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Psychoacoustics is the study of subjective human perception of sounds. Alternatively it can be described as the study of the psychological correlates of the physical parameters of acoustics. In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ...
Sound is a disturbance of mechanical energy that propagates through matter as a wave. ...
Psychology (ancient Greek: psyche = soul and logos = word) is the study of mind, thought, and behaviour. ...
Acoustics is a branch of physics and is the study of sound (mechanical waves in gases, liquids, and solids). ...
Background
Hearing is not a purely mechanical phenomenon of wave propagation, but is also a sensory and perceptual event. When a person hears something, that something arrives at the ear as a mechanical sound wave traveling through the air, but within the ear it is transformed into neural action potentials. These nerve pulses then travel to the brain where they are "perceived". such as audio processing,take into account not just the mechanics of the environment truthfully both the ear and the brain are involved wile listening. The ear for example, takes a spectral decomposition of sound as part of the process of turning sound into neural stimulus, so certain time domain effects are inaudible. MP3 compression makes use of this fact. In addition the ear has a logarithmic dynamic response. Telephone networks make use of this fact by logarithmically compressing data samples before transmission, and then exponentially expanding them for playback. Another side effect of the ear’s non linear logarithmic response is that sounds which appear on the ear drum in close spectral proximity produce phantom beat notes. This is the same principle that is used for down conversion of carrier frequencies in radio front ends by a non-linear amplifier. Such physiological effects due to the ear’s anatomy are properly called physiology-acoustic effects, though people commonly lump them in with psycho-acoustic effects. The ear is the sense organ that detects sounds. ...
Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ...
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is an audio encoding format. ...
The public switched telephone network (PSTN) is the concatenation of the worlds public circuit-switched telephone networks, in much the same way that the Internet is the concatenation of the worlds public IP-based packet-switched networks. ...
There are true psycho-acoustic effects introduced by the brain. For example, when a person listens to crackly and needle-on-vinyl hiss-filled records, he or she soon stops noticing the background noise, and enjoys the music. A person who does this habitually appears to forget about the noise altogether, and may not be able to tell you after listening if there was noise present. This effect is called psycho-acoustical masking. The brain’s ability to perform such masking has been important for the adoption of a number of technologies; though in this age of digital signaling and high fidelity playback the effect is typically used to hide losses in compression rather than to cover up "analog" white noise. As another example of a psycho-acoustic effect, the brain appears to use a correlative process for pattern recognition; much like is done in electronic circuits that look for signal patterns. When the threshold for acceptance of a correlative match is very low a person may perceive hearing a sought after pattern in pure noise or among sounds that are somewhat indicative, as the brain fills in the rest of the pattern. This is a psycho-acoustic phantom effect. For example when a radio operator is straining to hear a weak Morse Code signal in a noisy background, he or she often perceives hearing the pitch of tiny dots and dashes even when they are not present. In, such as when danger may be general psycho-acoustic phantom effects play an important role in any environment where people have heightened perceptions perceived to be near. (There is an analogous visual effect experienced by people standing watch in very dark places.) The psycho-acoustic phantom effect is conceptually distinct from hallucination, where the brain "auto" generates perceptions. Also, the psycho-acoustic phantom effect is distinct from the physiology-acoustic phantom effect. It is the estimation of masking threshold level. Calculated spectrum of a generated approximation of white noise White noise is a random signal (or process) with a flat power spectral density. ...
1922 Chart of the Morse Code Letters and Numerals Morse code is a method for transmitting telegraphic information, using standardized sequences of short and long elements to represent the letters, numerals, punctuation and special characters of a message. ...
A hallucination is a sensory perception experienced in the absence of an external stimulus, as distinct from an illusion, which is a misperception of an external stimulus. ...
Limits of perception The human ear can nominally hear sounds in the range 20 Hz to 20,000 Hz (20 kHz). This upper limit tends to decrease with age, most adults being unable to hear above 16 kHz. The ear itself does not respond to frequencies below 20 Hz, but these can be perceived via the body's sense of touch. (Some recent research has demonstrated a hypersonic effect which is that although sounds above 20 kHz cannot consciously be heard, they can have an effect on the listener.) MHZ redirects here. ...
The hypersonic effect is a term coined to describe the phenomenon reported in some scientific studies, which demonstrate that although humans cannot consciously hear sounds at very high frequency (above around 20 kHz), the presence or absence of those frequencies has a measurable effect on their psychological reaction. ...
