An audio watermark is a unique electronic identifier embedded in an audio signal, typically used to identify ownership of copyright. It is similar to a
watermark
A watermark is an identifying image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light (or when viewed by reflected light, atop a dark background), caused by thickness or density variations i ...
on a photograph.
Digital watermark
A digital watermark is a kind of marker covertly embedded in a noise-tolerant signal such as audio, video or image data.H.T. Sencar, M. Ramkumar and A.N. Akansu: ''Data Hiding Fundamentals and Applications: Content Security in Digital Multimedia'' ...
ing is the process of embedding information into a signal (e.g. audio, video or pictures) in a way that is difficult to remove. If the signal is copied, then the information is also carried in the copy. Watermarking has become increasingly important to enable copyright protection and ownership verification.
Spread spectrum
One technique for audio watermarking is spread spectrum audio watermarking (SSW). In SSW, a narrow-band signal is transmitted over a much larger bandwidth such that the signal energy presented in any signal frequency is undetectable. Thus the watermark is spread over many frequency bands so that the energy in one band is undetectable. An interesting feature of this watermarking technique is that destroying it requires noise of high amplitude to be added to all frequency bands.
Spreading spectrum is done by a
pseudonoise (PN) sequence. In conventional SSW approaches, the receiver must know the PN sequence used at the transmitter as well as the location of the watermark in the watermarked signal for detecting hidden information.
Although PN sequence detection is possible by using
heuristic
A heuristic or heuristic technique (''problem solving'', '' mental shortcut'', ''rule of thumb'') is any approach to problem solving that employs a pragmatic method that is not fully optimized, perfected, or rationalized, but is nevertheless ...
approaches such as
evolutionary algorithm
Evolutionary algorithms (EA) reproduce essential elements of the biological evolution in a computer algorithm in order to solve "difficult" problems, at least Approximation, approximately, for which no exact or satisfactory solution methods are k ...
s, the high computational cost of this task can make it impractical. Much of the
computational complexity
In computer science, the computational complexity or simply complexity of an algorithm is the amount of resources required to run it. Particular focus is given to computation time (generally measured by the number of needed elementary operations ...
involved in the use of
evolutionary algorithm
Evolutionary algorithms (EA) reproduce essential elements of the biological evolution in a computer algorithm in order to solve "difficult" problems, at least Approximation, approximately, for which no exact or satisfactory solution methods are k ...
s as an optimization tool is due to the
fitness function
A fitness function is a particular type of objective or cost function that is used to summarize, as a single figure of merit, how close a given candidate solution is to achieving the set aims. It is an important component of evolutionary algorit ...
evaluation that may either be very difficult to define or be computationally very expensive.
One of the recent proposed approaches—in fast recovering the PN sequence- is the use of fitness granulation as a promising "
fitness approximation
Fitness approximationY. JinA comprehensive survey of fitness approximation in evolutionary computation ''Soft Computing'', 9:3–12, 2005 aims to approximate the objective or fitness functions in evolutionary optimization by building up machine l ...
" scheme. With the use of the fitness granulation approach called "Adaptive Fuzzy Fitness Granulation (AFFG)",
the expensive fitness evaluation step is replaced by an approximate model. When evolutionary algorithms are used as a means to extract the hidden information, the process is called Evolutionary Hidden Information Detection, whether fitness approximation approaches are used as a tool to accelerate the process or not.
See also
*
Acoustic fingerprint
An acoustic fingerprint is a condensed digital summary, a digital fingerprint, deterministically generated from an audio signal, that can be used to identify an audio sample or quickly locate similar items in a music database.
Practical u ...
*
Activated Content
References
* M. Davarynejad, S. Sedghi, M. Bahrepour, C.W. Ahn, M. Akbarzadeh, C. A. Coello Coello,
Detecting Hidden Information from Watermarked Signal using Granulation Based Fitness Approximation, Applications of Soft Computing: From Theory to Praxis, Springer, Series: Advances in Intelligent and Soft Computing, Volume 58/2009, , pp. 463–472, 2009.
* M. Davarynejad, C.W. Ahn, J. Vrancken, J. van den Berg, C .A. Coello Coello,
", Applied Soft Computing, Vol. 10(3), pp. 719–729, 2010, .
{{DEFAULTSORT:Audio Watermark Detection
Digital audio
Digital watermarking