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A joint transform-domain-translated (JTT) algorithm, which can achieve fast MPEG-2 to H.264 downscaling intraframe transcoding, is proposed. The proposed JTT algorithm effectively combines the 8 x 8 inverse discrete cosine transform, the 2:1 downscaler and the 4 x 4 integer transform without involving any complex pixel processes in the spatial domain. The authors also suggest a fast realisation of the JTT algorithm to further reduce its computation. The proposed JTT-transcoding method saves a lot of computation compared with some of the existing approaches in transcoding processing. Experimental results show that the proposed JTT algorithm effectively converts the MPEG-2 intraframe to H.264 intraframe to achieve almost identical PSNR performance compared with the pixel-domain decode-downsize-encode transcoder, which involves MPEG-2 decoding, spatial-domain downsizing and H.264 encoding processes.