Abstract: Methods and encoders/decoders for applying in-loop deblocking to intra-coded images/frames. In a decoding context, a deblocking filter is applied to reconstructed pixels of an intra-coded block prior to decoding the subsequent block in the decoding sequence. In an encoding context, a deblocking filter is applied to reconstructed pixels of an intra-coded block in an inter-coding loop before encoding a subsequent block in the coding order for the image.

Abstract: A method and device that uses transform matrices to down-sample a DCT image directly in the DCT domain. The transform matrices have been selected to minimize an optimization problem which is a function of the visual quality of down-sampled images obtained using the matrices and the computational complexity associated with using the transform matrices. The transform matrices comprise a row transform matrix and a column transform matrix. A down-sampled image is produced by determining an intermediary matrix as the product of the DCT image and one of either the row transform matrix or the column transform matrix and then determining the down-sampled image as the product of the intermediary matrix and the transform matrix not already used to determine the intermediary matrix.

Abstract: Methods and devices for encoding and decoding that involve sorting bins according to their respective estimated probabilities to form subsequences, each subsequence having an associated estimated probability. Subsequences are encoded to form codewords. Ordered sets of phrases of known length are then formed from the codewords. Each first of the phrases in a set contains at least part of one codeword. The first phrase has an associated estimated probability and the probability estimates associated with each of the other phrases in the set are determined based upon the probability estimate associated with the first phrase, which permits the phrases to be decoded in parallel.

Abstract: There is provided a method of interactive compression using multiple compression state information entries. The method comprises receiving a request for data from a communicating party; retrieving the data; identifying, for use in compressing the data, at least two compression state information entries shared between the parties to the communication; compressing the data with each of the at least two compression state information entries; determining, from the set of compression state information entries, a preferred compression state information entry that provides a greatest compression ratio; and transmitting the data, compressed in accordance with the preferred compression state information entry to the communicating party.

Abstract: Methods and devices for encoding and decoding data using adaptive transform domain filtering are described. The encoder determines a set of transform domain filter coefficients to be applied to a transform domain prediction. The filtering may, in some cases, also apply to quantized transform domain coefficients. Rate-distortion optimization may be used to determine the optimal filter coefficients on a frame-based, coding-unit-basis, or other basis.

Abstract: In order to improve interactive compression using compression state information, the side information caches of communicating parties must be updated, or synchronized. The present invention is directed to a method of synchronizing side information databases within an interactive compression system comprising two communicating parties comprising the steps of transmitting, from the a first communicating party to the second communicating party, a device hierarchical node index; comparing the device hierarchical node index with a server hierarchical node index and then determining a shared hierarchical node index based on common entries in the two hierarchical node indexes.

Abstract: For context based compression techniques, for example Context Based YK compression, a method and system for grouping contexts from a given context model together to create a new context model that has fewer contexts, but retains acceptable compression gains compared to the original context model. According to an exemplary embodiment of the method empirical statistics are determined for a file type of a file to be compressed; and the context model is generated by iteratively grouping contexts of an initial context model in accordance with the empirical statistics, the context model having fewer contexts than an initial context model.

Abstract: A method and system for reducing the number of mathematical operations required in the JPEG decoding process without substantially impacting the quality of the image displayed is disclosed. Embodiments provide an efficient JPEG decoding process for the purposes of displaying an image on a display smaller than the source image, for example, the screen of a handheld device. According to one aspect of the invention, this is accomplished by reducing the amount of processing required for dequantization and inverse DCT (IDCT) by effectively reducing the size of the image in the quantized, DCT domain prior to dequantization and IDCT. This can be done, for example, by discarding unnecessary DCT index rows and columns prior to dequantization and IDCT. In one embodiment, columns from the right, and rows from the bottom are discarded such that only the top left portion of the block of quantized, and DCT coefficients are processed.

Abstract: A method, system and computer program product for progressively encoding a digitized color image is provided. This involves: initializing a tree structure with at least one starting leaf node; determining at least one representative color for each starting leaf node; and growing the tree structure by (i) selecting a leaf node n to become a non-leaf node n linked to two new leaf nodes based on an associated achievable cost; (ii) creating the two new leaf nodes by re-allocating each color in n; (iii) determining a representative color for each of the two new leaf nodes; and (iv) encoding the index information associated with the leaf node n, the representative colors of the two new leaf nodes, and information regarding a plurality of pixels of the digitized color image corresponding to the two representative colors of the two new leaf nodes.

Abstract: The present invention relates to the compression of color image data. A combination of hard decision pixel mapping and soft decision pixel mapping is used to jointly address both quantization distortion and compression rate while maintaining low computational complexity and compatibility with standard decoders, such as, for example, the GIF/PNG decoder.

Abstract: A method of encoding video data using soft decision quantization makes use of iterative encoding to provide the ability to optimize encoding across different functional elements in a hybrid video encoder. Iterative encoding is used to allow quantization step size, motion prediction and quantization levels to be optimized despite their interrelated nature.

