Abstract: A white background determination section performs a white background determination on the basis of a white threshold calculated by a white threshold calculation section and an area size selected by an area size determination section. A character discrimination section executes character recognition such that a condition for character discrimination is relaxed when the white background determination section determines that a pixel of interest belongs to a white background, and the condition for character discrimination is made stricter in other cases.

Abstract: Methods and systems for improving performance of data decoding using apriori information about the data steam. In one aspect a decoder may determine the degree of lossiness inherent in the data or in the application of the data as a maximum resolution of data to be decoded and may thereby streamline entropy decoding of the data. For example, in DCT-based image data compression coupled with Huffman or other entropy encoding, apriori data may be analyzed to determine the maximum required resolution in bits of the DCT encoded data so as to simplify the entropy decoding. Other aspects optimize DCT decoding computation with faster approximations where the quantization values indicate a higher degree of lossiness or noise in the DCT encoded data. Apriori information may generally comprise values in the quantization table of a DCT encoded image and may be analyzed to determine the maximum symbol size and/or degree of lossiness.

Abstract: A system for decompressing a bit stream of compressed data representing a plurality of image blocks. This includes a two-step method of processing both a DC code and a plurality of AC codes. With respect to the processing of the AC codes, a plurality of bits of compressed input data relating to the AC codes are first retrieved from the bit stream. A first decoding operation is then executed based on the obtained compressed input data in order to generate first output data. It is then determined whether sufficient space is available for the first output data. If it is determined that there is sufficient space for the first output data, the first output data is outputted. On the other hand, if it is determined that there is insufficient space for the first output data, an alternate second decoding operation is executed in order to generate second output data.

Abstract: Methods, devices and systems for compressing images are provided. One method includes creating halftone mask structures and applying compression coding techniques to arrayed pixels sorted using the halftone mask structures in order to convert an image to a compressed bi-level, halftoned image.

Abstract: The present invention teaches a method of compressing still images in a multi-purpose compression system. The current invention teaches preprocessing of the images to a YUV 4:2:0 format and decomposing the images using two-dimensional Discrete Wavelet Transformation. The current invention teaches that filters may be selected based on image dimensions. After the image is decomposed, the frequency coefficients are quantized and the data is entropy encoded. The image is restored by reversing the compression process.

Abstract: Encoded data using reversible variable length code words is input to a forward decoder (123) to be decoded in the forward direction. When an error is detected in the encoded data in the forward decode processing, backward decode processing is started by a backward decoder (126). A decode value determination unit (125) determines a decode value by using the forward and backward decode results and the error detection positions in the encoded data in units of bits and syntax which are respectively detected in the forward decoding and the backward decoding.

Abstract: Methods, medium, and machines which compress, enhance, encode, transmit, decompress and display digital video images in real time. Real time compression is achieved by sub-sampling each frame of a video signal, filtering the pixel values, and encoding. Real time transmission is achieved due to high levels of effective compression. Real time decompression is achieved by decoding and decompressing the encoded data to display high quality images. Receiver can alter various setting including but not limited to the format for the compression, image size, frame rate, brightness and contrast.

Abstract: Methods and apparatuses for blending two images using vector table look up operations. In one aspect of the invention, a method to blend two images includes: loading a vector of keys into a vector register; converting the vector of keys into a first vector of blending factors for the first image and a second vector of blending factors for the second image using a plurality of look up tables; and computing an image attribute for the blended image using the blending factors.

Abstract: Estimation of the code size of variable length encoding of quantized DCT coefficients by summation over histogram bins of products of number of bin members and a code size of an average run of zero coefficients coupled with a representative level from the bin. The estimation provides low-complexity feedback for quantization level adjustment to obtain variable length code size target without actual performance of a quantization level plus variable length encoding.

