JP2004023183A - Multiple electronic watermark embedding apparatus and program therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the detection accuracy of a lower-layer watermark in multiple electronic watermarking while avoiding interference between the upper-layer watermark and the lower-layer watermark. <P>SOLUTION: A multiple electronic watermark embedding apparatus produces an electronic watermark for a lower-layer of a content, and another electronic watermark for an upper-layer of the identical content, being capable of independent detection of these electronic watermarks. The multiple electronic watermark embedding apparatus includes a unit block dividing section 13 dividing the target content data for electronic watermarking into each embedding unit, and an electronic watermark padding section 15 for electronic watermarking by switching an electronic watermark produced according to a first method and an electronic watermark produced according to a second method on a padding unit basis, when an electronic watermark is to be produced for the upper layer of the target content. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multiplex digital watermark embedding device capable of embedding a digital watermark in a lower layer of the same content, further embedding a digital watermark in an upper layer, and independently detecting the digital watermark, and a program therefor.
[0002]
[Prior art]
Many techniques for embedding digital watermarks in digital contents of images and videos have been announced. In order to use these technologies more practically, digital watermarks have already been embedded in digital watermarks. A multiple digital watermarking scheme has been proposed.
FIG. 5 shows a conceptual diagram of the multiple digital watermark. As shown in FIG. 5, multiple digital watermarks are embedded in the same content data 51, and it is possible to detect each of them independently. Here, the watermark to be embedded first is a lower watermark 52, and Is referred to as an upper watermark 53.
This is described in, for example, "Tomoyuki Kaji, Shinobu Nagakawa:" Realization of Multiple Digital Watermarking in Digital Content Distribution System ", IPSJ 62nd Annual Convention Performance Papers 1R-0.5 (2001)" (Reference 1). It has been disclosed.
[0003]
[Problems to be solved by the invention]
In the above-mentioned document 1, there is a problem that the information of the watermark (the lower watermark 52) embedded earlier is destroyed by overwriting of the digital watermark (the upper watermark 53) to be embedded later. Basically, any digital watermarking method can be used for the lower watermark 52 and the upper watermark 53. However, a digital watermark developed without considering multiple embedding is used as the upper watermark 53. In this case, there is a high possibility that the information of the lower watermark 52 will be destroyed by overwriting.
Although it is possible to devise a lower watermark 52 and an upper watermark 53 as a set for multiplex digital watermarking, there is currently a demand for a digital watermark that has already been put into practical use as the lower watermark 52 and superimposing the upper watermark 53. There are more. Therefore, an upper watermark 53 that is incoherent with the conventional method developed without assuming that multiple embedding is performed is required.
[0004]
The present invention has been made in view of the above circumstances, and when embedding the digital watermark 53 in the upper layer of the content to be embedded with the digital watermark, for example, the digital watermark embedded according to the sample value direct operation type digital watermarking method, By embedding a digital watermark to be embedded in accordance with the component operation type digital watermarking method by switching between the two in an embedding unit block, interference between the upper watermark 53 and the lower watermark 52 is avoided as much as possible, and the detection accuracy of the lower watermark 52 is ensured. An object of the present invention is to provide a digital watermark embedding device and a program thereof.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention embeds a digital watermark in a lower layer of the same content, further embeds a digital watermark in an upper layer, a multiple digital watermark embedding device capable of independently detecting the digital watermark, A unit block dividing unit for dividing the content data to be embedded with the digital watermark into unit blocks to be embedded, and a digital watermark embedded according to the first method when the digital watermark is embedded in the upper layer of the content to be embedded with the digital watermark. And a digital watermark embedding means for embedding a digital watermark to be embedded according to the second method by switching between the two in the embedding unit block.
[0006]
According to the present invention, when the digital watermark embedding unit embeds a digital watermark in the upper layer of the content to be embedded with the digital watermark, the digital watermark embedded according to the first method and the digital watermark embedded according to the second method are used. By switching and embedding the two in the embedded unit block divided by the unit block dividing means, interference between the upper watermark and the lower watermark can be avoided as much as possible, and the detection accuracy of the lower watermark can be ensured.
[0007]
In the present invention, the first method is a sample value direct operation type in which a digital watermark is embedded by operating information obtained by sampling a luminance value or an RGB value of each pixel of the content to be embedded with the digital watermark. When embedding a digital watermark in the upper layer, a feature portion in which the lower layer digital watermark is likely to be embedded is avoided.
[0008]
Further, in the present invention, the second method uses a frequency transform method such as Fourier transform, discrete cosine transform, or wavelet transform, and samples a luminance value or an RGB value for each pixel of the content to be embedded with the digital watermark. A frequency component operation type digital watermark in which a digital watermark is embedded by manipulating the amplitude value of a frequency component obtained from the obtained information, and when embedding a digital watermark in the upper layer, a frequency band in which the lower layer digital watermark is likely to be embedded. Is avoided.
[0009]
In order to solve the above-mentioned problem, the present invention embeds a digital watermark in a lower layer of the same content, further embeds a digital watermark in an upper layer, and detects an electronic watermark used in a multiplex digital watermark embedding apparatus capable of independently detecting the digital watermark. A watermark embedding program, wherein the content data to be embedded with the digital watermark is divided into embedding unit blocks, and the digital watermark is embedded in a layer above the content to be embedded with the digital watermark according to the first method. The step of embedding the digital watermark to be embedded and the digital watermark to be embedded according to the second method by switching between the two in the embedding unit block.
