22-03-2011, 12:01 PM
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CONTENT DEPENDENT WATER MARKING SCHEME FOR SPEECH SIGNAL
Abstract:
Broadband communication networks and multimedia data available in a digital format opened many challenges and opportunities for innovation. Versatile and simple-to-use software and decreasing prices of digital devices have made it possible for consumers from all around the world to create and exchange multimedia data. Broadband Internet connections and near error-free transmission of data facilitate people to distribute large multimedia files and make identical digital copies of them. A perfect reproduction in digital domain has promoted the protection of intellectual ownership and the prevention of unauthorized tampering of multimedia data to become an important technological and research issue Digital watermarking has been proposed as a new, alternative method to enforce intellectual property rights and protect digital media from tampering.
Digital watermarking is defined as imperceptible, robust and secure communication of data related to the host signal, which includes embedding into and extraction from the host signal The main results of this project is the development of novel audio watermarking algorithms, with the state-of-the-art performance and an acceptable increase in computational complexity. The algorithms' performance is validated in the presence of the standard watermarking attacks. The main technical solutions include algorithms for embedding high data rate watermarks into the host audio signal, using channel models derived from communications theory for watermark transmission and the detection and modeling of attacks using attack characterization procedure. This project also includes a thorough review of the state-of-the-art literature in the digital audio watermarking and is being implemented using matlab using signal processing, data acquisition toolboxes.
CHAPTER 1
INTRODUCTION:
With the rapid development of the speech, audio, image, and video compression methods, currently it is not a difficult task to spread digital multimedia over Internet. This makes the protections of digital intellectual property rights and content authentications have been a serious problem. Hence the technology of digital watermarking is received a large deal of attention. Generally, digital watermarking techniques are based on either spread spectrum methods or changing the least significant bits of selected coefficients of a certain signal transform. For speech watermarking, to ensure the embedded watermark is
Imperceptible, the audio masking phenomena is considered together with these conventional techniques.
In addition, a speech watermarking system should be robust to various speech compression operations. The development of speech watermarking algorithms, therefore, involves a trade-off among speech fidelity, robustness, and watermark pattern embedding rate specifications. The speech watermarking techniques usually embed speech watermark in unnecessary parts of speech signal, or in human insensitivity auditory regions. Some of speech watermarking methods will change an interval to embed watermark. However, this kind of method has a drawback that is the unavoidably degradation of robustness. In the other methods, the watermarks are embedded by the use of counterfeit human speech. It is unfortunate that such type of method also has the defect of weak robustness especially when the counterfeit human speech is destroyed. The distortion of the counterfeit human speech will also lead to the damage of the watermark Therefore, we can define watermarking systems as systems in which the hidden message is related to the host signal and non-watermarking systems in which the message is unrelated to the host signal. On the other hand, systems for embedding messages into host signals can be divided into steganographic systems, in which the existence of the message is kept secret, and non-steganographic systems, in which the presence of the embedded message does not have to be secret.
APPLICATION AREAS:
Digital watermarking is considered as an imperceptible, robust and secure communication of data related to the host signal, which includes embedding into and extraction from the host signal. The basic goal is that embedded watermark information follows the watermarked multimedia and endures unintentional modifications and intentional removal attempts. The principal design challenge is to embed watermark so that it is reliably detected in a watermark detector. The relative importance of the mentioned properties significantly depends on the application for which the algorithm is designed. For copy protection applications, the watermark must be recoverable even when the watermarked signal undergoes a considerable level of distortion, while for tamper assessment applications, the watermark must effectively characterize the modification that took place. In this section, several application areas for digital watermarking will be presented and advantages of digital watermarking over standard technologies examined.
OWNERSHIP PROTECTION:
In the ownership protection applications, a watermark containing ownership information is embedded to the multimedia host signal. The watermark, known only to the copyright holder, is expected to be very robust and secure (i.e., to survive common signal processing modifications and intentional attacks), enabling the owner to demonstrate the presence of this watermark in case of dispute to demonstrate his ownership. Watermark detection must have a very small false alarm probability. On the other hand, ownership protection applications require a small embedding capacity of the system, because the number of bits that can be embedded and extracted with a small probability of error does not have to be large.
PROOF OF OWERSHIP:
It is even more demanding to use watermarks not only in the identification of the copyright ownership, but as an actual proof of ownership. The problem arises when adversary uses editing software to replace the original copyright notice with his own one and then claims to own the copyright himself. In the case of early watermark systems, the problem was that the watermark detector was readily available to adversaries. As ,anybody that can detect a watermark can probably remove it as well. Therefore, because an adversary can easily obtain a detector, he can remove owner’s watermark and replace it with his own. To achieve the level of the security necessary for proof the of ownership, it is indispensable to restrict the availability of the detector. When an adversary does not have the detector, the removal of a watermark can be made extremely difficult.
