1.
Information technology
–
Information technology is the application of computers to store, study, retrieve, transmit, and manipulate data, or information, often in the context of a business or other enterprise. IT is considered a subset of information and communications technology, the term is commonly used as a synonym for computers and computer networks, but it also encompasses other information distribution technologies such as television and telephones. Several industries are associated with technology, including computer hardware, software, electronics, semiconductors, internet, telecom equipment. Leavitt and Thomas L. Whisler commented that the new technology not yet have a single established name. We shall call it information technology, based on the storage and processing technologies employed, it is possible to distinguish four distinct phases of IT development, pre-mechanical, mechanical, electromechanical, electronic. This article focuses on the most recent period, which began in about 1940, devices have been used to aid computation for thousands of years, probably initially in the form of a tally stick. Electronic computers, using either relays or valves, began to appear in the early 1940s, the electromechanical Zuse Z3, completed in 1941, was the worlds first programmable computer, and by modern standards one of the first machines that could be considered a complete computing machine. Colossus, developed during the Second World War to decrypt German messages was the first electronic digital computer, although it was programmable, it was not general-purpose, being designed to perform only a single task. It also lacked the ability to store its program in memory, programming was carried out using plugs, the first recognisably modern electronic digital stored-program computer was the Manchester Small-Scale Experimental Machine, which ran its first program on 21 June 1948. The development of transistors in the late 1940s at Bell Laboratories allowed a new generation of computers to be designed with reduced power consumption. The first commercially available stored-program computer, the Ferranti Mark I, by comparison the first transistorised computer, developed at the University of Manchester and operational by November 1953, consumed only 150 watts in its final version. Early electronic computers such as Colossus made use of punched tape, a strip of paper on which data was represented by a series of holes. IBM introduced the first hard drive in 1956, as a component of their 305 RAMAC computer system. Most digital data today is stored magnetically on hard disks. Until 2002 most information was stored on analog devices, but that year digital storage capacity exceeded analog for the first time. As of 2007 almost 94% of the data stored worldwide was held digitally, 52% on hard disks, 28% on optical devices and 11% on digital magnetic tape. It has been estimated that the capacity to store information on electronic devices grew from less than 3 exabytes in 1986 to 295 exabytes in 2007. Database management systems emerged in the 1960s to address the problem of storing and retrieving large amounts of data accurately and quickly, one of the earliest such systems was IBMs Information Management System, which is still widely deployed more than 50 years later
2.
Data compression
–
In signal processing, data compression, source coding, or bit-rate reduction involves encoding information using fewer bits than the original representation. Compression can be lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy, no information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information, the process of reducing the size of a data file is referred to as data compression. In the context of data transmission, it is called coding in opposition to channel coding. Compression is useful because it reduces resources required to store and transmit data, computational resources are consumed in the compression process and, usually, in the reversal of the process. Data compression is subject to a space–time complexity trade-off, Lossless data compression algorithms usually exploit statistical redundancy to represent data without losing any information, so that the process is reversible. Lossless compression is possible because most real-world data exhibits statistical redundancy, for example, an image may have areas of color that do not change over several pixels, instead of coding red pixel, red pixel. The data may be encoded as 279 red pixels and this is a basic example of run-length encoding, there are many schemes to reduce file size by eliminating redundancy. The Lempel–Ziv compression methods are among the most popular algorithms for lossless storage, DEFLATE is a variation on LZ optimized for decompression speed and compression ratio, but compression can be slow. DEFLATE is used in PKZIP, Gzip, and PNG, LZW is used in GIF images. LZ methods use a table-based compression model where table entries are substituted for repeated strings of data, for most LZ methods, this table is generated dynamically from earlier data in the input. The table itself is often Huffman encoded, current LZ-based coding schemes that perform well are Brotli and LZX. LZX is used in Microsofts CAB format, the best modern lossless compressors use probabilistic models, such as prediction by partial matching. The Burrows–Wheeler transform can also be viewed as a form of statistical modelling. The basic task of grammar-based codes is constructing a context-free grammar deriving a single string, sequitur and Re-Pair are practical grammar compression algorithms for which software is publicly available. In a further refinement of the use of probabilistic modelling. Arithmetic coding is a more modern coding technique that uses the mathematical calculations of a machine to produce a string of encoded bits from a series of input data symbols
3.
Multimedia
–
Multimedia is content that uses a combination of different content forms such as text, audio, images, animations, video and interactive content. Multimedia contrasts with media that use only rudimentary computer displays such as text-only or traditional forms of printed or hand-produced material, Multimedia devices are electronic media devices used to store and experience multimedia content. Multimedia is distinguished from mixed media in art, for example. The term rich media is synonymous with interactive multimedia, the term multimedia was coined by singer and artist Bob Goldstein to promote the July 1966 opening of his LightWorks at LOursin show at Southampton, Long Island. Goldstein was perhaps aware of an American artist named Dick Higgins, two years later, in 1968, the term multimedia was re-appropriated to describe the work of a political consultant, David Sawyer, the husband of Iris Sawyer—one of Goldsteins producers at LOursin. In the intervening forty years, the word has taken on different meanings, in the late 1970s, the term referred to presentations consisting of multi-projector slide shows timed to an audio track. However, by the 1990s multimedia took on its current meaning, in the 1993 first edition of Multimedia, Making It Work, Tay Vaughan declared Multimedia is any combination of text, graphic art, sound, animation, and video that is delivered by computer. When you allow the user – the viewer of the project – to control what, when you provide a structure of linked elements through which the user can navigate, interactive multimedia becomes hypermedia. The German language society Gesellschaft für deutsche Sprache recognized the words significance, the institute summed up its rationale by stating has become a central word in the wonderful new media world. In common usage, multimedia refers to an electronically delivered combination of media including video, still images, audio, much of the content on the web today falls within this definition as understood by millions. That era saw also a boost in the production of educational multimedia CD-ROMs, the term video, if not used exclusively to describe motion photography, is ambiguous in multimedia terminology. Video is often used to describe the format, delivery format. Multiple forms of content are often not considered modern forms of presentation such as audio or video. Likewise, single forms of content with single methods of information processing are often called multimedia. Performing arts may also be considered multimedia considering that performers and props are multiple forms of content and media. Multimedia presentations may be viewed by person on stage, projected, transmitted, a broadcast may be a live or recorded multimedia presentation. Broadcasts and recordings can be analog or digital electronic media technology. Digital online multimedia may be downloaded or streamed, streaming multimedia may be live or on-demand
4.
Sound recording and reproduction
–
Sound recording and reproduction is an electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording, prior to the development of analog recording, there were mechanical systems for reproducing instrumental music, such as wind-up music boxes and later, in the late 19th century, player pianos. Analog sound reproduction is the process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Digital recording and reproduction converts the sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a variety of media. Whereas successive copies of an analog recording tend to degrade in quality, as noise is added. A digital audio signal must be reconverted to analog form during playback before it is amplified and connected to a loudspeaker to produce sound, long before sound was first recorded on cylinders or records, music was recorded—first by written music notation, then also by mechanical devices. Fowler, this. cylinder with raised pins on the surface remained the device to produce and reproduce music mechanically until the second half of the nineteenth century. The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine, according to Fowler, the automata were a robot band that performed. more than fifty facial and body actions during each musical selection. In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder, similar designs appeared in barrel organs, musical clocks, barrel pianos, and musical boxes. A music box is a musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth of a steel comb. They were developed from musical snuff boxes of the 18th century, some of the more complex boxes also have a tiny drum and/or bells, in addition to the metal comb. The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books, the player piano, first demonstrated in 1876, used a punched paper scroll that could store an long piece of music. The most sophisticated of the rolls were hand-played, meaning that the roll represented the actual performance of an individual. This technology to record a live performance onto a piano roll was not developed until 1904, piano rolls were in continuous mass production from 1896 to 2008. A1908 U. S. Supreme Court copyright case noted that, in 1902 alone, the use of piano rolls began to decline in the 1920s although one type is still being made today. The first device that could record actual sounds as they passed through the air was the phonautograph, the earliest known recordings of the human voice are phonautograph recordings, called phonautograms, made in 1857. They consist of sheets of paper with sound-wave-modulated white lines created by a stylus that cut through a coating of soot as the paper was passed under it
5.