Frequency resolution of the ear is, in the middle range, about 2 Hz. That is, changes in pitch larger than 2 Hz can be perceived. However, even smaller pitch differences can be perceived through other means. For example, the interference of two pitches can often be heard as a (low-)frequency difference pitch. This effect of phase variance upon the resultant sound is known as 'beating'. This article is about a portion of a periodic process. ...
In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies. ...
However, the effect of frequency on the human ear has a logarithmic basis. In other words, the perceived pitch of a sound is related to the frequency as an exponential function. The 12-tone musical scale is an example of this; it evolved due to the way tones are perceived. When the fundamental frequency of a note or tone is multiplied by approximately  (this factor is true in the average, but varies slightly depending on the tuning), the result is the frequency of the next higher semitone. Going 12 notes higher — an octave — is the same as multiplying the frequency by  , which is the same as doubling the frequency. In music, an octave (sometimes abbreviated 8ve or P8) is the interval between one musical note and another with half or double its frequency. ...
The impact of this is that the semitone scale used in Western musical notation is not a linear frequency scale but logarithmic. Other scales have been derived directly from experiments on human hearing perception, such as the Mel scale and Bark scale (these are used in studying perception, but not usually in musical composition), and these are approximately logarithmic in frequency as well. A semitone (also known in the USA as a half step) is a musical interval. ...
The mel scale, proposed by Stevens, Volkman and Newman in 1937 is a perceptual scale of pitches judged by listeners to be equal in distance from one another. ...
The Bark scale is a psychoacoustical scale. ...
The "intensity" range of audible sounds is enormous. Our ear drums are sensitive only to the sound pressure variation. The lower limit of audibility is defined to 0 dB, but the upper limit is not as clearly defined. The upper limit is more a question of the limit where the ear will be physically harmed or with the potential to cause a hearing disability. This limit depends also on the time exposed to the sound. The ear can be exposed to short periods in excess of 120 dB without permanent harm, but long term exposure to sound levels over 80 dB can cause permanent hearing loss. The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power) relative to a specified or implied reference level. ...
Hearing impairment is a full or partial decrease in the ability to detect or understand sounds. ...
A more rigorous exploration of the lower limits of audibility determines that the minimum threshold at which a sound can be heard is frequency dependent. By measuring this minimum intensity for testing tones of various frequencies, a frequency dependent Absolute Threshold of Hearing (ATH) curve may be derived. Typically, the ear shows a peak of sensitivity (i.e., its lowest ATH) between 1 kHz and 5 kHz, though the threshold changes with age, with older ears showing decreased sensitivity above 2 kHz. The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average ear with normal hearing can hear in a noiseless environment. ...
The ATH is the lowest of the equal-loudness contours. Equal-loudness contours indicate the sound pressure level (dB), over the range of audible frequencies, which are perceived as being of equal loudness. Equal-loudness contours were first measured by Fletcher and Munson at Bell Labs in 1933 using pure tones reproduced via headphones, and the data they collected are called Fletcher-Munson curves. Because subjective loudness was difficult to measure, the Fletcher-Munson curves were averaged over many subjects. An equal-loudness contour is a measure of sound pressure (dB SPL), over the frequency spectrum, for which a listener perceives a constant loudness. ...
Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ...
1933 (MCMXXXIII) was a common year starting on Sunday. ...
Robinson and Dadson refined the process in 1956 to obtain a new set of equal-loudness curves for a frontal sound source measured in an anechoic chamber. The Robinson-Dadson curves were standardized as ISO 226 in 1986. In 2003, ISO 226 was revised as equal-loudness contour using data collected from 12 international studies. Year 1956 (MCMLVI) was a leap year starting on Sunday (link will display full calendar) of the Gregorian calendar. ...
A picture of an anechoic chamber An anechoic chamber is a room that is isolated from external sound or electromagnetic radiation sources, sometimes using sound proofing, and prevents the reflection of wave phenomena (reverberation). ...
This article does not cite any references or sources. ...
Year 1986 (MCMLXXXVI) was a common year starting on Wednesday (link displays 1986 Gregorian calendar). ...
Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ...
An equal-loudness contour is a measure of sound pressure (dB SPL), over the frequency spectrum, for which a listener perceives a constant loudness. ...
Interpretation of sound Human hearing is basically like a spectrum analyzer, that is, the ear resolves the spectral content of the pressure wave without respect to the phase of the signal. In practice, though, some phase information can be perceived. Inter-aural phase difference, that is the difference in sound between the ears, is a notable exception by providing a significant part of the directional sensation of sound. The filtering effects of head-related transfer functions provide another important directional cue. A spectrum analyzer is a device used to examine the spectral composition of some electrical, acoustic, or optical waveform. ...
