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A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is "close enough" to be useful in some way. Lossy data compression is most commonly used to compress multimedia data (audio, video, still images) especially in applications, such as streaming media and internet telephony. On the other hand lossless compression is preferred for text and data files, such as, bank records, text articles etc. In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ...
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Audio can mean: Sounding that can be heard. ...
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images which represent scenes in motion. ...
Image of the Wikimedia Commons logo. ...
Streaming media is media that is consumed (heard or viewed) (mostly in the form of clips) while it is being delivered. ...
IP Telephony, also called Internet telephony, is the technology that makes it possible to have a telephone conversation over the Internet or a dedicated Internet Protocol (IP) network instead of dedicated voice transmission lines. ...
Lossless data compression is a class of data compression algorithms that allow the original data to be reconstructed exactly from the compressed data. ...
Most lossy data compression formats suffer from generation loss: repeatedly compressing and decompressing the file will cause it to progressively lose quality. This is in contrast with lossless data compression. Generation loss refers to the loss of quality between subsequent copies of data. ...
Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. ...
Types of lossy compression There are two basic lossy compression schemes: - In lossy transform codecs, samples of picture or sound are taken, chopped into small segments, transformed into a new basis space, and quantized. The resulting quantized values are then entropy coded.
- In lossy predictive codecs, previous and/or subsequent decoded data is used to predict the current sound sample or image frame. The error between the predicted data and the real data, together with any extra information needed to reproduce the prediction, is then quantized and coded.
In some systems the two techniques are combined, with transform codecs being used to compress the error signals generated by the predictive stage. A Codec is a device or program capable of performing encoding and decoding on a digital data stream or signal. ...
Quantized signal Digital signal In digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values. ...
An entropy encoding is a coding scheme that assigns codes to symbols so as to match code lengths with the probabilities of the symbols. ...
Quantized signal Digital signal In digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values. ...
Lossy vs. Lossless Compression 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. The compression ratio (that is, the size of the compressed file compared to that of the uncompressed file) of lossy video codecs are nearly always far superior to those of the audio and still-image equivalents. Audio can often be compressed at 10:1 with imperceptible loss of quality, 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. Many methods focus on the idiosyncrasies of the human physiology, taking into account, for example, that the human eye can see only certain frequencies of light. The psychoacoustic model describes how sound can be highly compressed without degrading the perceived quality of the sound. Flaws caused by lossy compression that are noticeable to the human eye or ear are known as compression artifacts. A bit (binary digit) refers to a digit in the binary numeral system, which consists of base 2 digits (ie. ...
Human physiology is the science of the mechanical, physical, and biochemical functions of normal humans or human tissues or organs. ...
Psychoacoustics is the study of subjective human perception of sounds. ...
A compression artifact (or artefact) is the result of an aggressive data compression scheme applied to an image, audio, or video that discards some data which is determined by an algorithm to be of lesser importance to the overall content but which is nonetheless discernible and objectionable to the user. ...
Example of Lossy Compression
 Original Cropped Lenna Image (Filesize: 12KB ) |
 Cropped Lenna Image, Compressed (File size: 85% smaller, 1.8KB) |
 Cropped Lenna Image, Highly Compressed (File size: 96% smaller, 0.56KB) | The above images show the use of lossy compression to reduce the file size of the image. The image is an excerpt of the image of Lenna, a de facto industry-standard test image. The Lena image File links The following pages link to this file: Lossy data compression ...
The Lena image, compressed to JPG quality 30 File links The following pages link to this file: Lossy data compression ...
The Lena image, compressed to JPG quality 5 File links The following pages link to this file: Lossy data compression ...
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Image of Lena Söderberg famously used in many image processing experiments. ...
De facto is a Latin expression that means in fact or in practice. It is commonly used as opposed to de jure (meaning by law) when referring to matters of law or governance or technique (such as standards), that are found in the common experience as created or developed without...
In order to intuitively test the effects of an image-processing algorithm on a natural picture a number of test images are in common use in the image-processing field. ...
- The first picture is 12,249 bytes.
- The second picture has been compressed (JPEG quality 30) and is 85% smaller, at 1,869 bytes. Notice the loss of detail.
- The third picture has been highly compressed (JPEG quality 5) and is 96% smaller, at 559 bytes. The compression artifacts are much more noticeable and the loss of detail is great.
Even though the third image has high distortion, the face is still recognizable. Good lossy compression algorithms are able to throw away "less important" information and still retain the "essential" information. In computing, JPEG(pronounced JAY-peg; IPA: ) is a commonly used standard method of compression for photographic images and not for movie files for which MPEG compression is used. ...
A compression artifact (or artefact) is the result of an aggressive data compression scheme applied to an image, audio, or video that discards some data which is determined by an algorithm to be of lesser importance to the overall content but which is nonetheless discernible and objectionable to the user. ...
