Abstract: For analysis-by-synthesis(AbS) compressed speech a steganalysis method based on statistics of the pulse position parameters was proposed. Speech compressed by G.729 coding algorithm was taken as an example to analyse the characteristic differences of the pulse position parameters of cover and stego speech, and a new feature, the histogram flatness was defined. In the steganalysis method,four statistics including histogram flatness,the center of mass of histogram characteristic function, histogram variance, and the probability difference of 0 and 1，were used as distinguishing features, and SVM classifiers were employed. Experiment results show the proposed algorithm has good performance for steganalysis of speech compressed by G.729 algorithm. As to compressed speech coded by other AbS-based coders, the proposed method is also applicable.

Key words: Steganalysis, Compressed speech, Pulse position parameters, Statistics