Quality-aware video adaptation over heterogeneous environment

Abstract

Video adaptation allows universal video access over user``s heterogeneous environments. The challenging key issue is to find the optimal adaptation operations to meet resource constraints given by the heterogeneous environments, while at the same time maximizing the user’s quality of experience. In this thesis, we concentrate on optimal transcoding decision techniques for video adaptation. There exist multidimensional scaling operations for video rate transcoding, such as spatial, temporal, and SNR resolution scaling operations. To efficiently allocate bits for video transcoding in heterogeneous environments, the multidimensional quality factors need to be exploited. Therefore, the transcoding decision problem can be formulized as a quality optimization problem to determine the best combination of the multidimensional transcoding operations satisfying the given resource constraints. In this thesis we propose two systematic schemes to deal with the quality optimization problem. In distortion model-based transcoding decision scheme, we mainly present the concrete distortion model for the multidimensional video transcoding. In case of multidimensional video transcoding, it should be noted that there are inter-dependencies among the transcoding operations. Because one transcoding operation can affect the distortion due to the other operations, we consider putting the inter-dependencies into our concrete distortion model through an extensive statistical analysis. We also develop computational methods to easily calculate the distortion (MSE) by using only the information extracted directly from the input bitstream through the minimum decoding process in DCT domain. In experiments, we compare the actually measured distortion with the estimated distortion by our proposed model. In semantic classification-based decision scheme, on the other hand, we investigate the impact of subjective perception and semantic information on the video transcoding choices. Specifica...