Research And Implementation Of Audio Digital Watermark Algorithm Oriented Air Channel Transmission

Digital Marking Technology can embed configuration information into digitalcarrier without influencing the usage of the carrier. The configuration information cannot be easily detected or modified except the manufacture.As an important branch ofDMT, audio digital marking technology has developed quickly.It has been an essentialdirection for study to keep the marking technology algorithm with good robustnessand imperceptibility, as well as to get rid of much noise.Based on the analysis of theexisting ADMT, the passage proposes an algorithm which is towards the air media.And in this passage, we build a model with related theories, which tends to bepractical through simulation analysis and actual test. Then, we take the algorithm intoexperiment to prove its performance.We first talk about some basic related theories about audio digital marking, andgive a short introduction about Wavelet Transform.Then we focus on an audio digitalmarking algorithm based on the discrete wavelet transform. The algorithm decreasesthe dimensionalities of the marking information of the binaryzation image whoseformat is “.bmp”. Using the characteristics of multi-resolution ratio and partialprocessing of discrete wavelet transform, the algorithm embeds the markinginformation into audio with Daubechies4wavelet.The algorithm is simple and haslittle computation amount. It also passes through the analysis of analyzing softwaresuch as MOS, Strimak audio marking test and so on. We can see that the algorithmpossesses high SNR and fine imperceptibility, but its robustness is not good.Facedwith the weak robustness, we can change the amplitude to realize the algorithm’smarking encrypting function.So the algorithm has great value in the areas of detectingaudio-vulnerability, secretly transporting encryption information and others. But whenit comes to air media, because of the weak robustness, the algorithm cannot workefficiently.Then, based on the frequency response characteristic of human ear towards audio,combining the features of microphone and voice box, the passage comes up with anaudio digital marking algorithm, for air media specially.This algorithm firstly encodesthe digital information into one dimensional code. And after that, with gradual ASKmodulation, the algorithm deals with the encoded message.With the test of MOS, wefind the algorithm possessing fine imperceptibility.In the part of drawing marking information, the sampled audio goes through filtering, enveloping, smoothing.According to the amplitude feature of enveloped marking carrier wave, then we offera synchronization algorithm to find out the start point of the wave roughly. At last,after judging the amplitude values, we extract the message in the markinginformation.With the test executed in the practical air media, we find that thisalgorithm has good signal resolution and fine robustness as well as imperceptibility.Even in the bad weather, the algorithm can still transport the information through airmedia with low bit error rate.