Abstract: To address the drawbacks of TMN8 rate control model in real-time video communications in practical scena-rios,this paper proposed three technical modifications:target bit rate computation,center-oriented perceptual weighting,and layered rate control.Meanwhile,a two-pass motion estimation approach was also established to deal with the dilemma of cause and effect between RDO estimation and rate control,in which the motion information generated by pre-estimation stage is further used to speed up and optimize formal encoding process.A high-precision H.264 rate control method employing TMN8 model was ultimately implemented on the basis of the presented improved techniques and the two-pass approach.Simulation experimental results and practical applications in SIP video conference system demonstrate that this method does play a positive effect on the visual experience of real-time video.

Key words: Rate control,H.264,TMN8 model