watermarking is a technique for embedding
additional data(for example image) along
with audio signal so that it will not effect its
perceptual quality of an audio signal
Embedded data is used for copyright owner
identification . the watermark (for example
image , data, random sequence)should be
against various signal processing
Audio watermarking is a
technique used to hide certain copyright
information (for example image, data,
random sequence etc) with audio signal in
such a way that This is not be hearable to
human ear and it should robust against all
kind of intentional and non intentional
attacks , and can be used for the purpose
of Intellectual Property Rights.
In the process of watermarking there are two signals
 Host signal (for example audio, video, image, text) which is to be
protected from unauthorized distribution.
Watermark: may be a binary data sequence or an image which is to be
embedded as a proof of ownership with host signal.
“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.”
NEED OF WATERMARKING
With the growth of the Internet, unauthorized copying and distribution of digital
media has never been easier. As a result, the music industry claims a multibillion
dollar annual revenue loss due to piracy,
Normally an application is developed by a person or a small group of people and
used by many. Hackers are the people who tend to change the original
application by modifying it or use the same application to make profits without
giving credit to the owner.
So we do require a technique which can protect our data from unauthorized
copying and distribution and can provide copyright owner identification
For our digital data over internet.
OTHER TECHNIQUE WHICH CAN PROTACT UNAUTHORIZED
ACCESS OF DATA
1. STNEOGRAPHY steganography is a technique to send
information by writing on the cover object invisibly. Steganography
comes from the Greek word that means covered writing (Stego =
covered and Graphy = writing). Here the authorized party is only
aware of the existence of the hidden message.
2. CRYPTOGRAPHY In cryptographic techniques significant
information is encrypted so that only the key holder has access to
that information, once the information is decrypted the security is
lost. Cryptography protects the contents of the message.
DIFFERENCES BETWEEN STEGANOGRAPHY AND WATERMARKING
Although steganography and watermarking both describe techniques used for
steganography typically relates only to covert point to point communication
between two parties. The main purpose of steganography is to hide the fact of
communication. The sender embeds a secret message into digital media (e.g.
image) where only the receiver can extract this message
Steganographic methods are not robust against attacks or modification of data
that might occur during transmission, storage or format conversion
Watermarking is techniques whose primary objective is the security of the
object rather than the invisibility of the object. The significant difference between
the two techniques is the superior robustness capability of watermarking
DIFFERENCE BETWEEN CRYPTOGRAPHY AND WATERMARKING:IN Cryptography technique message is encrypted and only intented receiver(Key
holder) can decrypt the message .
It is mainly useful for point to point communication.In cryptography once
message is decrypted then security lost.
In watermarking technique message is not encrypted but an another secreat
information is inserted with host signal in such a way that it will not effect
Its perceptual quality and can be used as Copyright.
APPLICATIONS OF WATERMARKING
Ownership protection and proof of ownership:
Authentication and tampering detection
Copy control and access control
Airline traffic monitoring
REQUIREMENTS OF WATERMARKING
According to IFPI (International Federation of the Phonographic Industry)
audio watermarking algorithms should meet certain requirements. The
most significant requirements are perceptibility,roubstness,security,
reliability, capacity, and speed performance.
PERCEPTIBILITY:One of the important features of the watermarking
technique is that the watermarked signal should not lose the quality of the
original signal. The signal to noise ratio (SNR) of the watermarked signal to the
original signal should be maintained greater than 20dB . In addition, the
technique should make the modified signal not perceivable by human ear.
ROUBSTNESS TO SIGNAL PROCESSING ATTACKS: Watermark should be
roubst against common signal processing attacks such as lossy compression
,linear filtering,Resampling,Requantization,cropping, jittering, D/A and A/D
conversion, Normal correlation (N.C.)is used for the measurement of roubstness.
 CAPACITY: The efficient watermarking technique should be able to carry
more information but should not degrade the quality of the audio signal.
REQUIREMENTS OF WATERMARKING
SPEED: Speed of embedding is one of the criteria for efficient
watermarking technique. The speed of embedding of watermark is important
in real time applications where the embedding is done on continuous signals
such as, speech of an official or conversation between airplane pilot and
ground control staff.
Security and Cost
COMPUTATIONAL COMPLEXITY:Computational complexity refers to
the processing required to embed watermark data into a host signal, and /or
to extract the data from the signal.
TRADE OFF BETWEEN THE VARIOUS REQUIREMENT OF WATERMARKING
The Imperceptibility, Roubustness and Capacity are the three most important
characteristics of a watermarking algorithm. However, there is a trade-off
between these three characteristics As seen from Figure imperceptibility,
robustness and capacity are conflicting characteristics of a watermarking
system . ie at the same time one can not fullfill all the requirement of
PROBLEMS AND ATTACKS ON WATERMARKING
COMPRESSION: To reduce the size of watermarked audio signal
Is called compression.
RESAMPLING: During Analog to digital conversion a signal can be
Resampled at different different sampling frequencies.
REQUANTIZATION: A signal can be Requantized with different quantization
Level as we change the quantization level the quantization error also changed
And no of bits used to represent per sample also changed.
FILTERING:filtering is used to filter certain frequency componants
of any signal or we can say that it attenuate certain frequency
componant of any signal.
ADDITIVE WHITE GAUSSION NOISE ATTACKS :A.W.G.N. can be
added to watermark signal during attack.
CROPPING: Cropping means to remove the certain part from
the watermarked signal.
THE HUMEN AUDIORATORY SYSTEM [H.A.S.]
Watermarking of audio signals is more challenging
compared to the watermarking of images or video , due to wider
dynamic range of the HAS in comparison with human visual system
The HAS perceives sounds over a range of power greater than 109:1
and a range of frequencies greater than 103:1.
