Abstract: The Moving Picture Experts Group (MPEG) standard addresses compression of video signals at approximately 1.5M-bits. MPEG is a generic standard and is independent of any particular applications. Applications of compressed video on digital storage media include asymmetric applications such as electronic publishing, games and entertainment. Symmetric applications of digital video include video mail, video conferencing, videotelephone and production of electronic publishing. Design of the MPEG algorithm presents a difficult challenge since quality requirements demand high compression that cannot be achieved with only intraframe coding. The algorithm’s random access requirement, however, is best satisfied with pure intraframe coding. MPEG uses predictive and interpolative coding techniques to answer this challenge. Extensive details are presented.

Abstract: Approaches to the zero-frequency problem in adaptive text compression are discussed. This problem relates to the estimation of the likelihood of a novel event occurring. Although several methods have been used, their suitability has been on empirical evaluation rather than a well-founded model. The authors propose the application of a Poisson process model of novelty. Its ability to predict novel tokens is evaluated, and it consistently outperforms existing methods. It is applied to a practical statistical coding scheme, where a slight modification is required to avoid divergence. The result is a well-founded zero-frequency model that explains observed differences in the performance of existing methods, and offers a small improvement in the coding efficiency of text compression over the best method previously known. >

Abstract: From the Publisher: Topics in this guide to data compression techniques include the Shannon-Fano and Huffman coding techniques, Lossy compression, the JPEG compression algorithm, and fractal compression. Readers also study adaptive Huffman coding, arithmetic coding, dictionary compression methods, and learn to write C programs for nearly any environment. The disk illustrates each learned technique and demonstrates how data compression works.

Abstract: From the Publisher: Topics in this guide to data compression techniques include the Shannon-Fano and Huffman coding techniques, Lossy compression, the JPEG compression algorithm, and fractal compression. Readers also study adaptive Huffman coding, arithmetic coding, dictionary compression methods, and learn to write C programs for nearly any environment. The disk illustrates each learned technique and demonstrates how data compression works.

Abstract: The compression of successive blocks of digital data is optimized by selecting between different compression algorithms or different data formats on a block-by-block basis. In one application, digitized interlaced video signals are processed for transmission in a compressed form. A set of pixel data presented in a field format is compressed to provide a first compressed video signal. The set of pixel data is also presented in a frame format and compressed to provide a second compressed video signal. Errors are evaluated in the first and second compressed video signals. The compressed video signal having the least error is selected for further processing. The technique is repeated for successive sets of pixel data and the selected signals are encoded to identify them as field formatted or frame formatted signals. The encoded selected signals are then combined to provide a compressed video signal data stream for transmission. Apparatus for receiving and decoding the signals is also disclosed.

Abstract: A technique for providing error protection without the additional overhead required for channel coding is presented. The authors start from the premise that, during source coder design, for the sake of simplicity or due to imperfect knowledge, assumptions have to be made about the source which are often incorrect. This results in residual redundancy at the output of the source coder. The residual redundancy can then be used to provide error protection in much the same way as the insertion of redundancy in convolutional coding provides error protection. The authors develop an approach for utilizing this redundancy. To show the validity of this approach, the authors apply it to image coding using differential pulse code modulation (DPCM), and obtain substantial performance gains, both in terms of objective and subjective measures. >

Abstract: The need to transmit large amounts of data over a band-limited channel has led to the development of various data compression schemes. Many of these schemes function by attempting to remove redundancy from the data stream. An unwanted side-effect of this approach is to make the information transfer process more vulnerable to channel noise. Efforts at pro- tecting against errors involve the reinsertion of redundancy and an increase in bandwidth requirements. We present a technique for providing error protection without the additional overhead required for channel coding. We start from the premise that, during source coder design, for the sake of simplicity or due to imperfect knowledge, assumptions have to be made about the source which are often incorrect. This results in residual redundancy at the output of the source coder. The residual redundancy can then be used to provide error protection in much the same way as the insertion of redundancy in convolutional coding provides error protection. In this paper we develop an approach for utilizing this redundancy. To show the validity of this approach, we apply it to image coding using DPCM, and obtain substantial performance gains, both in terms of objective as well as subjective measures.

