audiowatermarking-110820000227-phpapp02.ppt

7/29/2019 audiowatermarking-110820000227-phpapp02.ppt

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Audio Watermarking

Under the guidance of

Dr. Saroj Kumar Meher

Presented by

Suresh Chandra Martha EC200118335


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INTRODUCTION

Digital Data can be shared by multiple users, distributed

over network, and managed for long period time without

any damage.

In contrast to these, the copyright protection problemarises, since unauthorized copying and distribution of

digital data are simplified, too.

As a result, a technique called digital watermarking is

introduced to protect the ownership of these contents.


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AUDIO WATERMARKING

Digital Audio Watermarking is a technology to hide information

in an audio file without the information being audible to the

listener, and without affecting in any way the audio quality of

the original file.

What we can define

AIMS AT

Copy control of digital music

Ownership identification

Enforcement of usage policy

Fingerprinting


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CLASSIFICATION OF AUDIO WATERMARKING

Temporal watermarking

Temporal watermarking hides watermarks directly into

digital audio signals in the time domain.Spectral water-marking

The spectral audio watermarking applies certain

frequency transform, such as FFT, DCT, and DWT, etc,

to the data block of the audio signal, and hides thewatermark information Into the transformed data block.


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AUDIO WATERMARKING SCHEMES

DC level shifting

QMF bank band division

Frequency masking

Spread spectrum


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DC LEVEL SHIFTING

Here watermark is embedded by shifting the DC level of the

audio signal.

An input signal is divided into frames of fixed length.

DC level of each frame =Mean of a frame-value in the frame

After that a binary watermark sequence generated randomly

is introduced to the shifted signal. This is achieved by

introducing a DC offset level to each frame in the signal

according to the watermark bits.

If the watermark bit is 0, the signal is shifted downward.

If the watermark bit is 1, the signal is shifted upward.

Cont..


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DC LEVEL SHIFTING

level0=-DCBiasMultiplier x FramePower

level1=+DCBiasMultiplier x FramePower

wherelevel

0->DC level introduced when a watermark bit is 0

level1

-> the DC level introduced when a watermark bit is 1.

To extract a watermark, a watermarked signal is first divided

into frames. Then, the mean of each frame is calculated. If

the mean of a frame is positive, the corresponding

watermark bit is 1. Else, the watermark bit is 0. The original signal and watermark is not needed in the

extraction process. Therefore, DC level shifting is a blind

watermarking scheme


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Band Division Based on Quadrature Mirror Filter (QMF) Bank

Cont..


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Cont..


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Watermarked signal is filtered by the analysis filter bank and the

low frequency watermarked band is extracted out.

The modified MDCT coefficients are calculated out and

watermark can be determined by rounding the coefficients and

observe whether coefficients are even or odd.

Watermark is 1 when coefficients are odd.

Watermark is 0 when coefficients are even.

This technique has a High signal to noise ratio

The rate of detection or bit error rate is very high

WATERMARKED SIGNAL EXTRACTION USING QMF


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FREQUENCY MASKING

Watermarking involves hiding a faint but audible sound under

another louder sound (original sound), so the faint sound

becomes inaudible and it acts as a watermark for the original

sound.

Watermark is generated firstly by creating a pseudo-noisesequence (PN sequence) from a shift register. The shift

register consists ofm flip-flops with a maximum period of

(2m) 1.

PN sequence is filtered along with the filter that approximatesthe frequency characteristics of the human auditory system

(HAS). Consequently, it is put through to the time domain for

temporal masking.Cont..


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The frequency masking algorithm is robust to coding, multiple

watermarking, and resampling.

Different watermark can be embedded by this algorithm into

the same signal and is easy to detect by the owner. The detection scheme for this algorithm needs the original

input signal, which is not flexible

From the extraction scheme, frequency masking is a private

watermarking.


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SPREAD SPECTRUM

Where

wi is element of watermark

y is the watermarked signal

A correlation detector is carried out to detect the presence of the

watermark and is described by Eqn

whereNis vector cardinalityCont..


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SPREAD SPECTRUM

While x can be modelled as Gaussian random vector, the

normalised correlation test is described as Eqn

1

0, /^ 2 xC

Q p N N N

Ifp = 1, watermark is present

If p=0, watermark is not present


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ANALYSIS OF VARIOUS TECHNIQUES

DC level shifting algorithm

The robustness level for the DC level shifting is poor, the

watermark can be easily removed by altering the DC levels of the

signal and the watermark is destroyed.

Frequency MaskingThis method is not robust to filtering because watermark is

embedded to all frequency bands.

Attack by high pass filter MPEG can erase the watermark.

Spread Spectrum & Band Division Based On QMFBoth the band division method and the spread spectrum method are

capable of defending against the MP3 compression, but the spread

spectrum has a better detection rate than the band division method.

Cont..


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The implementation steps for spread spectrum are more complicated.

This makes it hard to hack and breakdown the algorithm.

Band Division Based On QMF

Band division technology performs extraction scheme with nooriginal signal require attacks are still not upgraded to hack down

this audio watermarking technology.


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CONCLUSION

Watermark can be embedded in an audio signal without

being recognized by hearing and the perceptibility

requirement is fulfilled .

Extraction can be done without the presence of the original

signal and the watermark itself, so can be classified as blind

or public watermarking.

Thank You !!!


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QUESTIONS??

audiowatermarking-110820000227-phpapp02.ppt

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