Efficient video transcoding with scan format conversion

General-purpose MPEG-2 video transcoders must be able to achieve any conversion between 18 ATSC (Advanced Television System Committee) video formats for DTV (digital television), e.g., scan format, size format, and frame rate format conversion. Especially, scan format conversion is hard to implement because frame rate and size format conversion often happen together. This paper proposes a fast motion estimation (ME) algorithm for MPEG-2 video transcoding supporting scan format conversion. Firstly, we extract and compose a set of candidate motion vectors (MVs) from the input bit-stream to comply with the re-encoding format. Secondly, the best MV is chosen among several candidate MVs by using a weighted median selector. Simulation results show that the proposed ME algorithm reduces significantly transcoding complexity with a minor PSNR degradation.