A Fast PU Mode Decision Algorithm for H.264/AVC to HEVC Transcoding

ABSTRACT

H.264/AVC is currently one of the most commonly applied video compression standard. However, the previous standards are not satisfied with the increasing demands on high quality video applications. Thus, a new video compression standard, High Efficient Video Coding (HEVC), had been finalized by JCT-VC in April 2013. It can be expected that HEVC will be widely adopted for many applications in the future. Therefore, it becomes an important issue to efficiently transcode H.264/AVC to HEVC.

In this thesis, we propose a fast transcoding algorithm for H.264/AVC to HEVC. The proposed algorithm reuses coding information from H.264/AVC decoder such as motion vectors, coding modes, and residual values to speed up the prediction time for the HEVC encoder. The proposed algorithm is composed of two parts to speed up the transcoding process. One is fast algorithm for the prediction unit (PU) mode decision, and the other is by applying the adaptive search range selection to save time for the motion estimation. Experimental results show that computational complexity can be saved up to 53%. More than half of the encoding time is reduced under good rate-distortion (R-D) performance. Therefore, the proposed algorithm has considerable advantage over encoding time saving.