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105-483: JPEG ( / ˈ dʒ eɪ p ɛ ɡ / JAY -peg , short for Joint Photographic Experts Group ) is a commonly used method of lossy compression for digital images , particularly for those images produced by digital photography . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality . JPEG typically achieves 10:1 compression with little perceptible loss in image quality. Since its introduction in 1992, JPEG has been
210-468: A better representation of data. Another use is for backward compatibility and graceful degradation : in color television, encoding color via a luminance - chrominance transform domain (such as YUV ) means that black-and-white sets display the luminance, while ignoring the color information. Another example is chroma subsampling : the use of color spaces such as YIQ , used in NTSC , allow one to reduce
315-451: A lossless graphics format such as TIFF , GIF , PNG , or a raw image format . The JPEG standard includes a lossless coding mode, but that mode is not supported in most products. As the typical use of JPEG is a lossy compression method, which reduces the image fidelity, it is inappropriate for exact reproduction of imaging data (such as some scientific and medical imaging applications and certain technical image processing work). JPEG
420-433: A master lossless file which can then be used to produce additional copies from. This allows one to avoid basing new compressed copies off of a lossy source file, which would yield additional artifacts and further unnecessary information loss . It is possible to compress many types of digital data in a way that reduces the size of a computer file needed to store it, or the bandwidth needed to transmit it, with no loss of
525-472: A JPEG of cover art in the ID3v2 tag. Many JPEG files embed an ICC color profile ( color space ). Commonly used color profiles include sRGB and Adobe RGB . Because these color spaces use a non-linear transformation, the dynamic range of an 8-bit JPEG file is about 11 stops ; see gamma curve . If the image doesn't specify color profile information ( untagged ), the color space is assumed to be sRGB for
630-403: A block boundary for all channels (because the edge would end up on top or left, where – as aforementioned – a block boundary is obligatory). Rotations where the image is not a multiple of 8 or 16, which value depends upon the chroma subsampling, are not lossless. Rotating such an image causes the blocks to be recomputed which results in loss of quality. When using lossless cropping, if
735-470: A calendar issued by the TSB. SGs are augmented by Focus Groups (FGs), an instrument created by ITU-T, providing a way to quickly react to ICT standardization needs and allowing great flexibility in terms of participation and working methods. The key difference between SGs and FGs is that the latter have greater freedom to organize and finance themselves, and to involve non-members in their work, but they do not have
840-403: A certain amount of information, and there is a lower bound to the size of a file that can still carry all the information. Basic information theory says that there is an absolute limit in reducing the size of this data. When data is compressed, its entropy increases, and it cannot increase indefinitely. For example, a compressed ZIP file is smaller than its original, but repeatedly compressing
945-688: A fourth lawsuit on January 8, 2008, in South Florida against the Boca Raton Resort & Club . A fifth lawsuit was filed against Global Patent Holdings in Nevada. That lawsuit was filed by Zappos.com , Inc., which was allegedly threatened by Global Patent Holdings, and sought a judicial declaration that the '341 patent is invalid and not infringed. Global Patent Holdings had also used the '341 patent to sue or threaten outspoken critics of broad software patents, including Gregory Aharonian and
1050-411: A lossy form of compression based on the discrete cosine transform (DCT) . This mathematical operation converts each frame/field of the video source from the spatial (2D) domain into the frequency domain (a.k.a. transform domain). A perceptual model based loosely on the human psychovisual system discards high-frequency information, i.e. sharp transitions in intensity, and color hue. In the transform domain,
1155-507: A lossy format and a lossless correction which when combined reproduce the original signal; the correction can be stripped, leaving a smaller, lossily compressed, file. Such formats include MPEG-4 SLS (Scalable to Lossless), WavPack , OptimFROG DualStream , and DTS-HD Master Audio in lossless (XLL) mode ). Researchers have performed lossy compression on text by either using a thesaurus to substitute short words for long ones, or generative text techniques, although these sometimes fall into
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#17327652963081260-545: A lot of fine detail during a very loud passage. Developing lossy compression techniques as closely matched to human perception as possible is a complex task. Sometimes the ideal is a file that provides exactly the same perception as the original, with as much digital information as possible removed; other times, perceptible loss of quality is considered a valid tradeoff. The terms "irreversible" and "reversible" are preferred over "lossy" and "lossless" respectively for some applications, such as medical image compression, to circumvent
1365-416: A profusion of software firms around the world were still furiously competing to shape the future of the electronic office , and was completed in 1999 long after Microsoft Office 's then-secret binary file formats had become established as the global de facto standard. The ITU-T now operates under much more streamlined processes. The time between an initial proposal of a draft document by a member company and
