"Preface
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Recently, when you look at the Hi Ti Hi3516A software development manual, some video codes in the table below are not very clear, and it is easy to confuse, so some information is checked, and H.264, JPEG, JPEG2000, Motion JPEG, H. 265, MPEG-4, etc. These common image coding formats are summarized and recorded. Among them, the meaning of BP, MP, and HP is sent to the door.
H.264
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H.264 is a new generation of digital video compression formats after MPEG4, which is the International Standardization Organization (ISO) and International Telecommunications Union (ITU). H.264 is one of the video codec technology standards named by ITU-T at the H.26X series. H.264 is a digital video coding standard developed by ITU-T VCEG (Video Coding Expert Group) and ISO / IEC MPEG (Active Image Coding Expert Group).
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H.264 is established on the basis of MPEG-4 technology, its codec process mainly includes 5 parts: inter-frame and intra prediction, transform and reverse transformation, quantization, and Inverse quantization, loop filter, entropy coding.
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The main objective of the H.264 standard is to provide more excellent image quality over the same bandwidth compared to other existing video coding standards. Through this standard, the compression efficiency under the same image quality is 2 times more than the previous standard (MPEG2).
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The maximum advantage of H.264 is to have a high data compression ratio. Under the conditions of the same image quality, the compression ratio of H.264 is 2 times the MPEG-2, which is 1.5 to 2 times the MPEG-4. For example, if the size of the original file is 88GB, it is 3.5GB after compressing the MPEG-2 compression standard, and the compression ratio is 25: 1, and the compression ratio is compressed by the compression standard to 879MB, from 88GB to 879MB, The compression ratio of H.264 is an amazing 102: 1.
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Low bit rats play an important role in the high compression ratio of H.264, compared to compression technology such as MPEG-2 and MPEG-4 ASP, will greatly save users' download time And data traffic charges. It is particularly worth mentioning that H.264 also has a high quality image while having a high compression ratio, as in this way, after the H.264 compressed video data, less bandwidth required in the network transmission process, It is also more economical.
The main features of the H264 standard are as follows:
1. Higher coding efficiency: A average amount of greater than 50% can be saved more than 50% compared to the standard efficiency of H.263 and other standards.
2. High quality video screen: H.264 can provide high quality video images in low yaw rates, providing high quality image transmission on lower bandwidth is a highlight of H.264.
3. Improve network adaptability: H.264 can operate in real-time communication applications (such as video conferencing) low delay mode, or in a video storage or video stream server without delay.
4. The mixed coding structure is used: the same H.263 is the same as H.264, also uses a mixed coding structure of differential encoding using DCT transform encoding DPCM, but also increases, such as multi-mode motion estimation, intra prediction, multi-frame prediction, content based A new coding method such as a long coding, 4x4 two-dimensional integer transformation, improves coding efficiency.
5. The H.264 is less code option: When encoding in H.263, a considerable number of options often need to be set, and the encoding is added, and the H.264 has achieved a simple "regression basics" and reduces the complexity of encoding.
6. H.264 can be applied to different occasions: H.264 can use different transmission and playback rates depending on different environments, and provide a wealth of error handling tools, which can control or eliminate packet loss and false.
7. Error Recovery Features: H.264 provides tools for solving the problem of network transfer packages, which are suitable for transmitting video data in wireless networks transmitted in high-error rate.
8. Higher complexity: 264 Performance improvement is obtained at the expense of increasing complexity. It is estimated that the computational complexity of H.264 encoding is approximately three times the H.263, and the decoding complexity is approximately twice the H.263.
JPEG
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JPEG (full name is Joint Photographic Experts Group) is a common image format. It is developed and named "" ISO 10918-1 ", JPEG is just a commonly known as a joint photo expert group.
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JPEG is the abbreviation of Joint Photography Expert Experts Group, which is represented after the document. " JPG "" or "". "JPEG" "is the most commonly used image file format, organized by a software development federation, is a lossless compression format, which can compress the image compression in small storage space, repetitive or unimportant data in the image. Lost, therefore it is easy to cause damage to image data. Especially the use of excessive compression ratios will make the image quality restored after the final decompression significantly decrease, and if high quality images are pursued, it is not advisable to use too high compression ratio.
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However, JPEG compression technology is very advanced, which removes redundant image data in a lossless compression, and can show a very rich image while obtaining extremely high compression ratios. In other words, it is possible to use the least disk space to get Good image quality. Moreover, JPEG is a very flexible format, with the function of adjusting image quality, allowing files to compress files with different compression ratios, supporting multiple compression levels, typically between 10: 1st to 40: 1, compression ratio The bigger the quality, the lower the quality, the smaller the compression ratio, the better the quality.
