基于最佳量化的序列图像编码转换码率控制策略

该文分析了编码转换缓冲区的状态,导出了编码转换缓冲区为防止解码器缓冲区下溢和上溢应满足的条件,建立了序列图像编码转换模型。并根据编码转换缓冲器的状态和信道速率,为待编码帧在图像层上预分配目的序列图像编码比特数,使用DCT系数分布特性来表征图像特性。继而为帧内每一具体宏块选定最佳量化因子,提出了基于最佳量化的码率控制策略,模拟实验表明,该码率控制策略能有效地减少、避免缓冲区出现上、下溢的情况,使输出码率趋于稳定,提高了重建序列图像的信噪比。

Rate control strategy in sequence image transcoding based on the quantizer optimization

In this paper, the status of transcoder buffer is analyzed. The conditions that have to be met by both the encoder and transcoder buffers for preventing the decoder buffer from underflowing or overflowing are derived also. A model of sequence image transcoding is established. A new rate control strategy based on the quantizer optimization is proposed, and the target number of bits firstly on picture layer based on the status of the buffer and the channel rate is allocated. Then the characteristics of the image by the distributed characteristics of the DCT coefficients are denoted and a best quantization parameter for every macroblock in a frame is selected. The experiment shows that this rate control strategy can effectively reduce or 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 image is raised.