1470-458: A selective loss of the least significant data, rather than losing data across the board. Further, a transform coding may provide a better domain for manipulating or otherwise editing the data – for example, equalization of audio is most naturally expressed in the frequency domain (boost the bass, for instance) rather than in the raw time domain. From this point of view, perceptual encoding is not essentially about discarding data, but rather about
1575-520: A slow connection, allowing a reasonable preview after receiving only a portion of the data. However, support for progressive JPEGs is not universal. When progressive JPEGs are received by programs that do not support them (such as versions of Internet Explorer before Windows 7 ) the software displays the image only after it has been completely downloaded. There are also many medical imaging, traffic and camera applications that create and process 12-bit JPEG images both grayscale and color. 12-bit JPEG format
1680-582: 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 compression methods focus on the idiosyncrasies of human physiology , taking into account, for instance, that the human eye can see only certain wavelengths of light. The psychoacoustic model describes how sound can be highly compressed without degrading perceived quality. Flaws caused by lossy compression that are noticeable to
1785-473: A wide array of topics in the field of information and communication technologies (ICT) and attract high-ranking experts as speakers, and attendees from engineers to high-level management from all industry sectors. The technical work, the development of Recommendations, of ITU-T is managed by Study Groups (SGs), such as Study Group 13 for network standards, Study Group 16 for multimedia standards, and Study Group 17 for security standards, which are created by
1890-463: Is "image/jpeg", except in older Internet Explorer versions, which provide a MIME type of "image/pjpeg" when uploading JPEG images. JPEG files usually have a filename extension of "jpg" or "jpeg". JPEG/JFIF supports a maximum image size of 65,535×65,535 pixels, hence up to 4 gigapixels for an aspect ratio of 1:1. In 2000, the JPEG group introduced a format intended to be a successor, JPEG 2000 , but it
1995-582: Is a fast-track approval procedure that was developed to allow standards to be brought to market in the timeframe that industry now demands. The AAP is defined in ITU-T Recommendation A.8. This dramatic overhaul of standards-making by streamlining approval procedures was implemented in 2001 and is estimated to have cut the time involved in this critical aspect of the standardization process by 80 to 90 percent. This means that an average standard that took around four years to approve and publish until
2100-617: Is a main goal of transform coding, it also allows other goals: one may represent data more accurately for the original amount of space – for example, in principle, if one starts with an analog or high-resolution digital master , an MP3 file of a given size should provide a better representation than a raw uncompressed audio in WAV or AIFF file of the same size. 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
2205-545: Is a minimal file format which enables JPEG bitstreams to be exchanged between a wide variety of platforms and applications. This minimal format does not include any of the advanced features found in the TIFF JPEG specification or any application specific file format. Nor should it, for the only purpose of this simplified format is to allow the exchange of JPEG compressed images. Image files that employ JPEG compression are commonly called "JPEG files", and are stored in variants of
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#17327652963082310-433: Is a type of data compression used for digital images , digital audio signals , and digital video . The transformation is typically used to enable better (more targeted) quantization . Knowledge of the application is used to choose information to discard, thereby lowering its bandwidth . The remaining information can then be compressed via a variety of methods. When the output is decoded, the result may not be identical to
2415-493: Is also not well suited to files that will undergo multiple edits, as some image quality is lost each time the image is recompressed, particularly if the image is cropped or shifted, or if encoding parameters are changed – see digital generation loss for details. To prevent image information loss during sequential and repetitive editing, the first edit can be saved in a lossless format, subsequently edited in that format, then finally published as JPEG for distribution. JPEG uses
2520-571: 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 – ideally lossy compression is transparent (imperceptible), which can be verified via an ABX test . Data files using lossy compression are smaller in size and thus cost less to store and to transmit over the Internet, a crucial consideration for streaming video services such as Netflix and streaming audio services such as Spotify . When
2625-616: Is followed by a period and the Recommendation number, which uniquely identifies the Recommendation within the series. Often, a range of related Recommendations are further grouped within the series and given adjacent numbers, such as "H.200-H.499: Infrastructure of audiovisual services" or "H.260-H.279: Coding of moving video". Many numbers are "skipped" to give room for future Recommendations to be adjacent to related Recommendations. Recommendations can be revised or "superseded" and keep their existing Recommendation number. In addition to
2730-525: Is included in an Extended part of the JPEG specification. The libjpeg codec supports 12-bit JPEG and there even exists a high-performance version. Several alterations to a JPEG image can be performed losslessly (that is, without recompression and the associated quality loss) as long as the image size is a multiple of 1 MCU block (Minimum Coded Unit) (usually 16 pixels in both directions, for 4:2:0 chroma subsampling ). Utilities that implement this include: Blocks can be rotated in 90-degree increments, flipped in
