Abstract: This paper proposes a new scheme of audio watermarking based on MP3 co
mpression for protecting copyright of MP3 music. During MP3 encoding, energy of each scale band is computed to get m scale bands having relatively high energy. The largest modified discrete cosine transform (MDCT) coefficient is found in each scale band. The watermark bits are embedded by modifying the sign of these coefficients. The watermark can be extracted in the decoding process without using the original audio signal. The presence of watermark is undetectable by human hearing, and the schemeis robust against attack which is performed by decoding the watermarked MP3 bitstream and then re-coding it.

Key words: audio watermarking, copyright protection, modified discrete cosine transform (MDCT) coefficient, scale band, MP3