Streaming video applications on the Internet generally have very high bandwidth requirements and yet are often unresponsive to network congestion. In order to avoid congestion collapse and improve video quality, these applications need to respond to congestion in the network by deploying mechanisms to reduce their bandwidth requirements under conditions of heavy load. In reducing bandwidth, video with high motion will look better if all the frames are kept but the frames have low quality, while video with low motion will look better if some frames are dropped but the remaining frames have high quality. Unfortunately current video applications scale to fit the available bandwidth without regard to the video content. In this thesis, we present an adaptive content-aware scaling mechanism that reduces the bandwidth occupied by an application by either dropping frames (temporal scaling) or by reducing the quality of the frames transmitted (quality scaling). We have designed a streaming video client and server with the server capable of quantifying the amount of motion in an MPEG stream and scaling each scene either temporally or by quality as appropriate, maximizing the appearance of each video stream. We have evaluated the impact of content-aware scaling by conducting a user study wherein the subjects rated the quality of video clips that were first scaled temporally and then by quality in order to establish the optimal mechanism for scaling a particular stream. We find that content-aware scaling can improve video quality by as much as 50%. We have also evaluated the practical impact of adaptively scaling the video stream by conducting a user study for longer video clips with varying amounts of motion and available bandwidth. We find that for such clips also the improvement in perceptual quality on account of adaptive content-aware scaling is as high as 30%

The first part of this thesis studies advanced wavelet transform techniques for scalable still image object coding. In order to adapt to the content of a given signal and obtain more flexible adaptive representation, two advanced wavelet transform techniques, wavelet packet transform and directional wavelet transform, are developed for object-based image coding. Extensive experiments demonstrate that the new wavelet image coding systems perform comparable to or better than state-of-the-art in image compression while possessing some attractive features such as object-based coding functionality and high coding scalability. / The objective of this thesis is to develop an object-based coding framework built upon a family of wavelet coding techniques for a variety of arbitrarily shaped visual object scalable coding applications. Two kinds of arbitrarily shaped visual object scalable coding techniques are investigated in this thesis. One is object-based scalable wavelet still image coding; another is object-based scalable wavelet video coding. / The second part of this thesis investigates various components of object-based scalable wavelet video coding. A generalized 3-D object-based directional threading, which unifies the concepts of temporal motion threading and spatial directional threading, is seamlessly incorporated into 3-D shape-adaptive directional wavelet transform to exploit the spatio-temporal correlation inside the 3-D video object. To improve the computational efficiency of multi-resolution motion estimation (MRME) in shift-invariant wavelet domain, two fast MRME algorithms are proposed for wavelet-based scalable video coding. As demonstrated in the experiments, the proposed 3-D object-based wavelet video coding techniques consistently outperform MPEG-4 and other wavelet-based schemes for coding arbitrarily shaped video object, while providing full spatio-temporal-quality scalability with non-redundant 3-D subband decomposition. / Liu, Yu. / Adviser: King Ngi Ngan. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3693. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 166-173). / 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, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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.

Firstly, the characteristics of HD videos are studied quantitatively. The results show that HD videos distinguish from other lower resolution videos by higher spatial correlation and special power spectral density (PSD), mainly distributed along the vertical and horizontal directions. / Secondly, two techniques for HD video coding are developed based on the aforementioned analysis results. To exploit the spatial property, 2D order-16 transforms are proposed to code the higher correlated signals more efficiently. Specially, two series of 2D order-16 integer transforms, named modified integer cosine transform (MICT) and non-orthogonal integer cosine transform (NICT), are studied and developed to provide different trade-offs between the performance and the complexity. Based on the property of special PSD, parametric interpolation filter (PIF) is proposed for motion-compensated prediction (MCP). Not only can PIF track the non-stationary statistics of video signals as the related work shows, but also it represents interpolation filters by parameters instead of individual coefficients, thus solving the conflict of the accuracy of coefficients and the size of side information. The experimental results show the proposed two coding techniques significantly outperform their equivalents in the state-of-the-art international video coding standards. / Thirdly, interlaced HD videos are studied, and to satisfy different delay constraints, two real-time de-interlacing algorithms are proposed specially for H.264 coded videos. They adapt to local activities, according to the syntax element (SE) values. Accuracy analysis is also introduced to deal with the disparity between the SE values and the real motions and textures. The de-interlacers provide better visual quality than the commonly used ones and can de-interlace 1080i sequences in real time on PCs. / Today, High-Definition (HD) videos become more and more popular with many applications. This thesis analyzes the characteristics of HD videos and develops the appropriate coding and processing techniques accordingly for hybrid video coding. / Dong, Jie. / Adviser: King Ngi Ngan. / Source: Dissertation Abstracts International, Volume: 72-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 153-158). / 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 Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Abstract not available