Video
–
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video systems vary greatly in the resolution of the display and refresh rate, video can be carried on a variety of media, including radio broadcast, tapes, DVDs, computer files etc. Video was originally exclusively a live technology, charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder. In 1951 the first video tape recorder captured live images from television cameras by converting the electrical impulses. Video recorders were sold for $50,000 in 1956, however, prices gradually dropped over the years, in 1971, Sony began selling videocassette recorder decks and tapes into the consumer market. The use of techniques in video created digital video, which allowed higher quality and, eventually. After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape, the advent of digital broadcasting and the subsequent digital television transition is in the process of relegating analog video to the status of a legacy technology in most parts of the world. PAL standards and SECAM specify 25 frame/s, while NTSC standards specify 29.97 frames, film is shot at the slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video. The minimum frame rate to achieve a comfortable illusion of an image is about sixteen frames per second. Video can be interlaced or progressive, analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. NTSC, PAL and SECAM are interlaced formats, abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is specified as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence, when displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material, aspect ratio describes the dimensions of video screens and video picture elements. All popular video formats are rectilinear, and so can be described by a ratio between width and height, the screen aspect ratio of a traditional television screen is 4,3, or about 1.33,1. High definition televisions use a ratio of 16,9. The aspect ratio of a full 35 mm film frame with soundtrack is 1.375,1. Therefore, a 720 by 480 pixel NTSC DV image displayes with the 4,3 aspect ratio if the pixels are thin, the popularity of viewing video on mobile phones has led to the growth of vertical video
6.
Image
–
Images may be two-dimensional, such as a photograph or screen display, or three-dimensional, such as a statue or hologram. They may be captured by optical devices – such as cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water. The word image is used in the broader sense of any two-dimensional figure such as a map, a graph. A volatile image is one that only for a short period of time. This may be a reflection of an object by a mirror, a fixed image, also called a hard copy, is one that has been recorded on a material object, such as paper or textile by photography or any other digital process. A mental image exists in a mind, as something one remembers or imagines. The subject of an image need not be real, it may be a concept, such as a graph, function. For example, Sigmund Freud claimed to have dreamed purely in aural-images of dialogs, a still image is a single static image, as distinguished from a kinetic image. This phrase is used in photography, visual media and the industry to emphasize that one is not talking about movies. A film still is a taken on the set of a movie or television program during production. In literature, imagery is a picture which appeals to the senses. It can both be figurative and literal, a moving image is typically a movie or video, including digital video. It could also be an animated display such as a zoetrope, library of Congress – Format Descriptions for Still Images Image Processing – Online Open Research Group Legal Issues Regarding Images Image Copyright Case
7.
Streaming media
–
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a provider. A client end-user can use their player to begin to play the data file before the entire file has been transmitted. For example, in the 1930s, elevator music was among the earliest popularly available streaming media, the term streaming media can apply to media other than video and audio such as live closed captioning, ticker tape, and real-time text, which are all considered streaming text. As of 2017, streaming is generally taken to refer to cases where a user watches digital video content or listens to audio content on a computer screen. With streaming content, the user does not have to download the digital video or digital audio file before they start to watch/listen to it. There are challenges with streaming content on the Internet, as of 2016, two popular streaming services are the video sharing website YouTube, which contains video and audio files on a huge range of topics and Netflix, which streams movies and TV shows. Live streaming refers to Internet content delivered in real-time, as events happen, Live internet streaming requires a form of source media, an encoder to digitize the content, a media publisher, and a content delivery network to distribute and deliver the content. Live streaming does not need to be recorded at the origination point, in the early 1920s, George O. Attempts to display media on computers date back to the earliest days of computing in the mid-20th century, however, little progress was made for several decades, primarily due to the high cost and limited capabilities of computer hardware. From the late 1980s through the 1990s, consumer-grade personal computers became powerful enough to various media. These technological improvement facilitated the streaming of audio and video content to users in their homes and workplaces. The band Severe Tire Damage was the first group to live on the Internet. On June 24,1993, the band was playing a gig at Xerox PARC while elsewhere in the building, as proof of PARCs technology, the bands performance was broadcast and could be seen live in Australia and elsewhere. Microsoft Research developed a Microsoft TV application which was compiled under MS Windows Studio Suite, realNetworks was also a pioneer in the streaming media markets, when it broadcast a baseball game between the New York Yankees and the Seattle Mariners over the Internet in 1995. The first symphonic concert on the Internet took place at the Paramount Theater in Seattle, the concert was a collaboration between The Seattle Symphony and various guest musicians such as Slash, Matt Cameron, and Barrett Martin. When Word Magazine launched in 1995, they featured the first-ever streaming soundtracks on the Internet.4 in 1999, in June 1999 Apple also introduced a streaming media format in its QuickTime 4 application. It was later widely adopted on websites along with RealPlayer. In 2000 Industryview. com launched its worlds largest streaming video archive website to help promote themselves
8.
Lossy compression
–
In information technology, lossy compression or irreversible compression is the class of data encoding methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size for storage, handling, different versions of the photo of the cat above show how higher degrees of approximation create coarser images as more details are removed. This is opposed to data compression which does not degrade the data. The amount of data reduction possible using lossy compression is often higher than through lossless techniques. Well-designed lossy compression technology often reduces file sizes significantly before degradation is noticed by the end-user, even when noticeable by the user, further data reduction may be desirable. Lossy compression is most commonly used to compress multimedia data, especially in such as streaming media. By contrast, lossless compression is required for text and data files, such as bank records. A picture, for example, is converted to a file by considering it to be an array of dots and specifying the color. If the picture contains an area of the color, it can be compressed without loss by saying 200 red dots instead of red dot. The original data contains an amount of information, and there is a lower limit to the size of file that can carry all the information. Basic information theory says there is an absolute limit in reducing the size of this data. When data is compressed, its entropy increases, and it cannot increase indefinitely, as an intuitive example, most people know that a compressed ZIP file is smaller than the original file, but repeatedly compressing the same file will not reduce the size to nothing. Most compression algorithms can recognize when further compression would be pointless, in many cases, files or data streams contain more information than is needed for a particular purpose. Developing lossy compression techniques as closely matched to human perception as possible is a complex task, the terms irreversible and reversible are preferred over lossy and lossless respectively for some applications, such as medical image compression, to circumvent the negative implications of loss. The type and amount of loss can affect the utility of the images, artifacts or undesirable effects of compression may be clearly discernible yet the result still useful for the intended purpose. Or lossy compressed images may be visually lossless, or in the case of medical images and this is because uncompressed audio can only reduce file size by lowering bit rate or depth, whereas compressing audio can reduce size while maintaining bit rate and depth. This compression becomes a loss of the least significant data. From this point of view, perceptual encoding is not essentially about discarding data, green, and 50 pixels of blue vs. red, which are proportional to human sensitivity to each component
9.
Computer file
–
A computer file is a computer resource for recording data discretely in a computer storage device. Just as words can be written to paper, so can information be written to a computer file, there are different types of computer files, designed for different purposes. A file may be designed to store a picture, a message, a video. Some types of files can store different several types of information at once, by using computer programs, a person can open, read, change, and close a computer file. Computer files may be reopened, modified, and copied a number of times. Typically, computer files are organised in a system, which keeps track of where the files are. The word file derives from the Latin filum, such a file now exists in a memory tube developed at RCA Laboratories. Electronically it retains figures fed into calculating machines, holds them in storage while it memorizes new ones - speeds intelligent solutions through mazes of mathematics, in 1952, file denoted, inter alia, information stored on punched cards. In early use, the hardware, rather than the contents stored on it, was denominated a file. For example, the IBM350 disk drives were denominated disk files, although the contemporary register file demonstrates the early concept of files, its use has greatly decreased. On most modern operating systems, files are organized into one-dimensional arrays of bytes, for example, the bytes of a plain text file are associated with either ASCII or UTF-8 characters, while the bytes of image, video, and audio files are interpreted otherwise. Most file types also allocate a few bytes for metadata, which allows a file to some basic information about itself. Some file systems can store arbitrary file-specific data outside of the file format, on other file systems this can be done via sidecar files or software-specific databases. All those methods, however, are susceptible to loss of metadata than are container. At any instant in time, a file might have a size, normally expressed as number of bytes, in most modern operating systems the size can be any non-negative whole number of bytes up to a system limit. Many older operating systems kept track only of the number of blocks or tracks occupied by a file on a storage device. In such systems, software employed other methods to track the exact byte count, the general definition of a file does not require that its size have any real meaning, however, unless the data within the file happens to correspond to data within a pool of persistent storage. A special case is a zero byte file, these files can be newly created files that have not yet had any data written to them, or may serve as some kind of flag in the file system, or are accidents
10.