2835-541: Is infringed by the downloading of JPEG images on either a website or through e-mail. If not invalidated, this patent could apply to any website that displays JPEG images. The patent was under reexamination by the U.S. Patent and Trademark Office from 2000 to 2007; in July 2007, the Patent Office revoked all of the original claims of the patent but found that an additional claim proposed by Global Patent Holdings (claim 17)
2940-403: Is lost and cannot be restored, possibly affecting image quality. There is an optional lossless mode defined in the JPEG standard. However, this mode is not widely supported in products. There is also an interlaced progressive JPEG format, in which data is compressed in multiple passes of progressively higher detail. This is ideal for large images that will be displayed while downloading over
3045-460: Is now free of charge online. (About 30 specifications jointly maintained by the ITU-T and ISO/IEC are not available for free to the public. ) ITU-T has moreover tried to facilitate cooperation between the various forums and standard-developing organizations (SDOs). This collaboration is necessary to avoid duplication of work and the consequent risk of conflicting standards in the market place. In
3150-478: Is often the case in practice, to produce a representation with lower resolution or lower fidelity than a given one, one needs to start with the original source signal and encode, or start with a compressed representation and then decompress and re-encode it ( transcoding ), though the latter tends to cause digital generation loss . Another approach is to encode the original signal at several different bitrates, and then either choose which to use (as when streaming over
3255-450: Is the discrete cosine transform (DCT), first published by Nasir Ahmed , T. Natarajan and K. R. Rao in 1974. Lossy compression is most commonly used to compress multimedia data ( audio , video , and images ), especially in applications such as streaming media and internet telephony . By contrast, lossless compression is typically required for text and data files, such as bank records and text articles. It can be advantageous to make
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3360-407: Is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size for storing, handling, and transmitting content. Higher degrees of approximation create coarser images as more details are removed. This is opposed to lossless data compression (reversible data compression) which does not degrade
3465-432: Is to ensure the efficient and timely production of standards covering all fields of telecommunications and Information Communication Technology (ICTs) on a worldwide basis, as well as defining tariff and accounting principles for international telecommunication services. The international standards that are produced by the ITU-T are referred to as " Recommendations " (with the word capitalized to distinguish its meaning from
3570-465: Is used in a number of image file formats . JPEG/ Exif is the most common image format used by digital cameras and other photographic image capture devices; along with JPEG/ JFIF , it is the most common format for storing and transmitting photographic images on the World Wide Web . These format variations are often not distinguished and are simply called JPEG. The MIME media type for JPEG
3675-851: The Plenipotentiary Conference (the top policy-making conference of ITU) saw a reform of ITU, giving the Union greater flexibility to adapt to an increasingly complex, interactive and competitive environment. The CCITT was renamed the Telecommunication Standardization Sector (ITU-T), as one of three Sectors of the Union alongside the Radiocommunication Sector ( ITU-R ) and the Telecommunication Development Sector ( ITU-D ). Historically,
3780-642: The World Telecommunication Standardization Assembly (WTSA) which is held every four years. As part of the deliberations, WTSA has instructed ITU to hold the Global Standards Symposium , which unlike WTSA is open to public for participation. The people involved in these SGs are experts in telecommunications from all over the world. There are currently 11 SGs. Study groups meet face to face (or virtually under exceptional circumstances) according to
3885-649: The chrominance channel). While unwanted information is destroyed, the quality of the remaining portion is unchanged. Some other transforms are possible to some extent, such as joining images with the same encoding (composing side by side, as on a grid) or pasting images such as logos onto existing images (both via Jpegjoin ), or scaling. Some changes can be made to the compression without re-encoding: The freeware Windows-only IrfanView has some lossless JPEG operations in its JPG_TRANSFORM plugin . Metadata, such as ID3 tags , Vorbis comments , or Exif information, can usually be modified or removed without modifying
3990-751: The French government invited international participants to a conference in Paris in 1865 to facilitate and regulate international telegraph services. A result of the conference was the founding of the forerunner of the modern ITU. At the 1925 Paris conference, the ITU created two consultative committees to deal with the complexities of the international telephone services, known as CCIF ( Comité Consultatif International Téléphonique ) and with long-distance telegraphy CCIT ( Comité Consultatif International des Communications Téléphoniques à grande distance ). In view of
4095-868: The ITU-T Recommendations, which have non-mandatory status unless they are adopted in national laws, ITU-T is also the custodian of a binding international treaty, the International Telecommunication Regulations. The ITRs go back to the earliest days of the ITU when there were two separate treaties, dealing with telegraph and telephone. The ITRs were adopted, as a single treaty, at the World Administrative Telegraphy and Telephone Conference held in Melbourne, 1988 (WATTC-88). The ITRs comprise ten articles which deal, inter alia , with
