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Topic: Lossy data compression

	Lossy data compression - Wikipedia, the free encyclopedia
		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.
		This is in contrast with lossless data compression.
		Flaws caused by lossy compression that are noticeable to the human eye or ear are known as compression artifacts.
	en.wikipedia.org /wiki/Lossy_data_compression (763 words)

	Lossless and lossy 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.
		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.
		In practice, lossy data compression will also come to a point where compressing again does not work, although an extremely lossy algorithm, which for example always removes the last byte of a file, will always compress a file up to the point where it is empty.
	www.maximumcompression.com /lossless_vs_lossy.php (1267 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)

	A DATA COMPRESSION PRIMER --
		The right choice of compression tools and libraries for a particular application depends on the characteristics of the data and application in question: streaming versus file; expected patterns and regularities in the data; relative importance of CPU usage, memory usage, channel demands and storage requirements; and other factors.
		Lossless compression involves a transformation of the representation of a data set such that it is possible to reproduce exactly the original data set by performing a decompression transformation.
		Lossy compression may be appropriate in these areas insofar as human observers do not perceive the literal bit-pattern of a digital image/sound, but rather more general "gestalt" features of the underlying image/sound.
	gnosis.cx /publish/programming/compression_primer.html (2692 words)

	Lossless Data Compression (Site not responding. Last check: 2007-11-05)
		The ultimate goal of data compression is to package the largest amount of data into the smallest amount of space so that the data can quickly be transmitted across a network.
		Lossy -- In lossy data compression, some of the data from the original file is intentionally discarded during compression.
		Compression techniques are constantly being refined and improved to increase compression ratios and reduce errors.
	www.amherst.edu /~mjcastiglia (612 words)

	Data compression - Wikipedia, the free encyclopedia
		For instance, a compression scheme for video may require expensive hardware for the video to be decompressed fast enough to be viewed as it's being decompressed (you always have the option of decompressing the video in full before you watch it, but this is inconvenient and requires storage space to put the uncompressed video).
		The design of data compression schemes therefore involve trade-offs between various factors, including the degree of compression, the amount of distortion introduced (if using a lossy compression scheme), and the computational resources required to compress and uncompress the data.
		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 (1502 words)

	Pattern Matching and Lossy Data Compression on Random Fields - Kontoyiannis (ResearchIndex)
		Several of the most commonly used algorithms are based on pattern matching: Given a distortion level D and a block of data to be compressed, the encoder rst nds a D- close match of this block into some database, and then describes the position of the match.
		0.3: Pointwise Redundancy in Lossy Data Compression and Universal..
		13 Pointwise redundancy in lossy data compression and universal..
	citeseer.ist.psu.edu /kontoyiannis01pattern.html (634 words)

	Wikinfo \| Lossless data compression
		Lossless data compression is a class of data compression algorithms that allow the original data to be reconstructed exactly from the compressed data.
		Lossless data compression is used in software compression tools such as the highly popular ZIP file format, used by PKZIP, WinZip and Mac OS 10.3, and the Unix programs bzip2, gzip and compress.
		This is called delta compression (from the Greek letter Δ which is commonly used in mathematics to denote a difference), but the term is typically only used if both versions are meaningful outside compression and decompression.
	www.wikinfo.org /wiki.php?title=Lossless_data_compression (993 words)

	WAVELET-TRANSFORM BASED COMPRESSION ALGORITHM
		Most of the lossy data compression algorithms follow similar methodology: the original data are mathematically transformed to a new domain in which they are better organized for data compression than in the normal spatial-temporal domain.
		Seismic data have the characteristic of localization, which is the main reason of choosing wavelet transform in seismic data compression.
		Among the four compression procedures, the key to the success of this lossy compression technique is the choice of quantization methods.
	sepwww.stanford.edu /public/docs/sep92/yalei/paper_html/node2.html (733 words)

	Chebyshev Data Compression
		To date, lossy data compression algorithms have found acceptance in applications where the need to achieve high compression ratios outweighs the information loss, but have not found acceptance in technical applications where preservation of absolute data values are important.
		To be useful for time series data, a lossy compression algorithm needs to be optimized to preserve absolute data values to the extent possible within the available bandwidth.
		The algorithm has the property of requiring few computations to compress data, and it is therefore well suited to applications requiring real-time data compression in extreme terrestrial or extra-terrestrial environments.
	www.jhuapl.edu /ott/technologies/technology/articles/P01825.asp (354 words)

	[No title] (Site not responding. Last check: 2007-11-05)
		Data compression is the general term for the various algorithms and programs developed to address this problem.
		Data that is used to consume lots of your time (during up/downloads) and space (as on your diskettes or hard drives) can now be made smaller and much more efficient.
		Because lossy compression cannot be decoded to yield the exact original message, it is not a good method of compression for critical data, such as textual data.
	c.1asphost.com /samiazmi/ebooks/compression.doc (6801 words)

	Compression in Audio Recordings (Site not responding. Last check: 2007-11-05)
		Compression ratios of perhaps 2:1 are common, so the output will rise (or fall) by one unit for every two units of input change.
		Compression is commonly used in the final mix, and this is where things can go seriously wrong - everything is at the same volume, peak to average ratio is minimal, and the resulting sound is almost always worse than it was before the compression was applied.
		Compression - A most excellent article by Bob Katz, on the perils of using compression or limiting on the final mix.
	sound.westhost.com /compression.htm (4146 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).
		THOR 0.3a and QazaR both have better compression while THOR, written in Delphi(!), is also faster then previous version; it now clocks a compression speed of almost 43 MB/s in MFC test.
		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 (4719 words)