Rate distortion theory is the branch of information theory addressing the problem of determining the minimal amount of entropy (or information) R that should be communicated over a channel such that the source (input signal) can be reconstructed at the receiver (output signal) with given distortion D. As such, rate...
Lossy compression methods
Graphic compression
Image compression is the application of data compression on digital images. ...
Fractal compression is a lossy compression method used to compress images using fractals. ...
In computing, JPEG(pronounced JAY-peg; IPA: ) is a commonly used standard method of compression for photographic images and not for movie files for which MPEG compression is used. ...
JPEG 2000 is a wavelet-based image compression standard. ...
Wavelet compression is a form of data compression well suited for image compression (sometimes also video compression and audio compression). ...
JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. ...
Cartesian Perceptual Compression (abbreviated CPC) is a file format specifically designed for the compression of black-and-white raster images in document image storage and transmission systems. ...
DjVu (pronounced deja-vu) is a computer file format designed primarily to store scanned images, especially those containing text and line drawings. ...
ICER is a wavelet-based image compression file format used by the NASA Mars Rovers. ...
JPEG 2000 is a wavelet-based image compression standard. ...
Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ...
// == Macromedia Flash == ==]] Using Macromedia Flash 8 (bundled in Studio 8) in Windows XP. Maintainer: Adobe Systems (formerly Macromedia) Latest release: 8 / September 30th, 2005 OS: Windows (no native Windows XP Professional x64 Edition support), Mac OS X, Linux (i386 only, via wine [1]) Use: Multimedia Content Creator License: Proprietary Website...
H.261 is an 1990 ITU video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s. ...
H.263 is a video codec designed by the ITU-T as a low-bitrate encoding solution for videoconferencing. ...
H.264, MPEG-4 Part 10, or AVC, for Advanced Video Coding, is a digital video codec standard which is noted for achieving very high data compression. ...
This page is about MNG, the animated image file format. ...
Motion JPEG, also known as M-JPEG, is a video file format consisting of a sequence of individual JPEG images; unlike other video compression algorithms, each frame is an image unto itself. ...
MPEG-1 defines a group of Audio and Video (AV) coding and compression standards agreed upon by MPEG (Moving Picture Experts Group). ...
MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ...
MPEG-4 is a standard used primarily to compress audio and video (AV) digital data. ...
OGG can refer to several items: Ogg is a multimedia bitstream container, used for audio and video files, especially Vorbis audio files. ...
Theora is a video codec being developed by the Xiph. ...
The Sorenson codec (also known as Sorenson Video Codec 3 or SVQ3) is a digital video codec devised by the company Sorenson Media and used by Apples QuickTime and the newest version of Macromedia Flash, a special version called Sorenson Spark. ...
VC-1 is the informal name of the SMPTE 421M video codec standard. ...
Audio compression
Music compression This article or section may be confusing or unclear for some readers, and should be edited to rectify this. ...
Apple Computer, Inc. ...
Pulse-code modulation (PCM) is a modulation technique. ...
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Description Dolby Digital is the trademark for Dolby Laboratories AC-3 audio coding system. ...
MP2 can refer to: MP2 (format) audio files This is a disambiguation page, a list of pages that otherwise might share the same title. ...
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular digital audio encoding and lossy compression format, designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners. ...
Musepack or MPC is an open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160-180 kbit/s. ...
OGG can refer to several items: Ogg is a multimedia bitstream container, used for audio and video files, especially Vorbis audio files. ...
Vorbis is an open and free lossy audio compression codec project headed by the Xiph. ...
Windows Media Audio (WMA) is a proprietary compressed audio file format developed by Microsoft. ...
Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ...
- CELP
- G.711
- G.726
- HILN
- AMR (used by GSM cell carriers, such as T-Mobile)
- Speex (noted for its lack of patent restrictions)
Speech coding is the compression of speech (into a code) for transmission with speech codecs that use audio signal processing and speech processing techniques. ...
CELP stands for Code Excited Linear Prediction and is a speech coding algorithm described by the US Federal Standard FIPS 1016. ...
G.711 is an ITU-T standard for audio companding. ...
G.726 is ITU-T speech codec operating at bit rates of 16-40 kbit/s. ...
HILN or Harmonic and Individual Lines and Noise is a parametric audio codec for audio. ...
Adaptive Multi-Rate (AMR) is a Audio data compression scheme optimized for speech coding. ...
Speex is a free software speech codec that claims to be unencumbered by patent restrictions. ...
Other types of data Technically, reducing text size by removing all vowels can be considered a lossy data compression as well. The text is usually still readable from the context given by the consonants. Researchers have also (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. Note: This page contains IPA phonetic symbols in Unicode. ...
In articulatory phonetics, a consonant is a sound in spoken language that is characterized by a closure or stricture of the vocal tract sufficient to cause audible turbulence. ...
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 may differ in some ways from the original. ...
See also 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 that discards some data which is determined by an algorithm to be of lesser importance to the overall content but which is nonetheless discernible and objectionable to the user. ...
The following is a list of codecs. ...
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