A Fast H.264 Spatial Downscaling Transcoder for Wireless Communication

Motivated by the wide adoption of H.264 and the demand of universal multimedia data access over wireless network , this paper studies H.264 homogeneous video transcoding with spatial resolution conversion. Firstly , we propose a fast video transcoder ,working entirely in the DCT-domain,to convert high quality H.264 bitstream into low bit rate stream with low spatial resolution for wireless video access. Then,a motion vector estimation algorithm based on mapping and merging process is proposed to utilize the original motion information to predict motion vectors for the down scaled video .Experimental results show that, compared with existing transcoder , the proposed method significantly reduces the transcoding complexity while maintaining comparable rate distortion performance.