Abstract: A sequence of n coefficients is compressed by determining a cost-determined sequence of n coefficient indices represented by a cost-determined sequence of (run, index derivative) pairs under a given quantization table and run-index derivative coding distribution, wherein each sequence of (run, index derivative) pairs defines a corresponding sequence of coefficient indices such that (i) each index in the corresponding sequence of coefficient indices is a digital number, (ii) the corresponding sequence of coefficient indices includes a plurality of values including a special value, and (iii) each (run, index derivative) pair defines a run value representing a number of consecutive indices of the special value, and an index-based value derived from a value of the index following the number of consecutive indices of the special value.

Abstract: Encoding and decoding methods that perform quantization using adaptive reconstruction levels are presented. The reconstruction levels for a given partitioning of the data space may be selected based upon the distribution of data points within each sub-part defined by the partitioning. In some cases, the adaptive reconstruction levels may be based upon an average of the data points within each sub-part. In some cases, the adaptive reconstruction levels may be selected using a rate-distortion analysis including the quantization distortion associated with the levels versus the data points and the rate associated with transmitting the encoded adaptive reconstruction levels. The methods relate to data compression in a range of applications including audio, images and video.

Abstract: A method and device that uses transform matrices to down-sample a DCT image directly in the DCT domain. The transform matrices have been selected to minimize an optimization problem which is a function of the visual quality of down-sampled images obtained using the matrices and the computational complexity associated with using the transform matrices. The transform matrices comprise a row transform matrix and a column transform matrix. A down-sampled image is produced by determining an intermediary matrix as the product of the DCT image and one of either the row transform matrix or the column transform matrix and then determining the down-sampled image as the product of the intermediary matrix and the transform matrix not already used to determine the intermediary matrix.

Abstract: There is provided a method of interactive compression using multiple compression state information entries. The method comprises receiving a request for data from a communicating party; retrieving the data; identifying, for use in compressing the data, at least two compression state information entries shared between the parties to the communication; compressing the data with each of the at least two compression state information entries; determining, from the set of compression state information entries, a preferred compression state information entry that provides a greatest compression ratio; and transmitting the data, compressed in accordance with the preferred compression state information entry to the communicating party.

Abstract: For context based compression techniques, for example Context Based YK compression, a method and system for grouping contexts from a given context model together to create a new context model that has fewer contexts, but retains acceptable compression gains compared to the context model with more contexts is provided. According to an exemplary embodiment a set of files that are correlated to the file to be compressed (hereafter called training files) are read to determine, for an initial context model, the empirical statistics of contexts and symbols. In some embodiments, this includes determining the estimated joint and conditional probabilities of the various contexts and symbols (or blocks of symbols). The initial context model is then reduced to a desired number of contexts, for example, by applying a grouping function g to the original set of contexts to obtain a new and smaller set of contexts.

Abstract: In order to improve interactive compression using compression state information, the side information caches of communicating parties must be updated, or synchronized. The present invention is directed to a method of synchronizing side information databases within an interactive compression system comprising two communicating parties comprising the steps of transmitting, from the a first communicating party to the second communicating party, a device hierarchical node index; comparing the device hierarchical node index with a server hierarchical node index and then determining a shared hierarchical node index based on common entries in the two hierarchical node indexes.

Abstract: The present invention relates to the compression of color image data. A combination of hard decision pixel mapping and soft decision pixel mapping is used to jointly address both quantization distortion and compression rate while maintaining low computational complexity and compatibility with standard decoders, such as, for example, the GIF/PNG decoder.

Abstract: A method and system for reducing the number of mathematical operations required in the JPEG decoding process without substantially impacting the quality of the image displayed is disclosed. Embodiments provide an efficient JPEG decoding process for the purposes of displaying an image on a display smaller than the source image, for example, the screen of a handheld device. According to one aspect of the invention, this is accomplished by reducing the amount of processing required for dequantization and inverse DCT (IDCT) by effectively reducing the size of the image in the quantized, DCT domain prior to dequantization and IDCT. This can be done, for example, by discarding unnecessary DCT index rows and columns prior to dequantization and IDCT. In one embodiment, columns from the right, and rows from the bottom are discarded such that only the top left portion of the block of quantized, and DCT coefficients are processed.

Abstract: Down-sampling of an image may be performed in the DCT domain. A multiple layered network is used to select transform matrices for down-sampling a DCT image of size M×N to a DCT image of size I×J. A spatial domain down-sampling method is selected and applied to the DCT image to produce a down-sampled DCT reference image. A learning with forgetting algorithm is used to apply a decay to the elements of the transform matrix and select a transform matrices which solve an optimization problem. The optimization problem is a function of the visual quality of images obtained using the transform matrices and the computational complexity associated with using the transform matrices. The visual quality is a measure of the difference between the down-sampled DCT image obtained using the transform matrices and the visual quality of the DCT reference image obtained using a spatial domain down-sampling method.