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A STUDY OF VECTOR transform coding OF SUBBAND-DECOMPOSED IMAGES

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1994年第4期4卷 383-391页

作者： LI, WP ZHANG, YQ GTE LABS INC WALTHAMMA 02254

This paper reports our study on vector transform coding (VTC), a new image coding scheme, on subband-decomposed images. It is shown that vector transformation (VT) reduces the inter-vector correlation, although not as much as the discrete cosine transform (DCT). However, it is also shown that VT preserves the intra-vector correlation much better than the DCT so that vector quantization (VQ) in the VT domain can be made more efficient. VTC of subband-decomposed image introduces another dimension of adaptivity, in which coding parameters, bit allocation, and VQ codebooks can be adapted to each level of the subband pyramid as well as to each vector in the VT domain. The new subband/VTC scheme is compared with VQ of original images, VQ of subband-decomposed images, DCT-based transform coding, and subband/DCT/VQ schemes. Simulation results indicate that the new scheme achieves 1 to 3dB improvement over the other schemes in terms of peak signal-to-noise ratio (PSNR). This improvement is also supported by subjective evaluations.

关键词： transform coding Discrete cosine transforms Image coding Filter bank Image analysis Vector quantization PSNR Decorrelation Bit rate Speech analysis

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High-rate quantization and transform coding with side information at the decoder

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SIGNAL PROCESSING 2006年第11期86卷 3160-3179页

作者： Rebollo-Monedero, David Rane, Shantanu Aaron, Anne Girod, Bernd Stanford Univ Dept Elect Engn Informat Syst Lab Stanford CA 94305 USA

We extend high-rate quantization theory to Wyner-Ziv coding, i.e., lossy source coding with side information at the decoder. Ideal Slepian-Wolf coders are assumed, thus rates are conditional entropies of quantization indices given the side information. This theory is applied to the analysis of orthonormal block transforms for Wyner-Ziv coding. A formula for the optimal rate allocation and an approximation to the optimal transform are derived. The case of noisy high-rate quantization and transform coding is included in our study, in which a noisy observation of source data is available at the encoder, but we are interested in estimating the unseen data at the decoder, with the help of side information. We implement a transform-domain Wyner-Ziv video coder that encodes frames independently but decodes them conditionally. Experimental results show that using the discrete cosine transform results in a rate-distortion improvement with respect to the pixel-domain coder. transform coders of noisy images for different communication constraints are compared. Experimental results show that the noisy Wyner-Ziv transform coder achieves a performance close to the case in which the side information is also available at the encoder. (c) 2006 Elsevier B.V. All rights reserved.

关键词： high-rate quantization transform coding side information Wyner-Ziv coding distributed source coding noisy source coding

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PREDICTIVE ORDERING TECHNIQUE AND FEEDBACK transform coding FOR DATA-COMPRESSION OF STILL PICTURES

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IEEE TRANSACTIONS ON COMMUNICATIONS 1992年第2期40卷 385-396页

作者： NEAGOE, VEI Faculty of Electronics and Telecommunications Polytechnic Institute of Bucharest Bucharest Romania

This paper presents a new method for efficient image coding, consisting of a cascade of the following processing stages: i) predictive ordering technique (POT);ii) feedback transform coding (FTC);iii) vertical subtraction of quantized coefficients (VSQC);iv) predictive coding refinements in the signal space consisting of either overshoot suppression (OS) as a first variant or hybrid block truncation coding (HBTC) as a second one. The POT algorithm uses the vertical correlation between adjacent pels to change the relative order of elements along a scan line, by putting them in decreasing order of amplitudes (taking as reference the previously received scan line);this ordering concentrates the signal energy into "low generalized frequency" regions. The FTC method is an iterative procedure for increasing with a given step the number of nonzero elements that belong to the orthogonally transformed picture vector, until the mean square error criterion is satisfied (the error representing the difference between the original image vector and the last reconstructed iteration). The VSQC computes the discrete differences between the quantized transform coefficients of the same order belonging to adjacent scan lines. The OS algorithm detects and eliminates the spatial reconstruction errors, whose absolute values exceed a given threshold. The HBTC uses a one-bit nonparametric quantization of the error vector representing the difference between the original picture vector and the last reconstructed vector (satisfying the FTC criterion), so that the first two sample moments are preserved. The reconstructed pictures are presented with their coding fidelity performances (mean square quantization error, mean absolute error and signal-to-noise ratio), using as test pictures a portrait and a LANDSAT image. Good quality images at low bit rate (0.55-1.1) bits/pixel have been obtained.

