Rate control for MPEG video coding

摘要

ISO/IEC MPEG-2 Test Model 5 (TM5) describes a rate control method which consists of three steps: bit allocation, rate control and modulation (ISO/MPEG II, Test Model 5, April 1993). There are, however, two problems associated with TM5 rate control: degradation in picture quality at scene cuts and nonuniform picture quality due to buffer-dependent variations of the quantization parameter. This paper presents a new rate control approach which addresses these issues. To eliminate the impact of scene cuts on the picture quality, the first scheduled P picture in a new scene is coded as an I picture, and the extra I picture is further balanced by coding the next scheduled I picture as a P picture. To achieve a relatively uniform picture quality, the same global quantization parameter is applied to all the macroblocks in a picture. The global quantization parameter is determined by using either an iterative or a binary search algorithm. The simulation results demonstrate that a significant improvement in performance is obtained using the proposed rate control approach.