The Research Of Digital Watermarking Method Based On LDPC Error Correcting Coding

As a novel technique to protect the intellectual copyright of multimedia information, digital watermark has been researched and applied more intensively. But until now, digital watermark is still an immature technique, and how to improve the practicability of digital watermark under different circumstances has become an urgent problem.This thesis addresses the watermarking based on Low Density Parity Check(LDPC) error correcting code. It introduces the usual algorithms of digital watermarking, method of channel coding and Wavelet transform. Besides, it analyzes the potential relationship between digital watermark system and communication system.Robustness is one of the important requirements of digital watermark. To improve the robustness of watermark, LDPC can be applied in watermarking, intending to lower the detection error rate. Currently, the high encoding complexity of a LDPC code is the main bottleneck for its practical applications. A quasi-cyclic LDPC(QC-LDPC) code is a class of LDPC codes with low encoding complexity.This paper has conducted some systematic research on the QC-LDPC codes. Especially analyzes a type of QC-LDPC code based on block-filling method and a new type of QC-LDPC code having lower triangular parity check matrix which leads to good error-rate Performance and fast encoding.Also, an improved scrambling algorithm based on reversible two-dimensional mapping is researched.The algorithm scrambles the original watermarking image in pretreatment, which improves the ability against attacks of the algorithm. This thesis presents an effective digital watermark algorithm based on improved Inoue algorithm. It improves embedding and extracting principles based on Inoue s significant wavelet coefficients algorithm, and it is used in digital watermarking algorithm for color images.This paper carries on various of the programming simulation research to the algorithm mentioned. Then we have some tests to compare the different watermarking. The test results prove the method has good robustness and invisibility of watermarking. Its credibility and practicality are very well.