Abstract: An inputted digital signal of a first format (DV video signal) is restored to a variable-length code by having its framing cancelled by a de-framing section 11, then decoded by a variable-length decoding (VLD) section 12, inversely quantized by an inverse quantizing (IQ) section 13, and inversely weighted by an inverse weighting (IW) section 14. Then, required resolution conversion in the orthogonal transform domain (frequency domain) is carried out on the inversely weighted video signal by a resolution converting section 16. After that, the video signal having the resolution converted is weighted by a weighting (W) section 18, then quantized by a quantizing (Q) section 19, coded by variable-length coding by a variable-length coding (VLC) section 20, and outputted as a digital signal of a second format (MPEG video signal).

Abstract: An optimal scanning method for coding/decoding an image signal is provided. In a method of coding an image signal through a discrete cosine transform, at least one is selected among a plurality of reference blocks. A scanning order in which to scan blocks to be coded of the reference blocks is generated and the blocks to be coded are scanned in the order of the generated scanning order. The at least one selected reference block is temporally or spatially adjacent to the block to be coded. When the blocks to be coded are scanned, probabilities that non-zero coefficients occur are obtained from the at least one selected reference block, and the scanning order is determined in descending order starting from the highest probability. Here, the scanning order is generated to be a zigzag scanning order if the probabilities are identical. The optimal scanning method increases signal compression efficiency.

Abstract: The invention is related to methods and apparatus that recover usable video data from partially corrupted data. Embodiments inspect corrupted data packets and identify the location or locations of an error, whether the corrupted data packet contains data expected to be error-free, and whether the error-free data should be used. Decoding of a packet in both the forward direction and the backward direction can be used to locate a position of an error. Intra-coded macroblocks can also be recovered. A decoder can elect to use or to drop an intra-coded macroblock recovered from a corrupted data packet according to further criteria that is applied to the recovered intra-coded macroblock. One embodiment inspects video bitstream data that has been encoded with an optional data partitioning feature enabled, and retrieves specified data in areas of a corrupted packet that are expected to be free from error.

Abstract: Provided are an image compression method and apparatus for differentially encoding digital image signals based on a Joint Photographic Experts Group (JPEG) image compression standard. RGB image signals are converted to luminance and chrominance data. Pixels of converted chrominance components are compared, difference values between the compared pixels are obtained, and representative pixel values are determined by comparing the obtained difference value and an allowable error. The representative pixel values are encoded. A data compression ratio can be improved by discrete-cosine-transforming only portions of an image having different colors from a background color.

Abstract: A method and an apparatus to encode a series of quantized coefficients of a transform of a block of image data. The transform is such that 0 is the most likely coefficient amplitude and 1 is the next most likely coefficient amplitude. The method includes forming symbols (called events) from the series of quantized transform coefficients. An event is a run of none or more zero-valued coefficients followed by a run of one of a predefined set of sequences, each sequence in the set being either a single coefficient of amplitude greater than one, or a sequence of 1's and 0's starting with a coefficient of amplitude 1. The method includes forming a codeword for each formed event. Relatively short codewords are formed to represent events that are relatively more likely to occur, and relatively long codewords are formed to represent events that are relatively less likely to occur.

Abstract: The method disclosed may be used together with any prefix oriented decoding method to enable faster decoding of variable length codes when a subset of most frequently used codes with relatively short prefixes may be determined. An embodiment of the present invention reads a number of bits, not less than the maximal possible length of a code, from a bit stream. Then a predetermined number of bits is selected and used as an index to a data structure that contains at least a decoded value and a validity indicator, along with other pre-decoded data, namely: prefix type and length, maximal code length for a group of codes, actual code length, the number of bits to return to the bit stream, etc. The validity indicator is used to determine whether to proceed with the decoding operation, or obtain the valid decoded value from the data structure and return excess bits to the bit stream.

Abstract: A robust fine granularity scalability video encoding includes a base layer encoder and an enhancement layer encoder in which motion compensated difference images are generated by comparing an original image to predicted images at base layer and enhancement layer with motion compensation. Based on leaky and partial predictions, a high quality reference image is constructed at the enhancement layer to improve temporal prediction. In the construction of the high quality reference image, one parameter ? controls the number of bitplanes of the enhancement layer difference coefficients used and another parameter ? controls the amount of predictive leak. A spatial scalability module allows the processed pictures at the base layer and the enhancement layer to have identical or different spatial resolutions.

