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Topic: Adaptive coding

	Adaptive Huffman coding - Wikipedia, the free encyclopedia
		Adaptive Huffman coding is an adaptive coding technique based on Huffman coding, building the code as the symbols are being transmitted, having no initial knowledge of source distribution, that allows one-pass encoding and adaptation to changing conditions in data.
		Code is represented as a tree structure in which every node has a corresponding weight and a unique number.
		Paul E. Black, adaptive Huffman coding at the NIST Dictionary of Algorithms and Data Structures.
	en.wikipedia.org /wiki/Adaptive_Huffman_coding (578 words)

	Adaptive coding - Wikipedia, the free encyclopedia
		Adaptive coding refers to variants of entropy encoding methods of lossless data compression.
		While sometimes the model is implicit in the compression method (for instance, in run-length encoding), in most methods it is separate, and because both the encoder and the decoder need to use the model, it must be transmitted with the data.
		In adaptive coding, the encoder and decoder are instead equipped with identical rules about how they will alter their models in response to the actual content of the data, and otherwise start with a blank slate, meaning that no initial model needs to be transmitted.
	en.wikipedia.org /wiki/Adaptive_coding (380 words)

	Data Compression -- Section 4
		The code is adaptive, changing so as to remain optimal for the current estimates.
		As discussed in the introduction, the adaptive method of Faller, Gallager and Knuth is the basis for the UNIX utility compact.
		Another reasonable assumption about adaptive coding is that the weights in the current tree correspond closely to the probabilities associated with the source.
	www.ics.uci.edu /~dan/pubs/DC-Sec4.html (1768 words)

	Adaptive coding and decoding of frames and fields of video - Patent 5227878
		The coding analyzer 14 examines predetermined characteristics of the video input signals on line 10 or of the estimate error signal on line 13, depending on the state of a switching element 13a and makes a decision as to the type of coding to be used by the encoder of FIG.
		The coding type signal is used by the quantizer 19 to adjust the quantization levels applied to the transform coefficients from discrete cosine transform circuit to improve the compression of video signals produced by the operation of the quantizer 19.
		A signal on line 47 related to the magnitudes of intra coded DC coefficients produced by the discrete cosine transform circuit 16 is directed to the input of an intra DC coefficient prediction circuit 45 and the non-inverting input of a summing element 46.
	www.freepatentsonline.com /5227878.html (16044 words)

	Data Compression -- Section 5
		Lempel-Ziv coding represents a departure from the classic view of a code as a mapping from a fixed set of source messages (letters, symbols or words) to a fixed set of codewords.
		Lempel-Ziv coding is asymptotically optimal, meaning that the redundancy approaches zero as the length of the source ensemble tends to infinity.
		This yields a prefix code with the length of the codeword for
	www.ics.uci.edu /~dan/pubs/DC-Sec5.html (2422 words)

	Digital video compression system and methods utilizing scene adaptive coding with rate buffer feedback - Patent 4394774
		The compressor adaptively determines the rate buffer capacity control feedback component in relation to instantaneous data content of the rate buffer memory in relation to its capacity, and it controls the absolute quantity of data resulting from the normalization step so that the buffer memory is never completely emptied and never completely filled.
		The compressor adaptively determines the rate buffer capacity control feedback component in relation to the instantaneous data content of the rate buffer memory in relation to its capacity to control at normalization the absolute quantity of data resulting from that process so that the buffer memory is never completely emptied and never completely filled.
		Coded luminance from the scene adaptive coder 20, coded chrominance from the chrominance encoder 22, and coded audio from the PCM encoder 26 are combined in a multiplexer 28 in a time division format in which the serial bit stream is divided into frames of, e.g.
	www.freepatentsonline.com /4394774.html (13478 words)

	Dr. Dobb's \| Memory-Efficient Adaptive Huffman Coding \| July 22, 2001
		Huffman coding is one way to generate a nearly optimal binary code for a given set of symbols and probability law.
		Huffman coding is efficient, since the average code length is generally close to the entropy.
		Codes are sometimes developed from a single large "corpus" of typical data, then used to compress a variety of files.
	www.ddj.com /184410697 (2688 words)

