A new audio watermarking based on modified discrete cosine transform of MPEG/audio layer III

This paper proposes a solution to authenticate copyrights of audio signals. The musical file in MP3 format is very popular on Internet due to its characteristically high compression ratio and tone quality. Still, problems occur in the protection function of musical file, which can be illegally duplicated. A new watermarking technique can resolve this problem. We can simultaneously accomplish embedding procedures when performing compression of MP3. As the processes of compression and embedding are finished at the same time, incidence of distorted musical files is also reduced. In the proposed method, a few values of coefficients are slightly modified in the frequency domain; the musical file of MP3 is still undetectable by human hearing. Hence the digital watermark is successfully embedded in MP3, thereby achieving the goal. In experimental results, an audio signal is compressed by MP3 at a ratio of 64 kbps; the detection ratio of extracted watermark is 96%. Even if these signals are truncated 75% in the latter part, the detection ratio of extracted watermark still remains 64%, with watermarks discernible to the human ear.