	DataCompression.info - Lossy Compression (Site not responding. Last check: 2007-11-05)
		This category covers lossy compression methods that can't be pinned down to one of the more refined topics, such as JPEG or MP3.
		Their home page advertises GeoEnergy as "The leader in fast data compression algorithms for the oil and gas industry." Quite a few algorithms are listed, all of which work on various types of collected seismic data.
		Compression is one of them, and there is certainly a great deal to learn about compression and media formats at this conference.
	datacompression.info /Lossy.shtml (390 words)

	ESC Dicom B'ham 96 - What is Lossy data compression? (Site not responding. Last check: 2007-11-05)
		This simple example demonstrates that Lossy data compression approaches do not guarantee exact replicas of the original data set, however, they are designed to minimize loss of "useful" information.
		In this example the data compression ratio is (23/4) or 5.75.
		It should be noted that the selection of a lossy compression scheme is very much correlated to the type of data that is being compressed and decompressed.
	www.uni-mainz.de /Cardio/dicom/links/219e.htm (340 words)

	Research in Data Compression (Site not responding. Last check: 2007-11-05)
		While it is know that the lossless Lempel-Ziv is asymptotically optimal (i.e., its compression ratio is close to the entropy), we have managed to prove recently that a lossy extension of Lempel-Ziv scheme (of low complexity) is suboptimal (cf.
		It is competitive with other competing technologies in terms of compression ratios, far superior in terms of decompression time (extremely fast even with weak computational resources), and promises to provide a way of treating uniformly all kinds of multimedia data (whereas current schemes use different technologies for each).
		When investigating this aspect of compression (i.e., extension of Lempel-Ziv type compression to graphical objects), we expect that some of our work in the area of computational geometry to be helpful.
	www.cs.purdue.edu /homes/spa/software.html (1087 words)

	DataCompression.info - Data Compression (Site not responding. Last check: 2007-11-05)
		This book is intended to provide an overview of the many different types of compression: it includes a taxonomy, an analysis of the most common systems of compression, discussion of their relative benefits and disadvantages, and their most common usages.
		In October 2002, the topic was data compression, which led to a fairly lengthy column with many, many references.
		Paolo Ferragina's research in data structures and string matching naturally lends itself to Data Compression and to the problem of indexing compressed data.
	datacompression.info /Compression.shtml (7319 words)

	Partial Subtractive Dither for Lossy Data Compression
		The technique may be applicable to compression of scientific and medical image data.
		To those skilled in the art of data compression, the use of subtractive dither to reduce the undesired quantization artifacts produced by lossy data-compression algorithms is well known.
		These artifacts include (1) biased average signal values in some regions of a signal, (2) steplike signal-value profiles in slowly changing portions of the signal, and (3) erasure of faint features that, if they occupied a sufficiently large area, would be detectable in the original signal.
	www.nasatech.com /Briefs/Mar01/NPO20964.html (378 words)

	2D-Pattern Matching Based Data Compression (Site not responding. Last check: 2007-11-05)
		The central theme of a lossy extension of Lempel-Ziv algorithm is the notion of approximate repetitiveness.
		If a portion of data recurs in an approximate sense, then subsequent occurrences can be stored as direct or indirect references to the first occurrence.
		A key issue for high quality image and video compression is the design of an adaptive distortion measure that automatically adjusts its maximum distortion to produce perceptually high quality results.
	www.cs.purdue.edu /homes/spa/Compression/2D-PMC.html (542 words)

	What is Lossy Compression? Data Restored Not Identical Lost (Site not responding. Last check: 2007-11-05)
		The data is eliminated based on a number of sophisticated mathematically-based formulae.
		A type of compression that results in the loss of some of the original data.
		Whereas lossless compressions results in a compression ratio of about 2:1, LossyCompression of video data can lead to ratios of between 10:1 and 50:1 without visibly degrading image quality.
	bugclub.org /beginners/imaging/LossyCompression.html (97 words)

	Polynomial-time, sequential, adaptive system and method for lossy data compression (US6798362)
		A system and method are provided for lossy compression of finite alphabet source sequences subject to an average-per-letter distortion constraint.
		The source sequence is sequentially parsed into phrases and each source phrase is mapped to a distorted phrase such that average per-letter distortion between the two phrases does not exceed the desired distortion.
		A lossy data compression method for converting a source sequence over a source alphabet to a distorted sequence over a reproduction alphabet by intentionally introducing errors, the method comprising:
	www.delphion.com /details?pn=US06798362__ (538 words)

	True Audio Codec Software - Lossy data compression
		This type of compression is used frequently on the Internet and especially in streaming media and telephony applications.
		Depending on the design of the format lossy data compression often suffers from generation loss, that is compressing and decompressing multiple times will do more damage to the data than doing it once.
		The image is an excerpt of the image of Lena, a de facto industry-standard test image.
	www.true-audio.com /Lossy_data_compression (658 words)

	Lossy Data Compression, Fall 2005
		An individual grade will be given for each student, based on the report and the weekly presentation (thus, the weekly presentations replaces the oral exam of "Lossless Data Compression").
		The daimi newsgroup: daimi.ldc has been set up for discussions related to the course and the first quarter course "Lossless Data Compression".
		The report may contain references (links) to data at your homepage which I may or may not look at.
	www.daimi.au.dk /~bromille/DC05/lossy.html (306 words)

	Ted's Radio Weblog
		It was five years ago tomorrow that lzip version 1.0 was released.
		Lossy Data Compression, with compression ratios far beyond those available with conventional zip, gzip or even bzip technologies, should have taken the world by storm.
		Instead, they have ended up in this dusty little corner of SourceForge.net.
	radio.weblogs.com /0117767/2005/03/31.html (349 words)

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