**1.4 Watermarking applications**

Although the main motivation behind the digital watermarking is the copyright protection, its applications are not that restricted. There is a wide application area of digital watermarking, including broadcast monitoring, fingerprinting, authentication and covet communication [7, 8, 9, 10].

By embedding watermarks into commercial advertisements, the advertisements can be monitored whether the advertisements are broadcasted at the correct instants by means of an automated system [7, 8]. The system receives the broadcast and searches these watermarks identifying where and when the advertisement is broadcasted. The same process can also be used for video and sound clips. Musicians and actors may request to ensure that they receive accurate royalties for broadcasts of their performances.

Fingerprinting is a novel approach to trace the source of illegal copies [7, 8]. The owner of the digital data may embed different watermarks in the copies of digital content customized for each recipient. In this manner, the owner can identify the customer by extracting the watermark in the case the data is supplied to third parties. The digital watermarking can also be used for authentication [7, 8]. The authentication is the detection of whether the content of the digital content has changed. As a solution, a fragile watermark embedded to the digital content indicates whether the data has been altered. If any tampering has occurred in the content, the same change will also occur on the watermark. It can also provide information about the part of the content that has been altered.

Covert communication is another possible application of digital watermarking [7,8]. The watermark, secret message, can be embedded imperceptibly to the digital image or video to communicate information from the sender to the intended receiver while maintaining low probability of intercept by other unintended receivers.

There are also non-secure applications of digital watermarking. It can be used for indexing of videos, movies and news items where markers and comments can be inserted by search engines [8]. Another non-secure application of watermarking is detection and concealment of image/video transmission errors [11]. For block based coded images, a summarizing data of every block is extracted and hidden to another block by data hiding. At the decoder side, this data is used to detect and conceal the block errors.
