A two-level rate control approach for video transcoding

We present a two-level rate control approach for VC-1 to H.264 transcoding. First, a low complexity algorithm in which the key is to find the relationship between quantization parameters (QPs) in VC-1 to QPs in H.264. Second, a medium complexity algorithm in which the key is to use mean absolute differences and sum of absolute transform differences calculated in VC-1 to estimate the complexity of macroblocks in H.264 for a pixel/transform domain transcoder. The low complexity rate control tool has a limitation of only able to rate-control transcode for QP ranges from 10 to 29. To transcode the entire QP range we propose a combination of low and median complexities tools. Results show that the proposed rate control transcoding is less complex than that of a full-cascaded transcoder with regular rate control turned on, while maintaining target bit-rate and PSNR.