CONDITIONAL MASKING FOR VIDEO ENCODER

摘要

This method and apparatus described herein imposes masking factors to the determined quantization step sizes of macroblocks of a video sequence such that encoding efficiency is increased. A conditional masking method can be used to take advantage of the fact that P-pictures are more important than B-pictures in terms of motion and scene updates as coding noise in such updates are likely propagated by P-pictures. The masking can be applied conditionally to motion/scene update regions of a picture such that coding noise is reduced and therefore bits are saved from less propagation of this noise. Before encoding each macroblock of a picture from an input video sequence, a video encoder with conditional masking determines if the macroblock type belongs to a significant motion or scene update region. A conditional masking factor is then determined for the macroblock based on the determined macroblock type and the picture coding type. The conditional masking factor is combined with a macroblock reference quantization step-size which may be calculated using conventional methods based on bit allocation and bit utilization, and an optional activity masking factor based on activity level of the macroblock and/or its surrounding region to form the final quantization step-size for coding of the macroblock.