4200-459: The ITU-T side, ITU-T SG16 is the respective body. The original JPEG Group was organized in 1986, issuing the first JPEG standard in 1992, which was approved in September 1992 as ITU-T Recommendation T.81 and, in 1994, as ISO / IEC 10918-1 . The JPEG standard specifies the codec , which defines how an image is compressed into a stream of bytes and decompressed back into an image, but not
4305-666: The JIF image format. Most image capture devices (such as digital cameras) that output JPEG are actually creating files in the Exif format, the format that the camera industry has standardized on for metadata interchange. On the other hand, since the Exif standard does not allow color profiles, most image editing software stores JPEG in JFIF format, and includes the APP1 segment from the Exif file to include
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4410-503: The JPEG image compression standard infringes the '056 patent and has sued large numbers of websites, retailers, camera and device manufacturers and resellers. The patent was originally owned and assigned to General Electric. The patent expired in December 2007, but Princeton has sued large numbers of companies for "past infringement" of this patent. (Under U.S. patent laws, a patent owner can sue for "past infringement" up to six years before
4515-492: The JPEG standard. The JPEG committee has as one of its explicit goals that their standards (in particular their baseline methods) be implementable without payment of license fees, and they have secured appropriate license rights for their JPEG 2000 standard from over 20 large organizations. Beginning in August 2007, another company, Global Patent Holdings, LLC claimed that its patent ( U.S. patent 5,253,341 ) issued in 1993,
4620-523: The Recommendations of the CCITT were presented at plenary assemblies for endorsement, held every four years, and the full set of Recommendations were published after each plenary assembly. However, the delays in producing texts, and translating them into other working languages, did not suit the fast pace of change in the telecommunications industry. The rise of the personal computer industry in
4725-476: The SG chairman, in consultation with TSB, sets up a comment resolution process by the concerned experts. The revised text is then posted on the web for an additional review period of three weeks. Similar to the last call phase, in additional review the Recommendation is considered as approved if no comments are received. If comments are received, it is apparent that there are some issues that still need more work, and
4830-579: The amendment of ITRs through a World Conference on International Telecommunications (WCIT). Accordingly, in 1998 there began a process of review of the ITRs; and in 2009 extensive preparations began for such a conference, WCIT-12. In addition to "regional preparatory meetings", the ITU Secretariat developed 13 "Background Briefs on key issues" that were expected to be discussed at the conference. Convened by former ITU secretary-general Hamadoun Touré,
4935-399: The amount of data used for an image is important for responsive presentation, JPEG's compression benefits make JPEG popular. JPEG/ Exif is also the most common format saved by digital cameras. However, JPEG is not well suited for line drawings and other textual or iconic graphics, where the sharp contrasts between adjacent pixels can cause noticeable artifacts. Such images are better saved in
5040-443: The anonymous operator of a website blog known as the " Patent Troll Tracker ." On December 21, 2007, patent lawyer Vernon Francissen of Chicago asked the U.S. Patent and Trademark Office to reexamine the sole remaining claim of the '341 patent on the basis of new prior art. On March 5, 2008, the U.S. Patent and Trademark Office agreed to reexamine the '341 patent, finding that the new prior art raised substantial new questions regarding
5145-429: The approval process by providing equal opportunities for both sector members and member states in the approval of technical standards. A panel of SG experts drafts a proposal that is then forwarded at an SG meeting to the appropriate body which decides if it is sufficiently ready to be designated a draft text and thus gives its consent for further review at the next level. After this Consent has been given, TSB announces
5250-595: The authority to approve Recommendations. Focus Groups can be created very quickly, are usually short-lived and can choose their own working methods, leadership, financing, and types of deliverables. Current Focus Groups include the ITU-WHO Focus Group on Artificial Intelligence for Health (FG-AI4H) as well as Machine Learning for 5G (which developed Y.3172 ), Quantum Information Technologies for Networks , and Artificial Intelligence for Assisted and Autonomous Driving . The Alternative Approval Process (AAP)
5355-655: The basic similarity of many of the technical problems faced by the CCIF and CCIT , a decision was taken in 1956 to merge them into a single entity, the International Telegraph and Telephone Consultative Committee ( CCITT , in French : Comité Consultatif International Téléphonique et Télégraphique ). The first Plenary Assembly of the new organization was held in Geneva, Switzerland in December 1956. In 1992,
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#17327652963085460-477: The bottom or right side of the crop region is not on a block boundary, then the rest of the data from the partially used blocks will still be present in the cropped file and can be recovered. It is also possible to transform between baseline and progressive formats without any loss of quality, since the only difference is the order in which the coefficients are placed in the file. Furthermore, several JPEG images can be losslessly joined, as long as they were saved with
5565-440: The case of audio data, a popular form of transform coding is perceptual coding , which transforms the raw data to a domain that more accurately reflects the information content. For example, rather than expressing a sound file as the amplitude levels over time, one may express it as the frequency spectrum over time, which corresponds more accurately to human audio perception. While data reduction (compression, be it lossy or lossless)
