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Original Image (lossless PNG, 60.1 KiB size) — uncompressed is 108.5 KiB
Original Image (lossless PNG, 60. Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data Portable Network Graphics ( PNG) is a bitmapped image format that employs Lossless data compression. 1 KiB size) — uncompressed is 108. A kibibyte (a contraction of ki lo bi nary byte) is a unit of Information or Computer storage, established by the International 5 KiB
Low compression (84% less information than uncompressed PNG, 9.37 KiB)
Low compression (84% less information than uncompressed PNG, 9. 37 KiB)
Medium compression (92% less information than uncompressed PNG, 4.82 KiB)
Medium compression (92% less information than uncompressed PNG, 4. 82 KiB)
High compression (98% less information than uncompressed PNG, 1.14 KiB)
High compression (98% less information than uncompressed PNG, 1. 14 KiB)

A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is close enough to be useful in some way. Lossy compression is most commonly used to compress multimedia data (audio, video, still images), especially in applications such as streaming media and internet telephony. Multimedia is media and content that utilizes a combination of different content forms. Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually Streaming multimedia is Multimedia that is constantly received by and normally presented to an end-user while it is being delivered by a streaming provider (the Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet On the other hand lossless compression is required for text and data files, such as bank records, text articles, etc. Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data

Lossy compression formats suffer from generation loss: repeatedly compressing and decompressing the file will cause it to progressively lose quality. Generation loss refers to the loss of quality and potential increase of file size between subsequent copies of data This is in contrast with lossless data compression. Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data

Information-theoretical foundations for lossy data compression are provided by rate-distortion theory. Information theory is a branch of Applied mathematics and Electrical engineering involving the quantification of Information. Rate–distortion theory is a major branch of Information theory which provides the theoretical foundations for Lossy data compression; it addresses the problem of Much like the use of probability in optimal coding theory, rate-distortion theory heavily draws on Bayesian estimation and decision theory in order to model perceptual distortion and even aesthetic judgment. Probability is the likelihood or chance that something is the case or will happen Estimation theory is a branch of Statistics and Signal processing that deals with estimating the values of parameters based on measured/empirical data Decision theory in Mathematics and Statistics is concerned with identifying the Values uncertainties and other issues relevant in a given Aesthetics or esthetics ( also spelled æsthetics) is commonly known as the study of sensory or sensori-emotional values sometimes called

Contents

Types

There are two basic lossy compression schemes:

In some systems the two techniques are combined, with transform codecs being used to compress the error signals generated by the predictive stage.

Lossy versus lossless

The advantage of lossy methods over lossless methods is that in some cases a lossy method can produce a much smaller compressed file than any known lossless method, while still meeting the requirements of the application. Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data

Lossy methods are most often used for compressing sound, images or videos. This is because these types of data are intended for human interpretation where the mind can easily "fill in the blanks" or see past very minor errors or inconsistencies. The compression ratio (that is, the size of the compressed file compared to that of the uncompressed file) of lossy video codecs is nearly always far superior to that of the audio and still-image equivalents. Audio can often be compressed at 10:1 with imperceptible loss of quality, and video can be compressed immensely (e. g. 300:1) with little visible quality loss. Lossily compressed still images are often compressed to 1/10th their original size, as with audio, but the quality loss is more noticeable, especially on closer inspection.

When a user acquires a lossily compressed file, (for example, to reduce download-time) the retrieved file can be quite different from the original at the bit level while being indistinguishable to the human ear or eye for most practical purposes. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication Many methods focus on the idiosyncrasies of the human physiology, taking into account, for example, that the human eye can see only certain wavelengths of light. Human physiology is the science of the mechanical physical and biochemical functions of Humans in good health their organs and the cells of which they are composed The psychoacoustic model describes how sound can be highly compressed without degrading the perceived quality of the sound. Psychoacoustics is the study of subjective human Perception of Sounds Alternatively it can be described as the study of the Psychological correlates Flaws caused by lossy compression that are noticeable to the human eye or ear are known as compression artifacts. A compression artifact (or artefact) is the result of an aggressive Data compression scheme applied to an Image, audio, or Video

