Efficient MPEG-2 to H.264/AVC intra transcoding in transform-domain

In this paper, we propose a transform-domain MPEG-2 to H.264/AVC intra video transcoder. In the transcoder, the input DCT coefficients are first converted to H.264 transform (HT) coefficients entirely in the transform-domain. A rate-distortion optimized macroblock mode decision is then performed, based on the HT coefficients. Finally, the HT coefficients are coded using the selected modes to generate the output H.264 bitstream. The proposed transcoder is equivalent to the conventional pixel-domain implementation in terms of functionality, but its complexity is significantly lower (on average over 20%). To further reduce its computational complexity, we propose a fast mode decision algorithm based on a simple cost function calculated in the HT-domain. This fast algorithm reduces the complexity requirement about 50%, while maintaining virtually the same coding efficiency.