NationMaster - Encyclopedia: Video codec

A video codec is a device or software that enables video compression and or decompression for digital video. The compression usually employs lossy data compression. Historically, video was stored as an analog signal on magnetic tape. Around the time when the compact disc entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge. A codec is a device or program capable of performing encoding and decoding on a digital data stream or signal. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ... A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is close enough to be useful in some way. ... Compact audio cassette Magnetic tape is a non-volatile storage medium consisting of a magnetic coating on a thin plastic strip. ... A compact disc or CD is an optical disc used to store digital data, originally developed for storing digital audio. ...

Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem. Engineering is the application of scientific and technical knowledge to solve human problems. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

There is a complex balance between the video quality, the quantity of the data needed to represent it, also known as the bit rate, the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, the state of the art of compression algorithm design, end-to-end delay, and a number of other factors. Video quality is a characteristic of video passed through a video processing system. ...

Applications

In daily life, digital video codecs are found in DVD (MPEG-2), VCD (MPEG-1), in emerging satellite and terrestrial broadcast systems, and on the Internet. Online video material is encoded in a variety of codecs, and this has led to the availability of codec packs - a pre-assembled set of commonly used codecs combined with an installer available as a software package for PCs.

Encoding media by the public has seen an upsurge with the availability of DVD-writers. Since commercially available DVDs are usually dual-layer, and hence bigger than the more common single layer writable DVDs, it is often the case that the material has to be compressed again, sacrificing quality so that the media will fit onto a single disc.

Video codec design

Video codecs seek to represent a fundamentally analog data set in a digital way. Because of the design of analog video signals, which represent luma and color information separately, a common first step in image compression in codec design is to represent and store the image in a YCbCr color space. The conversion to YCbCr provides two benefits: first, it improves compressibility by providing decorrelation of the color signals; and second, it separates the luma signal, which is perceptually much more important, from the chroma signal, which is less perceptually important and which can be represented at lower resolution to achieve more efficient data compression. It is common to represent the ratios of information stored in these different channels in the following way Y:Cb:Cr. Refer to the following article for more information about Chroma subsampling. As applied to analog television signals, two different words are used, luminance and luma, meaning two different things. ... A colour image and the Y, Cb and Cr elements of it. ... A colour image and the Y, Cb and Cr elements of it. ... As applied to analog television signals, two different words are used, luminance and luma, meaning two different things. ... Chrominance (chroma for short) comprises the two components of a television signal that encode color information. ... In digital image processing, chroma subsampling is the use of lower resolution for the colour (chroma) information in an image than for the brightness (intensity or luma) information. ...

Different codecs will use different chroma subsampling ratios as appropriate to their compression needs. Video compression schemes for Web and DVD use make use of a 4:2:0 color sampling pattern, and the DV standard uses 4:1:1 sampling ratios. Professional video codecs designed to function at much higher bitrates and to record a greater amount of color information for post-production manipulation sample in 3:1:1 (uncommon), 4:2:2 and 4:4:4 ratios. Examples of these codecs include Panasonic's DVCPRO50 and DVCPROHD codecs (4:2:2), and then Sony's HDCAM-SR (4:4:4) or Panasonic's HDD5 (4:2:2). Apple's new Prores HQ 422 codec also samples in 4:2:2 color space. More codecs that sample in 4:4:4 patterns exist as well, but are less common, and tend to be used internally in post-production houses. It is also worth noting that video codecs can operate in RGB space as well. These codecs tend not to sample the red, green, and blue channels in different ratios, since there is no perceptual motivation for doing so. In digital image processing, chroma subsampling is the use of lower resolution for the colour (chroma) information in an image than for the brightness (intensity or luma) information. ... A MiniDV Camcorder For other uses, see DV (disambiguation). ...