Information theory
–
Information theory studies the quantification, storage, and communication of information. A key measure in information theory is entropy, entropy quantifies the amount of uncertainty involved in the value of a random variable or the outcome of a random process. For example, identifying the outcome of a coin flip provides less information than specifying the outcome from a roll of a die. Some other important measures in information theory are mutual information, channel capacity, error exponents, applications of fundamental topics of information theory include lossless data compression, lossy data compression, and channel coding. The field is at the intersection of mathematics, statistics, computer science, physics, neurobiology, Information theory studies the transmission, processing, utilization, and extraction of information. Abstractly, information can be thought of as the resolution of uncertainty, Information theory is a broad and deep mathematical theory, with equally broad and deep applications, amongst which is the vital field of coding theory. These codes can be subdivided into data compression and error-correction techniques. In the latter case, it took years to find the methods Shannons work proved were possible. A third class of information theory codes are cryptographic algorithms, concepts, methods and results from coding theory and information theory are widely used in cryptography and cryptanalysis. See the article ban for a historical application, Information theory is also used in information retrieval, intelligence gathering, gambling, statistics, and even in musical composition. Prior to this paper, limited information-theoretic ideas had been developed at Bell Labs, the unit of information was therefore the decimal digit, much later renamed the hartley in his honour as a unit or scale or measure of information. Alan Turing in 1940 used similar ideas as part of the analysis of the breaking of the German second world war Enigma ciphers. Much of the mathematics behind information theory with events of different probabilities were developed for the field of thermodynamics by Ludwig Boltzmann, Information theory is based on probability theory and statistics. Information theory often concerns itself with measures of information of the associated with random variables. Important quantities of information are entropy, a measure of information in a random variable, and mutual information. The choice of base in the following formulae determines the unit of information entropy that is used. A common unit of information is the bit, based on the binary logarithm, other units include the nat, which is based on the natural logarithm, and the hartley, which is based on the common logarithm. In what follows, an expression of the form p log p is considered by convention to be equal to zero whenever p =0 and this is justified because lim p →0 + p log p =0 for any logarithmic base
11.
Zip (file format)
–
ZIP is an archive file format that supports lossless data compression. A. ZIP file may contain one or more files or directories that may have been compressed, the. ZIP file format permits a number of compression algorithms, though DEFLATE is the most common. This format was created in 1989 by Phil Katz, and was first implemented in PKWARE, Inc. s PKZIP utility. The. ZIP format is now supported by many software utilities other than PKZIP, Microsoft has included built-in. ZIP support in versions of Microsoft Windows since 1998. Apple has included built-in. ZIP support in Mac OS X10.3 and later. Most free operating systems have built in support for. ZIP in similar manners to Windows and Mac OS X. ZIP files generally use the file extensions. zip or. ZIP, ZIP is used as a base file format by many programs, usually under a different name. When navigating a file system via an interface, graphical icons representing. ZIP files often appear as a document or other object prominently featuring a zipper. The. ZIP file format was created by Phil Katz of PKWARE and they created the format after PKWARE had a lawsuits filed against them by Systems Enhancement Associates claiming that his archiving products were derivatives of SEAs ARC archiving system. The name zip was suggested by Katzs friend, Robert Mahoney and they wanted to imply that their product would be faster than ARC and other compression formats of the time. The earliest known version of. ZIP File Format Specification was first published as part of PKZIP0.9 package under the file APPNOTE. TXT in 1989, the. ZIP file format was released into the public domain. The. ZIP File Format Specification has its own version number, other companies or organizations support the PKWARE specifications at their own pace. The. ZIP file format specification is formally named APPNOTE -. ZIP File Format Specification, several versions of the specification were not published. Specifications of some such as BZIP2 compression, strong encryption specification. The URL of the specification was changed several times on the PKWARE website. A summary of key advances in various versions of the PKWARE specification,2.0, File entries can be compressed with DEFLATE,2.1, Deflate64 compression 4.5, Documented 64-bit zip format. 4.6, BZIP2 compression 5.0, DES, Triple DES, RC2, RC4 supported for encryption 5.2, AES encryption support, expanded list of supported hash, compression, encryption algorithms. 6.3.1, Corrected standard hash values for SHA-256/384/512,6.3.4, Updates the PKWARE, Inc. office address. WinZip, starting with version 12.1, uses the extension. zipx for. ZIP files that use compression methods newer than DEFLATE, specifically, methods BZip, LZMA, PPMd, Jpeg and Wavpack
12.
Domain of a function
–
In mathematics, and more specifically in naive set theory, the domain of definition of a function is the set of input or argument values for which the function is defined. That is, the function provides an output or value for each member of the domain, conversely, the set of values the function takes on as output is termed the image of the function, which is sometimes also referred to as the range of the function. For instance, the domain of cosine is the set of all real numbers, if the domain of a function is a subset of the real numbers and the function is represented in a Cartesian coordinate system, then the domain is represented on the X-axis. Given a function f, X→Y, the set X is the domain of f, in the expression f, x is the argument and f is the value. One can think of an argument as a member of the domain that is chosen as an input to the function, the image of f is the set of all values assumed by f for all possible x, this is the set. The image of f can be the set as the codomain or it can be a proper subset of it. It is, in general, smaller than the codomain, it is the whole codomain if, a well-defined function must map every element of its domain to an element of its codomain. For example, the function f defined by f =1 / x has no value for f, thus, the set of all real numbers, R, cannot be its domain. In cases like this, the function is defined on R\ or the gap is plugged by explicitly defining f. If we extend the definition of f to f = {1 / x x ≠00 x =0 then f is defined for all real numbers, any function can be restricted to a subset of its domain. The restriction of g, A → B to S, where S ⊆ A, is written g |S, S → B. The natural domain of a function is the set of values for which the function is defined, typically within the reals. For instance the natural domain of square root is the non-negative reals when considered as a real number function, when considering a natural domain, the set of possible values of the function is typically called its range. There are two meanings in current mathematical usage for the notion of the domain of a partial function from X to Y, i. e. a function from a subset X of X to Y. Most mathematicians, including recursion theorists, use the domain of f for the set X of all values x such that f is defined. But some, particularly category theorists, consider the domain to be X, in category theory one deals with morphisms instead of functions. Morphisms are arrows from one object to another, the domain of any morphism is the object from which an arrow starts. In this context, many set theoretic ideas about domains must be abandoned or at least formulated more abstractly, for example, the notion of restricting a morphism to a subset of its domain must be modified
13.
MP3
–
Compared to CD quality digital audio, MP3 compression commonly achieves 75 to 95% reduction in size. MP3 files are thus 1/4 to 1/20 the size of the digital audio stream. This is important for both transmission and storage concerns, the basis for such comparison is the CD digital audio format which requires 1411200 bit/s. A commonly used MP3 encoding setting is CBR128 kbit/s resulting in file size 1/11 of the original CD-quality file, the MP3 lossy compression works by reducing the accuracy of certain parts of a continuous sound that are considered to be beyond the auditory resolution ability of most people. This method is referred to as perceptual coding or psychoacoustics. It uses psychoacoustic models to discard or reduce the precision of less audible to human hearing. MP3 was designed by the Moving Picture Experts Group as part of its MPEG-1 standard, the first subgroup for audio was formed by several teams of engineers at Fraunhofer IIS, University of Hanover, AT&T-Bell Labs, Thomson-Brandt, CCETT, and others. MPEG-1 Audio, which included MPEG-1 Audio Layer I, II and III was approved as a draft of ISO/IEC standard in 1991, finalised in 1992. A backwards compatible MPEG-2 Audio extension with lower sample and bit rates was published in 1995, MP3 is a streaming or broadcast format meaning that individual frames can be lost without affecting the ability to decode successfully delivered frames. Storing an MP3 stream in a file enables time-shifted playback, the MP3 lossy audio data compression algorithm takes advantage of a perceptual limitation of human hearing called auditory masking. In 1894, the American physicist Alfred M. Mayer reported that a tone could be rendered inaudible by another tone of lower frequency, in 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon. Ernst Terhardt et al. created an algorithm describing auditory masking with high accuracy and this work added to a variety of reports from authors dating back to Fletcher, and to the work that initially determined critical ratios and critical bandwidths. A wide variety of compression algorithms were reported in IEEEs refereed Journal on Selected Areas in Communications. The genesis of the MP3 technology is described in a paper from Professor Hans Musmann who chaired the ISO MPEG Audio group for several years. The immediate predecessors of MP3 were Optimum Coding in the Frequency Domain, the first practical implementation of an audio perceptual coder in hardware, was an implementation of a psychoacoustic transform coder based on Motorola 56000 DSP chips. Another predecessor of the MP3 format and technology is to be found in the perceptual codec MUSICAM based on an integer arithmetics 32 sub-bands filterbank, driven by a psychoacoustic model. It was primarily designed for Digital Audio Broadcasting and digital TV and this codec incorporated into a broadcasting system using COFDM modulation was demonstrated on air and on the field together with Radio Canada and CRC Canada during the NAB show in 1991. F. As a doctoral student at Germanys University of Erlangen-Nuremberg, Karlheinz Brandenburg began working on music compression in the early 1980s
14.
