基于码率预分配的嵌入式图像编码

Embedded image coding based on rate pre-allocation

针对EBCOT嵌入式编码中码率控制部分计算复杂度高的问题,提出一种基于加权控制的码率预分配反馈算法。首先对原图像进行小波分解,然后根据子带的重要性权值对目标码率进行初步分配,并以视觉系数加权或比特平面深度加权进一步优化子带码率的分配。在同一子带内按照各码块的重要性权值进行排序,优先处理更重要的码块,最后采用码率反馈来控制编码精度。实验结果证明该算法码率预分配准确,编码器的计算量小,相对于RPFC算法,计算量减少率提高了10%,且算法的码率分配效率提高了50%以上;同时算法在低码率时重建图像峰值信噪比较PCRD算法提高了0.7 d B以上。

To resolve the problem that a large amount of data appeared in the rate control of EBCOT, this paper proposed a novel rate pre-allocation and feedback algorithm based on weighted control. First, it decomposed the original image by wave- let, then initially allocated the target rate according to the significant weight of subbands, and further optimized it by the visual coefficient or the depth of bit plane. It sorted each code block in the same subband according to the significant weight, a code block with large weight was priority and it controlled the coding accuracy by rate feedback. Experimental results prove that the proposed algorithm can pre-allocate bit rate accurately and reduce the calculation of encoder, increase the reduction rate of calculation 10% and the rate allocation efficiency more than 50% compared with RPFC algorithm. The algorithm can improve the peak signal to noise ratio of the reconstructed image O. 7 dB relative to the PCRD algorithm at low bit-rate.