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| | Lossy data compression - Wikipedia, the free encyclopedia |
 | | A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different to the original, but is "close enough" to be useful in some way. | | | Good lossy compression algorithms are able to throw away "less important" information and still retain the "essential" information. | | | In these cases, the retrieved file can be quite different to the original at the bit level while being indistinguishable to the human ear or eye for most practical purposes. |
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http://en.wikipedia.org/wiki/Lossy
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| | Sample Chapter: Data Compression |
| | Each time the compression algorithm encounters this sequence in the input file, code 523 is placed in the encoded file. | | | Data compression is the general term for the various algorithms and programs developed to address this problem. | | | A compression program is used to convert data from an easy-to-use format to one optimized for compactness. |
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http://www.dspguide.com/datacomp.htm
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| | Video Compression Tutorial |
| | Compression is performed by locating self-similar sections of an image, then using a fractal algorithm to generate the sections. | | | Lossy compression - reduces a file by permanently eliminating certain redundant information, so that even when the file is uncompressed, only a part of the original information is still there. | | | The algorithm is based on DCT and can be implemented in hardware or software and uses intraframe and interframe compression. |
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http://www.wave-report.com/tutorials/VC.htm
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| | Theory of Data Compression |
| | That is, given the code table and given the compressed data, we should be able to rederive the original data. | | | In lossy data compression, the decompressed data need not be exactly the same as the original data. | | | Thus, the theorem established that the entropy rate is the rate of an optimal lossless data compression code. |
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http://www.data-compression.com/theory.shtml
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| | Optimizing Web Graphics: Compression - webreference.com |
| | While the LZW compression algorithm used by GIFs is one of the better general purpose compression algorithms, it wasn't designed specifically for graphics. | | | The developers of PNG are currently working on formats for lossy image compression and animation, using the overall design and technologies of PNG and applying them to those tasks. | | | PNP will use a lossy compression algorithm, probably based on wavelets. |
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http://www.webreference.com/dev/graphics/compress.html
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| | Lossy Compression |
| | The compression algorithm we're using only works with one color component at a time, so when you extract the 128x128 chunks (or 8x8 chunck's in extra credit) of the image to pass to the SVD, you'll need to do this separately for the red, green, and blue components of the image. | | | You will be implementing a lossy compression algorithm using a technique adopted from linear algebra. | | | Read the compressed file for vectors U, V and singular values S (how you read the bytes depends on how you stored them in compressed file). |
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http://edbardsley.org/classes/15-211/lab4/lossy.html
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| | Graphics: Use Lossy Compression for Smaller GIFs and PNGs - gif lossy png compression for smaller images pngs lzw ... |
| | Lossy compression simply helps the process along, by intelligently tweaking pixel values to match other patterns along scan lines. | | | You can apply lossy compression to the entire image, or selectively using weighted optimization with alpha masks for less important areas of your images (see Figure 1). | | | By applying judicious amounts of lossy compression to GIFs and PNGs you can further optimize the size of your images destined for the web. |
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http://www.websiteoptimization.com/speed/tweak/lossy
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| | JPEG and JPEG2k Artifacts |
| | From here, special-purpose optimization programs such as PNGOUT and OptiPNG can be used to further reduce the file size by 8% to 24,623 bytes. | | | This way we achieve better compression, but the original and the decompressed files are no longer the same. | | | A section of text of size 787x392 was compressed to 26,823 bytes with PNG. |
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http://ai.fri.uni-lj.si/~aleks/jpeg/artifacts.htm
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| | Data Compression Algorithms |
| | This page is a research project in the field of data compression algorithms. | | | Some examples of lossy data compression algorithms are JPEG, MPEG, and Indeo. | | | Because all of the encoding is into the binary alphabet, every time log is written it will refer to log to the base 2. |
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http://www.ccs.neu.edu/groups/honors-program/freshsem/19951996/jnl22/jeff.html
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| | GIFs and JPEGs |
| | This is where the lossy bit comes in: depending on how much you want to compress the image the algorithm throws away the less significant part of the data (the smaller curves) which adds less to the overall "shape" of the image. | | | All that means is that when the program that creates a GIF squashes the original image down it takes care not to lose any data. | | | Compuserve, which created the GIF, did at one point say it would attempt to produce a 24-bit version of the GIF, but then along came problem number two: Unisys. |