Equalization (audio)
–
Equalization is the process of adjusting the balance between frequency components within an electronic signal. The most well known use of equalization is in recording and reproduction but there are many other applications in electronics. The circuit or equipment used to achieve equalization is called an equalizer and these devices strengthen or weaken the energy of specific frequency bands or frequency ranges. In sound recording and reproduction, equalization is the commonly used to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments, graphic and parametric equalizers have much more flexibility in tailoring the frequency content of an audio signal. An equalizer is the circuit or equipment used to achieve equalization, since equalizers, adjust the amplitude of audio signals at particular frequencies, they are, in other words, frequency-specific volume knobs. The term EQ specifically refers to this variant of the term, stereos and basic guitar amplifiers typically have adjustable equalizers which boost or cut bass or treble frequencies. Mid- to high-priced guitar and bass amplifiers usually have more bands of frequency control, such as bass, mid-range and treble or bass, low-mid, high-mid, some amps have an additional knob for controlling very high frequencies. Broadcast and recording studios use sophisticated equalizers capable of more detailed adjustments. The most common equalizers in music production are parametric, semi-parametric, graphic, peak, graphic equalizers are often included in consumer audio equipment and software which plays music on home computers. Parametric equalizers require more expertise than graphic equalizers, and they can provide more specific compensation or alteration around a chosen frequency and this may be used in order to remove unwanted resonances or boost certain frequencies. An acoustic guitarist who finds that her instrument sounds too boomy may ask the engineer to reduce the low frequency range response. A guitarist who finds that the instrument sound in the PA has too much finger noise may ask the engineer to reduce the frequency range response. The concept of equalization was first applied in correcting the frequency response of telephone lines using passive networks, a plot of the systems net frequency response would be flat, as its response to all frequencies would literally be equal. Much later the concept was applied in engineering to adjust the frequency response in recording, reproduction. Audio amplifiers have long had filters or controls to modify their frequency response and these are most often in the form of variable bass and treble controls, and switches to apply low-cut or high-cut filters for elimination of low frequency rumble and high frequency hiss respectively. Graphic equalizers and other equipment developed for improving fidelity have since used by recording engineers to modify frequency responses for aesthetic reasons. Hence in the field of audio electronics the term equalization is now used to describe the application of such filters regardless of intent
15.
Fault tolerance
–
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of some of its components. Fault tolerance is particularly sought after in high-availability or life-critical systems, the ability of maintaining functionality when portions of a system break down is referred to as graceful degradation. A fault-tolerant design enables a system to continue its operation, possibly at a reduced level, rather than failing completely. That is, the system as a whole is not stopped due to either in the hardware or the software. However, if the consequences of a system failure are catastrophic, or the cost of making it sufficiently reliable is very high, a better solution may be to use some form of duplication. In any case, if the consequence of a failure is so catastrophic. This is similar to recovery but can be a human action if humans are present in the loop. A highly fault-tolerant system might continue at the level of performance even though one or more components have failed. For example, a building with a electrical generator will provide the same voltage to wall outlets even if the grid power fails. In computers, a program might fail-safe by executing a graceful exit in order to prevent data corruption after experiencing an error, a similar distinction is made between failing well and failing badly. Fail-deadly is the strategy, which can be used in weapon systems that are designed to kill or injure targets even if part of the system is damaged or destroyed. A system that is designed to experience graceful degradation, or to fail soft operates at a level of performance after some component failures. In fault-tolerant computer systems, programs that are considered robust are designed to continue operation despite an error, exception, or invalid input, software brittleness is the opposite of robustness. Likewise, a fail-fast component is designed to report at the first point of failure, rather than allow downstream components to fail and this allows easier diagnosis of the underlying problem, and may prevent improper operation in a broken state. If each component, in turn, can continue to function when one of its subcomponents fails, this will allow the total system to continue to operate as well. Using a passenger vehicle as an example, a car can have run-flat tires, the punctured run-flat tire may be used for a limited time at a reduced speed. Redundancy is the provision of functional capabilities that would be unnecessary in a fault-free environment and this can consist of backup components that automatically kick in should one component fail. For example, large trucks can lose a tire without any major consequences
16.
Chrominance
–
Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal. Chrominance is usually represented as two color-difference components, U = B′ − Y′ and V = R′ − Y′, each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard. In digital-video and still-image color spaces such as Y′CbCr, the luma, separating RGB color signals into luma and chrominance allows the bandwidth of each to be determined separately. Typically, the bandwidth is reduced in analog composite video by reducing the bandwidth of a modulated color subcarrier. The idea of transmitting a color signal with distinct luma and chrominance components originated with Georges Valensi. Previous schemes for color television systems, which were incompatible with existing monochrome receivers, in analog television, chrominance is encoded into a video signal using a subcarrier frequency. Depending on the standard, the chrominance subcarrier may be either quadrature-amplitude-modulated or frequency-modulated. In the PAL system, the subcarrier is 4.43 MHz above the video carrier. The NTSC and PAL standards are the most commonly used, although there are other standards that employ different subcarrier frequencies. For example, PAL-M uses a 3.58 MHz subcarrier, the presence of chrominance in a video signal is indicated by a color burst signal transmitted on the back porch, just after horizontal synchronization and before each line of video starts. If the color burst signal were visible on a television screen, in NTSC and PAL, hue is represented by a phase shift of the chrominance signal relative to the color burst, while saturation is determined by the amplitude of the subcarrier. In SECAM and signals are transmitted alternately and phase does not matter, chrominance is represented by the U-V color plane in PAL and SECAM video signals, and by the I-Q color plane in NTSC. Digital video and digital photography systems sometimes use a luma/chroma decomposition for improved compression. On decompression, the Y′CbCr space is rotated back to RGB
17.
YUV
–
YUV is a color space typically used as part of a color image pipeline. The scope of the terms Y′UV, YUV, YCbCr, YPbPr, etc. is sometimes ambiguous, today, the term YUV is commonly used in the computer industry to describe file-formats that are encoded using YCbCr. The Y′UV model defines a space in terms of one luma. The Y′UV color model is used in the PAL and SECAM composite color video standards, previous black-and-white systems used only luma information. The YPbPr color model used in analog component video and its digital version YCbCr used in video are more or less derived from it. The Y′IQ color space used in the analog NTSC television broadcasting system is related to it, as for etymology, Y, Y′, U, and V are not abbreviations. The use of the letter Y for luminance can be traced back to the choice of X Y Z primaries and this lends itself naturally to the usage of the same letter in luma, which approximates a perceptually uniform correlate of luminance. Likewise, U and V were chosen to differentiate the U and V axes from those in other spaces, see the equations below or compare the historical development of the math. Y′UV was invented when engineers wanted color television in a black-and-white infrastructure and they needed a signal transmission method that was compatible with black-and-white TV while being able to add color. The luma component already existed as the black and white signal, the UV representation of chrominance was chosen over straight R and B signals because U and V are color difference signals. This meant that in a black and white scene the U and V signals would be zero, if R and B were to have been used, these would have non-zero values even in a B&W scene, requiring all three data-carrying signals. In addition, black and white receivers could take the Y′ signal and ignore the signals, making Y′UV backward-compatible with all existing black-and-white equipment. It was necessary to assign a narrower bandwidth to the channel because there was no additional bandwidth available. If some of the information arrived via the chrominance channel. Y′UV signals are created from RGB source. Weighted values of R, G, and B are summed to produce Y′, U and V are computed as scaled differences between Y′ and the B and R values. BT.601 defines the following constants, W R =0.299, W G =1 − W R − W B =0.587, W B =0.114, U max =0.436, V max =0.615. The resulting ranges of Y′, U, and V respectively are, equivalently, substituting values for the constants and expressing them as matrices gives these formulas for BT.601, =, =
18.
