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Topic: Data compression

Related Topics

Lossless data compression

Wavelet compression

Audio data compression

Image compression

PAQ

Lossy data compression

Universal code

Video compression

Delta encoding

PackBits

Arithmetic coding

LZW

LZ77

Huffman coding

Audio compression

	Data Compression
		Data compression is often referred to as coding, where coding is a very general term encompassing any special representation of data which satisfies a given need.
		Data compression may be viewed as a branch of information theory in which the primary objective is to minimize the amount of data to be transmitted.
		While the primary focus of this survey is data compression methods of general utility, Section 2 includes examples from the literature in which ingenuity applied to domain-specific problems has yielded interesting coding techniques.
	www.ics.uci.edu /~dan/pubs/DataCompression.html (1050 words)

	Data compression - Wikipedia, the free encyclopedia
		Compression is important because it helps reduce the consumption of expensive resources, such as disk space or connection bandwidth.
		In lossy audio compression, methods of psychoacoustics are used to remove non-audible (or less audible) components of the signal.
		Compression of human speech is often performed with even more specialized techniques, so that "speech compression" or "voice coding" is sometimes distinguished as a separate discipline than "audio compression".
	en.wikipedia.org /wiki/Data_compression (1402 words)

	Lossless data compression - Wikipedia, the free encyclopedia
		Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data.
		Whilst, in principle, any general-purpose lossless compression algorithm (general-purpose means that they can handle all binary input) can be used on any type of data, many are unable to achieve significant compression on data that is not of the form that they are designed to deal with.
		The most common class of real-world data files that fail to become shorter on compression are cases in which a file containing data compressed by one algorithm are fed to another algorithm (for instance, when already-compressed audio or image files are added to a zip or gzip compressed archive).
	en.wikipedia.org /wiki/Lossless_data_compression (1180 words)

	NationMaster - Encyclopedia: Data compression
		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.
		In data compression, a universal code for integers is a prefix-free code that maps the positive integers onto self-delimiting binary codewords, with the additional property that whatever the true probability distribution on integers, the lengths of the codewords are within a constant factor of the lengths that the...
		In data compression, vector quantization is a quantization technique often used in lossy data compression in which the basic idea is to code or replace with a key, values from a multidimensional vector space into values from a discrete subspace of lower dimension.
	www.nationmaster.com /encyclopedia/Data-compression (4474 words)

	Encyclopedia at AudioXchange: Audio data compression - Online Store & Product Reviews (Site not responding. Last check: 2007-10-26)
		This should not be confused with audio level compression (also known as companding), which reduces the dynamic range of audio signals.
		Audio compression is a form of data compression designed to reduce the size of audio data files.
		In contrast to image compression, lossless audio compression algorithms are not nearly as widely used.
	www.audioxchange.com /encyclopedia/Audio_compression.shtml (604 words)

	[No title] (Site not responding. Last check: 2007-10-26)
		A lossy data compression method is one where compressing a file and then decompressing it retrieves a file that may well be different to the original, but is "close enough" to be useful in some way.
		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.
		Flaws caused by lossy compression that are noticeable to the human eye or ear are known as compression artifacts.
	www.wikiwhat.com /encyclopedia/l/lo/lossy_data_compression.html (331 words)

	HardwareHell - Articles - Data Compression Explained - Review
		Modern compression is the technology used today by computers in order to pass data from place to place using less data then it would take to simply transfer these data as they are.
		Compression is quite common these days and is used transparently in many computer systems.
		Let's assume we have some data that we want to compress, and these data are made out of 4 symbols: A, B, C, D. Our compressor runs on the data and collects the probability for each character to appear based on the count of each synbol within the data.
	hardware.gamershell.com /articles/data_compression_explained (855 words)

	Theory of Data Compression
		In lossy data compression, the decompressed data does not have to be exactly the same as the original data.
		Compression rate is the rate of the compressed data (which we imagined to be transmitted in ``real-time'').
		Compression ratio is the ratio of the size or rate of the original data to the size or rate of the compressed data.
	www.data-compression.com /theory.html (2876 words)

