A lossless re-encoding of MPEG-2 coded file by integrating four motion vectors

Re-encoding of once compressed files is one of the difficult challenges in measuring the efficiency of coding methods. Variable length coding with a variable source delimiting scheme is a promising method for improving re-encoding efficiency. Analyses of coded files with fixed length delimiting and with variable length delimiting are reviewed. Motion vector codes of MPEG-2 encoded files are modified as a variable-to-variable coding point of view. Length, bit-rates, and varieties of videos are examined. One of the largest file is 16 seconds of D1 full size at 720 ×480, and in total, the length of videos used in the experiments is more than 750 seconds. By coding using Huffman codes and arithmetic codes, an improvement of more than 20% in coding efficiency over the conventional MPEG-2 is obtained. Because the proposed method is a lossless re-encoding, the video quality is the same as before.