Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Audio watermarking robust against D/A and A/D conversions | Xiang EURASIP Journal on Advances in Signal Processing 2011 2011 3 http content 2011 1 3 o EURASIP Journal on Advances in Signal Processing a SpringerOpen Journal RESEARCH Open Access Audio watermarking robust against D A and A D conversions Shijun Xiang1 2 Abstract Digital audio watermarking robust against digital-to-analog D A and analog-to-digital A D conversions is an important issue. In a number of watermark application scenarios D A and A D conversions are involved. In this article we first investigate the degradation due to DA AD conversions via sound cards which can be decomposed into volume change additional noise and time-scale modification TSM . Then we propose a solution for DA AD conversions by considering the effect of the volume change additional noise and TSM. For the volume change we introduce relation-based watermarking method by modifying groups of the energy relation of three adjacent DWT coefficient sections. For the additional noise we pick up the lowest-frequency coefficients for watermarking. For the TSM the synchronization technique with synchronization codes and an interpolation processing operation is exploited. Simulation tests show the proposed audio watermarking algorithm provides a satisfactory performance to DA AD conversions and those common audio processing manipulations. Keywords Audio watermarking D A and A D conversions Synchronization Magnitude distortion Time scaling Wavelet transform Introduction With the development of the Internet illegal copying of digital audio has become more widespread. As a traditional data protection method encryption cannot be applied in that the content must be played back in the original style. There is a potential solution to the problem that is to mark the audio signal with an imperceptible and robust watermark 1 - 3 . In the past 10 years attacks against audio watermarking are becoming more and more complicated with the development of watermarking technique. According to
