying for wireless communication MPEG-4 efficient bit rate compression, interaction and grading characteristics are particularly suitable for realizing multimedia communication on narrowband mobile network, future mobile phones will become multimedia mobile receivers, not only can mobile TV calls, mobile Internet access, you can also move to receive multimedia broadcasts and watch TV. (3) Applying to a still image compression still image (picture) uses a large number in the Internet, and now the picture compressed in the online picture is used in JPEG technology. The still image (texture) compression in MPEG-4 is based on wavelet transform. Under the same quality conditions, the compressed file size is about one-tenth of the JPEG compressed file. Converting the JPEG picture on the Internet into MPEG-4 format, which can greatly improve the transmission speed of the picture in the network. (4) Applying to a TV phone traditionally used for compression coding standards for narrowband television telephones, such as H261, using intra compression, inter-frame compression, reduction of pixels and draw frames, etc., but encoding efficiency and image quality It is difficult to be satisfactory. The compression coding of MPEG-4 can be used as a sound image signal that can be accepted with a very low yodular rate, so that the television telephone service can be implemented on a narrowband public telephone. (5) Applying to computer graphics, animation and simulation MPEG-4 special coding methods and powerful interaction capabilities, making MPEG-4-based computer graphics and animations to access material from various source multimedia databases, MPEG4 HD technology calculations The graphics card is combined in real time. The future computer graphics can be infinitely developed in the desired direction within the range allowed by the MPEG-4 syntax, resulting in an unimaginable animation and simulation effect today. (6) Applying to the electronic game MPEG-4 can perform a natural image and the synthesis of the sound and the synthesis of the sound, which has unprecedented flexibility in the encoding mode, and can call the material from various source multimedia databases in time. . This can create an interactive operation of a very high degree of freedom in the future. (7) The application above the hardware product is currently, and MPEG4 technology has also begun to gradually apply on hardware products. Especially in video surveillance, playback, this high-definition, high-compressed technology has been loved by many hardware vendors, while the market supporting MPEG4 technology is also a wide variety. The author lists some representative products to let readers understand that MPEG4 technology is widely used today. (1), the camera: Japan Xiapu launched a digital video camera VN-EZ1 applied to the Internet. This webcam uses the MPEG4 format to compress the image file into an ASF (Advanced Format), and the user can play directly on the computer as long as the Microsoft's MediaPlayer player is used. (2), Player: Philips launched a DVD player DVD737 that supported DivX in August this year. It can support MPEG4 standards such as DIVX 3.11, 4.xx, 5.xx, and support for new standards can be implemented by upgrading firmware. (3), Digital Camera: Japan Jing Porcelain Company released its latest digital camera FineCam L30 in mid-November, this is a digital camera product with 3 million pixels, 3 times optical zoom design, and L30 uses MPEG4 format dynamic video recording, You can make dynamic video recording screens better than traditional digital cameras. (4), mobile phone: MPEG4 technology has been widely used, and major mobile phone manufacturers have also launched mobile phone models that can shoot MPEG4 dynamic video, such as Siemens ST55, Sony Ericsson P900 / P908, LG color screen G8000 Wait. (5), MPEG4 digital hard drive: At this year's security exhibition, manufacturers who develop digital video surveillance products have launched their latest products, and the DVR compression technology that supports MPEG4 has also become the highlights of the change.
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