Abstract: Encoded data using reversible variable length code words is input to a forward decoder (123) to be decoded in the forward direction. When an error is detected in the encoded data in the forward decode processing, backward decode processing is started by a backward decoder (126). A decode value determination unit (125) determines a decode value by using the forward and backward decode results and the error detection positions in the encoded data in units of bits and syntax which are respectively detected in the forward decoding and the backward decoding.

Abstract: A method and an apparatus to encode a series of quantized coefficients of a transform of a block of image data. The transform is such that 0 is the most likely coefficient amplitude and 1 is the next most likely coefficient amplitude. The method includes forming modes for each encountered non-zero amplitude and forming events for the modes in the mode-modified series formed by setting to zero all non-zero amplitudes other than the amplitude defining the mode. An event for modes for amplitudes greater than 1 is a run of none or more zero-valued coefficients followed a non-zero amplitude in the mode-modified series. In one embodiment, a first mode is defined for amplitude 1 wherein an event is a run of none or more zero-valued coefficients followed the amplitude 1 coefficient in the mode-modified series.

Abstract: For always executing an efficient and appropriate error compensation process and improving the convenience of the user, an image processing apparatus and a method enters encoded image data including a marker code for a resynchronizing process within one picture, detects a code error in the encoded image data, and discriminates whether or not to execute an error compensation process utilizing the marker code according to a result of the detection and an attribute of the encoded image data.

Abstract: We present a communication system which enables two or more parties to secretly communicate through an existing digital channel which has a primary function other than this secret communication. A first party receives a series of cover data sets, hides a certain amount of auxiliary data in the cover data sets, and then relays these cover data sets containing hidden data to a second party, aware of the hidden data. This second party may then extract the hidden data and either restore it to its original state (the state it was in before the first party received it) and send it along to its original intended destination, or may just simply extract the hidden auxiliary data. There exist a plethora of techniques for hiding auxiliary data in cover data, and any of these can be used for the hiding phase of the system. For example, in a JPEG cover data set, a Huffman table may be modified in such a way as to have no impact on the observable nature of the image, and several such schemes are presented here.

Abstract: A method of representing encoding or non-encoding by extending a video information field of a block when coding video information, is provided. The method of representing encoding or non-encoding by extending an information field for representing encoding or non-encoding is applied to an error allowable mode. Also, the amount of bits depending on the characteristics of video information to be encoded can be reduced. In this method, an image is encoded by extending a code (COD) field which is used in H.263 and MPEG-4 to indicate the cases where neither a motion vector (MV) nor a discrete cosine transform (DCT) value are encoded, where both the MV and the DCT value are encoded, and where only the MV is encoded. Therefore, in a channel with errors, the extended OCD field can be used in the error allowable mode. Also, video information can be encoded using a smaller amount of bits where the motion of an image is constant, than in the conventional art.

Abstract: A method, apparatus, and information bearing medium for merging display items in encoded form involve providing display items to be merged in an encoded format, such as a run length encoded format (e.g., modified enhanced run length encoded format). The display items are examined on the basis of item priority. A target item having a target area is defined. The display items in the target area are merged according to item priority to produce the target item. The target item is representative of the merged display items. The encoded data associated with the display items to be merged includes control data and color data. In one embodiment, tokens are produced using the encoded data associated with the display items to be merged. The display items are merged using the tokens. The tokens represent counts of repeated data or pointers to pass-thru data associated with the display items to be merged.

Abstract: The present invention provides a system that compresses and decompresses an image. The system includes a first codec a first stage codec for identifying runs of pixels of a defined value in a data stream of the image data beginning from the left and right margins of a line, such that information regarding the runs is assigned as a header and appended to the data stream. The compression device includes a second stage codec for scanning over remaining data in the data stream and compressing all but the header by utilizing a Huffman encoding scheme to reduce amount of data stored in the data stream, wherein the Huffman encoding scheme interleaves Huffman code values with unencrypted data while maintaining long word boundaries for the unencrypted data. The second codec also performs the operation of decompressing a compressed image.

