中文摘要：

为了研究JPEG中熵编码模块硬件实现过程，概述了JPEG标准的熵编码原理．讨论了基于FPGA的熵编码器的功能，以及按功能划分的帧组装器、预解码器、熵编码模块和码流组装器4大模块的实现．同时针对直流系数差分编码和直接编码对水声图像的影响做了比较，结果表明直接编码对压缩比影响不大．对熵编码器进行了仿真验证，结果表明了本设计的正确性．

英文摘要：

In order to research hardware implementation process of entropy coding in JPEG, principles of entropy coding in JPEG were described. The function and realization of entropy encoder based on FPGA were discussed. The realization of four modules including frame assembler, predecoder, entropy coding module and stream linker were presented. Simultaneously, the impacts of DC coefficient＇ s direct encoding and differential encoding on underwater acoustic images were compared. The comparison result shows that DC coefficient＇ s direct encoding has little impact on the compression ratio. The result of simulation on entropy encoder indicates the accuracy of the design.