关键词： Feedback transform coding Data compression Predictive coding Signal processing Image reconstruction Image coding Performance evaluation Quantization Signal to noise ratio

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SMOOTH WAVELETS, transform coding, AND MARKOV-1 PROCESSES

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 1995年第11期43卷 2561-2569页

作者： USEVITCH, BE ORCHARD, MT UNIV ILLINOIS CTR SUPERCOMP RES & DEV URBANA IL 61801 USA UNIV ILLINOIS BECKMAN INST ADV SCI & TECHNOL URBANA IL 61801 USA

This paper compares the energy compacting properties of unitary transforms from transform coders and two-band paraunitary filter banks from subband coders using a cost criterion that is proposed. Stationary processes for which paraunitary filters have better energy compaction than unitary filters are denoted as subband optimal, and all subband optimal processes are analytically characterized for the case of length-4 filters. It is shown analytically for length-4 filters and empirically for longer-length filters that Markov-1 processes are subband optimal and that the Daubechies maximally smooth wavelet sequences achieve better energy compaction than the best unitary filters for Markov-1 inputs.

关键词： transform coding Filter bank Compaction Wavelet analysis Image coding Image edge detection USA Councils Distortion measurement Image reconstruction Energy measurement

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Convolutional effects in transform coding with TDAC: An optimal window

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IEEE TRANSACTIONS ON SPEECH AND AUDIO PROCESSING 1996年第2期4卷 104-114页

作者： Ferreira, AJS INESC-Porto Portugal

Perceptual coders have proven to be highly efficient in the context of audio or video applications involving bit rate reduction. However, this efficiency is strongly limited in very low bit rate coding conditions. This paper studies the multiplicative effects of quantization in the frequency domain, when an overlapped filter bank (TDAC) is used to shape the quantization noise in a perceptually optimal way. The associated circular convolution operation generates aliased components in the time domain that are examined and subjected to minimization. A closed form expression is suggested to approximate an optimal transform window offering a desired tradeoff between the reduction of the time artifacts produced by a coarse quantization and the reduction of the stop-band leakage, relative to other transform windows commonly used.

关键词： Convolutional codes transform coding Quantization Psychoacoustic models Humans Convolution Bit rate Filter bank Colored noise Frequency domain analysis

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Nonlinear transform coding

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IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING 2021年第2期15卷 339-353页

作者： Balle, Johannes Chou, Philip A. Minnen, David Singh, Saurabh Johnston, Nick Agustsson, Eirikur Hwang, Sung Jin Toderici, George Google Res Mountain View CA 94043 USA

We review a class of methods that can be collected under the name nonlinear transform coding (NTC), which over the past few years have become competitive with the best linear transform codecs for images, and have superseded them in terms of rate-distortion performance under established perceptual quality metrics such as MS-SSIM. We assess the empirical rate-distortion performance of NTC with the help of simple example sources, for which the optimal performance of a vector quantizer is easier to estimate than with natural data sources. To this end, we introduce a novel variant of entropy-constrained vector quantization. We provide an analysis of various forms of stochastic optimization techniques for NTC models;review architectures of transforms based on artificial neural networks, as well as learned entropy models;and provide a direct comparison of a number of methods to parameterize the rate-distortion trade-off of nonlinear transforms, introducing a simplified one.

关键词： transforms Entropy Distortion Image coding Vector quantization Stochastic processes Artificial neural networks data compression machine learning rate-distortion source coding transform coding unsupervised learning

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A high-throughput ASIC processor for 8 x 8 transform coding in H.264/AVC

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SIGNAL PROCESSING-IMAGE COMMUNICATION 2011年第2期26卷 93-104页

作者： Michell, Juan A. Solana, Jose M. Ruiz, Gustavo A. Univ Cantabria Fac Ciencias Dept Elect & Computadores E-39005 Santander Spain