Some amount of spatial and temporal downsampling may also be used to reduce the raw data rate before the basic encoding process. The most popular such transform is the 8x8 discrete cosine transform (DCT). Codecs which make use of a wavelet transform are also entering the market, especially in camera workflows which involve dealing with RAW image formatting in motion sequences. The output of the transform is first quantized, then entropy encoding is applied to the quantized values. When a DCT has been used, the coefficients are typically scanned using a zig-zag scan order, and the entropy coding typically combines a number of consecutive zero-valued quantized coefficients with the value of the next non-zero quantized coefficient into a single symbol, and also has special ways of indicating when all of the remaining quantized coefficient values are equal to zero. The entropy coding method typically uses variable-length coding tables. Some encoders can compress the video in a multiple step process called n-pass encoding (e.g. 2-pass), which performs a slower but potentially better quality compression. Downsampling (or subsampling) is the process of reducing the sampling rate of a signal. ... 2-D DCT compared to the DFT The discrete cosine transform (DCT) is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. ... A wavelet is a kind of mathematical function used to divide a given function into different frequency components and study each component with a resolution that matches its scale. ... A raw image file (sometimes written RAW image file ) contains minimally processed data from the image sensor of a digital camera or image scanner. ... Generally, quantization is the state of being constrained to a set of discrete values, rather than varying continuously. ... In information theory an entropy encoding is a data compression scheme that assigns codes to symbols so as to match code lengths with the probabilities of the symbols. ... In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. ...

The decoding process consists of performing, to the extent possible, an inversion of each stage of the encoding process. The one stage that cannot be exactly inverted is the quantization stage. There, a best-effort approximation of inversion is performed. This part of the process is often called "inverse quantization" or "dequantization", although quantization is an inherently non-invertible process. Look up quantization in Wiktionary, the free dictionary. ...

This process involves representing the video image as a set of macroblocks. For more information about this critical facet of video codec design, see B pictures. Macroblock is a term used in video compression, which represents a block of 16 by 16 pixels. ... B pictures (often called B frames) are one of the three major picture types found in typical video compression designs. ...

Video codec designs are often standardized or will be in the future- i.e., specified precisely in a published document. However, only the decoding process needs to be standardized to enable interoperability. The encoding process is typically not specified at all in a standard, and implementers are free to design their encoder however they want, as long as the video can be decoded in the specified manner. For this reason, the quality of the video produced by decoding the results of different encoders that use the same video codec standard can vary dramatically from one encoder implementation to another.

Commonly used standards and codecs

A variety of codecs can be implemented with relative ease on PCs and in consumer electronics equipment. It is therefore possible for multiple codecs to be available in the same product, avoiding the need to choose a single dominant codec for compatibility reasons. In the end it seems unlikely that one codec will replace them all. Some widely-used video codecs are listed below, starting with a chronological-order list of the ones specified in international standards. Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ...

H.261: Used primarily in older videoconferencing and videotelephony products. H.261, developed by the ITU-T, was the first practical digital video compression standard. Essentially all subsequent standard video codec designs are based on it. It included such well-established concepts as YCbCr color representation, the 4:2:0 sampling format, 8-bit sample precision, 16x16 macroblocks, block-wise motion compensation, 8x8 block-wise discrete cosine transformation, zig-zag coefficient scanning, scalar quantization, run+value symbol mapping, and variable-length coding. H.261 supported only progressive scan video. H.261 is an 1990 ITU video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... 2-D DCT compared to the DFT The discrete cosine transform (DCT) is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. ... Look up quantization in Wiktionary, the free dictionary. ... In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. ... Progressive scan Progressive or noninterlaced scanning is any method for displaying, storing or transmitting moving images in which the lines of each frame are drawn in sequence. ...

MPEG-1 Part 2: Used for Video CDs, and also sometimes for online video. The quality is roughly comparable to that of VHS. If the source video quality is good and the bitrate is high enough, VCD can look better than VHS, and all in all very good, but VCD requires high bitrates for this. However, to get a fully compliant VCD file, bitrates higher than 1150 kbit/s and resolutions higher than 352 x 288 should not be used (includes the *.mp3 standard). When it comes to compatibility, VCD has the highest compatibility of any digital video/audio system. Almost every computer in the world can play this codec, and very few DVD players do not support it. In terms of technical design, the most significant enhancements in MPEG-1 relative to H.261 were half-pel and bi-predictive motion compensation support. MPEG-1 supported only progressive scan video. MPEG-1 defines a group of Audio and Video (AV) coding and compression standards agreed upon by MPEG (Moving Picture Experts Group). ... Video CD (aka VCD, VideoCD, View CD, Compact Disc digital video) is a standard digital format for storing video on a Compact Disc. ... A kilobit per second (kbit/s or kbps or kBaud) is a unit of data transfer rate equal to 1,000 bits per second. ... For other uses, see MP3 (disambiguation). ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Progressive scan Progressive or noninterlaced scanning is any method for displaying, storing or transmitting moving images in which the lines of each frame are drawn in sequence. ...

