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Conference on digital video compression - algorithms and technologies 1995

作者： ORTEGA, A RAMCHANDRAN, K UNIV SO CALIF DEPT EE SYST & SIGNALLOS ANGELESCA 90089

ISBN: (纸本)0819417661

We address the problem of optimal forward-adaptive quantization in the video and image coding framework. In this framework, as is consistent with that of most practical coders like MPEG, the encoder has the capability of changing the quantizer periodically (e.g. at a macroblock interval in MPEG). In this paper, we formulate an optimal strategy, based on dynamic programming, for updating the quantizer choice for coding an image or video signal. While in some coding environments the overhead needed to specify the quantizer used by each block is equal for every choice of quantizer, in other situations (e.g. MPEG) the overhead cost is higher if the quantizer changes from one block to the next. We concentrate on the latter case which will be more likely encountered in situations where the overhead represents a significant fraction of the overall rate, as can be the case if a low bit rate is used (e.g. error frames in a typical motion-compensated video coder). We provide empirical evidence of the performance gain that can be obtained when applying our optimal algorithm to typical motion-compensated prediction error frames in MPEG, showing how the popular Viterbi algorithm can be used to find the optimal solution.

关键词： IMAGE compression video compression MPEG OVERHEAD BIT ALLOCATION QUANTIZATION

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MPEG-4 video verification model: A video encoding/decoding algorithm based on content representation

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SIGNAL PROCESSING-IMAGE COMMUNICATION 1997年第4期9卷 367-384页

作者： Ebrahimi, T Signal Processing Laboratory Swiss Federal Institute of Technology — EPFL CH-1015 Lausanne Switzerland

MPEG-4 video aims at providing standardized core technologies allowing efficient storage, transmission and manipulation of video data in multimedia environments. This is a challenging task given the broad spectrum of requirements and applications in multimedia. In order to achieve this broad goal, rather than a solution for a narrow set of applications, functionalities common to clusters of applications are under consideration. Therefore, video group activities in MPEG-4 aim at providing solutions in the form of tools and algorithms enabling functionalities such as efficient compression, object scalability, spatial and temporal scalability, and error resilience. The standardized MPEG-4 video will provide a toolbox containing tools and algorithms bringing solutions to the above-mentioned functionalities and more. The current focus of the MPEG-4 video group is the development of the video Verification Models. A Verification Model (VM) is a common platform with a precise definition of encoding and decoding algorithms which can be presented as tools addressing specific functionalities. It evolves through time by means of core experiments. New algorithms/tools are added to the VM and old algorithms/tools are replaced in the VM by successful core experiments. Until October 1996, the MPEG-4 video group has focused its efforts on a single VM which has gradually evolved from version 1.0 to version 4.0, and in the process has addressed increasing number of desired functionalities, namely, content based object and temporal scalabilities, spatial scalability, error resilience, and compression efficiency. This paper gives an overview of version 4.0 of the video VM in MPEG-4. In doing so, issues, algorithms, and majors tools used in the development of this future video standard are discussed. (C) 1997 Elsevier Science B.V.

关键词： video coding content based coding object based coding region based coding

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VOLUME DATA compression USING SMOOTHED PARTICLE TRANSFORMATION

VOLUME DATA COMPRESSION USING SMOOTHED PARTICLE TRANSFORMATI...

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Conference on digital video compression - algorithms and technologies 1995

作者： NAGASAWA, M HITACHI CRL ULTRA HIGH SPEED NETWORK & COMP TECHNOL LABSTOKYO 185JAPAN

ISBN: (纸本)0819417661

In 3D entertainment oriented games, most geometrical objects are represented by polygon sets. Thus, the handling of polygons is highly optimized in the hardware of graphic workstations. However, 3D scientific simulations do not ordinarily use polygon data but rather volume data in its original form, such as the scalar array p(x,y,z). If we had an effective volume data compression algorithm and a standard way of representing this data, it could be used in a more efficient manner in the network environment. This paper presents a Smoothed Particle Transformation (SPT) algorithm for volume data at several levels of compressed resolution from an original array description of a given variable. Representing data at various levels of detail is important for archiving the huge data in the network environment. SPT contributes not only to data compression but also for resolution rearrangement. As a result, it speeds up of the visualization of transferred data, especially for the direct volume rendering of compressed data.

