Exploiting pseudo-quadtree structure for accelerating HEVC spatial resolution downscaling transcoder

In this paper, a novel method to accelerate the spatial resolution downscaling transcoding operation for high efficiency video coding (HEVC) is proposed. The proposed transcoder first extracts the information about the coding unit (CU) structure during the decoding process and analyzes it to construct a pseudo-quadtree of the target resolution. By utilizing the constructed pseudo-quadtree, the encoder process is accelerated by searching only the optimal depth in the quadtree structure. To evaluate the performance of the proposed transcoding method, its transcoding time and bitrate loss are measured and compared with those of the HEVC reference encoder and decoder. Also, a comparison with state-of-the-art fast CU size decision methods and spatial resolution downscaling transcoding methods for HEVC is presented. The proposed method achieves an average speedup of 1.65 with an average bitrate loss of 2.06%.