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Companding
In telecommunications and signal processing, companding (occasionally called compansion) is a method of mitigating the detrimental effects of a channel with limited dynamic range. The name is a portmanteau of the words compressing and expanding, which are the functions of a compander at the transmitting and receiving ends, respectively. The use of companding allows signals with a large dynamic range to be transmitted over facilities that have a smaller dynamic range capability. Companding is employed in telephony and other audio applications such as professional wireless microphones and analog recording. How it works The dynamic range of a signal is compressed before transmission and is expanded to the original value at the receiver. The electronic circuit that does this is called a compander and works by compressing or expanding the dynamic range of an analog electronic signal such as sound recorded by a microphone. One variety is a triplet of amplifiers: a logarithmic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A-law
An A-law algorithm is a standard companding algorithm, used in European 8-bit PCM digital communications systems to optimize, i.e. modify, the dynamic range of an analog signal for digitizing. It is one of the two companding algorithms in the G.711 standard from ITU-T, the other being the similar μ-law, used in North America and Japan. For a given input x, the equation for A-law encoding is as follows: F(x) = \sgn(x) \begin \dfrac, & , x, < \dfrac, \\ ex \dfrac, & \dfrac \leq , x, \leq 1, \end where is the compression parameter. In Europe, . A-law expansion is given by the inverse function: The reason for this encoding is that the wide |
SIGSALY
SIGSALY (also known as the X System, Project X, Ciphony I, and the Green Hornet) was a secure voice, secure speech system used in World War II for the highest-level Allies of World War II, Allied communications. It pioneered a number of digital communications concepts, including the first transmission of speech using pulse-code modulation. The name SIGSALY was not an acronym, but a cover name that resembled an acronym—the SIG part was common in Army Signal Corps names (e.g., SIGABA). The prototype was called the "Green Hornet" after the radio show ''The Green Hornet (radio series), The Green Hornet'', because it sounded like a buzzing hornet, resembling the show's theme tune, to anyone trying to eavesdrop on the conversation. Development At the time of its inception, long-distance telephone communications used the "A-3" voice scrambler developed by Western Electric. It worked on the voice inversion principle. The Germans had a listening station on the Dutch coast which could int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wireless Microphone
A wireless microphone, or cordless microphone, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Also known as a radio microphone, it has a small, battery-powered Transmitter, radio transmitter in the microphone body, which transmits the audio signal from the microphone by radio waves to a nearby receiver unit, which recovers the audio. The other audio equipment is connected to the receiver unit by cable. In one type the transmitter is contained within the handheld microphone body. In another type the transmitter is contained within a separate unit called a "bodypack", usually clipped to the user's belt or concealed under their clothes. The bodypack is connected by wire to a "lavalier microphone" or "lav" (a small microphone clipped to the user's lapel), a headset or earset microphone, or another wired microphone. Most bodypack designs also support a wired instrument connection (e.g. to a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal Processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, Scalar potential, potential fields, Seismic tomography, seismic signals, Altimeter, altimetry processing, and scientific measurements. Signal processing techniques are used to optimize transmissions, Data storage, digital storage efficiency, correcting distorted signals, improve subjective video quality, and to detect or pinpoint components of interest in a measured signal. History According to Alan V. Oppenheim and Ronald W. Schafer, the principles of signal processing can be found in the classical numerical analysis techniques of the 17th century. They further state that the digital refinement of these techniques can be found in the digital control systems of the 1940s and 1950s. In 1948, Claude Shannon wrote the influential paper "A Mathematical Theory of Communication" which was publis ... [...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] |
Dynamic Range Compression
Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or ''compressing'' an audio signal's dynamic range. Compression is commonly used in sound recording and reproduction, broadcasting, sound reinforcement system, live sound reinforcement and some instrument amplifiers. A dedicated electronic hardware unit or audio software that applies compression is called a compressor. In the 2000s, compressors became available as software plugins that run in digital audio workstation software. In recorded and live music, compression parameters may be adjusted to change the way they affect sounds. Compression and limiting are identical in process but different in degree and perceived effect. A limiter is a compressor with a high #Ratio, ratio and, generally, a short #Attack and release, attack time. Compression is used to improve performance and clarity in public address ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Demo Of Mu-law Compression
