茅文深　俞　剑　刘文松　姜　军

(1.中国电子科技集团公司第二十八研究所　南京　210000)(2.东南大学信息科学与工程学院　南京　211189)



JPEG2000码率控制截断预测算法及VLSI设计

茅文深1俞剑1刘文松1姜军2

(1.中国电子科技集团公司第二十八研究所南京210000)(2.东南大学信息科学与工程学院南京211189)

摘要针对JPEG2000低码率下的码率控制算法在运算量和存储量上冗余较大的问题,论文提出一种基于预测的码率控制截断算法。论文算法根据目标码率对图像数据样本采样,进行率失真斜率的预测,提前截断块编码过程,并提出一种JPEG2000系统两级码率控制的VLSI结构,第一级采用论文提出的预测算法截断码流,第二级确定精确的分层截断点。测试结果表明论文算法在码率低于0.5比特/像素时,可节省运算量和存储量70%以上,而峰值信噪比基本没有降低。

关键词JPEG2000; 码率控制; 截断; VLSI

Rate Control Truncation Algorithm Based on Prediction and VLSI Architecture for JPEG2000

MAO Wenshen1YU Jian1LIU Wensong1JIANG Jun2

(1. 28thInstitute, China Electronics Technology Cooperation, Nanjing210000)

(1. School of Information Science and Engineering, Southeast University, Nanjing211189)

AbstractA rate control truncation algorithm based on prediction is proposed to resolve the problem of computation complexity and large memory usage in the traditional JPEG2000 rate control algorithm when the bit-rate is low. By taking samples of image data for target bit-rate and predicting the rate-distortion slope, the algorithm truncates the block coding in advance, and the VLSI architecture containing two stages rate control for JPEG2000 system is proposed. The code-stream is truncated by the prediction algorithm in the first stage, and the hierarchical truncation points are determined in the second stage. Experiment indicates that the proposed algorithm has efficiently reduced above 70% computations and memory usage with no reduction in the peak signal to noise ratio.

Key WordsJPEG2000, rate control, truncation, VLSI

Class NumberTP391

1引言

JPEG2000[1]作为新一代静态图像压缩标准,和传统的JPEG标准相比具有更优异的性能和更广泛的应用领域。其中重要技术是最佳截断嵌入式块编码[2](embedded block coding with optimized truncation,EBCOT),它将JPEG2000系统分为Tier-1层和Tier-2层,其中Tier-2层采用压缩后率失真最优化算法(Post-compression Rate-distortion optimization,PCRD-opt)控制码率,并要求在Tier-1层完成所有码字编码后,在Tier-2层中再进行码率控制,因而必须先保存Tier-1层产生的所有码字,这会导致占用大量的存储空间,另外,Tier-2层中根据目标码率进行码流截断,抛弃对图像质量影响不大的码字来实现压缩,会产生大量的冗余计算和存储空间的浪费。针对这个问题目前所提出的优化码率控制算法主要有两类:第一类是对率失真斜率进行预测,提前结束位平面编码扫描[3~5],第二类是改用其他参数作为码流截断标准[6~7]。……