Abstract: A method of encoding a digitised image including several pixel lines, which consists in encoding one line with a series of sub-codes characteristic of the length of the successive fields and their colour. When the image includes several identical successive lines, the method encodes the first one of the successive lines and completes with a sub-code characterising the repetition of the line and the number of times the line is repeated following the first line. When the image includes several lines including the same succession of colours, the method encodes the first one of the several lines including the same successive code and completes the code with a succession of sub-codes characterising the repetition of the succession of colours and the length of different fields of the different lines.

Abstract: There are provided a variable-length code decoding apparatus and method which can perform high-speed decoding processing without decreasing an image size and frame rate. A variable-length code decoding apparatus of this invention decodes a variable-length code containing a prefix and a suffix. This apparatus includes a prefix decoding unit which decodes the prefix of an input variable-length code and outputs a symbol and prefix length corresponding to the prefix, a suffix shifter unit which supplies the suffix on the basis of the prefix length output from the prefix decoding unit, and a symbol decoding unit which decodes a symbol corresponding to a variable-length code on the basis of the symbol corresponding to the prefix which is output from the prefix decoding unit, the suffix supplied by the suffix shifter unit, and a suffix length acquired in advance.

Abstract: A method of variable length coding classifies each received symbol into one of a plurality of classifications having a corresponding variable length code table selected based upon a probability distribution of received symbols within the classification. The variable length codeword output corresponds to the received symbol according to the variable length code table corresponding to the classification of that received symbol. The plurality of classifications and the corresponding variable length code tables may be predetermined and fixed. Alternatively, the variable length code table may be dynamically determined with data transmitted from encoder to decoder specifying the variable length code tables and their configurations. Universal variable length code (UVLC) is used to code the symbols. Universal variable length code can instantiate to different variable length code tables with different parameters.

Abstract: A frame group target bits number calculating unit (31) reads the total number of bits on frame group basis allocatable to residual frames from a storing unit (36), updates subtracting the number of generated bits used to code a preceding frame, and transmits to a next frame target bits number calculating unit (32). The next frame target bits number calculating unit (32) calculates the target number of bits to be allocated to a next frame based on the received total number of bits and the number of residual frames with considering a frame rate value, Rf. An average frame bits number calculating unit (33) calculates the average number of bits allocated to preceding frames. A calculating unit (34) multiplies the calculated average number of bits by a predetermined coefficient, compares the resulting value with above target number of bits, selects the greater number and transmits it to a quantization step calculating unit (35).

Abstract: A discrete cosine transform (DCT) level enhancement to Motion Picture Experts Group (MPEG) video encoding is described that results in a more concise bitstream than MPEG encoding without the enhancement. One degree of freedom provided by the MPEG encoding specifications is whether a frame- or field-based DCT operation will be used. In the field-based DCT operations, luminance sub-blocks are built from even or odd rows of the original image, which correspond to the top and bottom fields in field-based video. This allows the encoder to take advantage of the higher correlation between rows for the same field, especially in field-based video with a high level of motion. In one embodiment, both field- and frame-based DCT operations are performed and the results are quantized. On a macroblock-by-macroblock basis, the option that results in the fewest non-zero coefficients is selected and those coefficients are used for run-time encoding.

Abstract: Opportunistic image quality improvement in a digital camera. In a digital camera having a picture memory of fixed size for storing a predetermined number of pictures, raw image data is compressed to form primary and auxiliary data sets. The primary data set allows the image to be reconstructed at a first quality level. The primary and auxiliary data sets combined allow the reconstruction of the image at a higher quality level. As images are taken and processed, if sufficient storage space exists in the picture memory, both primary and auxiliary data sets are stored. This continues until the memory is full of primary and auxiliary data sets. Once the memory is full, as more images are taken and stored, the space used by auxiliary data sets is reclaimed for use by primary data sets, and the auxiliary data sets are not stored.

