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UBC Theses and Dissertations

Efficient and robust layered video coding Gallant, Michael David

Abstract

Layered coding and transport has become an attractive method for enabling video communications over the current non-uniform and sub-optimal network infrastructure. In this dissertation, we present video encoding algorithms for efficient and robust layered video encoding and transport in error-free and error-prone networks. In the first part of this dissertation, error-free layered video encoding is considered. We evaluate the effectiveness of key technical features of a layered approach to video encoding. We then determine an upper bound on the rate-distortion performance of a layered approach to video encoding. Finally, a general formulation for efficient error-free layered video encoding is presented, based on the concept of operational rate-distortion optimization. This algorithm is demonstrated to achieve significant improvement in rate-distortion performance. In the second part, we address complexity issues of this algorithm. Our goal is to find good tradeoffs between rate-distortion performance and computational complexity. We first motivate the need to make simplifications to an operational rate-distortion optimization framework. We then propose a model to control the operating mode of the layered video encoder. This model permits the encoder to compute a priori the rate-distortion optimized parameters such that a target bit rate can be achieved. The third part considers layered video encoding and transport in lossy packet-switched networks. A complete coding and transport framework is developed, including a packetization scheme, decoder error concealment method, and prioritization mechanism. We then introduce the general formulation for an efficient and robust layered video encoding algorithm for error-prone environments. This algorithm is also based on the concept of operational rate-distortion optimization and can be viewed as a generalization of the algorithm introduced for error-free environments. The algorithm incorporates a statistical distortion measure that considers the channel conditions, error recovery capability of the channel codec and error concealment capability of the source decoder to optimize the video encoding mode selection. Then, for a given layered bitstream and given channel conditions, optimal channel protection code rates are determined. This framework is shown to produce substantial improvement in reconstructed video quality for a wide range of packet loss rates. Moreover, it is demonstrated to yield graceful degradation of reconstructed video quality with increasing packet loss rate.

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