MPEG-2 Part 2 (a common-text standard with H.262): Used on DVD, SVCD, and in most digital video broadcasting and cable distribution systems. When used on a standard DVD, it offers good picture quality and supports widescreen. When used on SVCD, it is not as good as DVD but is certainly better than VCD. In terms of technical design, the most significant enhancement in MPEG-2 relative to MPEG-1 was the addition of support for interlaced video. MPEG-2 is now considered an aged codec, but has tremendous market acceptance and a very large installed base. MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... H.262 is an ITU-T digital video coding standard. ... Size comparison: A 12 cm Sony DVD+RW and a 19 cm Dixon Ticonderoga pencil. ... Super Video Compact Disc (SVCD) is a format used for storing video on standard compact discs or CD-Rs. ... Interlace is a technique of improving the picture quality of a video signal without consuming any extra bandwidth. ...

H.263: Used primarily for videoconferencing, videotelephony, and internet video. H.263 represented a significant step forward in standardized compression capability for progressive scan video. Especially at low bit rates, it could provide a substantial improvement in the bit rate needed to reach a given level of fidelity. H.263 is a video codec designed by the ITU-T as a low-bitrate encoding solution for videoconferencing. ... Progressive scan Progressive or noninterlaced scanning is any method for displaying, storing or transmitting moving images in which the lines of each frame are drawn in sequence. ...

MPEG-4 Part 2: An MPEG standard that can be used for internet, broadcast, and on storage media. It offers improved quality relative to MPEG-2 and the first version of H.263. Its major technical features beyond prior codec standards consisted of object-oriented coding features and a variety of other such features not necessarily intended for improvement of ordinary video coding compression capability. It also included some enhancements of compression capability, both by embracing capabilities developed in H.263 and by adding new ones such as quarter-pel motion compensation. Like MPEG-2, it supports both progressive scan and interlaced video. MPEG-4 is a standard used primarily to compress audio and visual (AV) digital data. ... The Moving Picture Experts Group or MPEG is a working group of ISO/IEC charged with the development of video and audio encoding standards. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Progressive scan Progressive or noninterlaced scanning is any method for displaying, storing or transmitting moving images in which the lines of each frame are drawn in sequence. ... Interlace is a technique of improving the picture quality of a video signal without consuming any extra bandwidth. ...

MPEG-4 Part 10 (a technically aligned standard with the ITU-T's H.264 and often also referred to as AVC). This emerging new standard is the current state of the art of ITU-T and MPEG standardized compression technology, and is rapidly gaining adoption into a wide variety of applications. It contains a number of significant advances in compression capability, and it has recently been adopted into a number of company products, including for example the XBOX 360, PlayStation Portable, iPod, the Nero Digital product suite, Mac OS X v10.4, as well as HD DVD/Blu-ray Disc. MPEG-4 is a standard used primarily to compress audio and visual (AV) digital data. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... H.264 is a standard for video compression. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... The Moving Picture Experts Group or MPEG is a working group of ISO/IEC charged with the development of video and audio encoding standards. ... It has been suggested that Xbox 360 Elite be merged into this article or section. ... The PlayStation Portable , officially abbreviated as PSP) is a handheld game console released and currently manufactured by Sony Computer Entertainment. ... iPod is a brand of portable media player designed and marketed by Apple and launched in October 2001. ... Nero Digital is a suite of MPEG-4-compatible video and audio compression codecs integrated into a DVD ripping tool, Recode 2. ... Mac OS X version 10. ... HD-DVD disc HD DVD (for High Density Digital Versatile Disc) is a digital optical media format which is being developed as one standard for high-definition DVD. HD DVD is similar to the competing Blu-ray Disc, which also uses the same CD sized (120 mm diameter) optical data... A blank rewritable Blu-ray disc (a BD-RE) A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital information, including high-definition video. ...