However, even if owner’s watermark cannot be removed, an adversary might try to undermine the owner. An adversary, using his own watermarking system, might be able to make it appear as if his watermark data was present in the owner’s original host signal. This problem can be solved using a slight alteration of the problem statement Instead of a direct proof of ownership by embedding e.g. "Dave owns this image" watermark signature in the host image, algorithm will instead try to prove that the adversary’s image is derived from the original watermarked image.
Such an algorithm provides indirect evidence that it is more probable that the real owner owns the disputed image, because he is the one who has the version from which the other two were created.
AUTHENTICATION AND TAMPERING DETECTION:
In the content authentication applications, a set of secondary data is embedded in the
host multimedia signal and is later used to determine whether the host signal was tampered. The robustness against removing the watermark or making it undetectable is not a concern as there is no such motivation from attacker’s point of view. However, forging a valid authentication watermark in an unauthorized or tampered host signal must be prevented. In practical applications it is also desirable to locate (in time or spatial dimension) and to discriminate the unintentional modifications (e.g. distortions incurred due to moderate MPEG compression from content tampering itself. In general, the watermark embedding capacity has to be high to satisfy the need for more additional data than in ownership protection applications. The detection must be performed without the original host signal because either the original is unavailable or its integrity has yet to be established. This kind of watermark detection is usually called a blind detection.
BROADCAST MONITORING:
Watermarking is an obvious alternative method of coding identification information
for an active broadcast monitoring. It has the advantage of being embedded within the multimedia host signal itself rather than exploiting a particular segment of the broadcast signal. Thus, it is compatible with the already installed base of broadcast equipment, including digital and analogue communication channels. The primary drawback is that embedding process is more complex than a simple placing data into file headers. There is also a concern, especially on the part of content creators, that the watermark would introduce distortions and degrade the visual or audio quality of multimedia. A number of broadcast monitoring watermark-based applications are already available on commercial basis. These include program type identification, advertising research, broadcast coverage research etc. Users are able to receive a detailed proof of the performance information that allows them to:
1. Verify that the correct program and its associated promos aired as contracted;
2. Track barter advertising within programming;
3. Automatically track multimedia within programs using automated software online.
INFORMATION CARRIER:
The embedded watermark application is expected to have a high capacity and to be detected and decoded using a using wavelets. While the robustness against intentional attack is not required, a certain degree of robustness against common processing like MPEG compression may be desired. A public watermark embedded into the host multimedia might be used as the page link to external databases that contain certain additional information about the multimedia file itself, such as copyright information and licensing conditions. One interesting application is the transmission of metadata along with multimedia. Metadata embedded in, e.g. audio clip, may carry information about composer, soloist, genre of music, etc.
PERCEPTUAL TRANSPARENCY:
In most of the applications, the watermark-embedding algorithm has to insert additional data without affecting the perceptual quality of the audio host signal. The fidelity of the watermarking algorithm is usually defined as a perceptual similarity between the original and watermarked audio sequence. However, the quality of the watermarked audio is usually degraded, either intentionally by an adversary or unintentionally in the transmission process, before a person perceives it. In that case, it is more adequate to define the fidelity of a watermarking algorithm as a perceptual similarity between the watermarked audio and the original host audio at the point at which they are presented to a consumer.
WATERMARK BIT RATE:
The bit rate of the embedded watermark is the number of the embedded bits within a
Unit of time and is usually given in bits per second (bps). Some audio watermarking applications, such as copy control, require the insertion of a serial number or author ID, with the average bit rate of up to 0.5 bps. For a broadcast monitoring watermark, the bit rate is higher, caused by the necessity of the embedding of an ID signature of a commercial within the first second at the start of the broadcast clip, with an average bit rate up to 15 bps. In some envisioned applications, e.g. hiding speech in audio or compressed audio stream in audio, algorithms have to be able to embed watermarks with the bit rate that is a significant fraction of the host audio bit rate, up to 150 kbps.
ROBUSTNESS:
The robustness of the algorithm is defined as an ability of the watermark detector to extract the embedded watermark after common signal processing manipulations. A detailed overview of robustness tests is given in Chapter 3. Applications usually require robustness in the presence of a predefined set of signal processing modifications, so that watermark can be reliably extracted at the detection side. For example, in radio broadcast monitoring, embedded watermark need only to survive distortions caused by the transmission process, including dynamic compression and low pass filtering, because the watermark detection is done directly from the broadcast signal. On the other hand, in some algorithms robustness is completely undesirable and those algorithms are labeled fragile audio watermarking algorithms
