(See Compression Formats and Standards for formats and Compression Software Implementations for codecs) In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ... Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. ... A bundle of optical fiber. ... 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. ... 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 Nyquist–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 μ-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 (μ-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. ... A video codec is a device or software module that enables video compression or decompression for digital video. ... 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. ... A video codec is a device or software module that enables video compression or decompression for digital video. ... 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. ...