Efficient Hevc Downscale Transcoding Based On Coding Unit Information Mapping

In this paper, a novel method that utilizes the information of coding unit (CU) from source video to accelerate the downscale transcoding process for High Efficiency Video Coding (HEVC) is proposed. Specifically, the CU depth and prediction mode information are first extracted into matrices in block level according to the decoded source video. Then we use the matrices to predict CU depth and prediction mode at CU level in the target video. Finally, some effective rules are introduced to determine CU partition and prediction mode based on the prediction. Our approach supports the spatial downscale transcoding with any spatial resolution downscaling ratio. Experiments show that the proposed method can achieve an average time reduction of 59.3% compared to the reference HEVC encoder, with a relatively small Bjontegaard Delta Bit rate (BDBR) increment on average. Moreover, our approach is also competitive compared to the state-of-the-art spatial resolution downscale transcoding methods for HEVC.