This article is about a portion of a periodic process. ...
Sound localization is a listeners ability to identify the location of origin of a detected sound or the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space (see binaural recording). ...
HRTFs for left and right ear (expressed here as HRIRs) describe the filtering of a sound source (x(t)) before it is perceived at the left and right ears as xL(t) and xR(t), respectively. ...
Masking effects -
Main article: Auditory masking In some situations an otherwise clearly audible sound can be masked by another sound. For example, conversation at a bus stop can be completely impossible if a loud bus is driving past. This phenomenon is called masking. A weaker sound is masked if it is made inaudible in the presence of a louder sound. The masking phenomenon occurs because any loud sound will distort the Absolute Threshold of Hearing, making quieter, otherwise perceptible sounds inaudible. It has been suggested that this article or section be merged with sound masking. ...
If two sounds occur simultaneously and one is masked by the other, this is referred to as simultaneous masking. Simultaneous masking is also sometimes called frequency masking. The tonality of a sound partially determines its ability to mask other sounds. A sinusoidal masker, for example, requires a higher intensity to mask a noise-like maskee than a loud noise-like masker does to mask a sinusoid. Computer models which calculate the masking caused by sounds must therefore classify their individual spectral peaks according to their tonality. - Masking between two concurrent sounds - Sometimes called frequency masking since it is often observed when the sounds share a frequency band - E.g. ...
In mathematics, the trigonometric functions are functions of an angle, important when studying triangles and modeling periodic phenomena. ...
For the Irish mythological figure, see Naoise. ...
Similarly, a weak sound emitted soon after the end of a louder sound is masked by the louder sound. Even a weak sound just before a louder sound can be masked by the louder sound. These two effects are called forward and backward temporal masking, respectively. Temporal masking occurs when a sudden stimulus sound makes inaudible other sounds which are present immediately preceding or following the stimulus. ...
'Phantom' fundamentals At the lower end of the ears' response, low notes can sometimes be heard when there is no sound at that frequency. This is due to the brain synthesising the low frequency sound from the differences of audible harmonics that are present. This effect is used in some commercial sound systems to give the effect of extended low frequency response when the system itself cannot reproduce that frequency adequately. See missing fundamental. A missing fundamental is a missing fundamental frequency which higher frequencies refer to. ...
Psychoacoustics in software The psychoacoustic model provides for high quality lossy signal compression by describing which parts of a given digital audio signal can be removed (or aggressively compressed) safely - that is, without significant losses in the (consciously) perceived quality of the sound. 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. ...
It can explain how a sharp clap of the hands might seem painfully loud in a quiet library, but is hardly noticeable after a car backfires on a busy, urban street. This provides great benefit to the overall compression ratio, and psychoacoustic analysis routinely leads to compressed music files that are 1/10 to 1/12 the size of high quality original masters with very little discernible loss in quality. Such compression is a feature of nearly all modern audio compression formats. Some of these formats include MP3, Ogg Vorbis, WMA, Musicam (used for digital audio broadcasting in several countries) and ATRAC, the compression used in MiniDisc. MPEG-1 Audio Layer 3, more commonly referred to as MP3, is an audio encoding format. ...
This page is about the audio compression codec. ...
WMA can refer to: Windows Media Audio World Medical Association William Morris Agency This is a disambiguation page, a list of pages that otherwise might share the same title. ...
MP2, also known as Musicam, is a short form of MPEG Audio Layer II, and it is also used as a file extension for files containing audio data of this type. ...
Digital Audio Broadcasting (DAB), also known as Eureka 147, is a technology for broadcasting of audio using digital radio transmission. ...
ATRAC (Adaptive TRansform Acoustic Coding) is a family of proprietary audio compression algorithms used to store information on MiniDiscs and other Sony-branded audio players. ...
See also IBMs VM operating system family, where minidisk refers to a logical unit of storage. ...
Psychoacoustics is based heavily on human anatomy, especially the ear's limitations in perceiving sound as outlined previously. To summarize, these limitations are: List of bones of the human skeleton Human anatomy is primarily the scientific study of the morphology of the adult human body. ...
Given that the ear will not be at peak perceptive capacity when dealing with these limitations, a compression algorithm can assign a lower priority to sounds outside the range of human hearing. By carefully shifting bits away from the unimportant components and toward the important ones, the algorithm ensures that the sounds a listener can hear most clearly are of the highest quality. The high frequency limit of hearing is the upper extent to which a particular animal can perceive sound. ...