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http://www.widearea.co.uk/designer/compress.html
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| | JPEG image compression FAQ, part 1/2 |
| | The disadvantages of MPEG are (1) it requires far more computation to generate the compressed sequence (since detecting visual similarities is hard for a computer), and (2) it's difficult to edit an MPEG sequence on a frame-by-frame basis (since each frame is intimately tied to the ones around it). | | | When I say "lossless", I mean mathematically lossless: a lossless compression algorithm is one that guarantees its decompressed output is bit-for-bit identical to the original input. | | | The only real solution is to combine lossy JPEG storage of the image with lossless storage of a transparency mask using some other algorithm. |
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http://www.faqs.org/faqs/jpeg-faq/part1
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| | Lossy Compression |
| | The result is that the error, rather than accumulating linearly, is dominated by the error of the final DCT pass. | | | An alternative approach is to encode the coefficients using run-length encoding of the zeros. | | | In this approach, the quantization and entropy coding are optimized separately for each block, based on its characteristics. |
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http://www.stanford.edu/~mbax/ee392c/node6.html
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| | Halfbakery: Lossy Text Compression |
| | Work has been done on lossy text compression on a word level, but to my knowledge it has not been done on the letter level as I described. | | | A modified zlib which allows lossy matching in the Lempel-Ziv stage. | | | Compress your text files using the technology that makes JPEG so great for pictures! |
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http://www.halfbakery.com/lr/idea/Lossy_20Text_20Compression
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| | data compression |
| | program compression various ways to compress executable software, especially methods that create executable software that executes and runs similar to the original. | | | The compressed file header just stores the *lengths* of the codeword for each symbol, and the decompressor regenerates the code words from that. | | | Compress it like any other binary data file. |
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http://www.rdrop.com/~cary/html/data_compression.html
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| | lossy - a Whatis.com definition - see also: lossless and lossy compression, lossless, lossy compression, lossless ... |
| | The JPEG image file, commonly used for photographs and other complex still images on the Web, is an image that has lossy compression. | | | This is generally the technique of choice for text or spreadsheet files, where losing words or financial data could pose a problem. | | | On the other hand, lossy compression reduces a file by permanently eliminating certain information, especially redundant information. |
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http://whatis.techtarget.com/definition/0,,sid9_gci214453,00.html
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| | Lossy Compression |
| | Difference between error free and lossy methods is the presence of a quantizer. | | | Usually a scheme is used where a small number of bits are used to code error values near the peak of zero while larger numbers of bits are used for values farther from the peak. | | | This function is usually a sharp peak around zero, but if want to cover all possible errors, then the value of the error must be quantized into many bits, which reduces the compression possibilities. |
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http://www.marquette.edu/~matthysd/web226/L0430.htm
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| | Lossy PNG (when it is implemented) |
| | The file size for the lossy Dilbert is 13794 bytes compared with 17434 bytes for the non-lossy PNG of that image, a 21% saving. | | | This compression has a Lempel-Ziv matching stage and then Huffman codes the results. | | | I developed the code by testing it against a Dilbert cartoon; this is a four-greyscale image originally but I converted it to 256 shades of grey because the lossy matching assumes it can compare numeric byte values. |
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http://membled.com/work/apps/lossy_png
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| | JPEG Lossy (DCT) Compression Encoding |
| | Compression encoding generally used for full color and grayscale continuous-tone pictorial images; does not work well with bitonal or palette-color images. | | | With this in mind, the committee developed the JPEG-LL (lossless) standard - ISO/IEC IS 14495-1 | | | Preferred file formats for JPEG_DCT include JPEG_EXIF (rich metadata) and JFIF; raw JPEG data (see Notes) is only acceptable if no other format is available. |
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http://www.digitalpreservation.gov/formats/fdd/fdd000017.shtml
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| | Compression Research |
| | Some investigation was also made into utilizing the compressed data storage format to aid in other common processing tasks. | | | Decompression was significantly faster, 10x to 20x than a DCT based algorithm, however compression was two to three times slower. | | | A set of experiments found this algorithm to be, on average, 2.5 dB worse in terms of PSNR than an image compressed by JPEG for the same bit rate. |