Abstract: Encoded data using reversible variable length code words is input to a forward decoder (123) to be decoded in the forward direction. When an error is detected in the encoded data in the forward decode processing, backward decode processing is started by a backward decoder (126). A decode value determination unit (125) determines a decode value by using the forward and backward decode results and the error detection positions in the encoded data in units of bits and syntax which are respectively detected in the forward decoding and the backward decoding.

Abstract: A bit-plane processor reads out a code block, which serves as a unit for arithmetic coding, from an SRAM. After converting the code block to the form of a bit-plane, the bit-plane processor supplies bit data to a pass processor. The pass processor includes an s pass processor, an r pass processor and a c pass processor. Each of s pass, r pass and c pass processings are executed in parallel in a state such that start time thereof is shifted by a predetermined unit time by operation of two delay units.

Abstract: An adaptive entropy coder is coupled with a localized conditioning context to provide efficient compression of images with localized high frequency variations. In one implementation, an arithmetic coder can be used as the adaptive entropy coder. The localized conditioning context includes a basic context region with multiple context pixels that are adjacent the current pixel, each of the context pixels having an image tone. A state is determined for the basic context region based upon a pattern of unique image tones among the context pixels therein. An extended context region that includes the basic context region is used to identify a non-local trend within the context pixels and a corresponding state. A current pixel may be arithmetically encoded according to a previously encoded pixel having the same tone or as a not-in-context element. In one implementation, a not-in-context element may be represented by a tone in a color cache that is arranged as an ordered list of most recent not-in-context values.

Abstract: An image recording apparatus is provided. The image recording apparatus includes a generator that generates information of recordable capacity of a storage and a holder for holding in advance data to be stored in the storage. A signal generator generates a signal indicating a data amount obtained when data held by the holder is variable-length encoded. A variable-length encoder means encodes the data held in the holder. A holder controller controls the holder so that the holder holds data to be stored, according to a comparison of the information generated by the generated by the generator and the data amount. A storage controller causes the storage to store the data controlled so as to be held by the holder, after encoding by the variable-length encoder means, on the basis of a predetermined condition.

Abstract: The present invention selectively applies one of VLC tables stored in a memory for encoding a coded block pattern of a macroblock according to the number of blocks having an object within the macroblock, the number of blocks obtained using shape information, thereby reducing the amount of data transmitted and increasing coding efficiency. The present invention also selectively applies one of VLD tables stored in a memory for decoding a coded block pattern of a macroblock according to the number of blocks having an object within the macroblock, the number of blocks obtained using shape information.

Abstract: A method and system of lossless compression of integer data using a novel backward-adaptive technique. The adaptive Run-Length and Golomb/Rice (RLGR) encoder and decoder (codec) and method switches between a Golomb/Rice (G/R) encoder mode only and using the G/R encoder combined with a Run-Length encoder. The backward-adaptive technique includes novel adaptation rules that adjust the encoder parameters after each encoded symbol. An encoder mode parameter and a G/R parameter are adapted. The encoding mode parameter controls whether the adaptive RLGR encoder and method uses Run-Length encoding and, if so, it is used. The G/R parameter is used in both modes to encode every input value (in the G/R only mode) or to encode the number or value after an incomplete run of zeros (in the RLGR mode). The adaptive RLGR codec and method also includes a decoder that can be precisely implemented based on the inverse of the encoder rules.

Abstract: An apparatus and method thereof to encode a moving image include a discrete cosine transform (DCT) unit performing a DCT process on input video data, a quantizer, and a motion estimation (ME) unit calculating a motion vector and a SAD per macro block. A DCT computational complexity calculator calculates a computational complexity of the ME unit, estimates a difference between the ME computational complexity and a target ME computational complexity, and updates a target DCT computational complexity based on the estimated difference. A DCT skipping unit sets a threshold value to determine whether to skip performing the DCT process on the input video data, based on the target DCT computational complexity updated by the DCT computational complexity calculator, compares the SAD per macro block, and the quantization parameter with the threshold value, and determines whether to allow the DCT unit to perform the DCT process on the input video data.

