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A codec is a device or program capable of encoding and/or decoding a digital data stream or signal. The word codec may be a combination of any of the following: 'compressor-decompressor', 'coder-decoder', or 'compression/decompression algorithm'. A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ...
An encoder is a device used to encode a signal (such as a bitstream) or data into a form that is acceptable for transmission or storage. ...
This article discusses common methods in communication theory for decoding codewords sent over a noisy channel (such as a binary symmetric channel). ...
For other uses, see Digital (disambiguation). ...
For other uses, see Data (disambiguation). ...
In information theory, a signal is the sequence of states of a communications channel that encodes a message. ...
Description
Related concepts An endec is a Jihad yet different concept mainly used for hardware. In the mid 20th century, a "codec" was hardware that coded analog signals into Pulse-code modulation (PCM) and decoded them back. Late in the century the name came to be applied to a class of software for converting among digital signal formats, and including compander functions. A decoder is a device which does the reverse of an encoder, undoing the encoding so that the original information can be retrieved. ...
For other uses, see Hardware (disambiguation). ...
PCM redirects here. ...
A waveform before and after the compression stage of companding In telecommunication, signal processing, and thermodynamics, companding (occasionally called compansion) is a method of reducing the effects of a channel with limited dynamic range. ...
Codecs (in the modern, software sense) encode a stream or signal for transmission, storage or encryption and decode it for viewing or editing. Codecs are often used in videoconferencing and streaming media applications. A video camera's analogue-to-digital converter (ADC) converts its analogue signals into digital signals, which are then passed through a video compressor for digital transmission or storage. A receiving device then runs the signal through a video decompressor, then a digital-to-analogue converter (DAC) for analogue display. A "codec" is a generic name for a video conferencing unit. Encrypt redirects here. ...
Categories: Wikipedia cleanup | Groupware | Telecommunications stubs ...
Streaming media is multimedia that is continuously received by, and normally displayed to, the end-user while it is being delivered by the provider. ...
AD on USB In electronics, an analog-to-digital converter (abbreviated ADC, A/D, or A to D) is a device that converts continuous signals to discrete digital numbers. ...
A video codec is a device or software that enables video compression and or decompression for digital video. ...
In electronics, a digital-to-analog converter (DAC or D-to-A) is a device for converting a digital (usually binary) code to an analogue signal (current, voltage or charges). ...
An audio compressor converts analogue audio signals into digital signals for transmission or storage. A receiving device then converts the digital signals back to analogue using an audio decompressor, for playback. An example of this are the codecs used in the sound cards of personal computers. An audio codec is a computer program that compresses/decompresses digital audio data according to a given audio file format or streaming audio format. ...
The raw encoded form of audio and video data is often called essence, to distinguish it from the metadata information that together make up the information content of the stream and any "wrapper" data that is then added to aid access to or improve the robustness of the stream. Metadata is data about data. ...
Robust means healthy, strong, durable, and often adaptable, innovative, flexible. ...
Compression quality Most codecs are lossy, allowing the compressed data to be made smaller than otherwise. This aids transmission across networks and storage on relatively expensive media, such as non-volatile memory and hard disk, as well as write-once read-many formats such as CD-ROM and DVD. A lossy data compression method is one where compressing a file and then decompressing it retrieves a file that may well be different to the original, but is close enough to be useful in some way. ...
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. ...
Typical hard drives of the mid-1990s. ...
The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ...
DVD (also known as Digital Versatile Disc or Digital Video Disc) is a popular optical disc storage media format. ...
There are also lossless codecs, but for most purposes the slight increase in quality might not be worth the increase in data size, which is often considerable. The main exception to this is if the data is to undergo further processing (for example editing) in which case the repeated application of lossy codecs (repeated encoding and subsequent decoding) will almost certainly degrade the quality of the edited file such that it is readily identifiable (visually or audibly or both). Using more than one codec or encoding scheme whilst creating a finished product can also degrade quality significantly (however there are many situations where this is all but unavoidable). The decreasing cost of storage capacity and network bandwidth may obviate the need for lossy codecs for some media over time. Lossless data compression is a class of data compression algorithms that allow the original data to be reconstructed exactly from the compressed data. ...
Editing is the process of preparing language, images, or sound for presentation through correction, condensation, organization, and other modifications. ...