5670-421: The common parlance sense of the word "recommendation"), as they become mandatory only when adopted as part of a national law. Since the ITU-T is part of the ITU, which is a United Nations specialized agency, its standards carry more formal international weight than those of most other standards development organizations that publish technical specifications of a similar form. At the initiative of Napoleon III ,
5775-417: The compressed data, optional 0xFF fill bytes may precede the marker"). Within the entropy-coded data, after any 0xFF byte, a 0x00 byte is inserted by the encoder before the next byte, so that there does not appear to be a marker where none is intended, preventing framing errors. Decoders must skip this 0x00 byte. This technique, called byte stuffing (see JPEG specification section F.1.2.3), is only applied to
5880-458: The data. The amount of data reduction possible using lossy compression is much higher than using 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 (e.g., for real-time communication or to reduce transmission times or storage needs). The most widely used lossy compression algorithm
5985-522: The definition of international telecommunication services, cooperation between countries and national administrations, safety of life and priority of telecommunications and charging and accounting principles. The adoption of the ITRs in 1988 is often taken as the start of the wider liberalization process in international telecommunications, though a few countries, including United States and United Kingdom, had made steps to liberalize their markets before 1988. The Constitution and Convention of ITU provides for
6090-601: The draft text and all comments are sent to the next Study Group meeting for further discussion and possible approval. Those Recommendations considered as having policy or regulatory implications are approved through what is known as the Traditional Approval Process (TAP), which allows a longer period for reflection and commenting by member states. TAP Recommendations are also translated into the six working languages of ITU (Arabic, Chinese, English, French, Russian, and Spanish). ITU-T Recommendations are
6195-505: The early 1980s created a new common practice among both consumers and businesses of adopting " bleeding edge " communications technology even if it was not yet standardized. Thus, standards organizations had to put forth standards much faster, or find themselves ratifying de facto standards after the fact. One of the most prominent examples of this was the Open Document Architecture project, which began in 1985 when
6300-624: The entropy-coded data, not to marker payload data. Note however that entropy-coded data has a few markers of its own; specifically the Reset markers (0xD0 through 0xD7), which are used to isolate independent chunks of entropy-coded data to allow parallel decoding, and encoders are free to insert these Reset markers at regular intervals (although not all encoders do this). There are other Start Of Frame markers that introduce other kinds of JPEG encodings. Lossy compression In information technology , lossy compression or irreversible compression
6405-506: The file format used to contain that stream. The Exif and JFIF standards define the commonly used file formats for interchange of JPEG-compressed images. JPEG standards are formally named as Information technology – Digital compression and coding of continuous-tone still images . ISO/IEC 10918 consists of the following parts: Ecma International TR /98 specifies the JPEG File Interchange Format (JFIF);
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#17327652963086510-444: The file size as if it had been compressed to a greater degree, but without more loss than this, is sometimes also possible. The primary programs for lossless editing of JPEGs are jpegtran , and the derived exiftran (which also preserves Exif information), and Jpegcrop (which provides a Windows interface). These allow the image to be cropped , rotated, flipped , and flopped , or even converted to grayscale (by dropping
6615-450: The file that were left for future use in the JIF standard and are not read by it, these standards add specific metadata. Thus, in some ways, JFIF is a cut-down version of the JIF standard in that it specifies certain constraints (such as not allowing all the different encoding modes), while in other ways, it is an extension of JIF due to the added metadata. The documentation for the original JFIF standard states: JPEG File Interchange Format
6720-563: The file will cause it to progressively lose quality. This is in contrast with lossless data compression , where data will not be lost via the use of such a procedure. Information-theoretical foundations for lossy data compression are provided by rate-distortion theory . 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. There are two basic lossy compression schemes: In some systems
6825-622: The filing of a lawsuit, so Princeton could theoretically have continued suing companies until December 2013.) As of March 2013, Princeton had suits pending in New York and Delaware against more than 55 companies. General Electric's involvement in the suit is unknown, although court records indicate that it assigned the patent to Princeton in 2009 and retains certain rights in the patent. The JPEG compression algorithm operates at its best on photographs and paintings of realistic scenes with smooth variations of tone and color. For web usage, where reducing
6930-412: The final approval of a full-status ITU-T Recommendation can now be as short as a few months (or less in some cases). This makes the standardization approval process in the ITU-T much more responsive to the needs of rapid technology development than in the ITU's historical past. New and updated Recommendations are published on an almost daily basis, and nearly all of the library of over 3,270 Recommendations