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For example, the 1.37MB BMP bitmap file can be compressed to 20.3kb. Of course, a balance point can also be found between image quality and file size. The main high frequency information is compressed. It is better to reserve the information of the color. It is suitable for applications to the Internet, which can reduce the transmission time of the image, can support 24bit true color, and is generally applied to images that require continuous tones.
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The JPEG format is the most popular image format on the network. It is possible to compress files to the smallest format. When you are stored in the Photoshop software, the 11-level compression level is provided at 0-10. Where is the top level compression ratio, the image quality is the worst. Even if the 10-level quality of the almost lossless level is saved, the compression ratio can be 5: 1. A 4.28MB image file is obtained when saved in BMP format, and when saved in JPG format, its file is only 178KB, and the compression ratio is 24: 1. After many comparisons, the 8th level is compressed into the best proportion of storage space and image quality. The advantage of the PG file is that the size is compact and is compatible.
JPEG2000
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JPEG 2000 is based on wavelet transform image compression criteria, created and maintained by Joint PhotoGraphic Experts Group. JPEG 2000 is often considered to be a next-generation image compression criteria for JPEG (based on discrete cosine transform) in the future. The secondary file name of the JPEG 2000 file is usually .jp2, the MIME type is image / jp2.
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The JPEG2000 is an upgraded version of JPEG, with a compression ratio of about 30% higher than JPEG, while supporting damage and lossless compression. The JPEG2000 format has an extremely important feature that it enables progressive transfer, first transmitting the outline of the image, then gradually transmitting data, constantly improving image quality, allowing the image to be clearly displayed by. Further, the JPEG2000 also supports the so-called "Issue" feature of "Issue", which can arbitrarily specify the compression quality of the area of interest on the image, and you can choose the specified portion to first decompress.
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The JPEG2000 and JPEG are obvious compared to the advantages, and it is compatible, so it can replace the traditional JPEG format. The JPEG2000 can be applied to traditional JPEG markets, such as scanners, digital cameras, etc., but also in emerging fields such as network transmission, wireless communications, etc. Comparison of JPEG2000 and JPEG
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Under lossless compression, JPEG2000 has a more obvious advantage that there is no mosaic distortion effect in JPEG compression. The distortion of JPEG2000 is mainly blurred. The main reason for the cause of fuzzy distortion is to attenuate high frequency during the encoding process. Traditional JPEG compression also has a blurred problem.
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In terms of image overall compression performance, there are some articles that may exaggerate the performance of JPEG2000. In fact, under low compression ratio (such as less than 10: 1), traditional JPEG image quality is likely to be better than JPEG2000. JPEG2000 has the advantage that the advantage begins obvious in situations where compression ratio is relatively high. For a whole, compared with traditional JPEG, JPEG2000 still has a large technical advantage, usually compressed performance can increase by more than 20%. Usually in the case of a compression ratio of 100: 1, an image with JPEG compression has been severe distortion and it is difficult to identify, but the JPEG2000's image can still be identified. It is generally measured by the degree of loss of compressed image quality or distortion. Although peak signal-to-noise can not completely reflect the human visual effect, it is still a more popular quantitative indicator.
Motion JPEG~~~~~~~
Motion JPEG (MAJG, MOTION JOINT PhotoGRAPHIC Experts Group, Fourcc: MJPG) is a video compression format, each of which use JPEG encoding separately.
Medium-layered compression encoding, the latter is high-level compression coding.
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At the same time, the formulation of video coding related standards is also improved. The video coding standard is mainly developed by ITU-T and ISO / IEC. The video standards released by ITU-T have MPEG-series standards with H.261, H.262, H.263, H.263 +, H.263 ++, H.264, H.265, ISO / IEC. 1, MPEG-2, MPEG-4 and MPEG-7, and plan to announce MPEG-21. "
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The same format JPEG video compression is different from the frame compression because the compressing bit is relatively low, so the encoding and decoding are relatively easy, and there is no need for too much calculation capabilities, which makes the software or chip can be easily performed on Motion JPEG. edit. Because of this, some mobile devices, such as digital cameras using Motion JPEG to make short-filtered encodings.
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For QuickTime format, Apple defines two types of encodings: MJPEG format A and MJPEG format B. MJPEG Format B no longer retains an effective JPEG intersection (INTERCHANGE FILES), no header, it cannot save separate frames to the JPEG file.
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Compared to other uncompressed formats (such as RGB, compression ratio 1: 1; YCBCR, compression ratio 1: 1.5) and MPEG (1: 100), the data rate is 29Mbit / s is very high, the result is that the file size is relatively Larger.
