Audio watermark detection
Encyclopedia
Watermarking 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. A signal may carry several different watermarks at the same time. Watermarking become more and more important to enable copyright protection and ownership verification.
One of the most secure techniques of audio watermarking
is spread spectrum audio watermarking (SSW). Spread Spectrum is a general technique for embedding watermarks that can be implemented in any transform domain or in the time domain. 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. So basically a watermark is spread over many frequency bins so that the energy in one bin is very small and certainly undetectable. An interesting feature of this watermarking technique is that destroying such a watermark requires noise of high amplitude to be added to all frequency bins. This type of watermarking is robust since to be confident of eliminating a watermark, an attack must attack all possible frequency bins with modifications of certain strength. This will create visible defects in the data.
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 watermarked signal for detecting hidden information. This method is attributed high security features, since any unauthorized user who does not access this information cannot detect any hidden information. Detection of the PN sequence is the key factor for detection of hidden information from SSW.
Although PN sequence detection is possible by using heuristic approaches such as evolutionary algorithms, the high computational cost of this task can make it impractical. Much of the computational complexity involved in the use of evolutionary algorithm
s as an optimization tool is due to the fitness function
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
scheme. With the use of 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 mean to extract the hidden information, it is called Evolutionary Hidden Information Detection, either fitness approximation approaches (as a tool to accelerate the process) are used or not.
One of the most secure techniques of audio watermarking
Digital watermarking
Digital watermarking is the process of embedding information into a digital signal which may be used to verify its authenticity or the identity of its owners, in the same manner as paper bearing a watermark for visible identification. In digital watermarking, the signal may be audio, pictures, or...
is spread spectrum audio watermarking (SSW). Spread Spectrum is a general technique for embedding watermarks that can be implemented in any transform domain or in the time domain. 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. So basically a watermark is spread over many frequency bins so that the energy in one bin is very small and certainly undetectable. An interesting feature of this watermarking technique is that destroying such a watermark requires noise of high amplitude to be added to all frequency bins. This type of watermarking is robust since to be confident of eliminating a watermark, an attack must attack all possible frequency bins with modifications of certain strength. This will create visible defects in the data.
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 watermarked signal for detecting hidden information. This method is attributed high security features, since any unauthorized user who does not access this information cannot detect any hidden information. Detection of the PN sequence is the key factor for detection of hidden information from SSW.
Although PN sequence detection is possible by using heuristic approaches such as evolutionary algorithms, the high computational cost of this task can make it impractical. Much of the computational complexity involved in the use of evolutionary algorithm
Evolutionary algorithm
In artificial intelligence, an evolutionary algorithm is a subset of evolutionary computation, a generic population-based metaheuristic optimization algorithm. An EA uses some mechanisms inspired by biological evolution: reproduction, mutation, recombination, and selection...
s as an optimization tool is due to the fitness function
Fitness function
A fitness function is a particular type of objective function that is used to summarise, as a single figure of merit, how close a given design solution is to achieving the set aims....
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 approximation
In function optimization, fitness approximation is a method for decreasing the number of fitness function evaluations to reach a target solution...
scheme. With the use of 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 mean to extract the hidden information, it is called Evolutionary Hidden Information Detection, either fitness approximation approaches (as a tool to accelerate the process) are used or not.