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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

An investigation into the coding of halftone pictures

Chao, Yao-Ming January 1982 (has links)
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaves 166-174. / by Yao-Ming Chao. / Sc.D.
72

Error resilient video coding over error prone networks. / 差错网络环境下的容错视频编码 / CUHK electronic theses & dissertations collection / Cha cuo wang luo huan jing xia de rong cuo shi pin bian ma

January 2009 (has links)
In the first part, decoder based error concealment methods are discussed. An adaptive partition size (APS) temporal error concealment method is developed for H.264. We propose to use Weighted Double-Sided External Boundary Matching Error (WDS-EBME) to jointly measure the inter-MB boundary discontinuity, inter-partition boundary discontinuity and intra-partition block artifacts in the corrupted MB. By minimizing the WDS-EBME value of each partition, the best motion vectors of each candidate partition mode can be estimated, overall WDS-EBME of the MB concealed by each partition mode can then be evaluated and the best partition mode for the corrupted Macroblocks (MB) will be determined as the one with the smallest overall WDS-EBME. We also propose a progressive concealment order for the 4x4 partition mode. / In this thesis, techniques for efficient error resilient video coding are investigated. Three parts of the work are discussed in this thesis. / The last part of the thesis concerns the joint encoder-decoder error control method. A joint temporal error control method is proposed for H.264. It combines RDO-based macroblock (MB) classification at the encoder and adaptive partition size error concealment at the decoder. The encoder classifies the MBs by evaluating the sensitivity of the MBs as the RD cost between the concealment error and the bits needed for the additional motion information. Additional motion information such as the original motion vector or motion vector index can be transmitted for the error sensitive MBs. The decoder utilizes the additional motion information if any of these MBs get lost. Non-sensitive MBs and blocks are concealed by the APS method. / The second part of this thesis investigates encoder based error control techniques. Firstly, a VLC/FLC data partitioning method is proposed for MPEG-4. It disables intra AC prediction and groups appropriate fixed length coded (FLC) syntaxes in a video packet (or slice) together to form a new partition. With intra AC prediction disabled, errors occurring in these FLC syntaxes will not cause spatial error propagation. It essentially classifies the syntaxes into two categories according to whether that syntax will cause spatial error propagation when an error occurs. Secondly, a redundant macroblock strategy is proposed for H.264. MB Differential Mean Square Error (DMSE) is employed to evaluate the error sensitivity of MBs. The most sensitive MBs are transmitted separately in additional slices while coarsely quantized copies of the MBs are placed in the original slice. When working with chessboard style Flexible Macroblock reordering (FMO) and fixed length slice mode (FMO-slicing), the scheme performs well against packet loss errors with acceptable overhead and it is highly compatible with original H.264 bitstream. Thirdly, a joint optimal bit allocation and rate control scheme is proposed for H.264 with redundant slice. The optimum ratio between each primary and redundant picture pair is analytically deduced. Rate function and distortion model for both representations are developed, and a simple close-form solution is provided to achieve joint optimum bit allocation. / Video communication and other web-based video applications become popular in recent years. However, the transmission of the compressed video bit stream often suffers from imperfection of the communication channel, like path loss, multipath fading, co-channel interference, congestion, etc. Error resilient video coding techniques need to be employed to mitigate the channel errors, which include error concealment in the decoder, forward error correction in the encoder and joint encoder-decoder error control techniques. / Li, Jie. / Adviser: Ngan King Ngi. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 137-146). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
73

Analysis and design of coefficient restoration in image coding. / CUHK electronic theses & dissertations collection

January 2000 (has links)
Tse Fu Wing. / "June 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 172-177). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
74

