A Novel Constant Quality Rate Control Scheme for Object-based Encoding

In this paper, a novel constant quality rate control (CQRC) algorithm is proposed for object-based (MPEG-4) video codecs. Instead of minimizing distortion of every single frame or minimizing average frame distortion, this controller seeks to minimize the variation of the frame distortion to achieve consistent good quality for whole video sequences. The CQRC algorithm uses a linear rate control model to estimate frame-level bit allocation based on a target distortion measure, and a quadratic rate-quantization model to calculate the quantization parameter for the current frame. The scheme is then further extended to encompass multiple (arbitrary shaped) video objects by means of a bitrate distribution algorithm. Experimental results demonstrate the ability of the CQRC algorithm to achieve a video sequence with less flickering effects and motion jerkiness compared to MPEG-4´s scalable rate control scheme, even in the scenario of using imperfect segmentation masks