7035-510: The first "Office Action" of the second reexamination, finding the claim invalid based on nineteen separate grounds. On Nov. 24, 2009, a Reexamination Certificate was issued cancelling all claims. Beginning in 2011 and continuing as of early 2013, an entity known as Princeton Digital Image Corporation, based in Eastern Texas, began suing large numbers of companies for alleged infringement of U.S. patent 4,813,056 . Princeton claims that
7140-576: The first edition was published in June 2009. In 2002, Forgent Networks asserted that it owned and would enforce patent rights on the JPEG technology, arising from a patent that had been filed on October 27, 1986, and granted on October 6, 1987: U.S. patent 4,698,672 by Compression Labs ' Wen-Hsiung Chen and Daniel J. Klenke. While Forgent did not own Compression Labs at the time, Chen later sold Compression Labs to Forgent, before Chen went on to work for Cisco . This led to Forgent acquiring ownership over
7245-431: The following Exif segment, being less strict about requiring it to appear first. The most common filename extensions for files employing JPEG compression are .jpg and .jpeg , though .jpe , .jfif and .jif are also used. It is also possible for JPEG data to be embedded in other file types – TIFF encoded files often embed a JPEG image as a thumbnail of the main image; and MP3 files can contain
7350-404: The full information contained in the original file. A picture, for example, is converted to a digital file by considering it to be an array of dots and specifying the color and brightness of each dot. If the picture contains an area of the same color, it can be compressed without loss by saying "200 red dots" instead of "red dot, red dot, ...(197 more times)..., red dot." The original data contains
7455-478: The horizontal, vertical and diagonal axes and moved about in the image. Not all blocks from the original image need to be used in the modified one. The top and left edge of a JPEG image must lie on an 8 × 8 pixel block boundary (or 16 × 16 pixel for larger MCU sizes), but the bottom and right edge need not do so. This limits the possible lossless crop operations, and prevents flips and rotations of an image whose bottom or right edge does not lie on
7560-420: The human eye or ear are known as compression artifacts . 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. An important caveat about lossy compression (formally transcoding), is that editing lossily compressed files causes digital generation loss from
7665-837: The image. Thus a partial transmission is enough to preview the final image, in a lower resolution version, without creating a scaled and a full version too. ITU-T The International Telecommunication Union Telecommunication Standardization Sector ( ITU-T ) is one of the three Sectors (branches) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Communication Technology , such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPEG-4 AVC for video compression, between its Member States, Private Sector Members, and Academia Members. The World Telecommunication Standardization Assembly (WTSA),
7770-470: The internet – as in RealNetworks ' " SureStream " – or offering varying downloads, as at Apple's iTunes Store ), or broadcast several, where the best that is successfully received is used, as in various implementations of hierarchical modulation . Similar techniques are used in mipmaps , pyramid representations , and more sophisticated scale space methods. Some audio formats feature a combination of
7875-499: The list is U.S. patent 4,698,672 , filed by Compression Labs ' Wen-Hsiung Chen and Daniel J. Klenke in October 1986. The patent describes a DCT-based image compression algorithm, and would later be a cause of controversy in 2002 (see Patent controversy below). However, the JPEG specification did cite two earlier research papers by Wen-Hsiung Chen, published in 1977 and 1984. "JPEG" stands for Joint Photographic Experts Group ,
7980-499: The metadata in an almost-compliant way; the JFIF standard is interpreted somewhat flexibly. Strictly speaking, the JFIF and Exif standards are incompatible, because each specifies that its marker segment (APP0 or APP1, respectively) appear first. In practice, most JPEG files contain a JFIF marker segment that precedes the Exif header. This allows older readers to correctly handle the older format JFIF segment, while newer readers also decode
8085-518: The mid nineties, and two years until 1997, can now be approved in an average of two months, or as little as five weeks. Besides streamlining the underlying procedures involved in the approval process, an important contributory factor to the use of AAP is electronic document handling. Once the approval process has begun the rest of the process can be completed electronically, in the vast majority of cases, with no further physical meetings. The introduction of AAP also formalizes public/private partnership in
8190-400: The most widely used image compression standard in the world, and the most widely used digital image format , with several billion JPEG images produced every day as of 2015. The Joint Photographic Experts Group created the standard in 1992. JPEG was largely responsible for the proliferation of digital images and digital photos across the Internet and later social media . JPEG compression
8295-621: The name of the committee that created the JPEG standard and other still picture coding standards. The "Joint" stood for ISO TC97 WG8 and CCITT SGVIII. Founded in 1986, the group developed the JPEG standard during the late 1980s. The group published the JPEG standard in 1992. In 1987, ISO TC 97 became ISO/IEC JTC 1 and, in 1992, CCITT became ITU-T. Currently on the JTC1 side, JPEG is one of two sub-groups of ISO / IEC Joint Technical Committee 1 , Subcommittee 29, Working Group 1 ( ISO/IEC JTC 1/SC 29 /WG 1) – titled as Coding of still pictures . On