	What is data compression? - A Word Definition From the Webopedia Computer Dictionary
		Data compression is particularly useful in communications because it enables devices to transmit or store the same amount of data in fewer bits.
		Data compression is also widely used in backup utilities, spreadsheet applications, and database management systems.
		Certain types of data, such as bit-mapped graphics, can be compressed to a small fraction of their normal size.
	www.webopedia.com /TERM/d/data_compression.html (293 words)

	Understanding Data Compression [Data Compression] - Cisco Systems
		Data compression provides a coding scheme at each end of a transmission link that allows characters to be removed from the frames of data at the sending side of the link and then replaced correctly at the receiving side.
		The compression ratio obtained using predictor is not as good as other compression algorithms, but it remains one of the fastest algorithms available.
		Data compression technology maximizes bandwidth and increases WAN link throughput by reducing frame size and thereby allowing more data to be transmitted over a link.
	www.cisco.com /en/US/tech/tk713/tk802/technologies_tech_note09186a00801b3b86.shtml (1406 words)

	Howstuffworks "How File Compression Works"
		This compression system is a very handy invention, especially for Web users, because it lets you reduce the overall number of bits and bytes in a file so it can be transmitted faster over slower Internet connections, or take up less space on a disk.
		Most compression programs use a variation of the LZ adaptive dictionary-based algorithm to shrink files.
		In an actual compression scheme, figuring out the various file requirements would be fairly complicated; but for our purposes, let's go back to the idea that every character and every space takes up one unit of memory.
	computer.howstuffworks.com /file-compression.htm (758 words)

	Entropy Coding (EC)
		Since the model is responsible for the probability of each symbol, modeling is one the most important tasks in data compression.
		Malte Clasen is a student of the RWTH Aachen, Germany, and is known as "the update" in the demoscene, a community of people whose target is to demonstrate their coding, drawing and composing skills in small programs called demos that have no purpose except posing.
		Mikael is interested in data compression, experimental electronic music and has written a BWT implementation, an improved range coder, a faster sort algorithm and a modified MTF scheme.
	www.data-compression.info /Algorithms/EC (1429 words)

	Data Compression - Storage & Servers - Network Computing
		Compression programs have been used to squeeze files since the 1980s, either to store more information on smaller-capacity media, such as floppies and disks, or to optimize data transport over low-bandwidth networks.
		Tape backup administrators know compression actually may not increase tape capacity at all, for dense data, but as much as five times that of uncompressed values for once loosely- packed databases.
		Using the two isn't helpful because once the data has been squeezed, it is not effective to squeeze it again using the same algorithm.
	www.networkcomputing.com /showArticle.jhtml?articleId=174300906 (721 words)

	LZW Data Compression at Mark Nelson
		Data compression has an undeserved reputation for being difficult to master, hard to implement, and tough to maintain.
		Compression occurs when a single code is output instead of a string of characters.
		This means that the compressed data is not burdened with carrying a large string translation table.
	marknelson.us /1989/10/01/lzw-data-compression (8377 words)

	The PAQ Data Compression Programs
		For programs that are not archivers (compress, gzip, epm, durilca, rkc, ash), the 14 file test size is the total size of 14 compressed files rather than the size of the archive (so grouping similar files in a tar file first might improve compression).
		Compressed size for the concatenated corpus is always about 150-200 bytes smaller (due solely to the archive header), and compression time is about the same.
		Instead, the compression option stored in the archive is used, which means that the decompressor needs the same amount of memory as was used to compress the files.
	www.cs.fit.edu /~mmahoney/compression (6281 words)

	Maximum Compression (lossless data compression software)
		Maximum Compression's goal is to show the maximum achievable data compression ratio for several filetypes (text, executable, jpeg etc).
		LZPX shows spectacular compression improvements compared to LZPX 1.5b (it now takes place #30 in SFC), but compression speed was also badly affected.
		In the multiple file compression section there now is a ranking based on efficiency of the compressors (please note there is still a lot of work to do here, like testing other programs, improving layout etc...).
	www.maximumcompression.com (5401 words)

	oberhumer.com: LZO real-time data compression library
		LZO is a data compression library which is suitable for data de-/compression in real-time.
		LZO is written in ANSI C. Both the source code and the compressed data format are designed to be portable across platforms.
		The FAQ of the newsgroup comp.compression is an invaluable source of information related to data compression.
	www.oberhumer.com /opensource/lzo (696 words)

