Study On The Robust Digital Watermark Algorithm Based On TURBO Codes

The excellent error-correcting performance of Turbo codes is generally approved in communication circles and the digital watermark system is in principle as effective as communication system. The key thought of Turbo codes lies in the decipher structure of circulation changes and replacement, not in the coding way nor in the adopted specific decipher algorithm.This article sketches the state of the study based on digital watermark technology of Turbo codes at present, the problems that watermark technology faces and its developing direction in the future. It analyses the essential distinction between Turbo codes and other channels, sums up the key thought of Turbo codes and enumerates the application of Turbo in balanced technology at the same time.Turbo codes when low signal-to-noise ratio has the outstanding error correction performance, it already became the correspondence research the front. In view of inserts the large capacity watermark difficulty major problem in the image, proposed applies the Turbo codes in the digital watermark system, uses for to enhance the watermark system robustness, uses the flag bit information in the algorithm the enhancement way, withdraws the secret information; Uses the Turbo codes decoding method, restores the primitive watermark. The experimental result indicated that, specially, under the Gauss noise influence, after the improvement plan obviously surpasses theoriginal plan.Based on the watermark scheme to make use of Turbo codes, which is put forward by Lee Jun and else, revealing the shortcoming that exists in this scheme, the ways of improvement are recommanded in three steps: First, to stipulate the modification of the picture DCT coefficient in the land range of intermediate frequency; Second, to mark the position of the revised coefficient; Finally, to adopt the modification method of adding or deducting a constant to DCT coefficient. Under the same attacking condition, the improved scheme is detected lower rate of mistake-making than the original scheme.From the coding features of Turbo codes, the article states that it's greatly difficult to study on digital watermark technology of Turbo codes. Then it analyses the basic theory of the dull and excellent digital watermark technology, the relative concept and research of which lay a foundation for the design and the realization of digital watermark technology of Turbo codes.