DivX, Xvid, FFmpeg MPEG-4 and 3ivx: Different implementations of MPEG-4 Part 2. DivX is a brand name of products created by DivX, Inc. ... Xvid (formerly XviD) is a video codec library following the MPEG-4 standard. ... FFmpeg is a collection of software libraries that can record, convert and stream digital audio and video in numerous formats. ... 3ivx is a video codec created by 3ivx Technologies. ...

VP6: A proprietary video codec developed by On2 Technologies and used in Adobe Flash Player 8 and above. TrueMotion VP6 is a video codec developed by On2 Technologies as a successor to earlier efforts such as VP3 and VP5. ...

Sorenson 3: A codec that is popularly used by Apple's QuickTime, basically the ancestor of H.264. Many of the QuickTime movie trailers found on the web use this codec. The Sorenson codec (also known as Sorenson Video Codec 3 or SVQ3) is a digital video codec devised by the company Sorenson Media and used by Apples QuickTime and the newest version of Macromedia Flash, a special version called Sorenson Spark. ... QuickTime is a multimedia framework developed by Apple Inc. ... H.264 is a high compression digital video codec standard written by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG) as the product of a collective partnership effort known as the Joint Video Team (JVT). ...

Sorenson Spark: A codec that was licensed to Macromedia for use in its Flash Player 6. In the same family as H.263. The Sorenson codec (also known as Sorenson Video Codec 3 or SVQ3) is a digital video codec devised by the company Sorenson Media and used by Apples QuickTime and the newest version of Macromedia Flash, a special version called Sorenson Spark. ... H.263 is a video codec designed by the ITU-T as a low-bitrate encoding solution for videoconferencing. ...

Theora: Developed by the Xiph.org Foundation as part of their Ogg project, based upon On2 Technologies' VP3 codec, and christened by On2 as the successor in VP3's lineage, Theora is targeted at competing with MPEG-4 video and similar lower-bitrate video compression schemes. Theora is a video codec being developed by the Xiph. ... The Xiph. ... Ogg is an open standard for a free container format for digital multimedia, unrestricted by software patents and designed for efficient streaming and manipulation. ... NatusRoma 00:49, 12 Jun 2005 (UTC) Categories: Possible copyright violations ... VP3 was originally a proprietary video codec developed by On2 Technologies. ... MPEG-4 is a standard used primarily to compress audio and visual (AV) digital data. ...

WMV (Windows Media Video): Microsoft's family of video codec designs including WMV 7, WMV 8, and WMV 9. It can do anything from low resolution video for dial up internet users to HDTV. The latest generation of WMV is standardized by SMPTE as the VC-1 standard. Windows Media Video (WMV) is a generic name for the set of streaming video technologies developed by Microsoft. ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... Projection screen in a home theater, displaying a high-definition television image. ... The Society of Motion Picture and Television Engineers or SMPTE (pronounced simptee or sometimes sumptee) is a US professional association of engineers. ... VC-1 is the informal name of the SMPTE 421M video codec standard initially developed by Microsoft. ...

VC-1: SMPTE standardized video compression standard (SMPTE 421M). Based on Microsoft's WMV9 video codec. One of the 3 mandatory video codecs in both HD-DVD and Blu-Ray high-definition optical disc standards. Commonly found in portable devices and on streaming video websites in its Windows Media Video implementation. VC-1 is the informal name of the SMPTE 421M video codec standard initially developed by Microsoft. ... Windows Media Video (WMV) is a generic name for the set of streaming video technologies developed by Microsoft. ... HD DVD, High-Definition DVD or High-Density DVD is a high-density optical disc format designed for the storage of data and high-definition video. ... Blu-ray discs Blu-ray Disc is a next-generation optical disc format jointly developed by a group of leading consumer electronics and PC companies called the Blu_ray Disc Association (BDA), which succeeds the Blu_ray Disc Founders (BDF). ... Windows Media Video (WMV) is a generic name for the set of video codec technologies developed by Microsoft. ...