In July 2004, a new amendment called Fidelity Range Extensions (FRExt) was added to the H.264/AVC as a standardization initiative motivated by the rapidly growing demands when coding higher-fidelity video material. One improvement present in the FRExt is the inclusion of a new 8 x 8 integer transform that only makes use of additions and shifters to avoid mismatches between encoders and decoders. This paper presents a processor with pipeline architecture for real-time implementation of the complete process for the 8 x 8 transform coding in H.264: forward 8 x 8 integer transform, quantization and scaling, re-scaling, inverse 8 x 8 integer transform and reconstruction of the image block. This architecture has been conceived with the aim of achieving a high operation frequency and high throughput without increasing the hardware complexity. In order to achieve an efficient implementation, hardware solutions have been developed for the different circuit modules. 8 x 8 forward and inverse transforms are calculated using the separability property with architecture more suitable for pipeline schemes made up of two 1D processors and a transpose register array. New expressions for forward quantization and scaling are presented allowing efficient hardware implementation by avoiding the sign conversion. The inverse quantization has also been optimized in terms of hardware complexity by minimizing the involved arithmetic operations. Furthermore, an exhaustive analysis in the dynamic range of the datapath is made to fix the optimum bus widths with the aim of reducing the size of the circuit while avoiding overflow. Finally, the critical paths of the various computing units have been carefully analyzed and balanced using a pipeline scheme in order to maximize the operation frequency without introducing an excessive latency. A prototype with the proposed architecture has been synthesized in a 130 nm HCMOS technology process, which achieves a maximum speed of 330 MHz with a throughpu

关键词： H.264/AVC 8 x 8 integer cosine transform Quantization transform coding ASIC processor

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AN OPTIMIZATION APPROACH FOR REMOVING BLOCKING EFFECTS IN transform coding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1995年第2期5卷 74-82页

作者： MINAMI, S ZAKHOR, A UNIV CALIF BERKELEY BERKELEYCA 94720

One of the drawbacks of the Discrete Cosine transform (DCT) is visible block boundaries due to coarse quantization of the coefficients, Most restoration techniques for the removing blocking effect are variations of low-pass filtering, and as such, result in unnecessary blurring of the image, In this paper, we propose a new approach for reducing the blocking effect which can be applied to conventional transform coding, such as JPEG standardized coding, without introducing additional information or significant blurring, Our technique exploits the correlation between the intensity values of boundary pixels of two neighboring blocks, Specifically, it is based on the theoretical and empirical observation that under mild assumptions, quantization of the DCT coefficients of two neighboring blocks increases the expected value of the Mean Squared Difference of Slope (MSDS) between the slope across two adjacent blocks, and the average between the boundary slopes of each of the two blocks, The amount of this increase is dependent upon the width of quantization intervals of the transform coefficients, Therefore, among all permissible inverse quantized coefficients, the set which reduces the expected value of this MSDS by an appropriate amount is most likely to decrease the blocking effect, To estimate the set of unquantized coefficients, we solve a constrained quadratic programming problem in which the quantization decision intervals provide upper and lower bound constraints on the coefficients, Our approach is based on the gradient projection method which is motivated by the ordinary method of steepest descent for unconstrained problems, Computer simulations are used to evaluate the performance of the proposed technique, We have shown that from a subjective viewpoint, the blocking effect is less noticeable in our processed images than in the ones using existing filtering techniques.

关键词： Quantization Blocking effects discrete cosine transforms EXPECTATION VALUE gradient projection method transform coding Material Safety Data Sheets

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ADAPTIVE transform coding BASED ON CHAIN coding CONCEPTS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1986年第2期34卷 112-117页

作者： SAGHRI, JA TESCHER, AG Aerospace Corporation El Segundo CA USA

Chain coding technique, originally developed for digital representation and processing of line drawing data, has been implemented in a transform image coding algorithm with significant performance improvement. The algorithm is based on the observation that the boundary of the regions of zero coefficients within a transform block can be efficiently represented by sequences of fixed line segments (chains). Preliminary results indicate significant improvements over the basic coder algorithm in which the consecutive zeros in the transform block were runlength coded. The additional implementation complexity is modest.

关键词： transform coding Image coding Entropy Clustering algorithms Image segmentation Degradation Image processing Pattern recognition Communications Society Logic

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ON transform coding OF MOTION-COMPENSATED DIFFERENCE IMAGES

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IEE PROCEEDINGS-I COMMUNICATIONS SPEECH AND VISION 1992年第3期139卷 372-376页

作者： CLARKE, RJ Department of Electrical and Electronic Engineering Heriot-Watt University Edinburgh UK

Motion-compensated interframe transform coding has been recommended as an efficient method of coding image sequences at low bit rates. The paper considers the effect of employing a variety of different transform and motion compensation techniques on the operation of the algorithm and also the interrelation between the predictive and transform parts of the scheme in terms of the spectral properties of the signal to be transformed. It is shown that, for a wide variety of source material, there is a complex interaction between the specific transform and motion compensation scheme employed, and that the efficiency of the motion-compensated predictive operation strongly influences the performance of the subsequent transform step.

关键词： MOTION COMPENSATION VIDEOPHONE transform coding

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