Chroma subsampling
–
It is used in many video encoding schemes — both analog and digital — and also in JPEG encoding. Digital signals are compressed to save transmission time and reduce file size. In compressed images, for example, the 4,2,2 YCbCr scheme requires two-thirds the bandwidth of RGB and this reduction results in almost no visual difference as perceived by the viewer. Because the human system is less sensitive to the position and motion of color than luminance. At normal viewing distances, there is no perceptible loss incurred by sampling the color detail at a lower rate, in video systems, this is achieved through the use of color difference components. The signal is divided into a component and two color difference components. In human vision there are three channels for detection, and for many color systems, three channels is sufficient for representing most colors. For example, red, green, blue or magenta, yellow, but there are other ways to represent the color. In many video systems, the three channels are luminance and two chroma channels, in video, the luma and chroma components are formed as a weighted sum of gamma-corrected RGB components instead of linear RGB components. As a result, luma must be distinguished from luminance, indeed, similar bleeding can occur also with gamma =1, whence the reversing of the order of operations between gamma correction and forming the weighted sum can make no difference. The chroma can influence the luma specifically at the pixels where the subsampling put no chroma, the parts are, J, horizontal sampling reference. A, number of samples in the first row of J pixels. B, number of changes of chrominance samples between first and second row of J pixels, may be omitted if alpha component is not present, and is equal to J when present. This notation is not valid for all combinations and has exceptions, the mapping examples given are only theoretical and for illustration. Also note that the diagram does not indicate any chroma filtering, to calculate required bandwidth factor relative to 4,4,4, one needs to sum all the factors and divide the result by 12. Each of the three YCbCr components have the sample rate, thus there is no chroma subsampling. This scheme is used in high-end film scanners and cinematic post production. Note that 4,4,4 may instead be referring to RGB color space, formats such as HDCAM SR can record 4,4,4 RGB over dual-link HD-SDI
19.
Color space
–
A color space is a specific organization of colors. In combination with physical device profiling, it allows for reproducible representations of color, for example, Adobe RGB and sRGB are two different absolute color spaces, both based on the RGB color model. When defining a color space, the reference standard is the CIELAB or CIEXYZ color spaces. For example, although several specific color spaces are based on the RGB color model, colors can be created in printing with color spaces based on the CMYK color model, using the subtractive primary colors of pigment. The resulting 3-D space provides a position for every possible color that can be created by combining those three pigments. Colors can be created on computer monitors with color spaces based on the RGB color model, a three-dimensional representation would assign each of the three colors to the X, Y, and Z axes. Note that colors generated on given monitor will be limited by the medium, such as the phosphor or filters. Another way of creating colors on a monitor is with an HSL or HSV color space, based on hue, saturation, with such a space, the variables are assigned to cylindrical coordinates. Many color spaces can be represented as three-dimensional values in this manner, but some have more, or fewer dimensions, Color space conversion is the translation of the representation of a color from one basis to another. The RGB color model is implemented in different ways, depending on the capabilities of the system used, by far the most common general-used incarnation as of 2006 is the 24-bit implementation, with 8 bits, or 256 discrete levels of color per channel. Any color space based on such a 24-bit RGB model is limited to a range of 256×256×256 ≈16.7 million colors. Some implementations use 16 bits per component for 48 bits total and this is especially important when working with wide-gamut color spaces, or when a large number of digital filtering algorithms are used consecutively. The same principle applies for any color space based on the color model. CIE1931 XYZ color space was one of the first attempts to produce a space based on measurements of human color perception. The CIERGB color space is a companion of CIE XYZ. Additional derivatives of CIE XYZ include the CIELUV, CIEUVW, RGB uses additive color mixing, because it describes what kind of light needs to be emitted to produce a given color. RGB stores individual values for red, green and blue, RGBA is RGB with an additional channel, alpha, to indicate transparency. Common color spaces based on the RGB model include sRGB, Adobe RGB, ProPhoto RGB, scRGB, one starts with a white substrate, and uses ink to subtract color from white to create an image
20.
YIQ
–
YIQ is the color space used by the NTSC color TV system, employed mainly in North and Central America, and Japan. I stands for in-phase, while Q stands for quadrature, referring to the used in quadrature amplitude modulation. Some forms of NTSC now use the YUV color space, which is used by other systems such as PAL. The Y component represents the information, and is the only component used by black-and-white television receivers. I and Q represent the chrominance information, in YUV, the U and V components can be thought of as X and Y coordinates within the color space. I and Q can be thought of as a pair of axes on the same graph, rotated 33°, therefore IQ. The YIQ system is intended to take advantage of human color-response characteristics, the eye is more sensitive to changes in the orange-blue range than in the purple-green range — therefore less bandwidth is required for Q than for I. Broadcast NTSC limits I to 1.3 MHz and Q to 0.4 MHz, I and Q are frequency interleaved into the 4 MHz Y signal, which keeps the bandwidth of the overall signal down to 4.2 MHz. In YUV systems, since U and V both contain information in the range, both components must be given the same amount of bandwidth as I to achieve similar color fidelity. Very few television sets perform true I and Q decoding, due to the costs of such an implementation. Compared to the cheaper R-Y and B-Y decoding which requires only one filter and these bandwidth differences also requires that the I filter include a time delay to match the longer delay of the Q filter. The Rockwell Modular Digital Radio was one I and Q decoding set, earlier, more than one brand of color TV used I/Q decoding in the 1954 or 1955 model year on models utilizing screens about 13 inches. The original Advent projection television used I/Q decoding, around 1990, at least one manufacturer of professional studio picture monitors advertised I/Q decoding. The YIQ representation is employed in color image processing transformations. For example, applying a histogram equalization directly to the channels in an RGB image would alter the balance of the image. Instead, the histogram equalization is applied to the Y channel of the YIQ or YUV representation of the image, E R ′, E G ′ and E B ′ are the gamma-corrected voltages corresponding to red, green, and blue signals. E I ′ and E Q ′ are the amplitudes of the components of the chrominance signal. It is still mandated for these transmissions as shown in this excerpt of the current FCC rules and regulations part 73 TV transmission standard, Buchsbaum
21.
NTSC
–
The first NTSC standard was developed in 1941 and had no provision for color. In 1953 a second NTSC standard was adopted, which allowed for television broadcasting which was compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system and remained dominant until 1997, North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries are adopting or have adopted other standards instead of ATSC. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on January 1,2010, the majority of NTSC transmissions ended in Japan on July 24,2011, with the Japanese prefectures of Iwate, Miyagi, and Fukushima ending the next year. In March 1941, the committee issued a standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association. Technical advancements of the side band technique allowed for the opportunity to increase the image resolution. The NTSC selected 525 scan lines as a compromise between RCAs 441-scan line standard and Philcos and DuMonts desire to increase the number of lines to between 605 and 800. The standard recommended a frame rate of 30 frames per second, other standards in the final recommendation were an aspect ratio of 4,3, and frequency modulation for the sound signal. In January 1950, the committee was reconstituted to standardize color television, in December 1953, it unanimously approved what is now called the NTSC color television standard. The compatible color standard retained full backward compatibility with existing black-and-white television sets, Color information was added to the black-and-white image by introducing a color subcarrier of precisely 315/88 MHz. These changes amounted to 0.1 percent and were tolerated by existing television receivers. The FCC had briefly approved a different color standard, starting in October 1950. However, this standard was incompatible with black-and-white broadcasts and it used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second. CBS rescinded its system in March 1953, and the FCC replaced it on December 17,1953, with the NTSC color standard, later that year, the improved TK-41 became the standard camera used throughout much of the 1960s. The NTSC standard has been adopted by countries, including most of the Americas. With the advent of television, analog broadcasts are being phased out. Most US NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009, low-power stations, Class A stations and translators were required to shut down by 2015. NTSC color encoding is used with the System M television signal, each frame is composed of two fields, each consisting of 262.5 scan lines, for a total of 525 scan lines
22.
