Conversion scheme for DCT-domain transcoding of MPEG-2 to H.264/AVC

Abstract

The 4×4 approximate discrete cosine transform (DCT) of H.264/AVC [1] makes it difficult to transcode the pre-coded video contents with the previous video coding standards to H.264/AVC in DCT domain. This is due to the difference between 8×8 DCT used previous standards and 4×4 DCT in H.264/AVC. In this paper, we propose an efficient algorithm that converts the quantized 8×8 DCT block of MPEG-2 into newly quantized four 4×4 DCT blocks of H.264/AVC to support DCT-domain transcoding. Experimental results show that the proposed scheme improves computational complexity by 5-11% and video quality by 0.1-0.5 dB compared with cascaded pixel-domain transcoding that exploits inverse quantization (IQ), inverse DCT (IDCT), DCT, and re-quantization (re-Q). © Springer-Verlag Berlin Heidelberg 2005.