ISSN:1124-318X    

DOI:10.1002/ett.4460060302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460060303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractImage Processing (IP) activities within the European Union RACE (Research in Advanced Communications in Europe) Programme are primarily oriented towards image coding which can be duly considered as the most striking success of IP yet. But other IP‐related areas essential to the deployment of advanced communications are equally well covered such as image generation, manipulation, segmentation, interpretation and modelling. Intelligent IP techniques, which can range from a simple signal‐adaptive filter to a complete scene analysis prior to model‐based coding, are increasingly being introduced and their potential recognised. Within the emerging ACTS (Advanced Communications Technology and Services) Programme, they will become common place and contribute to achieving high‐quality, flexible and ubiquitous communications evolving towards full virtual presence s

ISSN:1124-318X    

DOI:10.1002/ett.4460060304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractObject‐oriented approaches to still and moving picture coding, thanks to the extensive use of efficient algorithms for image segmentation and region coding, are expected to improve significantly the rate‐distortion performances of conventional block‐based methodologies. Recent results show that most of the chances to win this challenge depend on the efficiency in image segmentation: the precise aim of our investigation and the purpose of this paper is just to show the concrete possibility of employing fast adaptive algorithms for segmenting images and video frames and allowing high quality coding with very high compression. The segmentation algorithm we propose relies on the recursive computation of the Spatial Gray Level Dependence Matrix (SGLDM) and on a fast adaptive procedure for the statistics evaluation. Subsequent clustering of the image pixels in the 5‐dimensional statistical‐spatial space MVCXY, composed of local mean (M), local variance (V), local correlation (C) and spatial coordinates (XY) is encharged of providing final image segmentation. Target applications for videophone coding of color sequences at very low bitrate are

ISSN:1124-318X    

DOI:10.1002/ett.4460060305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractVideo transmission at very low bit rate has got growing attention in recent years. In this paper we propose an approach for the compression of 144 x 176 pixels Q‐CIF video conference sequences. The compression ratio well exceeds 200 : 1 (thus leading to bit‐rates under 10 kbit/s for 10 frames/s) with very good psycovisual quality of the reconstructed images. The algorithm integrates and improves different feature extraction and image coding techniques. At first the speaker's head is detected by means of active snakes. A new form of internal energy is defined that allows a very robust and fast head tracking. After head detection, internal facial features (i.e., eyes, nose, and mouth) are located by means of a new algorithm. The image is decomposed into different parts with different psicovisual relevance. This information is used to guide in an intelligent way the subsequent processing of the motion compensated difference image. The important areas are coded more accurately while the less relevant areas are coded in a coarser way. This approach grants very high compression while the image quality remains high. Subpixel block matching is used to obtain a motion compensated difference image. This image is segmented into homogeneous regions that are then coded by means of a technique based on differential chain c

ISSN:1124-318X    

DOI:10.1002/ett.4460060306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractNowadays, more and more images from every area need to be stored. If a lossless compression of the image is desired, the storage space requirements can still be enormous. The aim of this paper is to show how to store those images in such a way that a quick access AND a big storage capacity are available together. The tools used are a multi‐resolution entropy coding (the Haar transform and the Universal Variable Length Coder) combined with a hierarchical quantization (theslicing) of each resolution. The main idea is to have a small icon stored on a fast access media, instantly accessible, while the high resolution components are stored on mass media and are loaded only if needed. The total compression is lossles

ISSN:1124-318X    

DOI:10.1002/ett.4460060307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper we describe a real time object tracking system consisting of three modules (motion detection, object tracking, robot control), each working with a moderate accuracy, implemented in parallel on a workstation cluster, and therefore operating fast without any specialized hardware. The robustness and quality of the system is achieved by a combination of these vision modules with an additional attention module which recognizes errors during the tracking. For object tracking in image sequences we apply the method of active contour models (snakes) which can be used for contour description and extraction as well. We show how the snake is initialized automatically by the motion detection module, explain the tracking module, and demonstrate the detection of errors during the tracking by the attention module. Experiments show that this approach allows a robust real‐time object tracking over long image sequences. Using a formal error measurement presented in this paper it will be shown that the moving object is in the center of the image in 90 percent of all image

ISSN:1124-318X    

DOI:10.1002/ett.4460060308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThere are two major approaches to texture analysis, both supported by physiological evidence: those based on the spatial statistics, and those based on its spectral properties. One of the most sophisticated spectral approaches to texture is that based on the Wigner distribution where the attributes computed for each pixel encapsulate both the local spectral and phase properties of the local Fourier transform in a unique real spectrum. On the other hand, some of the most efficient methods which operate in the spatial domain alone, are those based on rank order functions. Before one embarks on the use of the sophisticated methods, it is worth exploring the efficient ones to the limit of their performance. In this paper we investigate these two major approaches and compare their performance both in terms of quality of results and efficiency. The problem we consider is that of detecting defective blobs and cracks on complex textural backgrounds. We show that in most cases rank order approaches can perform well, although no unique method can be employed for both types of defects. On the other hand, the Wigner approach with a very small modification can cope with both types of defects and handle even the identification of very subtle cracks. Thus, it seems that for any real time performance inspection system, the rank order approaches should form the front end with the more sophisticated methods coming in play when necessary.

ISSN:1124-318X    

DOI:10.1002/ett.4460060309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn efficient encoding scheme based on an improved Laplacian pyramid is proposed forlossless/lossycompression aimed at archival andprogressivetransmission of grayscale medical images. The major assets are: pyramid entropy is decreased by adopting two different filters forreductionandexpansion;encoding priority is given to major details through a hierarchicalcontent‐drivendecision rule; the binaryquad‐treeofsplit/unsplitnodes is blockwisezig‐zagscanned andrun‐lengthencoded. Errorfeedbackalong the levels of the Laplacian pyramid ensures control of the maximum absolute error, up to fully reversible reconstruction capability, and enhances the efficiency and the robustness of the whole scheme. While coding results on the standard greyscale imageLenaare pretty competitive with the most recent literature, reversible compression of scanned RX images achieves ratios of about 1:5, establishing improvements over DPCM schemes; high‐quality lossy versions at 0.15 bit/pel outperform JPEG both visually and quantitatively. Moreover,no floating‐pointcomputation is required in the algorithm, andon‐linecompression and reconstruction are feasible on general‐pu

ISSN:1124-318X    

DOI:10.1002/ett.4460060310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMinimization of the average symbol error probability is the central aim when designing a receiver structure of a digital communication system. It is well known that the maximum‐likelihood (ML) decision rule yields the best solution in this sense. In practical applications, the ML sequence estimation is realized by the computationally efficient Viterbi algorithm. As a drawback, however, the computational complexity of this algorithm depends exponentially on the length of the channel impulse response. In this paper, a new suboptimum receiver structure is presented containing a linear recursive equalizer for channel memory truncation and a Viterbi detector. The criterion for adjusting the equalizer and the remaining impulse response for the Viterbi detector is derived from the zeros of the channel transfer function. The proposed concept takes control of both the noise enhancement by the equalizer and the computational complexity of the Viterbi algorith

ISSN:1124-318X    

DOI:10.1002/ett.4460060311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY