Rate-distortion optimization for fast hierarchical B-picture transcoding

An efficient rate-distortion (R-D) optimal method for transcoding hierarchical B-pictures is proposed in this paper. A new R-D model is presented for fast transcoding hierarchical B-pictures in DCT domain, in which the total R-D optimization problem is adjusted to motion R-D optimization and texture R-D optimization separately. Accordingly, a mechanism for fast mode decision is proposed to enable the mode and motion adjustment in hierarchical B-picture DCT-domain transcoding. Experimental results show that the proposed transcoding scheme with the new R-D optimization can achieve 4-dB average PNSR improvement at low bit-rate, and similar performance at high bit-rate, compared to the transcoding by reusing the input motion information. Moreover, as the transcoding is performed in DCT domain, it is fast and simple enough for many real applications