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http://www-2.cs.cmu.edu/~chuck/nsipg/nsi.html
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| | Lossy Compression |
| | This degree of difference is not noticeable by the human eye. | | | For resistance to errors in the storage media / transmission across a channel, the stored / transmitted data must contain certain redundant data in order to be able to recover from any errors introduced. | | | For more information on the reponse of the human visual system, (see here). |
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http://www.iis.ee.ic.ac.uk/~frank/surp00/article1/jko98
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| | The GSM 06.10 lossy speech compression library and its applications |
| | These capabilities are sold both as `stand-alone'' software and as a convenient library for developers wishing to integrate multimedia Internet communication into their applications. | | | explains, and often provides references to software that implements, most lossy and non-lossy algorithms. | | | The site's hypertext version of the comp.speech Frequently Asked Questions posting has pointers to general information and tools concerned with speech encoding, compression, recognition, synthesis, and other forms of natural language processing. |
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http://kbs.cs.tu-berlin.de/~jutta/toast.html
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| | Lossy Compression |
| | Applications such as astronomical imaging also require lossless compression, since the image is going to be processed by computing devices instead of human eyes. | | | More sophisticated lossless compression methods such as Lempel-Ziv-Welch (LZW) and Huffman encoding analyze the data and look for repeating patterns. | | | Various digital image applications that require image compression do not allow error in the reconstructed image, thus lossless compression techniques are used. |
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http://www.csi.edu/support/itc/pres2/lossless.htm
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| | Lossless and Lossy Data Compression (ResearchIndex) |
| | Abstract: Data compression (or source coding) is the process of creating binary representations of data which require less storage space than the original data [7; 14; 15]. | | | Achieving optimal compression with respect to resource constraints is a difficult problem. | | | Lossless compression is used where perfect reproduction is required while lossy compression is used where perfect reproduction is not possible or requires too many bits. |
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http://citeseer.ist.psu.edu/38744.html
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| | A family of image watermarking schemes based on lossy compression |
| | This paper describes a methodology for obtaining watermarking schemes using different compression algorithms in the mark embedding process. | | | The result is a family of watermarking algorithms which are robust against different lossy image compression, filtering, cropping and row/column removal attacks, for a reasonable range of image qualities. | | | In addition, the experiments show that the JPEG2000 standard is a promising tool for creating new watermarking schemes. |
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http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/proceedings/&toc=comp/proceedings/itcc/2000/0540/00/0540toc.xml&DOI=10.1109/ITCC.2000.844177
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| | Digital Compression |
| | This information is accurate to the best of our knowledge and research. | | | The PCM file format consumes about 9 megabytes of file space for each minute of audio program length. | | | For example, the zip file format produced by the Winzip program on a PC produces exact copies of the original material that was encoded within the zip file. |
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http://www.puredigitalaudio.org/digitalcompression/index.shtml
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| | WavPack Audio Compression |
| | Instead of creating a single file, this mode creates both a relatively small, high-quality lossy file that can be used all by itself, and a "correction" file that (when combined with the lossy file) provides full lossless restoration. | | | Although the technology is loosely based on previous versions of WavPack, the new version 4 format has been designed from the ground up to offer unparalleled performance and functionality. | | | The compression ratio depends on the source material, but generally is between 30% and 70%. |
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http://www.wavpack.com
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| | What is lossy compression? - A Word Definition From the Webopedia Computer Dictionary |
| | You are in the: Small Business Computing Channel | | | SHOP.COM 103.58Description Four powerful agents to help you create smaller Adobe Portable Document Format (PDF) files, create accessible Adobe PDF documents and fil... | | | Lossy compression technologies attempt to eliminate redundant or unnecessary information. |
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http://www.webopedia.com/TERM/l/lossy_compression.html
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| | Lossy compression - AMV |
| | Many lossy compression algorithms are intended to minimize the detectability or salience of the loss of information. | | | Because of limitations on the human visual and auditory systems, much of visual and auditory information can be eliminated from a natural signal without any change to the perceived image or sound. | | | Lossy compression is the compression of a source with the loss of auditory or visual information. |
