Study Of Some Key Problems In Design And Implementation Of Video Codec

Digitalized image and video contain huge information. Mordern image and video compression techniques make it possible to transfer and store these multimedia data. H.264/AVC is the newest digital video coding standard, which was co-developed by Video Coding Expert Group-VCEG and ISO/IEC Moving Picture Expert Group-MPEG has applications in videophone, videoconference, television, DVD, hard-disk storation, stream media, digital photograpy and digital video processing. Although sharing the same basic framework of prediction transform and hybrid coding as some former video coding standards, such as MPEG-1, MPEG-2, MPEG-4, H.264/AVC ahieves 2 times higher coding efficience towards the same visual results on the decoding end, due to various coding tool and optimization schemes involved. This thesis focuses on some key techniques in the design and implementation of the H.264 codec.On the encoder end, this thesis discusses how to enhance the overall coding efficiency by improving the performance of H.264 rate control module. This part begins with the review of the key techniques, such as the bitrate constraint model, rate distortion model and the problem of existing rate control scheme. The exsiting H.264 one-pass and two-pass encoder are then analyzed in details together with some review of its performance and difficulties. Based on these analyses, the design and implementation of a two pass H.264 encoder based on sliding window is then introduced in detail. This part ends with extensive experimental results of the proposed encoder and the comparison of its performance with existing one-pass and two-pass H.264 encoders.On the decoding end, the thesis is focused on the design and implementation of a low cost H.264 HD down conversion decoder. The performances of existing HD down conversion decoders are analyzed and the limitations of its application in H.264 HD decoding are pointed out. Based on the study of the properties of H.264 HD streams, a novel H.264 HD down conversion decoder is proposed. This novel decoder is then compared in details to the existing methods by means of the hardware requirement, computational complexity and the quality of reconstructed pictures.In addition, a novel deranging scheme based on the concept of trilateral filter is also presented in this paper. The proposed trilateral filter is an extension of the traditional filter which consists of a domain filter, a range filter and a texture activity filter. Experimental results and comparative studies show the effectiveness and efficiency of the proposed algorithm.