关键词： compression TRANSFORMATION VOLUME DATA

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SCENE CHANGE DETECTION AND CONTENT-BASED SAMPLING OF video SEQUENCES

SCENE CHANGE DETECTION AND CONTENT-BASED SAMPLING OF VIDEO S...

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Conference on digital video compression - algorithms and technologies 1995

作者： SHAHRARAY, B AT&T BELL LABS MACHINE PERCEPT RES DEPTHOLMDELNJ 07733

ISBN: (纸本)0819417661

digital images and image sequences (video) are a significant component of multimedia information systems, and by far the most demanding in terms of storage and transmission requirements. Content-based temporal sampling of video frames is proposed as an efficient method for representing the visual information contained in the video sequence by using only a small subset of the video frames. This involves the identification and retention of frames at which the contents of the scene is `significantly' different from the previously retained frames. It is argued that the criteria used to measure the significance of a change in the contents of the video frames are subjective, and performing the task of content-based sampling of image sequences, in general, requires a high level of image understanding. However, a significant subset of the points at which the contextual information in the video frames change significantly can be detected by a `scene change detection' method. The definition of a scene change is generalized to include not only the abrupt transitions between shots, but also gradual transitions between shots resulting from video editing modes, and inter-shot changes induced by camera operations. A method for detecting abrupt and gradual scene changes is discussed. The criteria for detecting camera-induced scene changes from camera operations are proposed. Scene matching is proposed as a means of achieving further reductions in the storage and transmission requirements.

关键词： Cameras video Signal detection digital filtering Image segmentation Information visualization Visualization Image processing Signal processing Motion estimation

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A SEGMENTATION BASED SCHEME FOR VERY LOW BIT-RATE video CODING

A SEGMENTATION BASED SCHEME FOR VERY LOW BIT-RATE VIDEO CODI...

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Conference on digital video compression - algorithms and technologies 1995

作者： BHASKARAN, V LI, W KUNT, M HEWLETT PACKARD CORP PALO ALTOCA 94304

ISBN: (纸本)0819417661

A video coding/decoding system for very low bitrate video has been developed. This hybrid coding scheme employs intraframe and interframe coding techniques. For intraframe coding, a wavelet-based method is used. For interframe coding motionestimation is employed to compute the displaced frame differences (DFD) and the DFD image is coded using a segmentation based method wherein the displaced frame is segmented into active and inactive regions. To meet the low bit rate requirements the motion vectors are processed so as to reduce their contribution to the overall bitrate. Preprocessing techniques are also employed to generate a smooth motion-vector field. To reduce the coding artifacts, post-processing techniques have been developed for use at the decoder. In this paper, we present simulation results for several typical video sequences coded at 16 kbits/sec and at 32 kbits/sec. © 1995 SPIE. All rights reserved.

关键词： Image coding

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ORDERED KOHONEN VECTOR QUANTIZATION FOR VERY LOW RATE INTERFRAME video CODING

ORDERED KOHONEN VECTOR QUANTIZATION FOR VERY LOW RATE INTERF...

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Conference on digital video compression - algorithms and technologies 1995

作者： LIU, H QMS INC SANTA CLARACA 95051

ISBN: (纸本)0819417661

The new interframe video coding algorithm is presented using the topological ordering property of a self-organizing vector quantization (VQ). This algorithm utilizes the Kohonen learning algorithm to train a super VQ codebook which transforms the statistical characteristics of the training motion-compensated frame difference video signals into a 2D topologically ordered array. A new finite state VQ (FSVQ) scheme is proposed to make use of the correspondence between the image interblock correlation and the geometrical closeness of the codevectors in the ordered super codebook. A small state codebook is dynamically predicted purely based on the positions of codevectors used to encode the neighboring image blocks in the current frame as well as in the previous frame. Thus, this new FSVQ significantly reduces the computational complexity at the encoder and preserves the advantages of a simple VQ decoder. The experimental results show that the prediction accuracy ranges from 70 to 95%, depending on the moving information in a frame. It achieves an average bit rate of 0.082 bits per pixel with high image quality (37.86 dB) for the standard test image sequence `Miss America.' This algorithm is amenable to VLSI implementation because of its simple design, low memory requirement, and low computational complexity.

