Rate Control Based on Zero-Residue Pre-Selection for Video Transcoding
A common issue in video transcoding for heterogeneous network environment is to efficiently and accurately reduce the bit-rate such that the distortion is minimized under a given rate constraint. To convert the bit-rate of an encoded video to match the channel capacity, in general, re-quantization is done on the DCT coefficients with larger quantization step size. Most existing rate control algorithms for video transcoding in the literature calculate quantization parameters (QPs) of macroblocks (MBs) based on a relationship between certain properties of coded video and bit-rate. They reduce the computational complexity by simplifying the R-D model and reusing the statistics information of input video. In this paper, we propose a zero-residue pre-selection (ZRPS) mechanism to select only a portion of MBs to apply the rate control in video transcoding. TMN-8 is used to evaluate the impact of ZRPS. Experimental results show that, as compared to the original TMN-8 rate control scheme, TMN-8 with ZRPS achieves up to 1.60 dB gain, in term of PSNR, and requires less than 50% of the computational complexity compared to TMN-8, depending on the characteristics of the video content