RealVideo: Developed by RealNetworks. A popular codec technology a few years ago, now fading in importance for a variety of reasons. RealVideo is a proprietary video format developed by RealNetworks. ... This article does not cite any references or sources. ...

Cinepak: A very early codec used by Apple's QuickTime. Compressed with Cinepak, quality 40% Cinepak is a video codec, developed by Radius Inc to accommodate 1x (150 kbyte/s) CD-ROM transfer rates. ...

x264: A GPL-licensed implementation of H.264 encoding standard, x264 is only an encoder. x264 is a free software library for encoding H.264/MPEG-4 AVC video streams. ...

Huffyuv: Huffyuv (or HuffYUV) is a very fast, lossless Win32 video codec written by Ben Rudiak-Gould and published under the terms of the GPL as free software, meant to replace uncompressed YCbCr as a video capture format. See Lagarith as a more up-to-date codec. Huffyuv (or HuffYUV) is a lossless video codec created by Ben Rudiak-Gould which is meant to replace uncompressed YCbCr as a video capture format. ...

Lagarith: A more up-to-date fork of Huffyyuv is available as Lagarith. Lagarith is an open source lossless video codec written by Ben Goldman. ...

SheerVideo: A family of ultrafast lossless QuickTime and AVI codecs, developed by BitJazz Inc., for RGB[A], Y'CbCr[A] 4:4:4[:4], Y'CbCr[A] and 4:2:2[:4] formats; for both 10-bit and 8-bit channels; for both progressive and interlaced data; for both Mac and PC. SheerVideo is a fast lossless video codec created by BitJazz Inc. ...

All of the codecs above have their qualities and drawbacks. Comparisons are frequently published. The tradeoff between compression power, speed, and fidelity (including artifacts) is usually considered the most important figure of technical merit. A compression artifact (or artefact) is the result of an aggressive data compression scheme applied to an image, audio, or video that discards some data which is determined by an algorithm to be of lesser importance to the overall content but which is nonetheless discernible and objectionable to the user. ...

Missing Codecs and Video File Issues

A common problem when an end user wants to watch a video stream encoded with a specific codec is that if the exact codec is not present and properly installed on the user's machine, the video won't play (or won't play optimally).

Windows XP SP2 itself only has a very limited number of video and audio codecs installed; other than Microsoft formats, Intel Indeo is the only available .avi Codec that is installed per default. All other codecs, such as DivX, Xvid or Theora, must be installed manually.

Some video files and codec analysis tools have been made available to provide a user-friendly way to solve this common problem:

VideoInspector : Analyzes most containers (AVI, Matroska, MPEG, etc.) and gives direct download links for missing codecs.

GSpot : A pioneer in troubleshooting video applications, GSpot remains a useful tool despite missing some features present in other software.

AVI2Clipboard : An extension for the Explorer context menu to easily view and save information about videos with an AVI container.

Many people find that VLC media player resolves many of these issues because it contains many popular codecs in a portable standalone library, available for many operating systems, including Windows, Linux, and Mac OS X. This also resolves many issues within Windows in conflicting and poorly installed codecs. VLC media player is a free software media player by the VideoLAN project. ... In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ...

Video Codec Benchmarking

For directshow users who are interested in their benchmarking their video decoders try using the Haali TimeCodec. It requires that you install the latest version of the Haali Media Splitter before using it.

Another method is using the internal audio and video decoders built into TCPMP for both mobile devices and desktop PC's. See Shinos TCPMP benchmark page The Core Pocket Media Player (TCPMP) is the most versitile and dual license Media Player available today. ...

See also

Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ... Video quality is a characteristic of video passed through a video processing system. ... Subjective video quality is a subjective characteristic of video quality. ... This is a listing of open source multimedia codecs and containers. ... Comparison of video codecs - is a process of codecs evaluation of similarities and differences. ...

