Watemaking Implementation in Audio Digital


Background

Digital audio recorded give us many advantage in data processing or manipulation. However, it is also avoid violation of audio data royalty; for example illegally duplicating, cropping half or all of data and distributing without permission from owner of audio data. Watermarking technique can be implemented to protect its digital audio recorded.


Digital Watermarking

Digital Watermarking Watermarking is the process that embeds data called a watermark, tag or label into a multimedia object such that watermark can be detected or extracted later to make an assertion about the object. The object may be an image or audio or video. It may also be text only

Steganography Vs Digital Watermarking

They primarily differ by intent of use. A watermark can be perceived as an attribute of the carrier (cover). It may contain information such as copright, license, trackning and authorship etc. Whereas in case of steganography, the embedded message may have nothing to do with the cover. In steganography an issue of concern is bandwidth for the hidden message whereas robustness is of more concern with watermarking.


Types of Digital Watermarks

Watermarks and watermarking techniques can be divided into various categories in various ways. The watermarks can be applied in spatial domain. An alternative to spatial domain watermarking is frequency domain watermarking. It has been pointed out that the frequency domain methods are more robust than the spatial domain techniques. Different types of watermarks are shown in the figure below.

Types of watermarking techniques

Data hiding Technique used for Digital Watermarking Implementation


Low-bit coding

Low-bit coding is the simplest way to embed data into other data structures. By replacing the least significant bit of each sampling point by a coded binary string,we can encode a large amount of data in an audio signal. Ideally, the channel capacity is 1 kb per second (kbps) per 1 kilohertz (kHz), e.g., in a noiseless channel, the bit rate will be 8 kbps in an 8 kHz sampled sequence and 44 kbps in a 44 kHz sampled sequence. In return for this large channel capacity, audible noise is introduced. The impact of this noise is a direct function of the content of the host signal, e.g., crowd noise during a live sports event would mask low-bit encoding noise that would be audible in a string quartet performance. Adaptive data attenuation has been used to compensate this variation.

The major disadvantage of this method is its poor immunity to manipulation. Encoded information can be destroyed by channel noise, resampling, etc.,unless it is encoded using redundancy techniques.In order to be robust, these techniques reduce the data rate, often by one to two orders of magnitude. In practice, this method is useful only in closed, digital to digital environments.

Echo Hiding

Echo hiding schemes embed watermarks into a host signal by adding echoes to produce watermarked signal. The nature of the echo is to add resonance to the host audio. Therefore the acute problem of sensitivity of the HAS towards the additive noise is circumvented in this method. After the echo has been added, watermarked signal retains the same statistical and perceptual characteristics. The offset (or delay) between the original and a watermarked signal is small enough that the echo is perceived by the HAS as an added resonance. The four major parameters, the initial amplitude, decay rate, "one" offset and "zero" offset are given in Figure below

Parameters of echo embedding watermarking method

The watermark embedding process can be represented as a system that has one of two possible system functions. In the time domain, the system functions are discrete time exponentials, differing only in the delay between impulses. Processing host signal through any kernel will result in an encoded signal. The delay (number of sample intervals) between the original signal and the echo is dependent on the kernel being used, 1 if the "one" kernel is used and 0 if the "zero" kernel is used. The host signal is divided into smaller portions for encoding more than one bit. Each individual portion can then be considered as an independent signal and echoed with the desired bit. The final watermarked signal (containing several bits) is a composite of all independently encoded signal portions. A smooth transition between portions encoded with different bits should be adjusted using different methods to prevent abrupt changes in the resonance in the watermarked signal. Information is embedded into a signal by echoing the original signal with one of two delay kernels. Therefore, the extraction of the embedded information is to detect the spacing between the echoes. The magnitude of the autocorrelation of the encoded signal’s cepstrum


Echo Hiding Extract

where F represents the Fourier Transform and F¡1 the inverse Fourier Transform can be examined at two locations, corresponding to the delays of the "one" and "zero" kernel, respectively. If the autocepstrum is greater at ±1 than it is at ±0, an embedded bit is decoded as "one". For the multiple echo hiding, all peaks present in the autocepstrum are detected. The number of the peaks corresponding to the delay locations of the "one" and "zero" kernels are then counted and compared. If there are more peaks at the delay locations for the "one" echo kernel, the watermark bit is decoded as "one".


Technology used

  • Development OS and Programming Language: This software was implemented in windows and programming language is J2SE v.1.5.0_6
  • Audio Library: Java Sound API
  • Skin and GUI: Skin Look And Feel (skinlf) from L2FProd
  • Theme Picture: Audio-Therapy by airoke
  • Icons:

Application Screen shoot

Watermarking Application main form


Watermarking Application Insert Mark form


Watermarking Application Extract Mark form

Analysis Result

Low Bit Coding Technique result very little degradation of perceptual quality so the audience cant feel the different, in contrary Echo Hiding method occur much degradation of perceptual quality than Low Bit Coding Technique. Audience can hear the different between watermarked audio and original audio

In embedding test, Low Bit Coding Technique can embed data in very large of space, but Echo Hiding only can embedd small part of data.

In extraction test , Low Bit Coding Technique always have recovery rate with 100% accuracy, but in Echo Hiding technique, watermark recovery rate depend on initial amplitude and cover audio used. There is no change in size of audio file before and after watermarking process.

In robustness test result that Echo hiding Technique have highly robustness than Low Bit Coding Technique.


Advantage and Disadvantage


Advantage

  • User Friendly in User Interface
  • Can run anywhere, the requirement is only JRE Installed in Computer
  • Provide compression before embedding data
  • Provide good security by adding password in embedding and extraction process
  • Data to embed can be anything, examples: text, picture, even sound file as long as the size lower or same with max embedding capacity

Disadvantage

  • Can only use WAV files as Audio Cover
  • Large memory needed for smooth running
  • and there are still more bugs :), you'll find it

Downloads

Application Source and Distribution

  • Application Source can be download here
  • Application Distribution can be download here

Thesis Softcopy

My Thesis can be download here (only in Bahasa Indonesia, PDF Format)

About Me

Me, I Made Ady Dharmadi, an ordinary people, interest in web and computer programming. Like to learn new programming technology like AJAX and others. Graduated from Electrical Engineering Udayana University. See my complete profile

Reference

Comments