We consider the problem of coding video signals using motion compensation and a forward coded dense motion field. First, we develop a motion estimation technique that yields dense estimates suitable for the coding app...
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ISBN:
(纸本)0818688211
We consider the problem of coding video signals using motion compensation and a forward coded dense motion field. First, we develop a motion estimation technique that yields dense estimates suitable for the coding application; next, we develop a prototype of a video coder, which we use to verify that high coding performance is attainable within our framework. To find our sought motion estimates, we assume motion in an observed image sequence to be a stochastic process, modeled as a Markov random field (MRF). The standard maximum a posteriori (MAP) estimation problem with MRF priors is formulated as a constrained optimization problem (where the constraint is on the entropy of the sought estimate), but then transformed into a classical MAP estimation problem, and solved using standard techniques. A key advantage of the constrained formalization is that, in the process of transforming it back to the classical framework, parameters which in the classical framework are left unspecified (and often tweaked in an experimental stage) become now uniquely determined by the introduced entropy constraint. To verify that our motion estimates are indeed useful for coding, we compare the performance of a prototype video coder with that of an equivalent coder based on block-matching motion estimates. Experimental results reveal, for various types of video signals and at various rates, that: (a) in terms of PSNR, our system equals or improves upon the performance of full search block matching; and (b) in terms of visual quality our improvements are significant, since our images are completely free of blocking artifacts.
Operation of AUVs or other platforms that rely upon robust communications for navigation and mission critical tasks is facilitated by the use of on-board data compression. Data compression eliminates redundancy of tra...
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Operation of AUVs or other platforms that rely upon robust communications for navigation and mission critical tasks is facilitated by the use of on-board data compression. Data compression eliminates redundancy of transmitted information and therefore improves the efficiency of the entire mission. In some applications, acoustic and non-acoustic sensor information is acquired and processed to produce a visual representation for ease of human-in-the-loop analysis and interpretation. Many image and data compression methods are currently in development. Emphasis has been placed on achieving high efficiency as characterized by compression ratio while retaining the least error between the original image and the compressed image. Although some algorithms produce excellent results, computational complexity, and hence speed of compression or decompression, can become a limiting factor in real-time use depending upon the capability of the on-board processor. This paper describes the implementation of a high performance image compression transform using a dedicated DSP processor and supporting computer host. The system architecture and strategy for efficient code implementation are described. Example performance measures are presented for non-acoustic undersea studies. Future plans and developments for specialized applications are also discussed.
In this paper, some of the most significant image quality indexes are reviewed and compared with a new method for blockness distortion evaluation. The paper begins with a brief survey on classical measures based on nu...
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ISBN:
(纸本)0780339061
In this paper, some of the most significant image quality indexes are reviewed and compared with a new method for blockness distortion evaluation. The paper begins with a brief survey on classical measures based on numerical difference between original and reconstructed image data (e.g., MSE, SNR and PSNR) and advanced methods aiming at considering the perceptive aspects of image degradation (e.g., Hosaka Plots and other methods based on Human visual System properties like Information Content or Perceptual image Distortion). After, four innovative methods for blockness distortion measurement are proposed: two based on DCT analysis, and two on differential Sobel operator. Results on standard pictures confirm the efficiency of the proposed measures.
Fractal image compression is computationally expensive. Therefore speedup techniques are required to achieve time demands comparable to other compression techniques. In this paper we combine sequential and parallel te...
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ISBN:
(纸本)0819424358
Fractal image compression is computationally expensive. Therefore speedup techniques are required to achieve time demands comparable to other compression techniques. In this paper we combine sequential and parallel techniques suitable for MIMD architectures which moves this compression scheme closer to real-time processing. The algorithms introduced are especially designed for memory-critical environments.
Global motion estimation and compensation are important research issues in video compression. The main difficulty in global motion estimation resides in the disturbance of independently moving objects. The algorithm p...
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ISBN:
(纸本)0819424358
Global motion estimation and compensation are important research issues in video compression. The main difficulty in global motion estimation resides in the disturbance of independently moving objects. The algorithm presented in this paper exploits global motion information not only from stationary objects and the image background, but also from independently moving objects. Simulation results show that the new algorithm is more robust to the disturbance of independently moving objects, and computationally faster than an algorithm based on least-square approximation.
In this work we discuss several approaches fur designing fractal quantizers in the context of hybrid wavelet-fractal image compression algorithms. Moreover different subband-structures are compared concerning their su...
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ISBN:
(纸本)0819427497
In this work we discuss several approaches fur designing fractal quantizers in the context of hybrid wavelet-fractal image compression algorithms. Moreover different subband-structures are compared concerning their suitability for subsequent fractal quantization.
In this work we apply techniques originating from classical fractal still-image coding to block-matching motion compensation algorithms for digital video compression. Especially the method of adapting the gray-values ...
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ISBN:
(纸本)0819427497
In this work we apply techniques originating from classical fractal still-image coding to block-matching motion compensation algorithms for digital video compression. Especially the method of adapting the gray-values in image blocks of the current frame to those in blocks of the reference-frame shows promising performance.
An algorithm for image compression, based on local histogram analysis, is presented. A given image is compressed by dividing the image into nonoverlapping square blocks and coding the edge information in each block. T...
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ISBN:
(纸本)0819424358
An algorithm for image compression, based on local histogram analysis, is presented. A given image is compressed by dividing the image into nonoverlapping square blocks and coding the edge information in each block. The edge information is extracted by first differentiating the original image, quantising the differential image, then invistigated the local histogarm of small blocks of the differential image. Depending on the behaviour of the local histograms in the differential image, the corresponding blocks in the original image are classified into visually active and visually continuous blocks. The visually continous blocks are coded using the mean value only. A visually active block is coded using the location and orientation of the edge within the block. As a result, the compression ratio of the proposed algorithm depends on the behaviour of the local histogram, which in turn depends heavely on the quantisation process of the differential image. In this paper, the effect of the quantisation of the differential image on the compression ratio and the image quality is discussed.
In this paper we propose an image coding scheme based on the polynomial transform and multiresolution analysis. The polynomial transform is an image representation model that mimics some properties of the human visual...
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ISBN:
(纸本)0819424358
In this paper we propose an image coding scheme based on the polynomial transform and multiresolution analysis. The polynomial transform is an image representation model that mimics some properties of the human visual system, and which we use in order to model edges in terms of their characteristic parameters. Based on the polynomial transform, we build a pyramidal hierarchical predictive scheme for image coding. The feature parameters that we encode are: local average, edge orientation, edge position and edge magnitude.
Although block-based image compression techniques seem to be straightforward to implement on parallel MIMD architectures, problems might arise due to architectural restrictions on such parallel machines (e.g. memory c...
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ISBN:
(纸本)0819424358
Although block-based image compression techniques seem to be straightforward to implement on parallel MIMD architectures, problems might arise due to architectural restrictions on such parallel machines (e.g. memory constraints on distributed memory architectures). In this paper we discuss possible solutions to such problems occurring in different image compression techniques. Experimental results are included for adaptive wavelet block coding and fractal compression.
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