Abstract: A system, method and algorithm for performing statistical analysis on an input data source to determine an optimal token size resulting in an increased ratio value is described. Changes to the values of the tokens prior to compression may result in an overall compression increase even if the data source has been previously compressed. Specific techniques for modifying the tokens include varying the base size, rearrangement of the tokens, and modifications by matrix multiplication. After modification of the tokens, compression of the data using one or more lossless compression methods may be performed. The technique may be repeated by using the output of previous compression processes as input to additional entropy and compression optimization.

Abstract: The present invention aims to provide a variable-length coding apparatus that achieves a short processing cycle without causing an increase in circuit scale. Such a variable-length coding apparatus judges whether a VLC table has a variable-length code (VLC) corresponding to a combination (Last, Run, Level), by using an LMAX and an RMAX for the combination (Last, Run, Level). Based on the result of the judgment, the variable-length coding apparatus generates and outputs a code assigned to the combination (Last, Run, Level).

Abstract: A variable length decoding device for decoding variable length coding data and run length coding data according to the present invention comprises a variable length decoding unit 3 for serially decoding the variable length coding data and the run length coding data inputted from outside in a state in which “RUN” representing number of “0” and “LEVEL” representing a magnitude of a coefficient value are combined, a data buffer 4 for storing the “LEVEL”, address retainers 5 and 6 for retaining an address of the “LEVEL” corresponding to the “RUN” based on the number of “0” indicated by the “RUN”, a write control unit 7 for writing the “LEVEL” in the data buffer 4 based on the information of the address retainers, and a read control unit 8 for reading the “LEVEL” from the data buffer 4 based on the information of the address retainers.

Abstract: Transform coefficients of sample blocks of a macroblock of a video picture are encoded by adaptively encoding in combination, the number of non-zero coefficients before the trailing one coefficients and the number of trailing one coefficients. The transform coefficients may be further encoded by adaptively encoding one or more of the signs of the trailing one coefficients, the level measures of the non-zero coefficients, the total number of zero coefficients interposed in the non-zero coefficients, and the respective run lengths of the zero coefficients. Adaptive encoding of the number and trailing one coefficients may be performed in view of one or more neighboring sample blocks, whereas adaptive encoding of level measures may be performed in view of quantization parameters of a macroblock and previously encoded level measures. Decoding may be performed in an inverse manner.

Abstract: A system and method facilitating progressively transforming and coding digital pictures is provided. The present invention via employment of a multi-resolution lapped transform provides for progressive rendering as well as mitigation of blocking artifacts and ringing artifacts as compared to many conventional compression systems. The invention includes a color space mapper, a multi-resolution lapped transform, a quantizer, a scanner and an entropy encoder. The multi-resolution lapped transform outputs transform coefficients, for example, first transform coefficients and second transform coefficients. A multi-resolution representation can be obtained utilizing second transform coefficients of the multi-resolution lapped transform. The color space mapper maps an input image to a color space representation of the input image. The color space representation of the input image is then provided to the multi-resolution lapped transform.

Abstract: Previously-unused slots in a Huffman code table associated with a Joint Photographic Experts Group (JPEG) image file are associated with various quantization matrices (Q matrices) that are used to quantize data blocks of the JPEG image file. Huffman codes associated with the various Q matrices permit the particular Q matrix used to quantize a given data block to be signaled by a decoder as an end-of-block (EOB) code. The EOB codes and the Huffman code table are sent with the JPEG image file. Upon decoding of the image file, a standard JPEG decoder reads each of the EOB codes as a standard JPEG EOB code and does not vary the Q matrix. A modified decoder reads from each of the EOB codes which Q matrix was used to encode each particular data block of the image and uses that Q matrix to dequantize the data block.

Abstract: The method generates a compressed digital image from a original image. The compressed digital image allows random access to portions of the compressed image at a number of resolutions. The original image is first transformed (103) by a multi-level DWT to form a non redundant multiple resolution frequency domain representation of the image. The representation comprises a DC subband and a plurality of high frequency subbands arranged as levels, where each level represents a frequency contribution between adjacent resolutions and where each subband comprises a plurality of tiles. The DC subband is then entropy encoded (104) into the bitstream. The high frequency subbands are next entropy encoded (108,109, and 110) into the bitstream in level order (105,113,114) and tile order (107,111).

