支持ROI优先编码策略的自适应码率控制算法

ROI-codec-supported adaptive rate control algorithm

在低码率视频通信中,感兴趣区(ROI)优先编码策略有助于图像主观质量的提高。本文提出了一种简单有效的ROI提取方法,并根据图像复杂度和运动信息给ROI和非感兴趣区(NROI)分别分配码流。对于ROI的编码范畴,文中推导出了高低码率的判断准则,使算法可以自适应地选择码率模型,减少了码率控制误差。另外,本文采用的宏块层编码顺序方案提高了图像的客观质量。实验结果表明,与TMN7和TMN8的算法相比,本文算法能将码率更稳定地控制在目标码率附近,减少了跳帧;图像的客观和主观质量都有了明显的提高。

For low bit rate video communication, the codec priority of Region of Interest （ROI） can improve the subjective image quality. In this paper, a simple and efficient approach for extracting ROI is proposed. According to the image complexity and motion information, we distribute bits to ROI and non-ROl （NROI） respectively. As to ROI codec category, the judgment criterion of distinguishing between low and high bit rate coding category is derived, which makes the algorithm select the R-Q model adaptively and decrease the rate control errors. In addition, the scheme of modifying the coding order of Macro-blocks can enhance the objective image quality. Simulation results demonstrate that the algorithm achieves a bit rate closer to the target, provides fewer skipped frames, and gets better objective and subjective image quality significantly compared with TMN7 and TMN8 algorithm.