	Arithmetic Coding
		Arithmetic coding is a general technique for coding the outcome of a stochastic process based on an adaptive model.
		PPM, prediction by partial matching, is an adaptive statistical model of a symbol sequence which models the likelihood of the next byte based on a (relatively short) suffix of the sequence of previous bytes.
		The end-of-file outcome is coded as a separate outcome, mirroring the behavior of byte reading in both Java and C streams.
	www.colloquial.com /ArithmeticCoding/javadoc/tutorial.html (1274 words)

	[No title]
		The Huffman tree is initialized with a single node, known as the Not-Yet-Transmitted (NYT) or escape code.
		This code will be sent every time that a new character, which is not in the tree, is ecountered, followed by the ASCII encoding of the character.
		Whenever a character that is already in the tree is encountered, the code is sent and the weight is increased.
	www.cs.sfu.ca /cs/CC/365/li/squeeze/AdaptiveHuff.html (681 words)

	Adaptive Huffman Coding
		Adaptive Huffman coding also works at a universal level, but is far more effective than static huffman coding at a local level because the tree is constantly evolving.
		In adaptive huffman coding, the character will be inserted at the highest leaf possible to be decoded, before eventually getting pushed down the tree by higher-frequecy characters.
		This algorithm is called adaptive huffman coding because the tree is adaptive- it is created simultaneously with either the compressed or uncompressed file as it reads in the other.
	www.cs.duke.edu /csed/curious/compression/adaptivehuff.html (1951 words)

	Adaptive coding and decoding of frames and fields of video (US5227878) (Site not responding. Last check: 2007-11-01)
		Improved compression of digital signals relating to high resolution video images is accomplished by an adaptive and selective coding of digital signals relating to frames and fields of the video images.
		This coding type signal may be used to adaptively control the operation of one or more types of circuitry which are used to compress digital video signals so that less bits, and slower bit rates, may be used to transmit high resolution video images without undue loss of quality.
		For example, the coding type signal may be used to improve motion compensated estimation techniques, quantization of transform coefficients, scanning of video data, and variable word length encoding of the data.
	www.delphion.com /details?pn10=US05227878 (426 words)

	DataCompression.info - Adaptive Huffman Coding (Site not responding. Last check: 2007-11-01)
		Adaptive Huffman coding modifies the table as characters are encoded, which allows the encoder to adapt to changing conditions in the input data.
		Adaptive decoders don't need a copy of the table when decoding, they start with a fixed decoding table and update the table as characters are read in.
		The code for incorporating the last symbol grabs an extra input bit, but since this is usually the EOT symbol, the bug doesn't always cause problems.
	datacompression.info /AdaptiveHuffman.shtml (660 words)

	Shape Adaptive Discrete Wavelet Transforms for Arbitrarily Shaped Visual Object Coding
		Shape adaptive wavelet coding is needed for eÆciently coding arbitrarily shaped visual objects, which is essential for object-oriented multimedia applications.
		The challenge is to achieve high coding eÆciency while satisfying the functionality of representing arbitrarily shaped visual texture.
		Comparison of shape adaptive wavelet coding with other coding schemes for arbitrarily shaped visual objects shows that shape adaptive wavelet coding always achieves better coding eÆciency than other schemes.
	research.microsoft.com /research/pubs/view.aspx?pubid=873 (321 words)

	ECS EPrints Service - Adaptive Coding and Transmission Paradigms for Wireless Channels
		Following a brief historical perspective on channel coding the concept of near-instantaneously adaptive wireless transceivers is introduced as a counter-measure of mitigating the channel-quality fluctuations experienced in wireless communications.
		It is argued that channel coded adaptive modulation schemes can be viewed as a lower complexity alternative of mitigating the channel quality fluctuations of wideband wireless channels in comparison to multiple-transmitter and multiple-receiver based space-time codes.
		However, provided that the complexity of the latter schemes employing multiple transmitters and receivers is affordable, the performance advantages of adaptive modulation and adaptive channel coding schemes erode, since the channel quality fluctuations of the wireless channel are effectively mitigated.
	eprints.ecs.soton.ac.uk /8296 (225 words)

	Adaptive Huffman Coding
		Adaptive huffman coding has the advantage over static coding that the entire dataset does not need to be known in advance and the dictionary does not need to be transmitted separately from the data.
		It would be wrong to call this implementation adaptive huffman coding because well, it isn't.
		I intended to mate this code with the code in LZW, but the combination works pretty badly, probably because of my lack of a good idea for encoding the higher-ordered symbols effeciently.
	wiki.tcl.tk /12375 (195 words)