Scan line
–
A scanline is one line, or row, in a raster scanning pattern, such as a line of video on a cathode ray tube display of a television set or computer monitor. This is sometimes used today as an effect in computer graphics. The term is used, by analogy, for a row of pixels in a raster graphics image. Scan lines are important in representations of data, because many image file formats have special rules for data at the end of a scan line. For example, there may be a rule that each line starts on a particular boundary. This means that even otherwise compatible raster data may need to be analyzed at the level of scan lines in order to convert between formats, screen-door effect Fax Interlaced video Native resolution Progressive video Scanline fill Scanline rendering Flicker
23.
Generation loss
–
Generation loss is the loss of quality between subsequent copies or transcodes of data. Anything that reduces the quality of the representation when copying, and would cause further reduction in quality on making a copy of the copy, can be considered a form of generation loss. File size increases are a result of generation loss, as the introduction of artifacts may actually increase the entropy of the data through each generation. In analog systems, generation loss is due to noise and bandwidth issues in cables, amplifiers, mixers, recording equipment. Poorly adjusted distribution amplifiers and mismatched impedances can make these problems even worse, repeated conversion between analog and digital can also cause loss. Careful planning was required to minimize loss, and the resulting noise. According to ATIS, Generation loss is limited to analog recording because digital recording, used correctly, digital technology can eliminate generation loss. Copying a digital file gives a copy if the equipment is operating properly. This trait of digital technology has given rise to awareness of the risk of unauthorized copying, before digital technology was widespread, a record label, for example, could be confident knowing that unauthorized copies of their music tracks were never as good as the originals. Processing a lossily compressed file rather than an original usually results in loss of quality than generating the same output from an uncompressed original. For example, a digital image for a web page is better if generated from an uncompressed raw image than from an already-compressed JPEG file of higher quality. In digital systems, several techniques, used because of advantages, may introduce generation loss. However, copying a digital file itself incurs no generation loss--the copied file is identical to the original, some digital transforms are reversible, while some are not. Lossless compression is, by definition, fully reversible, while lossy compression throws away some data which cannot be restored, similarly, many DSP processes are not reversible. Thus careful planning of an audio or video signal chain from beginning to end, similarly, when using lossy compression, it will ideally only be done once, at the end of the workflow involving the file, after all required changes have been made. Repeated applications of lossy compression and decompression can cause generation loss, some lossy compression algorithms are much worse than others in this regard, being neither idempotent nor scalable, and introducing further degradation if parameters are changed. For example, with JPEG, changing the quality setting will cause different quantization constants to be used, causing additional loss. Further, as JPEG is divided into 16×16 blocks, cropping that does not fall on an 8×8 boundary shifts the encoding blocks and this can be avoided by the use of jpegtran or similar tools for cropping
24.
Probability
–
Probability is the measure of the likelihood that an event will occur. Probability is quantified as a number between 0 and 1, the higher the probability of an event, the more certain that the event will occur. A simple example is the tossing of a fair coin, since the coin is unbiased, the two outcomes are both equally probable, the probability of head equals the probability of tail. Since no other outcomes are possible, the probability is 1/2 and this type of probability is also called a priori probability. Probability theory is used to describe the underlying mechanics and regularities of complex systems. For example, tossing a coin twice will yield head-head, head-tail, tail-head. The probability of getting an outcome of head-head is 1 out of 4 outcomes or 1/4 or 0.25 and this interpretation considers probability to be the relative frequency in the long run of outcomes. A modification of this is propensity probability, which interprets probability as the tendency of some experiment to yield a certain outcome, subjectivists assign numbers per subjective probability, i. e. as a degree of belief. The degree of belief has been interpreted as, the price at which you would buy or sell a bet that pays 1 unit of utility if E,0 if not E. The most popular version of subjective probability is Bayesian probability, which includes expert knowledge as well as data to produce probabilities. The expert knowledge is represented by some prior probability distribution and these data are incorporated in a likelihood function. The product of the prior and the likelihood, normalized, results in a probability distribution that incorporates all the information known to date. The scientific study of probability is a development of mathematics. Gambling shows that there has been an interest in quantifying the ideas of probability for millennia, there are reasons of course, for the slow development of the mathematics of probability. Whereas games of chance provided the impetus for the study of probability. According to Richard Jeffrey, Before the middle of the century, the term probable meant approvable. A probable action or opinion was one such as people would undertake or hold. However, in legal contexts especially, probable could also apply to propositions for which there was good evidence, the sixteenth century Italian polymath Gerolamo Cardano demonstrated the efficacy of defining odds as the ratio of favourable to unfavourable outcomes
25.
Decision theory
–
Decision theory is the study of the reasoning underlying an agents choices. Decision theory is a topic, studied by economists, statisticians, psychologists, political and social scientists. Empirical applications of this theory are usually done with the help of statistical and econometric methods, especially via the so-called choice models. Estimation of such models is usually done via parametric, semi-parametric and non-parametric maximum likelihood methods, the practical application of this prescriptive approach is called decision analysis, and is aimed at finding tools, methodologies and software to help people make better decisions. In contrast, positive or descriptive decision theory is concerned with describing observed behaviors under the assumption that the agents are behaving under some consistent rules. The prescriptions or predictions about behaviour that positive decision theory produces allow for further tests of the kind of decision-making that occurs in practice, there is a thriving dialogue with experimental economics, which uses laboratory and field experiments to evaluate and inform theory. The area of choice under uncertainty represents the heart of decision theory and he gives an example in which a Dutch merchant is trying to decide whether to insure a cargo being sent from Amsterdam to St Petersburg in winter. In his solution, he defines a utility function and computes expected utility rather than expected financial value, the phrase decision theory itself was used in 1950 by E. L. Lehmann. At this time, von Neumann and Morgenstern theory of expected utility proved that expected utility maximization followed from basic postulates about rational behavior, the work of Maurice Allais and Daniel Ellsberg showed that human behavior has systematic and sometimes important departures from expected-utility maximization. The prospect theory of Daniel Kahneman and Amos Tversky renewed the study of economic behavior with less emphasis on rationality presuppositions. Pascals Wager is an example of a choice under uncertainty. Intertemporal choice is concerned with the kind of choice where different actions lead to outcomes that are realised at different points in time, what is the optimal thing to do. The answer depends partly on factors such as the rates of interest and inflation, the persons life expectancy. Some decisions are difficult because of the need to take into account how people in the situation will respond to the decision that is taken. The analysis of such decisions is more often treated under the label of game theory, rather than decision theory. From the standpoint of game theory most of the treated in decision theory are one-player games. Other areas of decision theory are concerned with decisions that are difficult simply because of their complexity, one example is the model of economic growth and resource usage developed by the Club of Rome to help politicians make real-life decisions in complex situations. Decisions are also affected by whether options are framed together or separately, one example of common and incorrect thought process is the gamblers fallacy, or believing that a random event is affected by previous random events
26.