	DataCompression.info - Source Code (Site not responding. Last check: 2007-10-26)
		Compression algorithms that are illustrated using source code.
		The average compression gain is in the range of 3 to 5 percent for the text files of the Calgary Corpus and between 2 to 9 percent for the text files of the large Canterbury Corpus.
		DCG Framework is a object oriented framework for lossless data compression.
	datacompression.info /SourceCode.shtml (8538 words)

	www.data-compression.info - The Data Compression Resource
		www.data-compression.info is intended as a central resource for information of the data compression field.
		ABC is a free data compression program based on the Burrows-Wheeler transformation.
		Besides data compression, I am concerned with another research topic: medical image processing.
	www.data-compression.info (375 words)

	Data Compression Technology
		The development of data compression procedures starts immediately after the appearance of the first computer systems.
		Moreover, the need for data compression has been strengthened due to larger and more complex contents.
		Selecting a proper compression procedure is always a compromise that tries to reconcile contrary characteristics.
	www.binaryessence.com /dct/en000003.htm (117 words)

	Open Directory - Computers: Software: Data Compression
		Maximum Compression - Aims to show the maximum achievable compression ratio for several filetypes (text, executable).
		USENET Compression FAQ - This URL takes you to a compression FAQ that explains compression to technical people as well as describing the various programs, and what they do to users.
		Zzip compression algorithm is mainly based on the Burrows-Wheeler Transform method developped by Mike Burrows and David Wheeler.
	dmoz.org /Computers/Software/Data_Compression (911 words)

	Background on Information Theory and Data Compression
		Compression algorithms are widely used in applications that depend on storing and transmitting data efficiently, including the Internet, fax machines, cell phones, DVD players, database applications, and satellite communications.
		provides the scientific basis for data compression and for other technologies such as encryption, error correction, pattern recognition, signal processing, and similarity comparisons.
		A nice overview of data compression, emphasizing huffman coding, markov modeling, and images (in a really long file)
	www.3dcompression.com /background.phtml (592 words)

	DataСompression.info: data compression link collection
		In this paper a detection method and a removal filter for corner outliers in order to improve visual quality in highly compressed video is proposed.
		This site is a catalog of links to data compression resources.
		Feel free to comment and rate data compression links or submit your own ones.
	www.datacompression.info (1219 words)

	PKWARE, Inc. - Data Security and File Compression Solutions for Home and Enterprise Users - Home
		Every day, your data is at risk of being compromised.
		Wherever data is and wherever it moves, SecureZIP® gives you the assurance that your data is secure without asking you to compromise.
		Our applications secure data from its point of origin to its delivery, and everywhere in between.
	www.pkware.com (161 words)

	Data Compression
		It was originally presented in the "A2Pro" forum of the GEnie online service, starting back in October 1992 (almost exactly 10 years ago to the day that I type this).
		For example, this was written before gzip and the "deflate" algorithm existed, at a time when "freeze" was being explored as a replacement for the UNIX "compress" command.
		For anyone intrigued by the "stackable" compression modules described in lesson 12, I have made the complete source code to HardPressed available on this site.
	www.fadden.com /techmisc/hdc (306 words)

	The Data Compression News Blog - c10n.info
		GTMT is first and foremost a development company, which specializes in the field of data compression, data manipulation and data communications.
		The concept of data compression is not new, but the concept of reducing redundant data truly is," said Robert Amatruda, an analyst at Framingham, Mass.
		The Data Compression News Blog is brought to you by Sachin Garg.
	www.c10n.info (1935 words)

	Mitsuharu ARIMURA's Bookmarks on Source Coding/Data Compression
		Ross Arnold and Tim Bell, "A Corpus for the Evaluation of Lossless Compression Algorithms", Proc.
		Charles Bloom, "LZP: a new data compression algorithm," Proc.
		S.Bunton, ``On-Line Stochastic Processis in Data Compression,'' Ph.D. Dissertation, University of Washington, 1996.(FTP)
	www.hn.is.uec.ac.jp /~arimura/compression_links.html (996 words)

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