Methods

Graphics

Image

Video

Audio

Music

Speech

Other data

Researchers have (half-jokingly) performed lossy compression on text by either using a thesaurus to substitute short words for long ones, or generative text techniques [1], although these sometimes fall into the related category of lossy data conversion. JBIG2 is an Image compression standard for bi-level images developed by the Joint Bi-level Image Experts Group. PGF ( Progressive Graphics File) is a Wavelet -based bitmapped image format that employs lossless and Lossy data compression Wavelet compression is a form of Data compression well suited for Image compression (sometimes also Video compression and Audio compression) H261 is a 1990 ITU-T video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s H263 is a Video codec standard originally designed as a low-bitrate compressed format for Videoconferencing. H264 is a standard for Video compression. It is also known as MPEG-4 Part 10, or MPEG-4 AVC (for Advanced Video Coding) Multiple-image Network Graphics ( MNG, ˈmɪŋ is a public Graphics file format for animated images In Multimedia, Motion JPEG ( M-JPEG) is an informal name for multimedia formats where each Video frame or Interlaced field of a Digital video MPEG-1 was an early Standard for Lossy compression of Video and audio. MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information" MPEG-4 is a collection of methods defining compression of audio and visual (AV digital data To learn how to create video or audio files for Wikipedia and its sister projects check WikipediaCreation and usage of media files. Theora is an open and royalty-free Lossy Video compression technology being developed by the Xiph The Sorenson codec (also known as Sorenson Video Codec, Sorenson Video Quantizer or SVQ) is a Digital video Codec devised by the company VC-1 is the informal name of the SMPTE 421M Video codec standard initially developed by Microsoft. Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. Adaptive Transform Acoustic Coding ( ATRAC) is a family of proprietary audio compression algorithms developed by Sony. Dolby Digital is the marketing name for a series of lossy audio compression technologies developed by Dolby MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a Digital audio encoding format using a form of Lossy data compression Musepack or MPC is an Open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160&ndash180 To learn how to create video or audio files for Wikipedia and its sister projects check WikipediaCreation and usage of media files. Vorbis is a free and open source, lossy audio Codec project headed by the Xiph Windows Media Audio ( WMA) is an Audio data compression technology developed by Microsoft. Code excited linear prediction ( CELP) is a Speech coding algorithm originally proposed by M G711 is an ITU-T standard for audio Companding. It is primarily used in Telephony. G726 is an ITU-T ADPCM Speech codec standard covering the transmission of voice at rates of 16 24 32 and 40 kbit/s Harmonic and Individual Lines and Noise ( HILN) is a parametric Codec for audio. Adaptive Multi-Rate (AMR is an Audio data compression scheme optimized for Speech coding. Speex is a Free software speech codec that may be used on VoIP applications and Podcasts Speex claims to be free of any patent restrictions Natural Language Generation (NLG is the Natural language processing task of generating Natural language from a machine representation system such as a Knowledge A lossy Data conversion method is one where converting data between one storage format and another displays data in a form that is "close enough" to be useful but

See also

Notes

  1. ^ I. Lenna or Lena is the name given to a Standard test image originally cropped from a Playboy magazine Centerfold picture of Lena Söderberg Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data A compression artifact (or artefact) is the result of an aggressive Data compression scheme applied to an Image, audio, or Video The following is a list of Codecs Audio codecs See also Audio codec Non-compression formats Audio Interchange File Format H. WITTEN, et al. . Semantic and Generative Models for Lossy Text Compression (PDF). The Computer Journal. Retrieved on 2007-10-13. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 54 - Nero ascends to the Roman throne 409 - Vandals and Alans crossed the Pyrenees

External links

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