H.265
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H.265 is a new video coding standard established after ITU-T VCEG followed by ITU-T VCEG followed. The H.265 standard surrounds the existing video coding standard H.264, reserves the original technologies, and improves some related technologies. New technology uses advanced technology to improve the relationship between code stream, coding quality, delay and algorithm complexity, reaching optimization settings. Specific research contents include: increasing compression efficiency, improving robustness and error recovery capabilities, reducing real-time delays, reducing channel acquisition time and random access delay, reducing complexity, etc. H.264 Due to the algorithm optimization, it can achieve digital image transfer at a speed of less than 1 Mbps; H.265 can achieve 720P (resolution 1280720) ordinary high-definition video can be transmitted by the transmission speed of 1 to 2 Mbps Transfer.
$ ~ ~~~~~~ $ August 2012, Ericsson has launched the first H.265 codec, and after six months, ITU (ITU) officially approved HEVC / H.265 Standard, the standard has a high efficiency video code, which has a considerable improvement in previous H.264 standards, China Huawei has the most core patents, which is the leader of the standard.
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The H.265 / HEVC encoding architecture is similar to the architecture of H.264 / AVC, mainly including, intra predetermined, inter-intermediction, transform, Quantization, Deblocking filter, entropy coding, etc., but in the HEVC encoding architecture, the overall division is divided into three basic units, named Coding Unit, Cu, predictive unit (Predict) Unit, PUs and conversion units (Transform Unit, TU).
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Compared to H.264 / AVC, H.265 / HEVC provides more different tools to reduce the yield, in the coding unit, each macroblock / mb size in H.264 is fixed 16x16 Pixels, and the coding unit of H.265 can choose from the smallest 8x8 to the maximum 64x64.
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As an example above, there is a region where the amount of information (color variation is not obvious, such as the red portion of the vehicle body and the gray portion of the ground) is large, and the encoded codeword is less, and more than a large place ( The macroblock divided by the tire has a corresponding small and more, the encoded codeword is much, which is equivalent to the encoding of the image, thereby reducing the overall code rate, and the coding efficiency is correspondingly improved.
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At the same time, the intra prediction mode of H.265 supports 33 directions (H.264 only supports only 8), and provides better motion compensation processing and vector prediction methods.
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Repeated quality comparison tests have shown that under the same image quality, video size encoded by H.265 will be reduced by approximately 39-44% compared to H.264. This data will also have corresponding changes due to differences in quality control measurement.
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According to the data derived by subjective visual test, the quality of the H.265 encoded video can be approximately even better with the H.264 encoded video in the case of a rate of 51-74%, which is essentially more than expected. The signal to noise ratio (PSNR) is better.
MPEG-4
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MPEG4 was announced 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 focusing on multimedia system interactive and flexible not only for video, audio coding, but also more interactive and flexible. 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.
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MPEG is MOVING PICTURE Expert Group, which is an international organization specializing in the development of multimedia video and audio compression coding standards. The MPEG series standard has become the most influential multimedia technical standards in the world, where MPEG-1 and MPEG-2 are first-generation data compression coding technologies such as Xiannong information on predictive coding, transform coding, entropy coding and motion compensation. The MPEG-4 (ISO / IEC 14496) is based on the international standards developed by the second generation compression coding technology. It uses the content-based compression encoding based on the audio-visual media object to achieve digital audio, graphical synthesis applications and Integration of interactive multimedia. The MPEG series standard has a huge and profound impact on the development of audio-visual consumer electronics and digital TVs such as VCD, DVD and high-definition TV (DTV && HDTV), multimedia communications.
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MPEG-4 utilizes very narrow bandwidth, compacts, and transmits data by frame reconstruction, to obtain optimal image quality at least with minimal data.
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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.
Summarize
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70% of the information acquired by human beings come from vision, video information plays an important role in multimedia information; the maximum video data redundancy is the largest, and the quality of video quality after compression processing is a key factor in determining multimedia service quality. Therefore, digital video technology is the core technology of multimedia applications, and research on video coding has become a hot topic in the field of information technology.
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The research topics of video coding mainly include data compression ratio, compression / decompression speed and rapid implementation algorithm. After compression / decompression, data is completely consistent as a measure standard before compression, and data compression can be divided into non-distortion compression (ie, reverse compression, lossless compression) and distortion compression (ie irreversable compression, lossless compression). .
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The traditional compression coding is based on the basis of Xiangnong Information. It uses the classic set theory as a tool, and the source statistics model is used to describe the source, and its compression idea is based on data statistics, so it can only remove data redundancy, which belongs to a category of low-layer compression coding.
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With the rapid development of video coding related disciplines and emerging disciplines, the new generation of data compression techniques is increasingly born and increasingly mature, and their coding ideas are converted to content based on pixels and pixel blocks. It broke through the shackles of the Fairy Nong Information Theory, fully considering the human eye visual characteristics and source characteristics, to achieve data compression by removing content redundancy, can be divided into object-based and based on semantics-based) Both, the former belongs to
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