Codecs are often designed to emphasise certain aspects of the media to be encoded. For example, a digital video (using a DV codec) of a sports event, such as baseball or soccer, needs to encode motion well but not necessarily exact colours, while a video of an art exhibit needs to perform well encoding colour and surface texture. There are hundreds or even thousands of codecs ranging from those downloadable for free to ones costing hundreds of dollars or more. This can create compatibility and obsolescence issues. By contrast, lossless PCM audio (44.1 kHz, 16 bit stereo, as represented on an audio CD or in a .wav or .aiff file) offers more of a persistent standard across multiple platforms and over time.
Many multimedia data streams need to contain both audio and video data, and often some form of metadata that permits synchronisation of audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for the multimedia data stream to be useful in stored or transmitted form, they must be encapsulated together in a container format. Look up Multimedia in Wiktionary, the free dictionary. ...
This article is about audible acoustic waves. ...
For other uses, see Video (disambiguation). ...
Encapsulation may refer to: information hiding and separation of concerns, in software engineering, the process of enclosing programming elements inside larger, more abstract entities integrated circuit encapsulation, in electronics the design and manufacture of protective packages micro-encapsulation, means to confine material molecular encapsulation, means to confine molecules encapsulation (pharmacology...
A container format is a computer file format that can contain various types of data, compressed by means of standardized codecs. ...
The widely spread notion of AVI being a codec is incorrect as AVI (nowadays) is a container format, which many codecs might use (although not to ISO standard). There are other well known alternative containers such as Ogg, ASF, QuickTime, RealMedia, Matroska, DivX, and MP4. Look up Avi in Wiktionary, the free dictionary. ...
A container format is a computer file format that can contain various types of data, compressed by means of standardized codecs. ...
This is an incomplete list of ISO standards. ...
Ogg is an open standard for a free container format for digital multimedia, unrestricted by software patents and designed for efficient streaming and manipulation. ...
Advanced Systems Format (formerly Advanced Streaming Format, Active Streaming Format) is Microsofts proprietary digital audio/digital video container format, especially meant for streaming media. ...
QuickTime is a multimedia framework developed by Apple Inc. ...
RealMedia is a multimedia container format created by RealNetworks. ...
// The Matroska Multimedia Container is an open standard free multimedia container format that can hold an unlimited number of video, audio, picture or subtitle tracks inside a single file. ...
This article is about the video codec. ...
MP4 can refer to: MPEG-4 Part 14 file format Møller-Plesset perturbation theory of the fourth order This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ...
See also Comparisons This article or section should include material from AD converters In electronics, an analog-to-digital converter (abbreviated ADC, A/D, or A to D) is a device that converts continuous signals to discrete digital numbers. ...
An audio codec is a computer program that compresses/decompresses digital audio data according to a given audio file format or streaming audio format. ...
A video codec is a device or software that enables video compression and or decompression for digital video. ...
This article or section does not cite its references or sources. ...
Digital signal processing (DSP) is the study of signals in a digital representation and the processing methods of these signals. ...
8-channel digital-to-analog converter Cirrus Logic CS4382 placed on Sound Blaster X-Fi Fatal1ty In electronics, a digital-to-analog converter (DAC or D-to-A) is a device for converting a digital (usually binary) code to an analog signal (current, voltage or electric charge). ...
The following is a list of codecs. ...
Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. ...
Original Image (lossless PNG, 60. ...
Video coding is the field in computer science that deals with finding efficient coding formats for digital video. ...
This is a listing of open source multimedia codecs and containers. ...
A comparison is an evaluation of similarities and differences - described by Gregory Bateson in his book Mind and Nature as the two quanta of experience. ...
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The following tables compare general and technical information for a variety of audio codecs. ...
This table compares features of container formats. ...
Comparison of video codecs - is a process of codecs evaluation of similarities and differences. ...
Source coding 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 . ...
Fibonacci, Elias Gamma, and Elias Delta vs binary coding Rice with k=2,3,4,5,8,16 vs binary In data compression, a universal code for integers is a prefix code that maps the positive integers onto binary codewords, with the additional property that whatever the true probability distribution...
Elias gamma code is a universal code encoding 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. ...
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. ...
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. ...
LZWL is a syllable-based variant of the character-based LZW 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. ...
The context tree weighting method (CTW) is a lossless compression and prediction algorithm by . ...
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 the branch of physics concerned with 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. ...
Code Excited Linear Prediction (CELP) is a speech coding algorithm originally proposed by M.R. Schroeder and B.S. Atal in 1985. ...
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 article is about the picture element. ...
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. ...
For other uses, see Video (disambiguation). ...
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 that enables video compression and 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 that enables video compression and 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. ...
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