Aesthetics
–
Aesthetics is a branch of philosophy that explores the nature of art, beauty, and taste, with the creation and appreciation of beauty. It is more defined as the study of sensory or sensori-emotional values, sometimes called judgements of sentiment. More broadly, scholars in the field define aesthetics as critical reflection on art, in modern English, the term aesthetic can also refer to a set of principles underlying the works of a particular art movement or theory, one speaks, for example, of the Cubist aesthetic. The word aesthetic is derived from the Greek αἰσθητικός, which in turn was derived from αἰσθάνομαι, for some, aesthetics is considered a synonym for the philosophy of art since Hegel, while others insist that there is a significant distinction between these closely related fields. In practice, aesthetic judgement refers to the sensory contemplation or appreciation of an object, philosophical aesthetics has not only to speak about art and to produce judgments about art works, but has also to give a definition of what art is. Art is an entity for philosophy, because art deals with the senses. Hence, there are two different conceptions of art in aesthetics, art as knowledge or art as action, any aesthetic doctrines that guided the production and interpretation of prehistoric art are mostly unknown. Western aesthetics usually refers to Greek philosophers as the earliest source of aesthetic considerations. Plato believed in beauty as a form in which beautiful objects partake and he felt that beautiful objects incorporated proportion, harmony, and unity among their parts. Similarly, in the Metaphysics, Aristotle found that the elements of beauty were order, symmetry. From the late 17th to the early 20th century Western aesthetics underwent a revolution into what is often called modernism. German and British thinkers emphasized beauty as the key component of art and of the aesthetic experience, and saw art as necessarily aiming at absolute beauty. For Alexander Gottlieb Baumgarten aesthetics is the science of the experiences, a younger sister of logic. For Immanuel Kant the aesthetic experience of beauty is a judgment of a subjective but similar human truth, however, beauty cannot be reduced to any more basic set of features. For Friedrich Schiller aesthetic appreciation of beauty is the most perfect reconciliation of the sensual and rational parts of human nature, for Friedrich Wilhelm Joseph Schelling, the philosophy of art is the organon of philosophy concerning the relation between man and nature. So aesthetics began now to be the name for the philosophy of art, Friedrich von Schlegel, August Wilhelm Schlegel, Friedrich Schleiermacher and Georg Wilhelm Friedrich Hegel also gave lectures on aesthetics as philosophy of art after 1800. For Hegel, all culture is a matter of absolute spirit coming to be manifest to itself, stage by stage, Art is the first stage in which the absolute spirit is manifest immediately to sense-perception, and is thus an objective rather than subjective revelation of beauty. It is thus for Schopenhauer one way to fight the suffering, the British were largely divided into intuitionist and analytic camps
27.
Quantization (signal processing)
–
Quantization, in mathematics and digital signal processing, is the process of mapping a large set of input values to a smaller set. Rounding and truncation are typical examples of quantization processes, quantization is involved to some degree in nearly all digital signal processing, as the process of representing a signal in digital form ordinarily involves rounding. Quantization also forms the core of essentially all lossy compression algorithms, the difference between an input value and its quantized value is referred to as quantization error. A device or algorithmic function that performs quantization is called a quantizer, an analog-to-digital converter is an example of a quantizer. Because quantization is a mapping, it is an inherently non-linear. The set of input values may be infinitely large, and may possibly be continuous. The set of output values may be finite or countably infinite. The input and output involved in quantization can be defined in a rather general way. For example, vector quantization is the application of quantization to multi-dimensional input data, outside the realm of signal processing, this category may simply be called rounding or scalar quantization. An ADC can be modeled as two processes, sampling and quantization, sampling converts a voltage signal into a discrete-time signal. Quantization replaces each real number with an approximation from a set of discrete values. Most commonly, these values are represented as fixed-point words or floating-point words. Common word-lengths are 8-bit, 16-bit, 32-bit, and so on, quantizing a sequence of numbers produces a sequence of quantization errors which is sometimes modeled as an additive random signal called quantization noise because of its stochastic behavior. The more levels a quantizer uses, the lower is its noise power. In general, both ADC processes lose some information, so discrete-valued signals are only an approximation of the continuous-valued discrete-time signal, which is itself only an approximation of the original continuous-valued continuous-time signal. But both types of errors can, in theory, be made arbitrarily small by good design. In this second setting, the amount of introduced distortion may be managed carefully by sophisticated techniques, a quantizer designed for this purpose may be quite different and more elaborate in design than an ordinary rounding operation. It is in this domain that substantial rate–distortion theory analysis is likely to be applied, however, the same concepts actually apply in both use cases
28.
Transparency (data compression)
–
In data compression and psychoacoustics, transparency is the result of lossy data compression accurate enough that the compressed result is perceptually indistinguishable from the uncompressed input. In other words, transparent compression has no or imperceptible compression artifacts, a transparency threshold is a given value at which transparency is reached. It is commonly used to describe compressed data bitrates, for example, the transparency threshold for MP3 to Linear PCM audio is said to be between 175 and 245 kbit/s, at 44.1 kHz, when encoded as VBR MP3. This means that when an MP3 that was encoded at those bitrates is being played back, it is indistinguishable from the original PCM, Transparency, like sound or video quality, is subjective. Despite this, sometimes general consensus is formed for what compression options should provide transparent results for most people on most equipment. Due to the subjectivity and the nature of compression, recording. Judging transparency can be difficult, due to bias, in which subjective like/dislike of a certain compression methodology emotionally influences his or her judgment. This bias is referred to as placebo, although this use is slightly different from the medical use of the term. To scientifically prove that a method is not transparent, double-blind tests may be useful. The ABX method is used, with a null hypothesis that the samples tested are the same. All lossless data compression methods are transparent, by nature, however, a double-blind comparison could still yield claims of perceived differences and thus lack of transparency, even though such claims would be in error. Codec listening test Ascertaining high fidelity, double-blind tests Bosi, Marina, introduction to digital audio coding and standards. ISBN 1-4020-7357-7 Cvejic, Nedeljko, Tapio Seppänen, digital audio watermarking techniques and technologies, applications and benchmarks. ISBN 0-07-144156-5 Spanias, Andreas, Ted Painter, Venkatraman Atti, multimedia technologies, concepts, methodologies, tools, and applications, Volume 3. ISBN 1-59904-953-8 Transparency, Hydrogen Audio Wiki
29.
ABX test
–
An ABX test is a method of comparing two choices of sensory stimuli to identify detectable differences between them. A subject is presented with two known samples followed by one unknown sample X that is selected from either A or B. The subject is required to identify X as either A or B. ABX tests can easily be performed as double-blind trials, eliminating any possible influence from the researcher or the test supervisor. Because samples A and B are provided just prior to sample X, thus, the ABX test answers whether or not, under ideal circumstances, a perceptual difference can be found. ABX tests are used in evaluations of digital audio data compression methods, sample A is typically an uncompressed sample. Audible compression artifacts that indicate a shortcoming in the algorithm can be identified with subsequent testing. ABX tests can also be used to compare the different degrees of fidelity loss between two different audio formats at a given bitrate, ABX tests can be used to audition input, processing, and output components as well as cabling, virtually any audio product or prototype design. The history of ABX testing and naming dates back to 1950 in a paper published by two Bell Labs researchers, W. A. Munson and Mark B, the procedure, which we have called the “ABX” test, is a modification of the method of paired comparisons. An observer is presented with a sequence of three signals for each judgment he is asked to make. During the first time interval he hears signal A, during the second, signal B and his task is to indicate whether the sound heard during the X interval was more like that during the A interval or more like that during the B interval. For a threshold test, the A interval is quiet, the B interval is signal, the test has evolved to other variations such as user control over duration and sequence of testing. A button was provided which would select at random component A or B, identifying one of these, the X component was greatly hampered by not having the known A and B available for reference. This was corrected by using three interlocked pushbuttons, A, B, and X, once an X was selected, it would remain that particular A or B until it was decided to move on to another random selection. However, another problem quickly became obvious, there was always an audible relay transition time delay when switching from A to B. When switching from A to X, however, the delay would be missing if X was really A. This extraneous cue was removed by inserting a fixed length dropout time when any change was made, the dropout time was selected to be 50 ms which produces a slight consistent click while allowing subjectively instant comparison. The ABX company is now defunct and hardware comparators in general as commercial offerings extinct, myriad of software tools exist such as Foobar ABX plug-in for performing file comparisons
30.
