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The joint temporal-spatial bit allocation problem with consideration of dependency arising from motion compensated prediction as well as frame interpolation is investigated in this research. After the problem formulation, several heuristic methods are proposed to provide near-optimal and suboptimal solutions to this problem. First, the selective iteration algorithm (SIA) based on the monotonic property of the rate-distortion (R-D) curve is proposed to achieve the near-optimal solution. Then, the greedy iteration algorithm (GIA) is presented as a suboptimal heuristic to reach an R-D performance close to that obtained using SIA, while at a much lower complexity. Furthermore, by adaptively grouping frames based on the mean of the absolute difference differentials and applying greedy pruning to groups of frames, the suboptimal solution is significantly expedited so that it can be applied in real-time applications. Frames to be skipped in the coding process and quantization parameters (QPs) exploited in coded frames are adaptively and jointly determined to reach a proper tradeoff between temporal and spatial qualities. Experimental results show that the proposed methods can enhance the overall quality of compressed video at various bit rates in comparison with H.263-I-/TMN8 [1] using fixed frame rates and QPs, as well as the adaptive quantization solution proposed in [2]. [ABSTRACT FROM AUTHOR]

The performance of a precoded ultrawideband impulse radio (UWB-IR) system using prerake as the inner code and superorthogonal turbo code (SOTC) or repetition code (RC) as outer codes is investigated in this paper. Prerake UWB-IR transmits information bits with time-reversed channel information. Due to the low transmission power of the UWE-IR, the sequence is repeated through outer coding. The prerake technique demands that the channel information be available to the transmitter. The tradeoff between the feedback channel information and several system performance metrics such as the length of the outer code and bit error rate (BER) is studied. It is shown that there exists a minimum feedback quantity required to achieve a target system performance in different communication scenarios. The optimal quantity of feedback channel knowledge and intersymbol interference (ISI) are investigated and verified by computer simulation. [ABSTRACT FROM AUTHOR]

A new rate control scheme for H.264 video encoding with enhanced rate and distortion models is proposed in this work. Compared with existing H.264 rate control schemes, our scheme has offered several new features. First, the inter-dependency between rate-distortion optimization (RDO) and rate control in H.264 is resolved via quantization parameter estimation and update. Second, since the bits of the header information may occupy a larger portion of the total bit budget, which is especially true when being coded at low bit rates, a rate model for the header information is developed to estimate header bits more accurately. The number of header bits is modeled as a function of the number of nonzero motion vector (MV) elements and the number of MVs. Third, a new source rate model and a distortion model are proposed. For this purpose, coded 4 × 4 blocks are identified and the number of source bits and distortion are modeled as functions of the quantization stepsize and the complexity of coded 4 × 4 blocks. Finally, a R-D optimized bit allocation scheme among macroblocks (MBs) is proposed to improve picture quality. Built upon the above ideas, a rate control algorithm is developed for the H.264 baseline-profile encoder under the constant bit rate constraint. It is shown by experimental results that the new algorithm can control bit rates accurately with the R-D performance significantly better than that of the rate control algorithm implemented in the H.264 software encoder JM8.1a. [ABSTRACT FROM AUTHOR]

A multihypothesis motion compensated prediction (MHMCP) scheme, which predicts a block from a weighted superposition of more than one reference blocks, is proposed and analyzed for error resilient visual communication in this research. By combining these reference blocks effectively, MHMCP can enhance the error resilient capability of compressed video as well as achieve a coding gain. In particular, we investigate the error propagation effect in the MHMCP coder and analyze the rate-distortion performance in terms of the hypothesis number and hypothesis coefficients. It is shown that MHMCP suppresses the short-term effect of error propagation more effectively than the intra-refreshing scheme. [ABSTRACT FROM AUTHOR]

Most existing coding techniques for three-dimensional (3-D) graphic models focus on coding efficiency. Due to irregular structure of the 3-D mesh and the use of variable length entropy codes, channel errors often propagate in the coded bite stream and severely distort the decoded model. By segmenting a 3-D graphic model (or its connected components) into small pieces, the impact Of channel errors is confined to directly corrupted pieces rather than the whole mesh. The mesh segmentation schemes should be compatible with the underlying encoding techniques to achieve the low computational and coding overhead. In this research, we examine four mesh segmentation schemes, i.e., multiseed traversal, threshold traversal, morphing-based volume splitting, and content-based segmentation, and apply them to the context of error resilient mesh coding based on the constructive traversal coding technique. The advantages and shortcomings of each segmentation method are discussed. These schemes segment a mesh into pieces according to the target piece size that is deters mined according to the channel error rate. [ABSTRACT FROM AUTHOR]

A view-dependent graphics streaming scheme is proposed in this work that facilitates interactive streaming and browsing of three-dimensional (3D) graphics models. First, a 3-D model is split into several partitions. Second, each partition is simplified and coded independently. Finally, the compressed data is sent in order of relevance to the user's requests to maximize visual quality. Specifically, the server can transmit visible parts in detail, while cutting out invisible parts. Experimental results demonstrate that the proposed algorithm reduces the required transmission bandwidth, and provides an acceptable visual quality even at low bit rates. [ABSTRACT FROM AUTHOR]

A content-based movie parsing and indexing approach is presented in this paper, which analyzes both audio and visual sources and accounts for their interrelations to extract high-level semantic cues. Specifically, the goal of this work is to extract meaningful movie events and assign them semantic labels for the content indexing purpose. Three types of key events, namely, 2-speaker dialogs, multiple-speaker dialogs, and hybrid events, are considered in this work. Moreover, speakers present in the detected movie dialogs are further identified based on the audio source parsing. The obtained audio and visual cues are then integrated to index the movie content. Our experiments have shown that an effective integration of the audio and visual sources can lead to a higher level of video content understanding, abstraction and indexing. [ABSTRACT FROM AUTHOR]

A Kalman filtering (KF) approach to on-line musical beat tracking with probabilistic data association (PDA) is investigated in this work. We first formulate the beat tracking process as a linear dynamic system of beat progression, and then apply the Kalman filtering algorithm to the dynamic system in estimating the time-varying tempo and beat locations. Musical beat tracking using traditional Kalman filtering is however not reliable in the presence of tempo fluctuations and expressive timing deviations. To address this problem, we adopt data association techniques to assign probability masses to all possible beat interpretations, and then locate the true beat according to the weighting. Two methods are proposed. The first one (PDA-I) weighs the distance between the candidate observation and the predicted beat location while the second method (PDA-II) considers not only the distance but also the onset intensity in weight selection. Superior performance of the proposed beat tracking algorithm is demonstrated with simulation results on the Music Information Retrieval Evaluation Exchange (MIREX) 2006 beat tracking competition practice dataset and the Billboard Top-10 database. [ABSTRACT FROM AUTHOR]

A novel transceiver design for ultrawideband (UWB) communication systems using the channel phase precoding (CPP) technique is proposed in this work. With the CPP-UWB transceiver, we encode data symbols using the reversed order of the channel phase. A simple phase estimation algorithm is presented for the CPP-UWB implementation. Owing to its ability to coherently combine the channel magnitude of every multipath, the CPP-UWB transceiver can achieve a higher data rate by shortening its symbol duration with a tolerable interference. The performance of the CPP-UWB can be further improved using an optimal code length and/or the MMSE receiver to suppress intersymbol interference. [ABSTRACT FROM AUTHOR]