Researches And Applications On Audio Watermarking Technology

Nowadays, there is a great wealth of information which can be accessed and shared from the Internet. It is also one of the most significant features that sets up today's unlimited broad digital world. With the development of information technology, the traditional media we have been familiar with, like text, images, audio and video, have gradually become digitalized as well; and such kinds of new media replace any particular physical medium and begin to prevail through the Internet. The popularity of these newly emerging digital multimedia techniques not only brings the fame to both the works and their authors, but also makes the protection against unauthorized copy and distribution a hot issue. These concerns motivate researchers to find ways to forbid copyright violation. Digital watermarking technology, which is proposed for this challenging problem, combines techniques from many fields together including information hiding, multimedia technology, communication theory, encoding and decoding theory, and cryptography and so on.The researches on image watermarking technology started early in academic world and have developed a strong basis with a growing number of algorithms and applications. However, the implementation of digital audio watermarking technology is more difficult because of the sensitivity of human auditory system (HAS). Digital audio watermarking technology is a process of embedding and extracting a message, also called the watermark, in and from audio sequences in robust and perceptually transparent manner. Data transferred through the watermark channel can be used for numerous applications including digital rights management, broadcost monitoring etc., and especially plays a practically significant role in the copyright protection industry.Built on basic theories such as multimedia technology, auditory system theory, signal processing theory and the previous works, researches on audio watermark technologies, primarily on spatial-domain based, time-domain based and transform-domain based algorithms, are summarized in this thesis. In the part of spatial-domain based algorithms, the Least Significant Bits (LSB) algorithm is introduced briefly, in which watermark information bits are embedded into the least significant bits of the original audio signal, giving original and watermark signals as bits sequences. In the section of time-domain based algorithms, the typical echo hiding algorithm is illustrated in details and furthermore, we use binary images as watermarks to improve it. The third aspect is the transform-domain based algorithms. Taking advantage of the theories of Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) in signal processing, the main contribution of this thesis is the research on a DWT domain digital audio watermarking algorithm based on chaos-scrambling and a DCT domain digital audio watermarking algorithm based on mean quantization both with Logistic-map Encryption technique. It shows that the security and robustness of watermark get improved by using Logistic-map Encryption and quantization.This thesis utilizes MATLAB R2007a to do the simulation experiments. Through the experiments, it observes and concludes that the four algorithms described in this thesis do well in transparency with producing ideal waveforms and rational data in two primary objective evaluation criteria, PSNR and NCC. Secondly, we could see that our algorithms also achieve good results in robustness by comparing the original watermark and the extracted one after the attack test using StirMark with again rational data in PSNR and NCC. Finally, it turns out that the digital audio watermarking algorithms based on signal processing theory generates better results in security and robustness of the watermark. Based on the research results obtained from this thesis, the author applies audio watermarking technology to the Online Excellent Curriculum System in his college, putting the procedure of embedding watermarks into the original multimedia teaching environment, such as simple upload, online learning, download etc., in order to enhance the intellectual property rights protection of teachers' education fruit.