Video analytics for security systems

Hassan, Waqas January 2013 (has links)
This study has been conducted to develop robust event detection and object tracking algorithms that can be implemented in real time video surveillance applications. The aim of the research has been to produce an automated video surveillance system that is able to detect and report potential security risks with minimum human intervention. Since the algorithms are designed to be implemented in real-life scenarios, they must be able to cope with strong illumination changes and occlusions. The thesis is divided into two major sections. The first section deals with event detection and edge based tracking while the second section describes colour measurement methods developed to track objects in crowded environments. The event detection methods presented in the thesis mainly focus on detection and tracking of objects that become stationary in the scene. Objects such as baggage left in public places or vehicles parked illegally can cause a serious security threat. A new pixel based classification technique has been developed to detect objects of this type in cluttered scenes. Once detected, edge based object descriptors are obtained and stored as templates for tracking purposes. The consistency of these descriptors is examined using an adaptive edge orientation based technique. Objects are tracked and alarm events are generated if the objects are found to be stationary in the scene after a certain period of time. To evaluate the full capabilities of the pixel based classification and adaptive edge orientation based tracking methods, the model is tested using several hours of real-life video surveillance scenarios recorded at different locations and time of day from our own and publically available databases (i-LIDS, PETS, MIT, ViSOR). The performance results demonstrate that the combination of pixel based classification and adaptive edge orientation based tracking gave over 95% success rate. The results obtained also yield better detection and tracking results when compared with the other available state of the art methods. In the second part of the thesis, colour based techniques are used to track objects in crowded video sequences in circumstances of severe occlusion. A novel Adaptive Sample Count Particle Filter (ASCPF) technique is presented that improves the performance of the standard Sample Importance Resampling Particle Filter by up to 80% in terms of computational cost. An appropriate particle range is obtained for each object and the concept of adaptive samples is introduced to keep the computational cost down. The objective is to keep the number of particles to a minimum and only to increase them up to the maximum, as and when required. Variable standard deviation values for state vector elements have been exploited to cope with heavy occlusion. The technique has been tested on different video surveillance scenarios with variable object motion, strong occlusion and change in object scale. Experimental results show that the proposed method not only tracks the object with comparable accuracy to existing particle filter techniques but is up to five times faster. Tracking objects in a multi camera environment is discussed in the final part of the thesis. The ASCPF technique is deployed within a multi-camera environment to track objects across different camera views. Such environments can pose difficult challenges such as changes in object scale and colour features as the objects move from one camera view to another. Variable standard deviation values of the ASCPF have been utilized in order to cope with sudden colour and scale changes. As the object moves from one scene to another, the number of particles, together with the spread value, is increased to a maximum to reduce any effects of scale and colour change. Promising results are obtained when the ASCPF technique is tested on live feeds from four different camera views. It was found that not only did the ASCPF method result in the successful tracking of the moving object across different views but also maintained the real time frame rate due to its reduced computational cost thus indicating that the method is a potential practical solution for multi camera tracking applications.
75

Low frequency coefficient restoration for image coding.

January 1997 (has links)
by Man-Ching Auyeung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 86-93). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Transform coding and the JPEG scheme --- p.2 / Chapter 1.2 --- Motivation --- p.5 / Chapter 1.3 --- Thesis outline --- p.6 / Chapter 2 --- MED and DC Coefficient Restoration scheme --- p.8 / Chapter 2.1 --- Introduction --- p.8 / Chapter 2.2 --- MED and DC Coefficient Restoration scheme --- p.10 / Chapter 2.2.1 --- Definition --- p.10 / Chapter 2.2.2 --- Existing schemes --- p.11 / Chapter 2.3 --- DC Coefficient Restoration scheme using block selection scheme --- p.14 / Chapter 2.4 --- Joint optimization technique --- p.16 / Chapter 2.4.1 --- Lagrange multiplier method --- p.17 / Chapter 2.4.2 --- Algorithm description --- p.18 / Chapter 2.5 --- Experimental results --- p.20 / Chapter 2.6 --- Summary --- p.32 / Chapter 3 --- Low Frequency Walsh Transform Coefficient Restoration scheme --- p.34 / Chapter 3.1 --- Introduction --- p.34 / Chapter 3.2 --- Restoration of low frequency coefficient using Walsh transform --- p.35 / Chapter 3.3 --- Selection of quantization table optimized for Walsh transform --- p.37 / Chapter 3.3.1 --- Image model used --- p.39 / Chapter 3.3.2 --- Infinite uniform quantization --- p.40 / Chapter 3.3.3 --- Search for an optimized quantization matrix --- p.42 / Chapter 3.4 --- Walsh transform-based LFCR scheme --- p.44 / Chapter 3.5 --- Experimental results --- p.46 / Chapter 3.6 --- Summary --- p.56 / Chapter 4 --- Low Frequency DCT Coefficient Prediction --- p.57 / Chapter 4.1 --- Introduction --- p.57 / Chapter 4.2 --- Low Frequency Coefficient Prediction scheme with negligible side information --- p.58 / Chapter 4.2.1 --- Selection of threshold --- p.63 / Chapter 4.2.2 --- Representation of the AC component --- p.63 / Chapter 4.3 --- Experimental results --- p.67 / Chapter 4.4 --- Summary --- p.84 / Chapter 5 --- Conclusions --- p.86 / Appendix A --- p.89 / Bibliography --- p.90
76