Abstract: A method and apparatus for variable accuracy inter-picture timing specification for digital video encoding is disclosed. Specifically, the present invention discloses a system that allows the relative timing of nearby video pictures to be encoded in a very efficient manner. In one embodiment, the display time difference between a current video picture and a nearby video picture is determined. The display time difference is then encoded into a digital representation of the video picture. In a preferred embodiment, the nearby video picture is the most recently transmitted stored picture. For coding efficiency, the display time difference may be encoded using a variable length coding system or arithmetic coding. In an alternate embodiment, the display time difference is encoded as a power of two to reduce the number of bits transmitted.

Abstract: In a compression and decompression coding method, arrangement and computer program product, a data signal containing a number of symbols is converted into a series of codewords. A set of codewords is established and the data signal is monitored to determine the most frequently occurring symbols therein and/or sequences of symbols therein containing at least two symbols. A codeword is then allocated to each of the most frequently occurring of the symbols and/or symbol sequences. At least one codeword is reserved for indicating uncompressed data. When compressing a signal, the incoming symbols are first checked to determine if they correspond to a codeword. If a symbol corresponds to more than one codeword, further symbols are read until a symbol occurs which corresponds to one codeword only. That codeword is then transmitted. Any symbol that does not correspond to a codeword is supplemented with a codeword indicative of no compression and is then transmitted.

Abstract: A system to decode compressed digital images decodes frequently occurring variable length symbols encoding a compressed image by selecting a corresponding quantized pixel value for inverse quantization from a table relating code symbols and precalculated quantized pixel values.

Abstract: In an image decoding apparatus that generates a decoded image from a code sequence. The decoding apparatus has a bus, a computer and a memory, wherein the computer and the memory are connected to each other via the bus. The code sequence is generated by performing orthogonal transform, quantization and entropy coding on image data, which is stored in the memory. The decoding apparatus includes an entropy decoding unit, achieved by the computer, for reading one code out of the code sequence, which is stored in the memory, via the bus and performing entropy decoding on the read code in to generate a decode value. The apparatus also includes a coefficient generating unit, achieved by the computer, for generating at least one orthogonal transform coefficient according to the generated decode value. Also, a writing unit is achieved by the computer, for writing the generated at least one orthogonal transform coefficient into the memory via the bus.

Abstract: A system and associated method automatically and very rapidly determine the dominant periodicity in sequential binary data. The method incorporates a fast binary autocorrelation function used to discover the dominant periodicity in a sequential binary signal, and exploits this information in a periodicity exploiting application, such as using any one or more of a pixel periodicity or an edge periodicity based compression method in order to compress periodic halftoned bitonal images. The method implements four processes: The first process describes setting up the data in a transition-based representation to facilitate an algorithm to quickly find an autocorrelation distribution derived from a sequential binary signal. The second process describes a fast dominant periodicity search algorithm. The third process describes an algorithm that estimates the dominant window for estimating the dominant periodicity within one line of two-dimensional sequential binary signal.

Abstract: An adaptive variable-length coding/decoding method performs an optimal variable-length coding and decoding depending on an intro mode/inter mode condition, quantization step size and a current zigzag scanning position, such that a plurality of variable-length coding tables having different patterns of a regular region and an escape region according to statistical characteristics of the run level data are set. One of the variable-length coding tables is selected according to mode, quantization step size and scanning position, and the orthogonal transform coefficients according to the selected variable-length coding table are variable-length-coded.

Abstract: An image processing device which processes a portion of the decompression process including a lot of comparatively complex operations like an inverse discrete cosine transform by software with using a high-performance, general-purpose processor capable of parallel processing, and the other portion of the decompression process which is compara- tively simple but requires frequent access to a memory, e.g., when other frame data is to be read out for processing of encoded interframe predictive image data, or is compara- tively simple but substantially hard to process in parallel, e.g., when variable length coded pixel values are to be decoded, by hardware with the use of a specialized periph- eral circuit.