The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average ear with normal hearing can hear in a noiseless environment. ...
Temporal masking occurs when a sudden stimulus sound makes inaudible other sounds which are present immediately preceding or following the stimulus. ...
- Masking between two concurrent sounds - Sometimes called frequency masking since it is often observed when the sounds share a frequency band - E.g. ...
Psychoacoustics and music Psychoacoustics include topics and studies which are relevant to music psychology. Theorists such as Benjamin Boretz consider some of the results of psychoacoustics to be meaningful only in a musical context. Music psychology, or the psychology of music, may be regarded either as a branch of psychology or as a branch of musicology. ...
Benjamin Boretz is a twentieth- and twenty-first-century music theorist and composer. ...
Applied psychoacoustics Psychoacoustics is presently applied within many fields from software development where developers map proven and experimental mathematical patterns; in the design of (high end) audio systems for accurate reproduction of music in theatres and homes, as well as defense systems where scientists have the capability to create new acoustic weapons {some of which emit frequencies that may impair, harm, or kill [with very limited success (http://www.nationaldefensemagazine.org/issues/2002/Mar/Acoustic-Energy.htm)]. It is also applied today within music, where musicians and artists continue to create new sonic sensory-breaking perceptions of sonic reality by masking unwanted frequencies of instrument while others are enhanced by the absence of the masked ones. Yet another application is to provide listeners of small loudspeakers the impression that they hear low notes by masking what is subsonic and enhancing what is perceived as low the frequencies (see references).
See also The Bark scale is a psychoacoustical scale. ...
The equivalent rectangular bandwidth or ERB is a measure used in psychoacoustics. ...
The mel scale, proposed by Stevens, Volkman and Newman in 1937 is a perceptual scale of pitches judged by listeners to be equal in distance from one another. ...
The horizontal axis shows frequency in Hz Loudness is the quality of a sound that is the primary psychological correlate of physical intensity. ...
Bel can mean: A unit of measurement for proportions and ratios; see Decibel and dB(A) The title of a Semitic god; see Bel (god) A Celtic deity; see Belenus Hindi name of the Bengal Quince tree or its fruit. ...
The sone is a unit of perceived loudness N after a proposal of S. Smith Stevens in 1936. ...
A missing fundamental is a missing fundamental frequency which higher frequencies refer to. ...
An auditory illusion is an illusion of hearing (sense), the sound equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or impossible sounds. ...
For other uses, see Telephone (disambiguation). ...
Auditory scene analysis (ASA) is a term coined by the psychologist Albert Bregman [1] to describe the process by which the human auditory system organizes complex mixtures of sound. ...
An equal-loudness contour is a measure of sound pressure (dB SPL), over the frequency spectrum, for which a listener perceives a constant loudness. ...
An auditory illusion is an illusion of hearing (sense), the sound equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or impossible sounds. ...
Audio compression can mean two things: Audio data compression - in which the amount of data in a recorded waveform is reduced for transmission. ...
Environmental noise can produce irreversible hearing loss Noise health effects, the collection of health consequences of elevated sound levels, constitute one of the most widespread public health threats in industrialized countries. ...
Speech recognition (in many contexts also known as automatic speech recognition, computer speech recognition or erroneously as Voice Recognition) is the process of converting a speech signal to a sequence of words, by means of an algorithm implemented as a computer program. ...
Sound localization is a listeners ability to identify the location of origin of a detected sound or the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space (see binaural recording). ...
Source separation problems in digital signal processing are those in which several signals have been mixed together and the objective is to find out what the original signals were. ...
In music, there are two common meanings for tuning: Tuning practice, the act of tuning an instrument or voice. ...
Artwork from the flyer announcing the Rorschach Audio presentation at The Royal British Society of Sculptors, 29 May 2000 (copyright the author) Rorschach Audio (aka Audio Rorschach) is the title of a research artwork, conceived in 1998, and initiated and conducted by Joe Banks, founder of the group Disinformation (see...
In music, timbre, or sometimes timber, (from Fr. ...
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...
The Haas effect is a psychoacoustic effect, also known as the Precedence Effect or law of the first wave front. ...
It has been suggested that this article or section be merged with Auditory masking. ...
References - E. Larsen and R.M. Aarts (2004), Audio Bandwidth extension. Application of Psychoacoustics, Signal Processing and Loudspeaker Design., J. Wiley.
External links (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. ...
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 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. ...
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