Video compression aims to reduce video file size without impacting visual quality. Existing algorithms mostly use transform coders to convert information from the spatial to frequency domain, and attenuate or remove high frequency components from the sequence. This enables the omission of a large proportion of high frequency information with no discernible visual impact. Sprite-based compression encodes large portions of a scene as a single object in the video sequence, recreating the object in subsequent frames by warping or morphing the sprite to mimic changes in subsequent frames. This thesis sought to improve several aspects of existing sprite based compression approaches, employing a temporal motion model using a low order polynomial to represent the motion of an object across multiple frames in a single model rather than a series of models. The main outcome is the demonstration that motion models used by sprite based video compression can be extended to a full three dimensional model, reducing the overall size of the model, and improving the quality of the sequence at low bit rates. A second outcome is the demonstration that super-resolution processing is not necessary if lanczos spatial interpolation is used instead of bilinear or bi-cubic interpolation, resulting in a savings in computational time and resources. A third outcome is the introduction of a new blending model used to generate image mosaics that improves the quality of the synthesised sequence when zoom is present in the sequence for a given bit-rate. A final outcome is demonstrating that performing superresolution processing and sub-sampling back to the original resolution prior to compression provides benefits in some circumstances.

Compressed video bitstream transmissions over wireless networks are addressed in this work. We first consider error control and power allocation for transmitting wireless video over CDMA networks in conjunction with multiuser detection. We map a layered video bitstream to several CDMA fading channels and inject multiple source/parity layers into each of these channels at the transmitter. We formulate a combined optimization problem and give the optimal joint rate and power allocation for each of linear minimum mean-square error (MMSE) multiuser detector in the uplink and two types of blind linear MMSE detectors, i.e., the direct-matrix-inversion (DMI) blind detector and the subspace blind detector, in the downlink. We then present a multiple-channel video transmission scheme in wireless CDMA networks over multipath fading channels. For a given budget on the available bandwidth and total transmit power, the transmitter determines the optimal power allocations and the optimal transmission rates among multiple CDMA channels, as well as the optimal product channel code rate allocation. We also make use of results on the large-system CDMA performance for various multiuser receivers in multipath fading channels. We employ a fast joint source-channel coding algorithm to obtain the optimal product channel code structure. Finally, we propose an end-to-end architecture for multi-layer progressive video delivery over space-time differentially coded orthogonal frequency division multiplexing (STDC-OFDM) systems. We propose to use progressive joint source-channel coding to generate operational transmission distortion-power-rate (TD-PR) surfaces. By extending the rate-distortion function in source coding to the TD-PR surface in joint source-channel coding, our work can use the ??equal slope?? argument to effectively solve the transmission rate allocation problem as well as the transmission power allocation problem for multi-layer video transmission. It is demonstrated through simulations that as the wireless channel conditions change, these proposed schemes can scale the video streams and transport the scaled video streams to receivers with a smooth change of perceptual quality.

No description available.

Motion estimation is the key issue in video compressing. Several methods for motion estimation based on the center biased strategy and minimum mean square error trend searching have been proposed, such as TSS, FSS, UCBDS and MIBAS, but these methods yield poor estimates or find local minima. Many other methods predict the starting point for the estimation, these can be fast but are inaccurate. This study addresses the causes of wrong estimates, local minima and incorrect predictions in the prior estimation methods. The Multiple Searching Trend (MST) is proposed to overcome the problems of ineffective searches and local minima, and the Adaptive Dilated Searching Field (ADSF) is described to prevent prediction from wrong location. Applying MST and ADSF to the listed estimating methods, such as UCBDS, a fast and accurate can be reached. For this this reason, the method is called CockTail Searching (CTS). In another proposed method, we try to define the new criteria used to determine a referent macro block within the search window in a referent frame, which matches the estimated current macro block in the current frame, in motion estimation process used in MPEG standard. The Prediction Error(PE) in the Pixel Difference(PD) between the referent macro block and the current macro block is defined to be a new criterion which can get better performance in compressed data length than the Mean Square Error(MSE) used by most of motion estimation methods. The other criterion combined PE and MSE is proposed to get better performance than the PE. Two new criteria is applied to a famous motion estimation method, UCBDS, to show the performance of the new criteria. The evaluation results show that using new criteria in UCBDS can get more 40% reduction in compressed data size than the UCBDS with MSE.

This thesis applies the one-dimensional (1-D) and two-dimensional (2-D) cubic-spline interpolation (CSI) schemes to MPEG standard for very low-bit rate video coding. In addition, the CSI scheme is used to implement the scalable video compression scheme in this thesis. The CSI scheme is based on the least-squares method with a cubic convolution function. It has been shown that the CSI scheme yields a very accurate algorithm for smoothing and obtains a better quality of reconstructed image than linear interpolation, linear-spline interpolation, cubic convolution interpolation, and cubic B-spline interpolation. In order to obtain a very low-bit rate video, the CSI scheme is used along with the MPEG-1 standard for video coding. Computer simulations show that this modified MPEG not only avoids the blocking effect caused by MPEG at high compression ratio but also gets a very low-bit rate video coding scheme that still maintains a reasonable video quality. Finally, the CSI scheme is also used to achieve the scalable video compression. This new scalable video compression scheme allows the data rate to be dynamically changed by the CSI scheme, which is very useful when operates under communication networks with different transmission capacities.