Adaptive Down-sampling Coding Scheme for High-definition Video

Abstract

High-definition (HD) video that provides enhanced viewing experience is becoming increasingly popular. However, HD video requires large transmission bandwidth and computation complexity. This thesis proposes an efficient coding scheme for HD video by utilizing sub-sampling technique. First, we propose a down-sampling coding scheme with adaptive resolution-ratio to achieve better rate-distortion performance for video signals. And then, the computational complexity is greatly reduced by skipping un-necessary encoding modes.

The Down-sampling coding, which sub-samples the image and encodes the smaller sized images, is one of the solutions to raise the image quality under insufficient rates. An adaptive resolution-ratio for down-sampling coding is utilized instead of fixed resolution-ratio. The optimum resolution-ratio is derived based on the models of down-sampling distortion and coding distortion. Simulation results show that the rate-distortion performance of adaptive resolution-ratio is higher than H.264 by 2 to 4 dB at low to medium rates.

The complexity analysis of encoding tools for video at different resolutions has not been addressed much. This work analyzed quality gain of high complexity tools at different resolutions. Based on this analysis, we propose an adaptive encoding configuration scheme to reduce the computation complexity by skipping modes with low quality gains. As simulation results are shown, with almost the same rate-distortion performance, the proposed scheme further reduces complexity of the down-sampling coding. Compared with H.264, it has 90% complexity reduction at low to medium bitrates.