Research And Implemention Of EBCOT Algorithm In JPEG2000

In order to meet the requirements of image quality and processing operations, the Joint Photographic Experts Group has launched a still image coding standard JPEG2000. JPEG2000uses wavelet transformation and a new entropy coding algorithm EBCOT(Embedded Block Coder with Optimized Truncation), not only make the image having a higher compression ratio in the case of the same image quality, but also achieving the progressive transmission of images, coding and transmiting the region of interest, random intercepting and accessing the code stream and so on. Along with the improvement of the performance the algorithm complexity has increases, and brought difficulties to achieve the system, so we should to study and improve the coding system.In this paper, EBCOT algorithm is in-depth studied, according to Tierl code parallel is not high and have more redundant scanning, proposed a kind scheme based on the zero coefficient detection and channel parallel. The algorithm makes use of the features of wavelet subband, adds to the detection about zero block and zero band, reduce the redundant scanning, at the same time using channel parallel acceleration program, shorten the encoding time. According to Tier2compressed rate control algorithm is not enough real time, proposed a kind of rate control algorithm based on the content of the code,it based on the characteristics of wavelet transform energy concentrated to the lowest sub-band, transmission the lowest sub-band with no loss to protect the quality of the image. Improve the software of jasper, and compare the compressed image PSNR and the number of encoded channels.The main contents are as follows:(1) Introduced the background, scope of application and development status of JPEG2000. Describe the principle and structure of EBCOT algorithm in JPEG2000standard. Analysis the problems faced by EBCOT algorithm.(2) Analysis the distribution characteristics of the zero coefficients of the wavelet transform, we found that there are a lot of zero coefficients and zero bands and zero block. According to this, detect the coefficient of zero when the encoding block, detect whether there are all zero stripe with the coding, reducing the redundant scanning.(3) In the channel encoding process, the use of dual-window encoding mechanism and updated in real time to avoid mutual interference of the state in the channel encoding.(4) Improve the rate control algorithm of distribution of the code, proposed lossless coding transmission of the lowest sub-band information. Priority encodes the code blocks that have the large amount of information. It can guarantee the truncated bitstream carrying amount of information is the largest. Experiments prove that this method effectively reduces the error of the pre-allocation algorithm.Finally, this paper gives the bit plane encoder implementation structure. Based on FPGA platform, and using a hardware description language verilog simulation some modules. And through the JPEG2000algorithm reasoning proves the correctness of the experimental result.