基于率失真最佳的视频编码码率控制方法

Rate-distortion Optimal Rate Control for Video Coding

提出一种通过图像层和宏块层相结合的途径来实现视频编码器码率控制的策略。在图像层首先在总体上对每帧图像的编码速率进行预分配,从而确定一个参考量化系数。然后在对每帧图像具体编码时,根据率失真定理,在保证失真最小的情况下,为帧内不同的宏块选用最佳的量化系数。仿真结果表明:采用此视频编码码率控制策略能有效地减少或避免缓冲区出现上、下溢,使得输出码流趋于稳定,同时提高重建视频信号的信噪比。

The strategy of video coding rate control by picture layer and macroblock layer is proposed. Rate control on picture layer actually allocates a target rate for current frame to be encoded. Based on this number,a reference quantization parameter is selected on picture layer,which is a macro allocating in advance. In the course of determining the quantization step of every macroblock in a frame,the characteristics of an image itself should be fully considered. A new method for rate-distortion optimized coding mode selection is presented. Using this method,the distortion subjecting to the target rate constraint is minimized and the formulas that indicate how to choose the quantization parameters are obtained. The experiment shows that the rate control strategy proposed can effectively reduce and avoid the overflow and underflow of the encoder buffer,and the output bit rates tend to stabilization. The peak signal-to -noise ratio （PSNR） of the reconstructed picture is raised.