8400-421: The names given to telecommunications and computer protocol specification documents published by ITU-T. ITU-T assigns each Recommendation a name based on the series and Recommendation number. The name starts with the letter of the series the Recommendation belongs to. Each series encompasses a broad category of Recommendations, such as "H-Series Recommendations: Audiovisual and multimedia systems". The series letter
8505-515: 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, so-called diagnostically acceptable irreversible compression (DAIC) may have been applied. Some forms of lossy compression can be thought of as an application of transform coding , which
8610-523: The original input, but is expected to be close enough for the purpose of the application. The most common form of lossy compression is a transform coding method, the discrete cosine transform (DCT), which was first published by Nasir Ahmed , T. Natarajan and K. R. Rao in 1974. DCT is the most widely used form of lossy compression, for popular image compression formats (such as JPEG ), video coding standards (such as MPEG and H.264/AVC ) and audio compression formats (such as MP3 and AAC ). In
8715-403: The original, format conversion may be needed in the future to achieve compatibility with software or devices ( format shifting ), or to avoid paying patent royalties for decoding or distribution of compressed files. By modifying the compressed data directly without decoding and re-encoding, some editing of lossily compressed files without degradation of quality is possible. Editing which reduces
8820-463: The output bitstream. Nearly all software implementations of JPEG permit user control over the compression ratio (as well as other optional parameters), allowing the user to trade off picture-quality for smaller file size. In embedded applications (such as miniDV, which uses a similar DCT-compression scheme), the parameters are pre-selected and fixed for the application. The compression method is usually lossy , meaning that some original image information
8925-462: The patent's validity. In light of the reexamination, the accused infringers in four of the five pending lawsuits have filed motions to suspend (stay) their cases until completion of the U.S. Patent and Trademark Office's review of the '341 patent. On April 23, 2008, a judge presiding over the two lawsuits in Chicago, Illinois granted the motions in those cases. On July 22, 2008, the Patent Office issued
9030-577: The patent. Forgent's 2002 announcement created a furor reminiscent of Unisys ' attempts to assert its rights over the GIF image compression standard. The JPEG committee investigated the patent claims in 2002 and were of the opinion that they were invalidated by prior art , a view shared by various experts. Between 2002 and 2004, Forgent was able to obtain about US$ 105 million by licensing their patent to some 30 companies. In April 2004, Forgent sued 31 other companies to enforce further license payments. In July of
9135-583: The prior art, yet it intentionally avoided telling the Patent Office. This makes any appeal to reinstate the patent highly unlikely to succeed. Forgent also possesses a similar patent granted by the European Patent Office in 1994, though it is unclear how enforceable it is. As of October 27, 2006, the U.S. patent's 20-year term appears to have expired, and in November 2006, Forgent agreed to abandon enforcement of patent claims against use of
9240-526: The process of reducing information is called quantization. In simpler terms, quantization is a method for optimally reducing a large number scale (with different occurrences of each number) into a smaller one, and the transform-domain is a convenient representation of the image because the high-frequency coefficients, which contribute less to the overall picture than other coefficients, are characteristically small-values with high compressibility. The quantized coefficients are then sequenced and losslessly packed into
9345-402: The purposes of display on webpages. A JPEG image consists of a sequence of segments , each beginning with a marker , each of which begins with a 0xFF byte, followed by a byte indicating what kind of marker it is. Some markers consist of just those two bytes; others are followed by two bytes (high then low), indicating the length of marker-specific payload data that follows. (The length includes
9450-467: The re-encoding. This can be avoided by only producing lossy files from (lossless) originals and only editing (copies of) original files, such as images in raw image format instead of JPEG . If data which has been compressed lossily is decoded and compressed losslessly, the size of the result can be comparable with the size of the data before lossy compression, but the data already lost cannot be recovered. When deciding to use lossy conversion without keeping
9555-407: The related category of lossy data conversion . A general kind of lossy compression is to lower the resolution of an image, as in image scaling , particularly decimation . One may also remove less "lower information" parts of an image, such as by seam carving . Many media transforms, such as Gaussian blur , are, like lossy compression, irreversible: the original signal cannot be reconstructed from
9660-514: The resolution on the components to accord with human perception – humans have highest resolution for black-and-white (luma), lower resolution for mid-spectrum colors like yellow and green, and lowest for red and blues – thus NTSC displays approximately 350 pixels of luma per scanline , 150 pixels of yellow vs. green, and 50 pixels of blue vs. red, which are proportional to human sensitivity to each component. Lossy compression formats suffer from generation loss : repeatedly compressing and decompressing
9765-422: The same file will not reduce the size to nothing. Most compression algorithms can recognize when further compression would be pointless and would in fact increase the size of the data. In many cases, files or data streams contain more information than is needed. For example, a picture may have more detail than the eye can distinguish when reproduced at the largest size intended; likewise, an audio file does not need
