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μ-law Algorithm
The μ-law algorithm (sometimes written Mu (letter), mu-law, often abbreviated as u-law) is a companding algorithm, primarily used in 8-bit PCM Digital data, digital telecommunications systems in North America and Japan. It is one of the two companding algorithms in the G.711 standard from ITU-T, the other being the similar A-law. A-law is used in regions where digital telecommunication signals are carried on E-1 circuits, e.g. Europe. The terms PCMU, G711u or G711MU are used for G711 μ-law. Companding algorithms reduce the dynamic range of an audio signal. In analog systems, this can increase the signal-to-noise ratio (SNR) achieved during transmission; in the digital domain, it can reduce the quantization error (hence increasing the signal-to-quantization-noise ratio). These SNR increases can be traded instead for reduced Bandwidth (signal processing), bandwidth for equivalent SNR. At the cost of a reduced peak SNR, it can be mathematically shown that μ-law's non-linear q ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparison Of A-law And μ-law Compression On An Input Signal
Comparison or comparing is the act of evaluating two or more things by determining the relevant, comparable characteristics of each thing, and then determining which characteristics of each are Similarity (psychology), similar to the other, which are Difference (philosophy), different, and to what degree. Where characteristics are different, the differences may then be evaluated to determine which thing is best suited for a particular purpose. The description of similarities and differences found between the two things is also called a comparison. Comparison can take many distinct forms, varying by field: To compare things, they must have characteristics that are similar enough in relevant ways to merit comparison. If two things are too different to compare in a useful way, an attempt to compare them is colloquially referred to in English as "comparing apples and oranges." Comparison is widely used in society, in science and the arts. General usage Comparison is a natural act ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Range Of A Function
In mathematics, the range of a function may refer either to the codomain of the function, or the image of the function. In some cases the codomain and the image of a function are the same set; such a function is called ''surjective'' or ''onto''. For any non-surjective function f: X \to Y, the codomain Y and the image \tilde Y are different; however, a new function can be defined with the original function's image as its codomain, \tilde: X \to \tilde where \tilde(x) = f(x). This new function is surjective. Definitions Given two sets and , a binary relation between and is a function (from to ) if for every element in there is exactly one in such that relates to . The sets and are called the '' domain'' and ''codomain'' of , respectively. The ''image'' of the function is the subset of consisting of only those elements of such that there is at least one in with . Usage As the term "range" can have different meanings, it is considered a good practice to define ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SPARCstation 1
The SPARCstation 1 (Sun 4/60, code-named ''Campus'') is the first of the SPARCstation series of SPARC-based workstations sold by Sun Microsystems. The design originated in 1987 by a Sun spin-off company, UniSun, which was soon re-acquired. The SPARCstation 1 has a distinctive slim enclosure (a square 3-inch-high " pizza box") and was first announced in April 1989; the first units shipped in July that year. Based on an LSI Logic RISC CPU running at 20 MHz, with a Weitek 3170 (or 3172) FPU coprocessor, it was the fourth Sun computer (after the 4/260, 4/110 and 4/280) to use the SPARC architecture and the first of the sun4c architecture. The motherboard has three SBus slots, built-in AUI Ethernet, 8 kHz audio, and a 5 MB/s SCSI-1 bus. The basic display runs at in 256 colours, and monitors shipped with the computer were 16 to 19 inch greyscale or colour. Sun released the SPARCstation 1+, an upgrade to the SPARCstation 1 which increased the clock speed of the CPU t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Au File Format
The Au file format is a simple audio file format introduced by Sun Microsystems. The format was common on NeXT systems and on early Web pages. Originally it was headerless, being 8-bit μ-law algorithm, μ-law-encoded data at an 8000 Hz sample rate. Hardware from other vendors often used sample rates as high as 8192 Hz, often integer multiples of video clock signal frequencies. Newer files have a header that consists of six Signedness, unsigned 32-bit computing, 32-bit words, an optional information chunk which is always of non-zero size, and then the data (in Endianness, big-endian format). Although the format now supports many digital audio, audio encoding formats, it remains associated with the μ-law logarithmic encoding. This encoding was native to the SPARCstation 1 hardware, where SunOS exposed the encoding to application programs through the /dev/audio device file interface. This encoding and interface became a de facto standard for Unix sound. New format All fields a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal representing sound or a video signal representing images, in an electronic device or communication channel. Distortion is usually unwanted, and so engineers strive to eliminate or minimize it. In some situations, however, distortion may be desirable. For example, in noise reduction systems like the Dolby noise-reduction system, Dolby system, an audio signal is deliberately distorted in ways that emphasize aspects of the signal that are subject to electrical noise, then it is symmetrically "undistorted" after passing through a noisy communication channel, reducing the noise in the received signal. Distortion is also used as a Distortion (music), musical effect, particularly with electric guitars. The addition of Electronic noise, noise o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Coding