Streaming video
–
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a provider. A client end-user can use their player to begin to play the data file before the entire file has been transmitted. For example, in the 1930s, elevator music was among the earliest popularly available streaming media, the term streaming media can apply to media other than video and audio such as live closed captioning, ticker tape, and real-time text, which are all considered streaming text. As of 2017, streaming is generally taken to refer to cases where a user watches digital video content or listens to audio content on a computer screen. With streaming content, the user does not have to download the digital video or digital audio file before they start to watch/listen to it. There are challenges with streaming content on the Internet, as of 2016, two popular streaming services are the video sharing website YouTube, which contains video and audio files on a huge range of topics and Netflix, which streams movies and TV shows. Live streaming refers to Internet content delivered in real-time, as events happen, Live internet streaming requires a form of source media, an encoder to digitize the content, a media publisher, and a content delivery network to distribute and deliver the content. Live streaming does not need to be recorded at the origination point, in the early 1920s, George O. Attempts to display media on computers date back to the earliest days of computing in the mid-20th century, however, little progress was made for several decades, primarily due to the high cost and limited capabilities of computer hardware. From the late 1980s through the 1990s, consumer-grade personal computers became powerful enough to various media. These technological improvement facilitated the streaming of audio and video content to users in their homes and workplaces. The band Severe Tire Damage was the first group to live on the Internet. On June 24,1993, the band was playing a gig at Xerox PARC while elsewhere in the building, as proof of PARCs technology, the bands performance was broadcast and could be seen live in Australia and elsewhere. Microsoft Research developed a Microsoft TV application which was compiled under MS Windows Studio Suite, realNetworks was also a pioneer in the streaming media markets, when it broadcast a baseball game between the New York Yankees and the Seattle Mariners over the Internet in 1995. The first symphonic concert on the Internet took place at the Paramount Theater in Seattle, the concert was a collaboration between The Seattle Symphony and various guest musicians such as Slash, Matt Cameron, and Barrett Martin. When Word Magazine launched in 1995, they featured the first-ever streaming soundtracks on the Internet.4 in 1999, in June 1999 Apple also introduced a streaming media format in its QuickTime 4 application. It was later widely adopted on websites along with RealPlayer. In 2000 Industryview. com launched its worlds largest streaming video archive website to help promote themselves
31.
Netflix
–
Netflix is an American entertainment company founded by Reed Hastings and Marc Randolph on August 29,1997, in Scotts Valley, California. It specializes in and provides streaming media and video-on-demand online and DVD by mail, in 2013, Netflix expanded into film and television production, as well as online distribution. As of 2017 the company has its headquarters in Los Gatos, Netflixs initial business model included DVD sales and rental, although Hastings jettisoned DVD sales about a year after Netflixs founding to focus on the DVD rental by mail business. In 2007, Netflix expanded its business with the introduction of streaming media, while retaining the DVD, Netflix entered the content-production industry in 2013, debuting its first series, House of Cards. It has greatly expanded the production of film and television series since then, offering Netflix Original content through its online library of films. Netflix released an estimated 126 original series or films in 2016, in January 2017, Netflix reported having over 93 million subscribers worldwide, including more than 49 million in the United States. Netflix was founded on August 29,1997, in Scotts Valley, California, by Marc Randolph, Randolph worked as marketing director for Hastings company, Pure Atria Corporation. Randolph was a co-founder of MicroWarehouse, a mail order company. Hastings, a computer scientist and mathematician, sold Pure Atria to Rational Software Corporation in 1997 for $700 million in what was then the richest acquisition in Silicon Valley history. Hastings, Randolphs mother and Integrity QA founder Steve Kahn invested $2.5 million in cash for Netflix. Randolph admired the fledgling e-commerce company Amazon and wanted to find a category of portable items to sell over the internet using a similar model. He and Hastings considered and rejected VHS tapes as too expensive to stock and too delicate to ship. When they heard about DVDs, which were available in only a few markets in 1997, when the disc arrived intact, they decided to take on the $16 billion home video sales and rental industry. Netflix introduced the monthly subscription concept in September 1999, and then dropped the model in early 2000. Since that time, the company has built its reputation on the model of flat-fee unlimited rentals without due dates, late fees, shipping and handling fees. In 2000, Netflix offered to be acquired by Blockbuster for $50 million, Netflix initiated an initial public offering on May 29,2002, selling 5.5 million shares of common stock at the price of US$15.00 per share. On June 14,2002, the company sold an additional 825,000 shares of stock at the same price. After incurring substantial losses during its first few years, Netflix posted its first profit during fiscal year 2003, in 2005,35,000 different films were available, and Netflix shipped 1 million DVDs out every day
32.
Streaming audio
–
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a provider. A client end-user can use their player to begin to play the data file before the entire file has been transmitted. For example, in the 1930s, elevator music was among the earliest popularly available streaming media, the term streaming media can apply to media other than video and audio such as live closed captioning, ticker tape, and real-time text, which are all considered streaming text. As of 2017, streaming is generally taken to refer to cases where a user watches digital video content or listens to audio content on a computer screen. With streaming content, the user does not have to download the digital video or digital audio file before they start to watch/listen to it. There are challenges with streaming content on the Internet, as of 2016, two popular streaming services are the video sharing website YouTube, which contains video and audio files on a huge range of topics and Netflix, which streams movies and TV shows. Live streaming refers to Internet content delivered in real-time, as events happen, Live internet streaming requires a form of source media, an encoder to digitize the content, a media publisher, and a content delivery network to distribute and deliver the content. Live streaming does not need to be recorded at the origination point, in the early 1920s, George O. Attempts to display media on computers date back to the earliest days of computing in the mid-20th century, however, little progress was made for several decades, primarily due to the high cost and limited capabilities of computer hardware. From the late 1980s through the 1990s, consumer-grade personal computers became powerful enough to various media. These technological improvement facilitated the streaming of audio and video content to users in their homes and workplaces. The band Severe Tire Damage was the first group to live on the Internet. On June 24,1993, the band was playing a gig at Xerox PARC while elsewhere in the building, as proof of PARCs technology, the bands performance was broadcast and could be seen live in Australia and elsewhere. Microsoft Research developed a Microsoft TV application which was compiled under MS Windows Studio Suite, realNetworks was also a pioneer in the streaming media markets, when it broadcast a baseball game between the New York Yankees and the Seattle Mariners over the Internet in 1995. The first symphonic concert on the Internet took place at the Paramount Theater in Seattle, the concert was a collaboration between The Seattle Symphony and various guest musicians such as Slash, Matt Cameron, and Barrett Martin. When Word Magazine launched in 1995, they featured the first-ever streaming soundtracks on the Internet.4 in 1999, in June 1999 Apple also introduced a streaming media format in its QuickTime 4 application. It was later widely adopted on websites along with RealPlayer. In 2000 Industryview. com launched its worlds largest streaming video archive website to help promote themselves
33.
Spotify
–
Spotify is a music, podcast, and video streaming service, officially launched on 7 October 2008. It is developed by startup Spotify AB in Stockholm, Sweden and it provides digital rights management-protected content from record labels and media companies. Spotify is available in most of Europe, most of the Americas, Australia, New Zealand and it is available for most modern devices, including Windows, macOS, and Linux computers, as well as iOS and Android smartphones and tablets. Music can be browsed or searched for via various parameters, such as artist, album, genre, playlist, users can create, edit and share playlists, share tracks on social media, and make playlists with other users. Spotify provides access to over 30 million songs, as of June 2016, it has 100 million monthly active users, and as of March 2017, it has 50 million paying subscribers. They distribute approximately 70% of total revenue to rights holders, who then pay based on their individual agreements. Spotify operates under a freemium model, Spotify makes its revenues by selling premium streaming subscriptions to users and advertising placements to third parties. In December 2013, the company launched a new website, Spotify for Artists, Spotify gets its content from major record labels as well as independent artists, and pays copyright holders royalties for streamed music. The company pays 70% of its revenue to rights holders. Spotify for Artists states that the company does not have a fixed rate, instead considers factors such as the users home country. Rights holders received an average per-play payout between $.006 and $.0084, Spotify offers an unlimited subscription package, close to the Open Music Model —estimated economic equilibrium—for the recording industry. However, the incorporation of digital rights management protection diverges from the OMM and competitors such as iTunes Store, Spotify encourages people to pay for music, with subscriptions as its main revenue source. The subscription removes advertisements and limits, and increases song bitrates to 320 kbit/s, the website also claims that a Spotify customer is 1. 6x more financially valuable than the average adult non-Spotify U. S. music consumer. Additionally, the website includes a section entitled Spotifys impact on piracy as a response to the criticisms against the company regarding the exploitation of musicians. For example, in Norway, the figure of 1.2 billion unauthorized song downloads in 2008 is compared to a figure of 210 million from 2012, BBC Music Week editor Tim Ingham wrote, Unlike buying a CD or download, streaming is not a one-off payment. Hundreds of millions of streams of tracks are happening each and every day, which quickly multiplies the potential revenues on offer – and is a constant long-term source of income for artists. As of June 2016, the three Spotify subscription types, all offering unlimited listening time, are, In 2008, just after launch, in October 2010, Wired reported that Spotify was making more money for labels in Sweden than any other retailer online or off. Years after growth and expansion, a November 2012 report suggested strong momentum for the company
. PMID 22347940.