关键词： Computer programming Quantization video coding video compression Image quality Image compression Transform theory video Image processing Signal processing

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FAST MOTION VECTOR ESTIMATION WITH A MARKOV MODEL FOR MPEG

FAST MOTION VECTOR ESTIMATION WITH A MARKOV MODEL FOR MPEG

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Conference on digital video compression - algorithms and technologies 1995

作者： KIM, SG KUO, CCJ UNIV SO CALIF DEPT ELECT ENGN SYSTINST SIGNAL & IMAGE PROCLOS ANGELESCA 90089

ISBN: (纸本)0819417661

This paper presents a new approach for motion vector estimation. We first propose a stochastic model to describe the temporal correlation of motion vectors. We show that the optimal motion vectors can be obtained through maximum a posteriori sequence estimation method. This method is however not practically implementable due to its high computational complexity and many unknown modeling parameters. However, motivated by this theoretical framework, we propose a modified algorithm which is simple, accurate, and fast. First a set of good motion vector candidates is determined. By examining the distribution of these motion vector candidates, we can estimate the noise level as well as select the best motion vector by using the temporal correlations. Then, the next search window can be predicted by examining the trend of the motion vector variation and the noise level (a higher noise level leading to a large search window). In this way, we can reduce the search operation up to less than 0.5% compared to full block search. The excellent performance of the proposed algorithm is demonstrated through extensive experiments.

关键词： video Motion estimation Image processing Motion models Stochastic processes Computer programming Image compression video processing video compression Distortion

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A COMPUTATIONALLY FAST WAVELET-BASED video CODING SCHEME

A COMPUTATIONALLY FAST WAVELET-BASED VIDEO CODING SCHEME

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Conference on digital video compression on Personal Computers: algorithms and technologies

作者： SENGUPTA, A HILTON, M JAWERTH, B UNIV S CAROLINA DEPT COMP SCICOLUMBIASC 29208

ISBN: (纸本)0819414824

Wavelet transforms have recently been used with great success in software-only still image coding applications;their use in software-only video coding, however, has been impeded by the high computational cost of performing the wavelet transform. For example, performing a full inverse wavelet transform on a 251 by 256 pixel, 8-bits per pixel greyscale image takes about 0.25 seconds on a 66Mhz 80486 PC. We present a new technique for rapidly evaluating the inverse wavelet transform in video compression applications. The wavelet transform decomposes each pixel in an image into a linear combination of basis functions. Typically, very few pixels in a video sequence change from one image to the next;therefore, very few of the coefficients in the transformed video sequence change from one image to the next. We capitalize on this fact, and speed up the reconstruction of transformed image sequences by computing the inverse transform for only those coefficients that have changed since the previous image. Our prototype software-only video decompressor based on this idea is capable of reconstructing 256 by 256, 8-bits per pixel, greyscale images at a rate of 18 frames per second at a compression ratio of about 22:1. © 1994 SPIE. All rights reserved.

关键词： Pixels

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Adaptive depletion for improvement of MPEG video compression

Adaptive depletion for improvement of MPEG video compression

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digital video compression: algorithms and technologies 1996

作者： Tan, Daniel Venkatesh, Svetha West, Geoffrey A. Curtin Univ. of Technology Perth WA Aust

ISBN: (纸本)0819420425

Traditional data compression algorithms for 2D images work using the information theoretic paradigm, attempting to reduce redundant information by as much as possible. However, through the use of a depletion algorithm that takes advantage of characteristics of the human visual system, images can be displayed using only half or a quarter of the original information with no appreciable loss of quality.

关键词： video signal processing

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TRANSFORM CODING FOR LOW BIT-RATE APPLICATIONS

TRANSFORM CODING FOR LOW BIT-RATE APPLICATIONS

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Conference on digital video compression on Personal Computers: algorithms and technologies

作者： PONCELEON, DB WANG, KS WU, H NORMILE, J APPLE COMP INC CUPERTINOCA 95014

ISBN: (纸本)0819414824

Low bit rate image coding at 10 kbit/s and less is a difficult problem and does not appear possible with the current generation of block transform based methods. Current research efforts center around the use of transforms with less objectionable artifacts such as wavelets or model based methods. We examine a method that is transform based but captures specific features of the image to be represented. The transform uses principal component analysis to generate a basis set specific to the particular class of images to be coded. We present results from a transform designed for use in a `talking head' sequence. Significant improvement in reconstructed quality is shown when perceptual weighting is used in generating the basis set. The appendix includes details of computationally efficient methods for deriving the basis set as well as a description of the weighting method.

关键词： Signal to noise ratio Mouth Head video Eye Image compression Detection and tracking algorithms Facial recognition systems Image quality Principal component analysis

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