	Rate-constrained Conditional Replenishment Video Coding with Adaptive Change Detection
		For conditional replenishment video coding algorithms, typically a change detection mask is transmitted as side information in addition to the signal within the changed areas.
		Further, we propose an adaptive change detection algorithm that is based on the inherent noise characteristics of digital imaging system.
		However, the paper only studied the case of distortionless coding, and the threshold values used in their simulation are arbitrary and lack of theoretical support.
	www.stanford.edu /class/ee368b/Projects/chiao (2395 words)

	[No title] (Site not responding. Last check: 2007-11-01)
		Arithmetic coding gives greater compression, is faster for adaptive models, and clearly separates the model from the channel encoding.
		Shannon's fundamental theorem of coding states that given messages randomly generated from a model, it is impossible to encode them into less bits (on average) than the entropy of that model (Shannon & Weaver, 1949).
		For example, the techniques mentioned above which code English text in 2.2\ bit/char both use arithmetic coding as the final step, and performance would be impacted severely if Huffman coding were substituted.
	www.cs.cmu.edu /afs/cs.cmu.edu/project/pscico-guyb/realworld/99/code/calgary/datadir/paper1 (1397 words)

	Adaptive Coding of Moving Objects for Very Low Bit-rates - Han, Woods (ResearchIndex) (Site not responding. Last check: 2007-11-01)
		The moving objects in a video are extracted by means of a joint motion estimation and segmentation algorithm based on the Markov Random Field (MRF) model.
		The two important features of the presented technique are the temporal linking of the objects, and the guidance of the motion segmentation with spatial color information.
		Han and J. Woods, "Adaptive coding of moving objects for very low bit-rates," IEEE Journal on Selected Areas in Communications, issue on very low bit-rate video coding, to be published, Jan 1998.
	citeseer.ist.psu.edu /han98adaptive.html (792 words)

	CodeGuru: Optimizing Tip on Adaptive Arithmetic Coding
		For details (including source code samples), you can refer to the Mark Nelson's article on arithmetic coding.
		In the practical implementations I've seen, the cumulative symbol frequency table (a component of the algorithm) was represented by an array of integer numbers containing, for each given symbol, the sum of frequencies of all the symbols having indices less than given.
		Both actions are followed by updating the adaptive model, what's commonly done by increasing the non-cumulative symbol's frequency (= increasing the cumulative frequencies of all the symbols having indices not less than the one of the symbol encoded/decoded).
	www.codeguru.com /Cpp/Cpp/algorithms/compression/article.php/c5089 (1044 words)

	Adaptive Huffman Coding
		As an example, the Adaptive Huffman Coding is examined below.
		The idea is however applicable to other adaptive compression algorithms.
		Note: Code for a particular symbol changes during the adaptive coding process.
	www.cs.cf.ac.uk /Dave/Multimedia/node212.html (279 words)

	Adaptive Huffman coding (Site not responding. Last check: 2007-11-01)
		The Huffman coding algorithm works when the source is stationary and the probabilities are known.
		In the circumstance in which the source is non-stationary or the probabilities are not known in advance, then the adaptive Huffman coding algorithm is a possibility.
		In this case, the relative probabilities of the symbols are estimated by keeping counts of the occurrences of the source symbols.
	www.engineering.usu.edu /classes/ece/7680/lecture6/node10.html (128 words)

	Data Compression Using Adaptive Coding and Partial String Matching - Cleary, Witten (ResearchIndex) (Site not responding. Last check: 2007-11-01)
		Abstract: The recently developed technique of arithmetic coding, in conjunction with a Markov model of the source, is a powerful method of data compression in situations where a linear treatment is inappropriate.
		Adaptive coding allows the model to be constructed dynamically by both encoder and decoder during the course of the transmission, and has been shown to incur a smaller coding overhead than explicit transmission of the model's statistics.
		Cleary, J.G. and Witten, I.H. (1984) "Data compression using adaptive coding and partial string matching," IEEE Trans Communications COM-32(4): 396-402.
	citeseer.ist.psu.edu /cleary84data.html (597 words)