External links

Categories: Video codecs | Codecs David Slepian (born June 30, 1923) is an American mathematician. ... â€œSource codingâ€ redirects here. ... Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. ... Not to be confused with information technology, information science, or informatics. ... Claude Shannon In information theory, the Shannon entropy or information entropy is a measure of the uncertainty associated with a random variable. ... In computer science, the Kolmogorov complexity (also known as descriptive complexity, Kolmogorov-Chaitin complexity, stochastic complexity, algorithmic entropy, or program-size complexity) of an object such as a piece of text is a measure of the computational resources needed to specify the object. ... Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. ... In information theory an entropy encoding is a data compression scheme that assigns codes to symbols so as to match code lengths with the probabilities of the symbols. ... In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. ... Adaptive Huffman coding is an adaptive coding technique based on Huffman coding, building the code as the symbols are being transmitted, having no initial knowledge of source distribution, that allows one-pass encoding and adaptation to changing conditions in data. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... In the field of data compression, Shannon-Fano coding is a technique for constructing a prefix code based on a set of symbols and their probabilities (estimated or measured). ... Range encoding is a form of arithmetic coding, a data compression method, that is believed to be free from arithmetic coding related patents. ... Golomb coding is a form of entropy encoding invented by Solomon W. Golomb that is optimal for alphabets following geometric distributions, that is, when small values are vastly more common than large values. ... An Exponential-Golomb code (or just Exp-Golomb code) of order is a type of universal code, parameterized by a whole number . ... In data compression, a universal code for integers is a prefix-free code that maps the positive integers onto self-delimiting binary codewords, with the additional property that whatever the true probability distribution on integers, the lengths of the codewords are within a constant factor of the lengths that the... Elias gamma code is a universal code encoding the positive integers. ... The Fibonacci code is a universal code which encodes positive integers into binary code words. ... A dictionary coder, also sometimes known as a substitution coder, is any of a number of data compression algorithms which operate by searching for matches between the text to be compressed and a set of strings contained in a data structure (called the dictionary) maintained by the encoder. ... LZ77 and LZ78 are the names for the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. ... LZW (Lempel-Ziv-Welch) is a lossless data compression algorithm. ... Lempel-Ziv-Oberhumer (LZO) is a data compression algorithm that is focused on decompression speed. ... DEFLATE is a lossless data compression algorithm that uses a combination of the LZ77 algorithm and Huffman coding. ... Lempel-Ziv-Markov chain-Algorithm (LZMA) is a data compression algorithm in development since 1998 and used in the 7z format of the 7-Zip archiver. ... LZX is the name of an LZ77 family compression algorithm. ... Run-length encoding (RLE) is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. ... The Burrows-Wheeler transform (BWT, also called block-sorting compression), is an algorithm used in data compression techniques such as bzip2. ... PPM is an adaptive statistical data compression technique based on context modeling and prediction. ... Dynamic Markov Compression (DMC) is a lossless data compression algorithm developed by Gordon Cormack and Nigel Horspool [1]. It uses predictive arithmetic coding similar to prediction by partial matching (PPM), except that the input is predicted one bit at a time (rather than one byte at a time). ... Audio compression is a form of data compression designed to reduce the size of audio files. ... Acoustics is a branch of physics and is the study of sound (mechanical waves in gases, liquids, and solids). ... In mathematics and, in particular, functional analysis, convolution is a mathematical operator which takes two functions f and g and produces a third function that in a sense represents the amount of overlap between f and a reversed and translated version of g. ... In signal processing, sampling is the reduction of a continuous signal to a discrete signal. ... The Nyquistâ€“Shannon sampling theorem is a fundamental result in the field of information theory, in particular telecommunications and signal processing. ... An audio codec is a computer program that compresses/decompresses digital audio data according to a given audio file format or streaming audio format. ... It has been suggested that this article or section be merged with Code Excited Linear Prediction. ... Log Area Ratios (LAR) can be used to represent Reflection Coefficients (another from for Linear Prediction Coefficients) for transmission over a channel. ... Line Spectral Pairs (LSP) are used to represent Linear Prediction Coefficients (LPC) for transmission over a channel. ... Warped Linear Predictive Coding (Warped LPC or WLPC) is a variant of Linear predictive coding in which the spectral representation of the