9870-547: The same quality and the edges coincide with block boundaries. The file format known as "JPEG Interchange Format" (JIF) is specified in Annex B of the standard. However, this "pure" file format is rarely used, primarily because of the difficulty of programming encoders and decoders that fully implement all aspects of the standard and because of certain shortcomings of the standard: Several additional standards have evolved to address these issues. The first of these, released in 1992,
9975-729: The same year, a consortium of 21 large computer companies filed a countersuit, with the goal of invalidating the patent. In addition, Microsoft launched a separate lawsuit against Forgent in April 2005. In February 2006, the United States Patent and Trademark Office agreed to re-examine Forgent's JPEG patent at the request of the Public Patent Foundation. On May 26, 2006, the USPTO found the patent invalid based on prior art. The USPTO also found that Forgent knew about
10080-614: The sector's governing conference, convenes every four years. ITU-T has a permanent secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland . The current director of the TSB is Seizo Onoe (of Japan), whose 4-year term commenced on 1 January 2023. Seizo Onoe succeeded Chaesub Lee of South Korea, who was director from 1 January 2015 until 31 December 2022. The ITU-T mission
10185-549: The start of the AAP procedure by posting the draft text to the ITU-T website and calling for comments. This gives the opportunity for all members to review the text. This phase, called last call , is a four-week period in which comments can be submitted by member states and sector members. If no comments other than editorial corrections are received, the Recommendation is considered approved since no issues were identified that might need any further work. However, if there are any comments,
10290-474: The transformed signal. However, in general these will have the same size as the original, and are not a form of compression. Lowering resolution has practical uses, as the NASA New Horizons craft transmitted thumbnails of its encounter with Pluto-Charon before it sent the higher resolution images. Another solution for slow connections is the usage of Image interlacing which progressively defines
10395-509: The two bytes for the length, but not the two bytes for the marker.) Some markers are followed by entropy-coded data; the length of such a marker does not include the entropy-coded data. Note that consecutive 0xFF bytes are used as fill bytes for padding purposes, although this fill byte padding should only ever take place for markers immediately following entropy-coded scan data (see JPEG specification section B.1.1.2 and E.1.2 for details; specifically "In all cases where markers are appended after
10500-430: The two techniques are combined, with transform codecs being used to compress the error signals generated by the predictive stage. 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 lossless method, while still meeting the requirements of the application. Lossy methods are most often used for compressing sound, images or videos. This
10605-821: The underlying data. One may wish to downsample or otherwise decrease the resolution of the represented source signal and the quantity of data used for its compressed representation without re-encoding, as in bitrate peeling , but this functionality is not supported in all designs, as not all codecs encode data in a form that allows less important detail to simply be dropped. Some well-known designs that have this capability include JPEG 2000 for still images and H.264/MPEG-4 AVC based Scalable Video Coding for video. Such schemes have also been standardized for older designs as well, such as JPEG images with progressive encoding, and MPEG-2 and MPEG-4 Part 2 video, although those prior schemes had limited success in terms of adoption into real-world common usage. Without this capacity, which
10710-637: The work of standardization, ITU-T cooperates with other SDOs, e.g., the International Organization for Standardization (ISO) and the Internet Engineering Task Force (IETF). Most of the work of ITU-T is carried out by its Sector Members and Associates, while the Telecommunication Standardization Bureau (TSB) is the executive arm of ITU-T and coordinator for a number of workshops and seminars to progress existing work areas and explore new ones. The events cover
10815-481: Was the JPEG File Interchange Format (or JFIF), followed in recent years by Exchangeable image file format (Exif) and ICC color profiles . Both of these formats use the actual JIF byte layout, consisting of different markers , but in addition, employ one of the JIF standard's extension points, namely the application markers : JFIF uses APP0, while Exif uses APP1. Within these segments of
10920-581: Was unable to replace the original JPEG as the dominant image standard. The original JPEG specification published in 1992 implements processes from various earlier research papers and patents cited by the CCITT (now ITU-T ) and Joint Photographic Experts Group. The JPEG specification cites patents from several companies. The following patents provided the basis for its arithmetic coding algorithm. The JPEG specification also cites three other patents from IBM. Other companies cited as patent holders include AT&T (two patents) and Canon Inc. Absent from
11025-624: Was valid. Global Patent Holdings then filed a number of lawsuits based on claim 17 of its patent. In its first two lawsuits following the reexamination, both filed in Chicago, Illinois, Global Patent Holdings sued the Green Bay Packers , CDW , Motorola , Apple , Orbitz , Officemax , Caterpillar , Kraft and Peapod as defendants. A third lawsuit was filed on December 5, 2007, in South Florida against ADT Security Services , AutoNation , Florida Crystals Corp., HearUSA, MovieTickets.com , Ocwen Financial Corp. and Tire Kingdom , and
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