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http://www.amvwiki.org/index.php/Lossy_compression
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| | lossy compression - definition of lossy compression by the Free Online Dictionary, Thesaurus and Encyclopedia. |
| | (Computers) The compression of binary data into a form which, when it is re-expanded, has most, but not all, of the original information. | | | Images compressed by a lossy compression algorithm are re-expanded into an image close, but not identical to the original image; the difference between the original and the reconstructed image may be imperceptible to normal viewing by the eye. | | | It is used primarily for compression of images and sounds, and is designed to provide a high degree of compression at the cost of a slight loss of data. |
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http://www.thefreedictionary.com/lossy+compression
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| | DataCompression.info - Lossy Compression |
| | 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. | | | A study of lossy compression algorithms, including discussion of JPEG, MPEG, and the DCT. | | | Ideally, when compression image or sound files, the loss is either minimal or undetectable by human observors. |
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http://datacompression.info/Lossy.shtml
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| | Definition: lossy compression |
| | Note: Lossy compression accepts loss of information and introduction of artifacts that can be ignored as unimportant when viewed in direct comparison with the original. | | | In video technology, a digital image compression technique that removes redundant bits from an image in return for a minor loss of image quality. | | | Lossy compression takes advantage of the subtended viewing angle for the intended display, the perceptual characteristics of human vision, the statistics of image populations, and the objectives of the display. |
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http://www.atis.org/tg2k/_lossy_compression.html
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| | Hi Fi Writer - Dolby Digital vs DTS |
| | Dolby says that you can't draw any conclusions from the raw compression figures because it all depends on how well the codec (compression/decompression system) is designed. | | | Most Dolby Digital DVDs use 384kb/s but some use 448kb/s, which Dolby says is the maximum possible on a DVD. | | | Both use a lossy compression system and in their 5.1 varieties, each offers the DVD producer two bit rates. |
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http://www.hifi-writer.com/he/dolbydts/dolbydts.htm
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| | Lossy Compression |
| | Here's an example of a picture saved at three different quality levels. | | | The more compression, the smaller the file, but the less the accuracy. | | | Since the JPEG formulas are a “best fit” to the pixels that it starts with, rather than an exact fit, the pixels you started with won't be the same ones you end up with when you view the picture. |
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http://catcode.com/imgguide/lossy.html
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| | Lossy compression |
| | A MP3 file is an example of a lossy compressed audio file. | | | Lossy compression methods are used most often for graphics and audio files. | | | Some type of files do not support lossy compression or if compressed in this method will not work when uncompressed. |
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http://www.xmission.com/~comphope/jargon/l/lossy.htm
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| | Lossy Compression |
| | These lossless compression techniques are suitable for wide range of applications, from hard disk file compression to digital medical image archiving, where data loss is usually not allowed. | | | Thus, they can afford some loss of information during the coding process. | | | Predictive techniques (such as ADPCM) predict subsequent values by observing previous values. |
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http://www.csi.edu/support/itc/pres2/lossy.htm
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| | Lossy compression |
| | If the compression is done judiciously, this process greatly reduces file size with little change that is visible to someone looking at the image resulting from decompressing the JPEG file. | | | Since human hearing extends up to 20,000 Hz, the sampling rate for high-quality digital sound has to be at least twice this. | | | Trimming transformed information is an effective compression technique. |
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http://www.csc.calpoly.edu/~rtross/csc310/C3LossyCompression.htm
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| | Lossy and lossless audio compression |
| | Investigating the quality of lossy algorithms including MPEG Audio Layer 3 (MP3), AAC and Yamaha's SoundVQ. | | | Back to the First Principles main page - for material on telecommunications, music marketing via Internet delivery, stick insects. |
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http://www.firstpr.com.au/audiocomp
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| | CS 105 -- "LOSSY" COMPRESSION |
| | This page is part of a section of lecture slides related to " Why GIF? | | | JPEG FILES USE A LOSSY COMPRESSION TECHNIQUE TO REDUCE THE NUMBER OF SYMBOLS (BITS) REQUIRED TO REPRESENT AN IMAGE. | | | ALTHOUGH THE RESULTS MAY PRODUCE SOME CONFUSION, THEY PRESERVE MOST OF THE INFORMATION FROM THE ORIGINAL. |
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http://www.cs.williams.edu/~cs105/f01/outlines/CS105_114.html
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