Demo, usually short for demonstration, may refer to: Music and film *Demo (music), a song typically recorded for reference rather than for release * ''Demo'' (Behind Crimson Eyes), a 2004 recording by the band Behind Crimson Eyes * ''Demo'' (Deafheaven album), a 2010 EP by Deafheaven * ''Demo'' (The Flatliners album), a 2002 album by the band The Flatliners * ''Demo'' (Miss May I album), a 2008 recording by the metalcore band Miss May I *"Demo", a 1990 single by Die Krupps * "Demo" (P-Model song), a 1979 recording by songwriters Susumu Hirasawa and Yasumi Tanaka *'' Demo (Skinless)'', a 1994 recording by the band Skinless * ''Demo 2004'' (Year of No Light album), a 2004 recording by Year of No Light *'' Demo #2'', an unreleased recording by Neutral Milk Hotel *''Demo'', 2008 debut EP by Yuna Computing and technology *Demo (computer programming), a multimedia spectacle of programming skill * The Demo, a computer demonstration in 1968, sometimes called "the mother of all demos" * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Data Compression
In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression reduces bits by identifying and eliminating Redundancy (information theory), statistical redundancy. No information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information. Typically, a device that performs data compression is referred to as an encoder, and one that performs the reversal of the process (decompression) as a decoder. The process of reducing the size of a data file is often referred to as data compression. In the context of data transmission, it is called source coding: encoding is done at the source of the data before it is stored or transmitted. Source coding should not be confused with channel coding, for error detection and correction or line coding, the means ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Reduction Scheme
Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an undesired signal component from the desired signal component, as with common-mode rejection ratio. All signal processing devices, both analog and digital, have traits that make them susceptible to noise. Noise can be random with an even frequency distribution (white noise), or frequency-dependent noise introduced by a device's mechanism or signal processing algorithms. In electronic systems, a major type of noise is ''hiss'' created by random electron motion due to thermal agitation. These agitated electrons rapidly add and subtract from the output signal and thus create detectable noise. In the case of photographic film and magnetic tape, noise (both visible and audible) is introduced due to the grain structure of the medium. In photogr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Telephone & Telegraph
AT&T Corporation, an abbreviation for its former name, the American Telephone and Telegraph Company, was an American telecommunications company that provided voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agencies. During the Bell System's long history, AT&T was at times the world's largest telecommunications company, the world's largest cable television operator, and a regulated monopoly. At its peak in the 1950s and 1960s, it employed one million people and its revenue ranged between US$3 billion in 1950 ($ in present-day terms) and $12 billion in 1966 ($ in present-day terms). In 2005, AT&T was acquired by "Regional Bell Operating Company, Baby Bell" and former subsidiary SBC Communications for more than $16 billion ($ in present-day terms). SBC then changed its name to AT&T, AT&T Inc., with AT&T Corporation continuing to exist as a long-distance calling subsidiary until its dissolution o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roland Corporation
is a Japanese multinational manufacturer of electronic musical instruments, electronic equipment, and software. It was founded by Ikutaro Kakehashi in Osaka on 18 April 1972. In 2005, its headquarters relocated to Hamamatsu in Shizuoka Prefecture. It has factories in Malaysia, Taiwan, Japan, and the United States. As of December 2022, it employed 2,783 people. In 2014, it was subject to a management buyout by its CEO, Junichi Miki, supported by Taiyo Pacific Partners. Roland has manufactured numerous instruments that have had lasting impacts on music, such as the Juno-106 synthesizer, TB-303 bass synthesizer, and TR-808 and TR-909 drum machines. It was also instrumental in the development of MIDI, a standardized means of synchronizing electronic instruments manufactured by different companies. In 2016, ''Fact'' wrote that Roland had arguably had more influence on electronic music than any other company. History Background Roland founder Ikutaro Kakehashi had founded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Successive-approximation ADC
A successive-approximation ADC (or SAR ADC) is a type of analog-to-digital converter (ADC) that Digitization, digitizes each Sampling (signal processing), sample from a continuous analog waveform using a binary search through all possible Quantization (signal processing), quantization levels. History The SAR ADC was first used for experimental pulse-code modulation (PCM) by Bell Labs in the 1940s. In 1954, Bernard Marshall Gordon, Bernard Gordon introduced the first commercial vacuum tube SAR ADC, converting 50,000 11-bit samples per second. Algorithm The successive-approximation analog-to-digital converter circuit typically contains four chief subcircuits: # A sample-and-hold circuit that acquires the input voltage . # An analog voltage comparator that compares to the output of a digital-to-analog converter (DAC). # A successive-approximation Processor register, register that is updated by results of the comparator to provide the DAC with a digital code whose accuracy in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