	Adaptive Coding
		Although the theory of adaptive coding demonstrates large throughput gains over non-adaptive coding, it has been avoided in practice because of perceived problems with the variation of the fading channel between channel estimation and data transmission.
		The consideration of noise in the channel estimates and preliminary indications that the adaptive coding may be very useful in environments with limited diversity available is presented in:
		"Adaptive Coding for Fading Channels using Outdated Channel Estimates" (.ps file), Proceedings of the IEEE 48th Vehicular Technology Conference, pp.
	www-unix.ecs.umass.edu /~goeckel/adaptive.html (437 words)

	ATRAC: Adaptive Transform Acoustic Coding for MiniDisc
		The goal of many audio coding systems [1-6] is to control the time-frequency distribution of this noise in such a way as to render it inaudible to the human ear.
		This analysis indicates which units are critical and must be coded with high precision, and which units are less sensitive and can tolerate some quantization noise without degrading the perceived sound quality.
		Using a combination of subband coding and transform coding techniques, the input signal is analyzed in nonuniform frequency divisions which emphasize the important low-frequency regions.
	www.minidisc.org /aes_atrac.html (2390 words)

	Efficient Approximate Adaptive Coding
		The notion of approximate minimum-redundancy coding is introduced, in which a minimum-redundancy code is calculated for an approximate probability distribution.
		The characteristics of one particular class of approximate probability distribution allow extremely fast calculation of the minimum-redundancy code, and we describe a mechanism that uses this fast recalculation method in a pseudo-adaptive coder.
		Huffman code, prefix-free code, minimum-redundancy code, adaptive coding, dynamic coding.
	www.cs.mu.oz.au /~alistair/abstracts/dcc97.html (141 words)

	Huffman coding algorithms (Site not responding. Last check: 2007-11-01)
		Thus, excluding adaptive Huffman coding algorithm, these algorithms often require two passes through the input text - one for calculating probability function and one for coding process.
		In opposite, adaptive Huffman coding algorithm requires only single pass through the input text while simultaneously estimating probability function and coding.
		Certainly these algorithms can be applied for assigning codewords to whole messages, thus, according to noiseless coding theorem, achieving greater efficiency.
	www.cs.technion.ac.il /Labs/Isl/Project/Projects_done/VisionClasses/DIP/Lossless_Compression/node8.html (143 words)

	ImageQual
		Details on the algorithm, experiments, and results are contained in the manuscripts Archer and Leen, "Adaptive Transform Coding as Constrained Optimization" submitted to IEEE Transactions on Image Processing.
		A probabilistic generative model from which the coding algorithm is derived is in Archer and Leen, "From Mixtures of Mixtures to Adaptive Transform Codes", submitted to NIPS 2000.
		Earlier related work on adaptive coding is in Optimal Dimension Reduction and Transform Coding with Mixture Principal Components, Archer and Leen, International Joint Conference on Neural Networks (IJCNN), 1999.
	www.cse.ogi.edu /~tleen/Research/ImageQual.html (690 words)

	adaptive Huffman coding (Site not responding. Last check: 2007-11-01)
		As characters are processed, frequencies are updated and codes are changed (or, the coding tree is modified).
		Note: The total message length can be less than that produced by a static Huffman coding since the coding can be different at different places in the message.
		Explanation of algorithm FGK and Vitter's Algorithm (algorithm V), two different adaptive Huffman coding algorithms.
	www.nist.gov /dads/HTML/adaptiveHuffman.html (134 words)

	(WO/1998/029979) TRANSMITTER METHOD AND TRANSMISSION SYSTEM USING ADAPTIVE CODING BASED ON CHANNEL CHARACTERISTICS (Site not responding. Last check: 2007-11-01)
		The first code circuit (110) may, for example, encode the information using a FEC Code 1, such as convolutional coding, and the second code circuit (112) may encode the information using a FEC Code 2, such as repetition coding.
		The code switch (108) selects either the first or second code circuit (110 or 112) based on detected characteristics of the channel (101).
		After the code switch (108) selects the first or second code circuit (110 or 112), the information is appropriately coded to produce a coded signal which is transmitted over the channel (101) by a transmission circuit (116).
	www.wipo.int /pctdb/en/wo.jsp?KEY=98/29979.980709 (632 words)

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