Image analysis – Applications
Reexamination Certificate
1999-12-03
2004-03-23
Patel, Jayanti K. (Department: 2625)
Image analysis
Applications
C382S232000, C380S051000, C380S054000, C713S176000
Reexamination Certificate
active
06711276
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an information embedding method, and apparatus. In particular, the present invention relates to a method, and apparatus, for embedding information such as copy control information and copyright information in digitized contents information of a still picture or moving picture, and to a program medium for implementing the method.
In recent years, contents of images and music have been digitized and circulated via storage media or communication networks. In order to protect the copyright of such digitized contents information, a digital watermark technique is regarded as important. In this digital watermark technique, copy control information and copyright information are embedded in contents information by making a change of such a degree as not to be noticed by human visual and auditory senses in the contents information. As a result, it is possible to limit the number of times of copy of contents information utilizing data processing apparatuses or specify the copyright holder on the basis of illegally copied contents information.
For putting the digital watermark technique to practical use, it is necessary to satisfy the following two requirements.
(1) Suppression of degradation of contents information:
For example, in embedding digital watermark information in image data, a change made in image must not prevent enjoyment of contents. In other words, a change made in a part of contents information must not be conspicuous to human visual and auditory senses.
(2) Improvement of survivability:
Even if image processing and voice processing are applied, embedded information, i.e., a change made in contents information must not be easily degraded.
For satisfying the above described conditions, it is necessary to optimize change positions and degrees or intensities of changes in contents according to the property of the contents. By taking an image which is representative of contents information, as an example, conventional digital watermark techniques will hereafter be analyzed.
In the case of image data, making an unsuitable change in a state value (luminance or color) of a pixel in such an area that the state change of an image is comparatively flat typically causes conspicuous unnaturalness in the changed position. However, a portion where a pixel value variation is violent, such as an edge portion of a subject, has a property that a comparatively large change made in pixels is not conspicuous to human eyes. Paying attention to this property, a digital watermark technique of edge preservation type has been proposed in, for example, The Transactions of the Information Processing Society of Japan, Vol. 38, No. 12, 1997, pp. 2640-2647. In this technique, an edge portion of a subject is identified by analyzing the luminance variation of an image frame in which watermark information should be embedded. In the above described edge portion where a pixel value change is hard to be conspicuous, a large change is made. In a portion where a pixel value change is easy to be conspicuous, a change is not made, or the degree of a change is made low even if the change is made.
The subject of embedding of digital watermark information is not limited to still pictures, but moving pictures also become the subject. Moving picture data is formed of a plurality of still picture frames arranged in time series. In some cases, the frame feed is stopped during enjoyment of a moving picture to enjoy individual frames as still pictures.
In embedding digital watermark information in a moving picture, it is necessary to make pixel value change positions inconspicuous in both the still picture state and the moving picture state, for the above described reason. Therefore, it is desirable to optimize pixels to be changed and the degree of the change by considering both the property as viewed as a still picture and the property as viewed as a moving picture. As for conventional techniques concerning embedding digital watermark information in a moving picture, however, only the property as viewed as a still picture is considered in, for example, a system reported in 1997 Symposium on Cryptography and Information Security, 31-G. On the other hand, in a system reported in 1997 Symposium on Cryptography and Information Security, 31-F, only the property as viewed as a moving picture is considered. There has not been proposed yet an example in which pixel value change positions and/or change intensities are optimized by considering both the property as viewed as a still picture and the property as viewed as a moving picture.
Furthermore, conspicuousness of a pixel value change does not depend upon only one property such as, for example, a luminance variation, but differs according to a property other than luminance such as a color variation. When embedding watermark information in a still picture or a moving picture, therefore, it is necessary to optimize change positions and degrees of the change, i.e., change intensities while considering these plural properties. In conventional digital watermark techniques, however, the pixel value change is optimized depending upon one property of an image. An optimization technique considering a plurality of properties has been neither proposed nor well known.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a technique of optimizing change positions i.e., change positions and/or change intensities on the basis of a plurality of properties possessed by contents information in which watermark information should be embedded.
A second object of the present invention is to provide a method, and apparatus, for embedding watermark information in a moving picture optimized in change position and/or change intensities on the basis of both the property as viewed as a moving picture and the property as viewed as a still picture.
Another object of the present invention is to provide a computer program for implementing the above described information embedding method, and contents information obtained by implementing the method.
In order to achieve the above described first object, an information embedding method according to an aspect of the present invention includes a step of determining a plurality of change positions and/or change degrees of states respectively depending upon a plurality of properties possessed by contents information serving as an embedding subject of watermark information, a step of selecting change positions and/or change degrees to be applied to each of sub-contents information pieces representing divisional contents information according to the contents information, among the plurality of change positions and/or change degrees determined on the basis of the respective properties, and a step of making a change serving as watermark information in the contents information in accordance with the selected change positions and/or change degrees.
In a more concrete aspect, the information embedding method includes the steps of dividing contents information serving as an embedding subject of watermark information into a plurality of information blocks, determining change positions and/or change degrees for the information blocks, and for each of information blocks, selecting at least one among the determined change positions and/or change degrees according to contents information of the information block.
If priority is given to inconspicuousness of the change, then, for example, a result of a logical product (AND) operation conducted on change positions and/or change degrees selected for respective properties may be used as final change positions and/or change degrees at the selection step so as to minimize the number of change positions and/or change degrees. On the other hand, if priority is given to survivability of the change result, than a result of a logical sum (OR) operation conducted on change positions and/or change degrees selected for respective properties may be used as final change positions and/or change degrees at the selection step so as to maximize the number of
Arai Takao
Echizen Isao
Kimura Hiroyuki
Moriyama Yoshiaki
Ogino Akira
Antonelli, Terry, Stout & Krauss, LLP
Carter Aaron
Hitachi , Ltd.
Patel Jayanti K.
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