In computing, telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for error control, controlling errors in data transmission over unreliable or noisy communication channels. The central idea is that the sender encodes the message in a Redundancy (information theory), redundant way, most often by using an error correction code, or error correcting code (ECC). The redundancy allows the receiver not only to error detection, detect errors that may occur anywhere in the message, but often to correct a limited number of errors. Therefore a reverse channel to request re-transmission may not be needed. The cost is a fixed, higher forward channel bandwidth. The American mathematician Richard Hamming pioneered this field in the 1940s and invented the first error-correcting code in 1950: the Hamming (7,4) code. FEC can be applied in situations where re-transmissions are costly or impossible, such as one-way communic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weber–Fechner Law
The Weber–Fechner laws are two related scientific law, scientific laws in the field of psychophysics, known as Weber's law and Fechner's law. Both relate to human perception, more specifically the relation between the actual change in a physical Stimulus (physiology), stimulus and the perceived change. This includes stimuli to all senses: vision, hearing, taste, touch, and smell. Ernst Heinrich Weber states that "the minimum increase of stimulus which will produce a perceptible increase of sensation is proportionality (mathematics), proportional to the pre-existent stimulus," while Gustav Fechner's law is an inference from Weber's law (with additional assumptions) which states that the intensity of our sensation increases as the logarithm of an increase in energy rather than as rapidly as the increase. History and formulation of the laws Both Weber's law and Fechner's law were formulated by Gustav Fechner, Gustav Theodor Fechner (1801–1887). They were first published in 18 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loudness
In acoustics, loudness is the subjectivity, subjective perception of sound pressure. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of physical attributes of sound to perceived loudness consists of physical, physiological and psychological components. The study of apparent loudness is included in the topic of psychoacoustics and employs methods of psychophysics. In different industries, loudness may have different meanings and different measurement standards. Some definitions, such as ITU-R BS.1770 refer to the relative loudness of different segments of electronically reproduced sounds, such as for broadcasting and cinema. Others, such as ISO 532A (Stevens loudness, measured in sones), ISO 532B (Eberhard Zwicker, Zwicker loudness), DIN 45631 and ASA/ANSI S3.4, have a more general scope and are often used to characterize loudness of environmental noise. More modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Intensity Level
Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area, also called the sound power density and the sound energy flux density. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2). One application is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity. Sound intensity is not the same physical quantity as sound pressure. Human hearing is sensitive to sound pressure which is related to sound intensity. In consumer audio electronics, the level differences are called "intensity" differences, but sound intensity is a specifically defined quantity and cannot be sensed by a simple microphone. Sound intensity level is a logarithmic expression of sound intensity relative to a reference intensity. Mathematical definition Sound intensity, denoted I, is defined by \mathbf I = p \mathbf v where * ''p'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speech
Speech is the use of the human voice as a medium for language. Spoken language combines vowel and consonant sounds to form units of meaning like words, which belong to a language's lexicon. There are many different intentional speech acts, such as informing, declaring, asking, persuading, directing; acts may vary in various aspects like enunciation, Intonation (linguistics), intonation, loudness, and Speech tempo, tempo to convey meaning. Individuals may also unintentionally communicate aspects of their social position through speech, such as sex, age, place of origin, physiological and mental condition, education, and experiences. While normally used to facilitate communication with others, people may also use speech without the intent to communicate. Speech may nevertheless express emotions or desires; people Talking to oneself, talk to themselves sometimes in acts that are a development of what some psychologists (e.g., Lev Vygotsky) have maintained is the use of silent spee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analog-to-digital Converter
In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a Digital signal (signal processing), digital signal. An ADC may also provide an isolated measurement such as an electronic device that converts an analog input voltage or Electric current, current to a digital number representing the magnitude of the voltage or current. Typically the digital output is a two's complement binary number that is proportional to the input, but there are other possibilities. There are several ADC hardware architecture, architectures. Due to the complexity and the need for precisely matched electronic component, components, all but the most specialized ADCs are implemented as integrated circuits (ICs). These typically take the form of metal–oxide–semiconductor (MOS) mixed-signal integrated circuit chips that integrate both Analogue electronics, anal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
