Audio Signal Processing and Coding

11.5 DIGITAL AUDIO WATERMARKING

Audio content protection from unauthorized users and the issue of copyright management are very important these days, considering the vast amount of multimedia resources available. Moreover, with the popularity of efficient search engines and fast Internet connections, it became feasible to search/download an audio clip over the World Wide Web in the MP3 format that can offer CD-quality high-fidelity audio. For example, an audio clip of 6-minute duration in the MP3 format, in general, would require 3–5 MB of storage space; and note that at 20 kB/s, it would take no more than 5 minutes to download the entire audio clip. Because of this, security issues in MP3 audio streaming have become important [Horv02] [Thor02]. Furthermore, with the advancements in the computer industry, any unprotected CD can be reproduced (i.e., copied) with minimal effort. The need for “intellectual property management and protection” (IPMP) [Spec98] [Spec99] [Rose01] [Beck04], motivated content creators and service providers to seek efficient encryption and data hiding techniques. The main idea behind these data hiding techniques is to insert (or hide) an auxiliary data string into the digital media, in order to resolve rightful ownership. Some of the important tasks of these encryption/data-hiding techniques include the ability: to ensure that the encryption is imperceptible and robust to a variety of signal processing manipulations (e.g., down-sampling, up-sampling, filtering, ...