The sensitivity of the HAS to the additive white Gaussian noise
(AWGN) is high as well noise in a sound ﬁle can be detected as low
as 70 dB below ambient level.
Most audio watermarking schemes rely on the imperfections of the human
auditory system (HAS).
HAS is insensitive to small amplitude changes in the time and frequency
domains, allowing the addition of weak noise signals (watermarks) to the
host audio signal such that the changes are inaudible.
In the time domain, it has been demonstrated that the HAS is insensitive to
small level changes and insertion of low-amplitude echoes .
Data hiding in the frequency domain takes advantage of the insensitivity of
the HAS to small spectral magnitude changes .
Further, HAS is insensitive to a constant relative phase shift in a
stationary audio signal and some spectral distortions are interpreted
as natural, perceptually non-annoying ones .
Two Properties of the HAS dominantly used in watermarking algorithms are
1. frequency (simultaneous) masking
Frequency (simultaneous) masking is a frequency
domain observable fact where low levels signal (the maskee) can be made
inaudible (masked) by a simultaneously appearing stronger signal (the
masker), if the masker and maskee are close enough to each other in
.In the time domain, it has been demonstrated that the HAS is insensitive to
small level changes and insertion of low-amplitude echoes .
Frequency domain techniques, in particular, have been more effective than
time-domain techniques since watermarks are added to selected regions in
the transformed domain of the host audio signal, such that inaudibility an
robustness are maintained 
DIFFERENT ALGORITHMs FOR AUDIO WATERMARKING
THE MOST COMMON ALGORITHMS ARE
1 LSB CODING
2 ECHO WATERMARKING
3 PATCHWORK TECHNIQUE
4 QUANTIZATION INDEX MODULATION
5 PHASE CODING
6 SPREAD SPECTURM MODULATION
Further the wathermarking can be done in time domain as well as in
The commenly used time domain algorithms are
patchwork algorithms etc
Whereas frequency domain algorithms are
Embedding the watermark by modifying the cofficients of the transform
outputs such as
(Fast Fourier Transform) ,
S.T.F.T. (Sort time fourier Transform),
D.C.T. (Discrete fourier transform),
D.W.T. (Discreat wavelet transform) etc.
This technique is one of the common techniques employed in signal
processing applications. It is based on the substitution of the LSB of the
carrier signal with the bit pattern from the watermark noise. The
robustness depends on the number of bits that are being replaced in the
Fig L.S.B. CODING
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.
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 data to be watermarked is divided into two distinct
subsets. One feature of the data is selected and customized in opposite
directions in both subsets . For an example let the original signal is divided
into two parts A and B, then the part A is increased by a fraction Δ and the
part B is decreased by some amount Δ. The samples separation is the secret
key which is termed as watermarking key.
Let NA and NB indicate the size(s) of the individual A and B parts and Δ be
the total of the change made to the host signal. Suppose that a[i] and b[i]
represent the sample values at ith position in blocks A and B. The difference
of the sample values can be written as 
The expectation of the difference is used to extract the watermark which
is expressed as follo765ws .
QUANTIZATION INDEX MODULATION
The quantization index modulation (QIM) is a technique
which uses quantization of samples to embed watermark. The basic
principle of QIM is to find the maximum value of the samples and to divide
the range 0 to the maximum value into intervals of step size Δ. The intervals
are assigned a value of 0 or 1 depending on any pseudo random sequence.
Each sample has quantized value, thus, a polarity is assigned based on the
location of the interval. The watermark is embedded by changing the value
of the median for created interval and by the similarity of the polarity and
Modification of samples using QIM
PHASE CODING [Watermarking the phase of the host signal]
Algorithms that embed watermark into the phase
of the host audio signal do not use masking properties of the HAS, but the
fact that the HAS is insensitive to a constant relative phase shift in a
stationary audio signal .
SPREAD-SPECTRUM WATERMARKING ALGORITHM
Spread-spectrum watermarking scheme is an example of the correlation
method which embeds pseudorandom sequence and detects watermark
by calculating correlation between pseudo-random noise sequence and
watermarked audio signal.
The modulated signal is then added to the original audio to produce the
watermarked audio x(n) such as
x(n) = s(n) + αw(n)
The detection scheme uses linear correlation. Because the pseudorandom sequence r(n) is known and can be regenerated generated by
means of a secret key, watermarks are detected by using correlation
between x(n) and r(n) such as
where N denotes the length of signal. Equation yields the
correlation sum of two components as follows:
DOMAIN OF WATERMARKING
The audio watermarking can be classified as
1.TIME DOMAIN WATERMARKING (Temporal watermarking).
Temporal watermarking hides watermarks directly into digital audio signals in
the time domain, time-domain audio watermarking is relatively easy to
implement, and requires few computing resources, low cost, fast speed
however, it is weak against signal processing attacks such as compression
2.FREQUENCY DOMAIN WATERMARKING (spectral watermarking).
whereas spectral watermarking methods hides watermarks in the transform
domain. FFT, DCT, DWT,are commonly used transform.Frequency domain
watermarking is very roubst again various signal processing attacks.
TIME DOMAIN AUDIO WATERMARKING
In time domain watermarking techniques, watermark is directly embedded
into audio signal. No domain transform is required in this process.
Watermark signal is shaped before embedding operation to ensure its
FREQUENCY DOMAIN AUDIO WATERMARKING
The input signal is first transformed to frequency domain where the
watermark is embedded, the resulting signal then goes through inverse
frequency transform to get the watermarked signal as output as shown
in Figure . Watermark can be embedded into frequency