Audio Watermarking

Digital watermarking is the process of embedding information into a digital signal in a way that is difficult to remove. The signal may be audio, pictures or video, for example. If the signal is copied, then the information is also carried in the copy. A signal may carry several different watermarks at the same time.

In visible watermarking, the information is visible in the picture or video. Typically, the information is text or a logo which identifies the owner of the media. The image on the right has a visible watermark. When a television broadcaster adds its logo to the corner of transmitted video, this is also a visible watermark.

In invisible watermarking, information is added as digital data to audio, picture or video, but it cannot be perceived as such (although it may be possible to detect that some amount of information is hidden). The watermark may be intended for widespread use and is thus made easy to retrieve or it may be a form of Steganography, where a party communicates a secret message embedded in the digital signal. In either case, as in visible watermarking, the objective is to attach ownership or other descriptive information to the signal in a way that is difficult to remove. It is also possible to use hidden embedded information as a means of covert communication between individuals.

One application of watermarking is in copyright protection systems, which are intended to prevent or deter unauthorized copying of digital media. In this use a copy device retrieves the watermark from the signal before making a copy; the device makes a decision to copy or not depending on the contents of the watermark. Another application is in source tracing. A watermark is embedded into a digital signal at each point of distribution. If a copy of the work is found later, then the watermark can be retrieved from the copy and the source of the distribution is known. This technique has been reportedly used to detect the source of illegally copied movies.

Annotation of digital photographs with descriptive information is another application of invisible watermarking.

While some file formats for digital media can contain additional information called metadata, digital watermarking is distinct in that the data is carried in the signal itself.

The use of the word of watermarking is derived from the much older notion of placing a visible watermark on paper.

For more about Watermarking.........

Digital watermarking - Wikipedia, the free encyclopedia

Digital Audio Watermarking

Digital watermarking is a technology which allows a secret message to be hidden in a computer file, without the detection of the user.  The watermark is not apparent to the user, and does not affect in any way, the use of the original file.  Watermark information is predominantly used to identify the creator of a digital file, i.e. a picture, a song, or text.

Digital audio watermarking involves the concealment of data within a discrete audio file.  Applications for this technology are numerous.  Intellectual property protection is currently the main driving force behind research in this area.  To combat online music piracy, a digital watermark could be added to all recording prior to release, signifying not only the author of the work, but the user who has purchased a legitimate copy.  Newer operating systems equipped with digital rights management software (DRM) will extract the watermark from audio files prior to playing them on the system.  The DRM software will ensure that the user has paid for the song by comparing the watermark to the existing purchased licences on the system.

Other non-rights related uses for watermarking technology include embedding auxiliary information which is related to a particular song, like lyrics, album information, or a small web page, etc.  Watermarking could be used in voice conferencing systems to indicate to others which party is currently speaking.  A video application of this technology would consist of embedding subtitles or closed captioning information as a watermark.

DC Watermarking Scheme

This section details the implementation of a digital audio watermarking scheme, which can be used to hide auxiliary information within a sound file.  Although this watermarking scheme is for instructional use as a tool for perceptual audio education, it provides an overview of techniques which are common to all digital audio watermarking schemes.

The DC watermarking scheme hides watermark data in lower frequency components of the audio signal, which are below the perceptual threshold of the human auditory system.

For more about DC watermarking......


Download power point presentation slide.




Audio Watermarking .(ppt)