Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2000-01-21
2004-02-17
Parsons, Charles (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C382S100000, C382S175000, C382S232000, C382S251000, C382S250000
Reexamination Certificate
active
06693965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatuses for and methods of embedding and extracting digital information as well as a medium having a program for carrying out the method recorded thereon, and more particularly, to an apparatus for and a method of embedding, in order to protect the copyright of digital data, digital data such as copyright information (hereinafter referred to as digital information) in an image signal and extracting the embedded digital information as well as a medium having a program for carrying out the method recorded thereon.
2. Description of the Background Art
In recent years, information utilizing the Internet has been extensively provided. Particularly, WWW (World Wide Web) has been frequently utilized as an information transmitting/receiving service in which image, voice and so forth are integrated.
However, digital data such as an image which is made public on a network of the Internet can be easily copied by many and unspecified users. Therefore, some problems have arisen. For example, an image whose copyright is owned by a third person is secondarily utilized by making unauthorized copying thereof without the permission of the copyright holder. Further, also in expanding the business on the Internet using image-based contents, measures to prevent the unauthorized copying have been also a problem. Therefore, the establishment of a technique for protecting the copyright of an image signal has been damanded.
An example of the measures conventionally known is an electronic (digital) watermark technique. The digital watermarking is a technique for embedding digital information in image data in such a form that the embedded digital information cannot be perceived by human being.
Examples of the conventional digital watermark technique include a digital watermark technique using discrete wavelet transform described in an article entitled by Matsui, Ohnishi, Nakamura, “Embedding a Signature to Pictures under Wavelet Transformation” (Journal of the Institute of Electronics, Information and Communication Engineers D-II VOL. J79-D-II, No. 6, PP.1017-1024, June 1996) (hereinafter referred to as a technique by Matui et al.). Further, another example is a digital watermark technique using discrete cosine transform (DCT) described in an article entitled by Nakamura, Ogawa, Takashima “A method of Watermarking under Frequency Domain for Protecting Copyright of Digital Image” (The Symposium on Cryptography and Information Security, SCIS'97-26A, January 1997) (hereinafter referred to as a technique by Nakamura et al.).
The technique by Matui et al. will be first described with reference to
FIGS. 23
to
25
.
First, band division by discrete wavelet transform processing is described.
FIG. 23
is a block diagram showing an example of the configuration of a conventional band dividing device
11
for division into three hierarchies. In
FIG. 23
, the conventional band dividing device
11
comprises first to third band dividing filters
100
,
200
and
300
having the same configuration. Each of the first to third band dividing filters
100
,
200
and
300
divides an input image into four frequency bands, and calculates wavelet coefficients for each of the frequency bands. As to the wavelet coefficients, sub-band division will do, which is not described herein.
The band dividing device
11
inputs a digitized image signal
71
into the first band dividing filter
100
. The first band dividing filter
100
divides the image signal
71
into signals in four bands, i.e., an LL
1
signal, an LH
1
signal, an HL
1
signal and an HH
1
signal (hereinafter generically referred to as first hierarchical signal) on the basis of parameters of its horizontal and vertical frequency components. The second band dividing filter
200
receives the LL
1
signal in the lowest band in the first hierarchical signal, and further divides the LL
1
signal
71
into an LL
2
signal, an LH
2
signal, an HL
2
signal and an HH
2
signal in four bands (hereinafter generically referred to as second hierarchical signal). The third band dividing filter
300
receives the LL
2
signal in the lowest band in the second hierarchical signal, and further divides the LL
2
signal into an LL
3
signal, and LH
3
signal, an HL
3
signal and an HH
3
signal in four bands (hereinafter generically referred to as third hierarchical signal).
FIG. 24
is a block diagram showing an example of the detailed configuration of the first band dividing filter
100
shown in FIG.
23
. In
FIG. 24
, the first band dividing filter
100
comprises first to third two-band division portions
101
to
103
. The first to third two-band division portions
101
to
103
respectively comprise one-dimensional low-pass filters (LPFs)
111
to
113
, one-dimensional high-pass filters (HPFs)
121
to
123
, and sub-samplers
131
to
133
and
141
to
143
for decimating a signal at a ratio of 2:1.
The first two-band division portion
101
receives the image signal
71
, and respectively subjects the image signal
71
to low-pass filtering and high-pass filtering with respect to its horizontal component by the LPF
111
and the HPF
121
to output two signals. The signals obtained by the low-pass filtering and the high-pass filtering are respectively decimated at a ratio of 2:1 using the sub-samplers
131
and
141
, and are then outputted to the subsequent stage. The second two-band division portion
102
receives the signal from the sub-sampler
131
, and respectively filters the signal with respect to its vertical component by the LPF
112
and the HPF
122
to obtain two signals, decimates the signals at a ratio of 2:1 using the sub-samplers
132
and
142
, and then outputs the signals, i.e., an LL signal and an LH signal. On the other hand, the third two-band division portion
103
receives the signal from the sub-sampler
141
, respectively filters the signal with respect to its vertical component by the LPF
113
and the HPF
123
to obtain two signals, decimates the signals at a ratio of 2:1 using the sub-samplers
133
and
143
, and then outputs the signals, i.e., an HL signal and an HH signal.
Consequently, the four signals, i.e., the LL
1
signal which is low in both its horizontal and vertical components, the LH
1
signal which is low in its horizontal component but is high in its vertical component, the HL
1
signal which is high in its horizontal component but is low in its vertical component, and the HH
1
signal which is high in both its horizontal and vertical components, that is, wavelet coefficients are outputted from the first band dividing filter
100
. The second and third bank dividing filters
200
and
300
also respectively subject the received signals to the same processing as described above.
As a result of the band division processing performed by the first to third band dividing filters
100
,
200
and
300
, the image signal
71
is divided into ten band signals, i.e., an LL
3
signal, an LH
3
signal, an HL
3
signal, an HH
3
signal, an LH
2
signal, an HL
2
signal, an HH
2
signal, an LH
1
signal, an HL
1
signal and an HH
1
signal.
FIG. 25
is a diagram showing representation of the ten band signals by a two-dimensional frequency region.
In
FIG. 25
, the vertical axis represents a vertical frequency component, which increases as is directed downward, and the horizontal axis represents a horizontal frequency component, which increases as is directed rightward. Each of regions shown in
FIG. 25
is data serving as one image, and the area ratio of the regions coincides with the ratio of the respective numbers of data in the band signals. That is, in a case where the number of data in the LL
3
signal, the LH
3
signal, the HL
3
signal and the HH
3
signal which are the third hierarchical signal is taken as one, the number of data in the LH
2
signal, the HL
2
signal and the HH
2
signal which are the second hierarchical signal is
4
, and the number of data in the LH
1
signal, the HL
1
signal and the HH
1
signal which are the f
Inoue Hisashi
Katsura Takashi
Matsushita Electric - Industrial Co., Ltd.
Parsons Charles
Wenderoth , Lind & Ponack, L.L.P.
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