Noninvertible watermarking methods for MPEG-encoded audio

Nowadays the multimedia technology in distributed environments becomes realistic and the multimedia copyright protection issue becomes more and more important. Various digital watermarking techniques have been proposed in recent years as the methods to protect the copyright of multimedia data. Although, conceptually, these techniques can be easily extended for protecting digital audio data, it is challenging to apply these techniques to MPEG Audio streams because we need to design the watermarking schemes working directly in the compressed data domain. In this paper, we present watermarking methods which will embed the watermark directly into the MPEG audio bit streams rather than going through expensive decoding/encoding process in order to apply watermarking schemes in uncompressed data domain. Among the two presented schemes, one embeds the watermark into the Scale Factors of the MPEG audio streams and another one embeds the watermark into the MPEG encoded samples. Our experimental results show that both methods perform well and the distortion could be controlled at the minimal level. While we use MPEG Audio Layer II streams in our experimental tests, the proposed schemes can be applied to MPEG Audio Layer I and III. Furthermore, by enforcing creation of the watermark through a standard encryption function such as DES, the proposed schemes will be successful in resolving rightful ownership of watermarked MPEG audio.