An improved all-pass watermarking scheme for speech and audio

This paper investigates some problems encountered in the all-pass watermarking scheme developed by Yardymcy, et al. (1997) and suggests ways to eliminate them. The system under consideration uses all-pass filters to embed data into a speech or music signal by phase modification in consecutive blocks creating some artefacts in doing so. The two approaches we suggest remove these artefacts while keeping the watermark detectable and all the advantages of the method. The results of experimental studies related to the relationship between the block length, and perceptibility and misdetection rate are presented. Studies are carried out to determine immunity against additive noise and ways are suggested to improve the method.