Fast DCT to IT conversion using integer approximation for H.263 to H.264 video transcoding

In this paper, a compressed domain video transcoder for H.263 to H.264 is proposed. The proposed video transcoder focuses on the conversion of DCT coefficients to integer transform (IT) coefficients. A set of operators is derived for converting the DCT coefficients to integer transform coefficients in the compressed domain. Using these operators, the proposed architecture is able to transcode the DCT coefficients to the integer transform coefficients directly. The integer approximation of the operators is proposed to avoid the floating point implementation for the proposed transcoder. Experimental results show that the proposed video transcoder can reduce substantially the amount of computation and provide transcoded videos with similar quality as compared with those obtained from the conventional cascaded video transcoder.