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UBC Theses and Dissertations

Perceptually based compression of emerging digital media content Azimi Hashemi, Maryam

Abstract

Digital video has become ubiquitous in our everyday lives; everywhere we look, there are devices that can display, capture, and transmit video. The recent advances in technology have made it possible to capture and display HD stereoscopic (3D) and High Dynamic Range (HDR) videos. However, the current broadcasting networks do not even have sufficient capacity to transmit large amounts of HD content, let alone 3D and High Dynamic Range. The limitations of the current compression technologies are the motivations behind this thesis, which proposes novel methods for further improving the efficiency of the compression techniques when used on emerging digital media formats. As a first step, we participated in the standardization efforts of High Efficiency Video Coding (HEVC), the latest video compression standard. The knowledge gained from this study became the foundation for the research that followed. We first propose a new method for encoding stereoscopic videos asymmetrically. In traditional asymmetric stereoscopic video coding, the quality of one of the views is reduced while the other view is of original quality. However, this approach is not fair for people with one dominant eye. We address this problem by reducing the quality of horizontal slices in both views. Subjective tests show that the quality, sharpness and depth of the videos encoded by our method are close to those of the original one and that the proposed method is an effective technique for stereoscopic videos coding. In this Thesis we also focus on HDR video technology and we modify the HEVC standards to better characterize HDR content. We first identify a quality metric whose performance on compressed HDR content is highly correlated with subjective results. We then propose a new Lagrangian multiplier that uses this quality metric to strike the best balance between the bit-rate and distortion of the HDR video inside the Rate-Distortion process of the encoder. The updated Lagrange multiplier is implemented on the HEVC reference software. Our experiment results show that, for the same bitrate, the subjective quality scores of the videos encoded by the HDR-accustomed encoder are higher than the ones encoded with the reference encoder.

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Attribution-NonCommercial-NoDerivs 2.5 Canada

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