On Optimization Design Of MQ Coding And Rate Control And Its Application In Mars Exploration

Mars exploration,the latest space exploration engineering program of China,is the first step taken by CASC to explore the deep space.Given the Earth-Mars communications channel with limited bandwidth and the large amount of photographs of Mars to be taken,JPEG2000,the new still image coding standard,has been applied to conduct image compression.Although the standard has superior compression performance,its algorithm structure is quite complicated,specially the MQ coding and rate control in EBCOT.MQ coding involves substantial bit-level computation and complex control relationship,while rate control requires enormous memory space and repeated iterative interception,making the two the major bottleneck for the implementation of JPEG2000 algorithm on Mars exploration hardware platform with limited resources.In this light,area optimization design of MQ coding and rate control is of great significance for the implementation of JPEG2000 image coding system.This thesis gives a research on the algorithm principle and working procedure of JPEG2000 standard and analyzed the characteristics of the algorithm of MQ arithmetic coding and rate control as well as the technical bottleneck to be overcome in hardware implementation.Based on current technology and specific demands of image coding,this thesis implemented and optimized two modules and came out with the following results:1?MQ arithmetic coding algorithm was studied in-depth.Given the highly-serialized data in the algorithm,an MQ coder based on three-stage pipeline architecture was designed.After analyzing the circuit architecture of the first-stage and second-stage pipeline,it was found that the fan-outs of multiplexer are too high,and to solve this problem,the number of input and output branches of multiplexer was reduced,which has helped reduce area consumption greatly.Besides,the output characteristics of the MQ coder was analyzed.To ensure continuous data throughput,a shift register was added into the third-stage pipeline.It was proved that the minimum effective bit wide of the register is 3 bytes and no-internal throughput of input data in the MQ coder was realized.2?In this thesis,rate control algorithm was studied and a kind of EBCOT hardware structure that can lift slope computing module from Tier2 coding to Tier1 coding was proposed to make intermediate cache no longer necessary for channel information generated by Tier1 coding,which has effectively reduced the consumption of memory space.Besides,a rate control module was designed and implemented on the basis of such structure.The module consists of two parts: a slope computing module that can eliminate singularities for three times forwardly and a parallel interception module supporting the packet header preestimation.The former consumes fewer resources than modules eliminating singularities completely and has better interception performance than modules eliminating current singularities,while the latter has optimized the precision and speed of rate control comparing with existing implementations.3?The MQ coder and rate control module implemented in this thesis has been applied in Mars exploration image coding system based on JPEG2000.The system supports various compression mode and can meet real-time image processing requirements on various indexes,including 12 bit depth and a max resolution of 3072*4096.Through collaborative software and hardware verification,large-scale image tests as well as analysis of hardware implementation results,it was finally proved that the bit stream of codes output by the system conforms to JPEG2000 standard and its compression performance and resource consumption both meet the demands of Mars exploration program.This thesis,taking Mars exploration program as the backdrop,has designed and implemented an MQ coder and rate control module whose area consumption has been optimized to ensure low resource consumption of image processing unit in Mars exploration program.However,since the working frequency of circuits and processing speed adopted in the thesis is low,the processing objects are limited to images of medium resolution and high resolution in Mars exploration program,but not images generated in such other scenarios as network communications,medical imaging,digital libraries,etc.It is suggested that future studies focus on more application fields to further optimize the coding system to improve its performance and versatility.