DC coefficient restoration for transform image coding.

January 1996 (has links)
by Tse, Fu Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 155-[63]). / Acknowledgment --- p.iii / Abstract --- p.iv / Contents --- p.vi / List of Tables --- p.x / List of Figures --- p.xii / Notations --- p.xvii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- DC coefficient restoration --- p.1 / Chapter 1.2 --- Model based image compression --- p.5 / Chapter 1.3 --- The minimum edge difference criterion and the existing estima- tion schemes --- p.7 / Chapter 1.3.1 --- Fundamental definitions --- p.8 / Chapter 1.3.2 --- The minimum edge difference criterion --- p.9 / Chapter 1.3.3 --- The existing estimation schemes --- p.10 / Chapter 1.4 --- Thesis outline --- p.14 / Chapter 2 --- A mathematical description of the DC coefficient restoration problem --- p.17 / Chapter 2.1 --- Introduction --- p.17 / Chapter 2.2 --- Mathematical formulation --- p.18 / Chapter 2.3 --- Properties of H --- p.22 / Chapter 2.4 --- Analysis of the DC coefficient restoration problem --- p.22 / Chapter 2.5 --- The MED criterion as an image model --- p.25 / Chapter 2.6 --- Summary --- p.27 / Chapter 3 --- The global estimation scheme --- p.29 / Chapter 3.1 --- Introduction --- p.29 / Chapter 3.2 --- the global estimation scheme --- p.30 / Chapter 3.3 --- Theory of successive over-relaxation --- p.34 / Chapter 3.3.1 --- Introduction --- p.34 / Chapter 3.3.2 --- Gauss-Seidel iteration --- p.35 / Chapter 3.3.3 --- Theory of successive over-relaxation --- p.38 / Chapter 3.3.4 --- Estimation of optimal relaxation parameter --- p.41 / Chapter 3.4 --- Using successive over-relaxation in the global estimation scheme --- p.43 / Chapter 3.5 --- Experiments --- p.48 / Chapter 3.6 --- Summary --- p.49 / Chapter 4 --- The block selection scheme --- p.52 / Chapter 4.1 --- Introduction --- p.52 / Chapter 4.2 --- Failure of the minimum edge difference criterion --- p.53 / Chapter 4.3 --- The block selection scheme --- p.55 / Chapter 4.4 --- Using successive over-relaxation with the block selection scheme --- p.57 / Chapter 4.5 --- Practical considerations --- p.58 / Chapter 4.6 --- Experiments --- p.60 / Chapter 4.7 --- Summary --- p.61 / Chapter 5 --- The edge selection scheme --- p.65 / Chapter 5.1 --- Introduction --- p.65 / Chapter 5.2 --- Edge information and the MED criterion --- p.66 / Chapter 5.3 --- Mathematical formulation --- p.70 / Chapter 5.4 --- Practical Considerations --- p.74 / Chapter 5.5 --- Experiments --- p.76 / Chapter 5.6 --- Discussion of edge selection scheme --- p.78 / Chapter 5.7 --- Summary --- p.79 / Chapter 6 --- Performance Analysis --- p.81 / Chapter 6.1 --- Introduction --- p.81 / Chapter 6.2 --- Mathematical derivations --- p.82 / Chapter 6.3 --- Simulation results --- p.92 / Chapter 6.4 --- Summary --- p.96 / Chapter 7 --- The DC coefficient restoration scheme with baseline JPEG --- p.97 / Chapter 7.1 --- Introduction --- p.97 / Chapter 7.2 --- General specifications --- p.97 / Chapter 7.3 --- Simulation results --- p.101 / Chapter 7.3.1 --- The global estimation scheme with the block selection scheme --- p.101 / Chapter 7.3.2 --- The global estimation scheme with the edge selection scheme --- p.113 / Chapter 7.3.3 --- Performance comparison at the same bit rate --- p.121 / Chapter 7.4 --- Computation overhead using the DC coefficient restoration scheme --- p.134 / Chapter 7.5 --- Summary --- p.134 / Chapter 8 --- Conclusions and Discussions --- p.136 / Chapter A --- Fundamental definitions --- p.144 / Chapter B --- Irreducibility by associated directed graph --- p.146 / Chapter B.1 --- Irreducibility and associated directed graph --- p.146 / Chapter B.2 --- Derivation of irreducibility --- p.147 / Chapter B.3 --- Multiple blocks selection --- p.149 / Chapter B.4 --- Irreducibility with edge selection --- p.151 / Chapter C --- Sample images --- p.153 / Bibliography --- p.155
77

