A novel steganographic method for algebraic-code-excited-linear-prediction speech streams based on fractional pitch delay search

Although a large number of steganography algorithms based on algebraic-code-excited-linear-prediction have been proposed, their performance, such as embedding capacity, embedding transparency and capability for resisting detection, can be further enhanced. Therefore, we are motivated to present a new steganographic scheme based on pitch delay search, which can achieve better performance by embedding secret information into the fractional pitch delay parameters while keeping the integer pitch delay parameters unchanged. Specifically, we treat all fractional pitch delays as replaceable cover bits to achieve maximum embedding capacity. Further, the steganographic process is encrypted and guided by m sequences for flexibility and security. The proposed method is evaluated with a large number of adaptive multi-rate speech samples and compared with the existing works. Experimental results show that the proposed method can provide larger embedding capacity than the existing works while achieving excellent embedding transparency. Moreover, we evaluate the performance of the proposed method for resisting the state-of-the-art steganalysis methods. The experimental results demonstrate that the proposed method is highly secure, since the state-of-the-art steganalysis methods cannot detect it efficiently.