Abstract: A connection specific compression system is selectively implemented in connections having the greatest data redundancy and utilizes modularity in implementing data compression in a layered network communication system. A data compression facility is interfaced in the layered system and intercepts data at a protocol layer prior to the data being packetized for transmission. A system acting as a compression host comprises a data packet switch driver which intercepts application data packets passing over layered network interfaces and routes selected client application data packets to an associated local compression process which has an integral network protocol and which compresses the data stream in accordance with a selected compression algorithm. The compressed data passes through the system network protocol and the packet switch driver subsequently sends the compressed data back into the communications stream through a network driver. The compressed data passes across the network communication channel and is received by a decompression host having peer compression/decompression capabilities. The peer compression process decompresses the received data and sends it, via a second/decompression host resident packet switch driver, as though received from the network, into the decompression host system network protocol for connection with an application running on the second host.

Abstract: High-resolution digital images make up very large data sets that are relatively slow to transmit and expensive to store. Data compression techniques are being developed to address this problem, but significant image deterioration can occur at high compression ratios. In this study, the authors evaluated a form of adaptive block cosine transform coding, a new compression technique that allows considerable compression of digital radiographs with minimal degradation of image quality. To determine the effect of data compression on diagnostic accuracy, observer tests were performed with 60 digitized chest radiographs (2,048 x 2,048 matrix, 1,024 shades of gray) containing subtle examples of pneumothorax, interstitial infiltrate, nodules, and bone lesions. Radiographs with no compression, with 25:1 compression, and with 50:1 compression ratios were presented in randomized order to 12 radiologists. The results suggest that, with this compression scheme, compression ratios as high as 25:1 may be acceptable for pr...

Abstract: A method and apparatus for storing a representation of a cardiac signal by compressing the data using scan correlation and temporal data compression techniques. The method and apparatus sense cardiac signals when the heart is functioning in a known cardiac state, then characterize this known state by storing a temporally compressed template of time sequence samples. The method and apparatus may perform testing for multiple different cardiac states and store templates associated with each state. Subsequently when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac signals by temporally compressing samples and scan correlating these samples with the previously stored templates to derive correlation coefficients. These correlation coefficients are a basis for identifying and classifying cardiac signal waveforms. For waveforms which correlate highly with a particular template, analysis of the timing of the maximum correlation coefficient provides a fiducial time which designates the time relationship of waveforms within different cardiac cycles. The method and apparatus store information in the form of templates, fiducial timing markers, and waveform occurrence counts. This data provides the information necessary to subsequently reproduce a long-term signal record.

Abstract: An image data compression technique is described which utilizes calculating means and a selected series of bit calculating stages having delays, to estimate one or more quantization parameters for such data. The estimation process preferably is iterated a number of times, with the values found through each estimation being used as the trial values for subsequent estimations. In addition, an initial trial value is selected by a data look ahead technique, which assures that its value is within range of the final quantization parameter used to quantize the data. The final quantization parameter insures that the compressed data fits within a predetermined number of encoded data bits to be transmitted or recorded, for example, in a recording medium.

Abstract: An algorithm is presented for estimating and compensating camera zooms and pans. It models the global motion in each frame with just two parameters: a zoom factor and a two-dimensional pan vector both based on local displacement vectors found by conventional means (such as block matching). Since motion by objects in the scene obscures global motion, the algorithm can iterate to refine its estimate. Simulations suggest the algorithm is robust and accurate, and can significantly reduce both the energy of the motion compensated residual image as well as the zeroth-order entropy of the local displacement vector field. >

Abstract: A new, simple, extremely fast, locally adaptive data compression algorithm of the LZ77 class is presented. The algorithm, called LZRW1, almost halves the size of text files, uses 16 K of memory, and requires about 13 machine instructions to compress and about 4 instructions to decompress each byte. This results in speeds of about 77 K and 250 K bytes per second on a one-MIPS machine. The algorithm runs in linear time and has a good worst-case running time. It adapts quickly and has a negligible initialization overhead, making it fast and efficient for small as well as large blocks of data. >

Abstract: The authors describe a method for optimizing in a rate-distortion sense the performance of block matching motion compensation for video compression using fixed or variable size blocks. They apply recent advances in rate allocation theory and optimal tree structures to the choice of motion vector and block size for each region of the prediction image. They show that a variable block size algorithm using an optimized tree structure yields a significant improvement in rate-distortion performance over traditional motion compensation with a fixed block size. The computational complexity of such a system is not significantly higher than that of a fixed block size system. >

Abstract: A two-computer system and method wherein data is transferred between the computers as complete disk images rather than as files. The transfer is made between the parallel ports of the two computers, for greater speed; amd RLL data compression is used to increase the effective rate of data transfer.

