MOTION ESTIMATION FOR HIGH-PERFORMANCE TRANSCODING

Traditionally, the re-use of motion vectors extracted from incoming vi deo bit-stream during transcoding has been widely accepted. However, t his simple re-use scheme introduces significant quality degradation in many applications including the situation when the frame-rate convers ion is needed. In this paper, we analyzed the quantization errors that cause the extracted motion vectors to be non-optimal and we performed simulations to show the quality degradation due to the inaccurate mot ion vectors during transcoding. To improve the video quality, we propo sed an adaptive motion vector refinement. With a highly reduced comput ational complexity, the proposed adaptive motion vector refinement ach ieves significant quality improvement in comparison to the conventiona l motion vector re-use scheme. In addition, the adaptive motion vector refinement is almost as good as performing a new full-scale motion es timation.