system is modified, for example by replacing the unit delays used in an LPC implementation with first-order allpass filters. ... CELP stands for Code Excited Linear Prediction and is a speech coding algorithm originally proposed by M.R. Schroeder and B.S. Atal in 1984. ... Algebraic Code Excited Linear Prediction or ACELP is a speech encoding algorithm where a limited set of pulses is distributed as excitation to linear prediction filter. ... Graph of Î¼-law & A-law algorithms An a-law algorithm is a standard companding algorithm, used in European digital communications systems to optimize, modify, the dynamic range of an analog signal for digitizing. ... In telecommunication, a mu-law algorithm (Î¼-law) is a standard analog signal compression or companding algorithm, used in digital communications systems of the North American and Japanese digital hierarchies, to optimize (in other words, modify) the dynamic range of an audio analog signal prior to digitizing. ... modified discrete cosine transform (MDCT) is a Fourier-related transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where subsequent blocks are overlapped so that the last half... In mathematics, the Fourier transform is a certain linear operator that maps functions to other functions. ... Psychoacoustics is the study of subjective human perception of sounds. ... Audio level compression, also called dynamic range compression, volume compression, compression, limiting, or DRC (often seen in DVD player settings) is a process that manipulates the dynamic range of an audio signal. ... Speech coding is the compression of speech (into a code) for transmission with speech codecs that use audio signal processing and speech processing techniques. ... Sub-band coding is any form of transform coding that breaks a signal into a number of different frequency bands and encodes each one independently. ... Image compression is the application of Data compression on digital images. ... A comparison of different color spaces. ... This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen. ... In digital image processing, chroma subsampling is the use of lower resolution for the colour (chroma) information in an image than for the brightness (intensity or luma) information. ... A compression artifact (or artefact) is the result of an aggressive data compression scheme applied to an image, audio, or video that discards some data which is determined by an algorithm to be of lesser importance to the overall content but which is nonetheless discernible and objectionable to the user. ... Run-length encoding (RLE) is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. ... Fractal compression is a lossy compression method used to compress images using fractals. ... Wavelet compression is a form of data compression well suited for image compression (sometimes also video compression and audio compression). ... Set Partitioning in Hierarchical Trees (SPIHT) is an image compression algorithm that exploits the inherent similarities across subbands in a wavelet decomposition of an image. ... 2-D DCT compared to the DFT The discrete cosine transform (DCT) is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. ... In statistics, principal components analysis (PCA) is a technique that can be used to simplify a dataset; more formally it is a linear transformation that chooses a new coordinate system for the data set such that the greatest variance by any projection of the data set comes to lie on... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... In order to intuitively test the effects of an image-processing algorithm on a natural picture a number of test images are in common use in the image-processing field. ... The phrase peak signal-to-noise ratio, often abbreviated PSNR, is an engineering term for the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation. ... Quantization, involved in image processing. ... Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ... This article does not cite any references or sources. ... It has been suggested that video frame be merged into this article or section. ... The three major picture types found in typical video compression designs are I(ntra) pictures, P(redicted) pictures, and B(i-predictive) pictures (or B(i-directional) pictures). ... Video quality is a characteristic of video passed through a video processing system. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... 2-D DCT compared to the DFT The discrete cosine transform (DCT) is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. ... Quantized signal Digital signal In digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values. ... Rate distortion theory is the branch of information theory addressing the problem of determining the minimal amount of entropy (or information) R that should be communicated over a channel such that the source (input signal) can be reconstructed at the receiver (output signal) with given distortion D. As such, rate... Constant bit rate (CBR) is a term used in telecommunications, relating to the quality of service. ... Average bit rate refers to the average amount of data transferred per second. ... Variable bit rate (VBR) is a term used in telecommunications and computing that relates to sound or video quality. ... A timeline of events related to information theory, data compression, error correcting codes and related subjects. ...

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