Video resolution, frame rate and grayscale tradeoffs under limited bandwidth for undersea teleoperation

Ranadivé, Vivek January 1980 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Vivék Ranadivé. / M.S.
78

A novel distance-dependent thresholding strategy for block-based performance scalability and true object motion estimation

Sorwar, Golam, 1969- January 2003 (has links)
Abstract not available
79

Progressive Lossless Image Compression Using Image Decomposition and Context Quantization

Zha, Hui 23 January 2007 (has links)
Lossless image compression has many applications, for example, in medical imaging, space photograph and film industry. In this thesis, we propose an efficient lossless image compression scheme for both binary images and gray-scale images. The scheme first decomposes images into a set of progressively refined binary sequences and then uses the context-based, adaptive arithmetic coding algorithm to encode these sequences. In order to deal with the context dilution problem in arithmetic coding, we propose a Lloyd-like iterative algorithm to quantize contexts. Fixing the set of input contexts and the number of quantized contexts, our context quantization algorithm iteratively finds the optimum context mapping in the sense of minimizing the compression rate. Experimental results show that by combining image decomposition and context quantization, our scheme can achieve competitive lossless compression performance compared to the JBIG algorithm for binary images, and the CALIC algorithm for gray-scale images. In contrast to CALIC, our scheme provides the additional feature of allowing progressive transmission of gray-scale images, which is very appealing in applications such as web browsing.
80

Progressive Lossless Image Compression Using Image Decomposition and Context Quantization

Zha, Hui 23 January 2007 (has links)
Lossless image compression has many applications, for example, in medical imaging, space photograph and film industry. In this thesis, we propose an efficient lossless image compression scheme for both binary images and gray-scale images. The scheme first decomposes images into a set of progressively refined binary sequences and then uses the context-based, adaptive arithmetic coding algorithm to encode these sequences. In order to deal with the context dilution problem in arithmetic coding, we propose a Lloyd-like iterative algorithm to quantize contexts. Fixing the set of input contexts and the number of quantized contexts, our context quantization algorithm iteratively finds the optimum context mapping in the sense of minimizing the compression rate. Experimental results show that by combining image decomposition and context quantization, our scheme can achieve competitive lossless compression performance compared to the JBIG algorithm for binary images, and the CALIC algorithm for gray-scale images. In contrast to CALIC, our scheme provides the additional feature of allowing progressive transmission of gray-scale images, which is very appealing in applications such as web browsing.

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