Abstract: A new motion compensation technique using a window which satisfies the perfect reconstruction condition is proposed. THe conventional motion compensation using rectangular blocks often gives discontinuities between neighboring motion compensation blocks in the predicted image. The proposed method is based on a window operation to the data which overlaps an area of the conventional motion compensation block. Computer simulation is carried out using MPEG video coding algorithm to evaluate the proposed method. The performance of the proposed method is better than the conventional method in terms of mean square error, and large improvement can be obtained at the block boundaries. This gives a smooth predicted image for a typical MC + DCT coding scheme.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: A data processing system augments compression of non-zero values of significant coefficients by coding entries of a significance map independently of coding the values of significant non-zero coefficients. A dedicated symbol represents a zerotree structure encompassing a related association of insignificant coefficients within the tree structure, thereby compactly representing each tree of insignificant coefficients. The zerotree symbol represents that neither a root coefficient of the zerotree structure nor any descendant of the root coefficient has a magnitude greater than a given reference level. The zerotree structure is disclosed in the context of a pyramid-type image subband processor together with successive refinement quantization and entropy coding to facilitate data compression.

Abstract: How new standards for video compression and new IC chips will change the worlds of computing, broadcasting, and communication is discussed. An explanation of how video compression works is given. The three digital video standards that have been proposed are described. They are the Joint Photographic Experts Group (JPEG) standard for still picture compression, the Consultative Committee on International Telephony and Telegraphy (CCITT) Recommendation H.261 for video teleconferencing, and the Moving Pictures Experts Group (MPEG) for full-motion compression on digital storage media. Some available chip sets are described, and the issue of design flexibility is considered. >

Abstract: A method and apparatus for encoding interframe error data in an image transmission system, and in particular in a motion compensated image transmission system for transmitting a sequence of image frames from a transmitter (8) to a receiver (21), employ hierarchical entropy coded lattice threshold quantization (46) to increase the data compression of the images being transmitted. The method and apparatus decimate (502) an interframe predicted image data and an uncoded current image data (504), and apply hierarchical entropy coded lattice threshold quantization encoding (506) to the resulting pyramid data structures. Lossy coding is applied on a level-by-level basis for generating the encoded data representation of the image difference between the predicted image data and the uncoded original image. The method and apparatus are applicable to systems transmitting a sequence of image frames (or other pattern data, such as speech) both with and without motion compensation.

Abstract: A circuit for compressing and expanding video color component data comprises a FIFO line memory and a delay circuit. A timing circuit generates control signals for writing data into the line memory and for reading data from the line memory to compress and expand the data. The delay circuit matches the data compressed or expanded in the FIFO line memory to luminance data which is similarly compressed or expanded. A switching network selectively establishes a first signal path in which the line memory precedes the delay circuit for implementing the data expansion and a second signal path in which the delay circuit precedes the line memory for implementing the data compression. The switching network is controlled according to selected display formats requiring compression or expansion, for example by a microprocessor.

Abstract: A system of data transmission by packets in which certain data-exchange links use a transmission chain comprising two transmitter/receiver terminals and at least two intermediate units, and in which each packet is associated with the transmission of data belonging to only one link, at least some of the intermediate units including means for the compression and/or decompression, in at least one direction of transmission, of the data elements contained in the data fields of the packets transmitted, according to at least one compression algorithm. The compression and decompression units are allocated selectively to some of the links, to compress the data elements transmitted on at least a portion of the transmission chain. The compression/decompression function is selectively activated in the allocated units for at least one series of consecutive packets of the corresponding link, and is selectively deactivated for the other packets.

Abstract: Summary form only given. The author surveys the menagerie of quantization and compression algorithms in the specific context of image compression and provides some general comparisons based on performance, complexity, and side benefits of particular coding techniques. >

Abstract: A lossless data compression circuit compares a new data string with a set of comparison data, and produces a sequence of codewords representing a sequence of successive, non-overlapping substrings of the new data string. A shift register stores and shifts the comparison data until all of the characters in the comparison data have been compared with the new data string. A composite reproduction length circuit finds the maximum length string within the set of comparison characters matching substrings of characters in the new data string beginning at each position in the new data string. The composite reproduction length circuit produces a multiplicity of data pairs, one for each position of the new data string. Each data pair comprises a maximum length value, corresponding to the maximum length matching comparison string found for the new data substring starting at the corresponding position, and a pointer value denoting where the maximum length matching comparison string is located in the comparison data. A codeword generator then generates a sequence of codewords representing the new data string, each codeword including one of these data pairs and representing a substring of the new data string. By using N such data compression units in parallel, with each storing an identical new data string, and each unit's shift register storing and shifting a different subset of a specified comparison string, processing time for generating codewords is reduced by a factor of approximately (N-1)/N.

Abstract: Lossless text compression methods involve some form of moderately high-order exact string matching. However, this work cannot easily be carried over to lossless image compression, because images are two-dimensional and (more important) essentially quantized analog data. A better plan is to find and encode as much of the image structure of the data as possible, and then to encode efficiently the unstructured, noisy residual. In three steps the authors predict the value of each pixel, model the error of the prediction, and encode the error of the prediction. Having a probabilistic model for the errors, they can use arithmetic coding to encode the errors efficiently with respect to the model. >

Abstract: In a video compression system odd and even fields of video signal are independently compressed in sequences of intraframe and interframe compression modes. The odd and even fields of independently compressed data are interleaved for transmission. The fields are interleaved such that intraframe even field compressed data occurs midway between successive fields of intraframe odd field compressed data. The interleaved sequence provides receivers with twice the number of entry points into the signal for decoding without increasing the amount of data transmitted.

Abstract: Several topics connecting basic vision research to image compression and image quality are discussed: (1) A battery of about 7 specially chosen simple stimuli should be used to tease apart the multiplicity of factors affecting image quality. (2) A 'perfect' static display must be capable of presenting about 135 bits/min2. This value is based on the need for 3 pixels/min and 15 bits/pixel. (3) Image compression allows the reduction from 135 to about 20 bits/min2 for perfect image quality. 20 bit/min2 is the information capacity of human vision. (4) A presumed weakness of the JPEG standard is that it does not allow for Weber's Law nonuniform quantization. We argue that this is an advantage rather than a weakness. (5) It is suggested that all compression studies should report two numbers separately: the amount of compression achieved from quantization and the amount from redundancy coding. (6) The DCT, wavelet and viewprint representations are compared. (7) Problems with extending perceptual losslessness to moving stimuli are discussed. Our approach of working with a 'perfect' image on a 'perfect' display with 'perfect' compression is not directly relevant to the present situation with severely limited channel capacity. Rather than studying perceptually lossless compression we must carry out research to determine what types of lossy transformations are least disturbing to the human observer. Transmission of 'perfect', lossless images will not be practical for many years.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: A method and apparatus for compressing digital data uses data which has been previously compressed as a dictionary of substrings which may be replaced in an input data stream. The method and apparatus uses a hash table to take advantage of principles of locality and probability to solve the maximal matching substring problem inherent in this type of compressing apparatus, most of the time. The hash table consists of first-in, first-out (FIFO) collision chains of fixed, uniform numbers of pointers to substrings of data already compressed which potentially match an input substring. A link list is maintained for linking pointers to corresponding potentially matching strings. A companion decompressing method and apparatus receives compressed data from the compressing apparatus and expand that data back to its original form.

Abstract: The encoding schemes utilize the first- and second-order Markov models to describe the source structure. Two coding techniques, Huffman encoding and arithmetic encoding, are used to achieve a high coding efficiency. Universal code tables which match the statistics of contour line drawings obtained from 64 contour maps are presented and can be applied to encode all contour line drawings with chain code representations. Experiments have shown about a 50% improvement on the code amount over the conventional chain encoding scheme with arithmetic coding schemes, and also have shown a compression rate comparable to that obtained by T. Kaneko and M. Okudaira (1985) with Huffman coding schemes, while this implementation is substantially simpler. >

Abstract: For pt.I, see ibid., vol.37, no.3, p.97-101 (1991). A predictive block-matching motion estimation scheme was implemented for efficient video code design. The scheme is based on the so-called inertia effect of natural video scenes and takes advantage of the motion vectors obtained in the previous frames. The benefits from this prediction process are threefold. First, the searching area is greatly reduced, and so is the computational complexity. Second, the motion vector overhead information is reduced since motion vectors are decorrelated by the prediction process. Finally, the motion vectors estimated from this procedure are more realistic since it reflects the real physical phenomena. These advantages were also demonstrated by simulation results including the coded data rate, displaced frame difference entropy, motion vectors, and reconstructed signal-to-noise ratio. Only a simple prediction model was implemented; further results in more general autoregressive (AR) modes are still under study. >