| JPEG2000 image compression algorithms are now the most advanced.It has been officially named as ISO15444 by ISO Standardization Group.The biggest difference between JPEG2000 and the traditional JPEG is that JPEG2000 has abandoned the use of block coding based on the discrete cosine transform(DCT),and introduced the use of multi-resolution coding based on discrete wavelet transform(DWT).Sweldens proposed the lifting wavelet transform technique in 1995.This technique abandons the traditional convolution way of the wavelet transform,and introduces the new lifting format which increases the transform speed,saves storage space and is more suitable for hardware and software implementations.This paper studies JPEG2000 image coding theory,algorithms and implementation of the key issues.The thesis will emphasis on research of bit-plane code and the realization and optimization of JPEG2000 encoder based on ADSP TS201 platform. Introduce the process and structure of JPEG2000 codec,the bitstream syntax and format of documents,and analysis and test JPEG2000 code.The JPEG2000 achieves great compression rate by means of EBCOT and adaptive arithmetic coding.To fulfil the distinct requirement of the application,JPEG2000 carries out various controls over allocation of the packets,precincts,layers.Multi-channel bit-plane coding algorithm are described detailedly.Based on the analysis of the original bit-plane coding algorithm,this paper makes two improvements to reduce the encoding time.In order to migrate the code into ADSP TS201 chip,the issues of migration process are detailedly described and a series of optimization for DSP is developed. Firstly,based on the structural characteristics of DSP,c code has been optimized,and then the optimization of memory allocation and DMA transfer is made.Make full use of DSP-chip storage space,improve code performance and alleviate the bottleneck of bus read/write.The coding speed on DSP is improved,and the compression ratio and image quality are ensured.E... |
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