[0010]
In the present invention, the method further includes a step of obtaining a block type based on characteristics of pixels in the embedding unit block and selecting an embedding method according to an embedding rule defined based on the block type. It is characterized by making it.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing the internal configuration of a multiple digital watermark embedding device according to the present invention by developing its functions.
The multiple digital watermark embedding device of the present invention includes an image input unit 11, a unit block division unit 13, an identification unit 14, a digital watermark embedding unit 15, and an image output unit 16.
[0012]
The image input unit 11 selects an image to be processed from an image storage unit (not shown), and extracts luminance data from the image. The unit block dividing unit 13 divides the content data to be embedded with the electronic watermark into embedded unit blocks and supplies the data to the identifying unit 14.
[0013]
The identification unit 14 calculates a feature amount for each block, identifies a block type (contour, high-frequency portion, flat portion, noteworthy portion), calculates an embedding strength for each block, and supplies the digital watermark embedding unit 15. .
The digital watermark embedding unit 15 embeds a digital watermark embedded according to a sample value direct operation type and an electronic watermark embedded according to a frequency component operation type when embedding an electronic watermark in an upper layer of the content to be embedded. It has a function of switching and embedding both in the embedding unit block specified by the unit block dividing unit 13. The image output unit 16 outputs the digital content in which the multiple digital watermark is embedded to a display (not shown) or an image storage unit.
[0014]
By the way, an area generally used for embedding in digital watermarking for digital contents of images and videos is a limited area from the viewpoint of securing images and durability. Therefore, by selecting an area to be embedded while avoiding the most commonly used area as much as possible, and by embedding the digital watermark, it is possible to realize an upper layer watermark in which interference with the lower layer watermark that has been embedded earlier is suppressed.
At present, methods mainly used as digital watermarking for images and videos can be roughly classified into a digital watermarking method of direct operation of sample value and a digital watermarking of frequency component operation type. The patchwork method proposed by IBM is used as a representative method of the sample value direct manipulation type digital watermarking system, and the DCT proposed by NTT is used as a typical method of the frequency component manipulation type digital watermarking method. There is a method.
The former is W.S. Bender, D .; Gruhl, N .; Morimoto: "Techniques for data hiding", Proceedings of SPIE vol. 1, 2020, pp. 2420-2440 (1995) (Literature 2), the latter of which is described by Takao Nakamura, Hiroshi Ogawa, Yoichi Takashima: “Digital Watermarking in the Frequency Domain for Copyright Protection of Digital Images”, Symposium on Cryptography and Information Security, SCIS, 97-26A (1997) (Reference 3).
[0015]
Summarizing the above-described sample value direct operation type digital watermarking method, a method of embedding watermark information by manipulating sampled information such as a luminance value and an RGB value for each pixel.
To summarize the frequency component operation type digital watermarking method, the digital watermarking method is obtained from the sample values (brightness values, RGB values, etc.) of the watermark embedding destination image by a frequency conversion method such as Fourier transform, discrete cosine transform, or wavelet transform. In this method, watermark information is embedded by manipulating the amplitude value of the frequency component. After the embedding operation, the watermarked content is produced by returning to the image state by inverse transformation.
Both the above-described sample value direct operation type digital watermarking method and frequency component operation type digital watermarking method are existing technologies.
[0016]
In the present invention, non-interference with a lower watermark is realized by changing a spatial embedding position in the sample value direct operation type digital watermarking system and a frequency band to be embedded in the frequency component operation type digital watermarking system. I do.
However, since it is very difficult to completely specify the embedding position, the watermark is also superimposed on the embedding area of the lower-level watermark. Therefore, by providing an area in which the upper watermark is not embedded, an area in which the lower watermark is completely left is secured, and the detection accuracy of the lower watermark is secured.
Also, when the upper watermark is superimposed by a method similar to the lower watermark, the possibility that the watermark information of the lower watermark is destroyed by overwriting is increased. Therefore, by using both techniques and complementing each other, the digital watermark information is retained regardless of whether the lower-layer watermark is of the sample value direct operation type or the frequency component operation type.
[0017]
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 2 is a diagram cited for explaining an example of a digital watermark embedding pattern according to the present invention. Here, the digital content data to be embedded is a still image or a frame image extracted from video content.
First, a lower watermark 52 and an upper watermark 53 are embedded in the content data 51 by the multiple digital watermark shown in FIG. As the lower layer watermark 52, a method generally used at present is used. In particular, those not developed in consideration of superimposing another watermark on this watermark are targeted. Then, an upper watermark 53 in which interference with the lower watermark 52 is suppressed is realized by the following method.
[0018]
That is, first, an area where no embedding is performed is provided. For this purpose, it is necessary to embed a watermark in block units and to provide a block in which a watermark is not embedded. FIG. 2 shows an example.
Here, this is realized by combining a plurality of methods. For example, the sample value direct operation type and the frequency component operation type are used together, and the embedding method is switched for each block. Specifically, it is to embed in the area that is not expected to be used for embedding in the conventional method, the embedding position in the sample value direct operation type, the frequency band to be embedded in the frequency component operation type, The embedding is performed while avoiding the area used in the general method. FIG. 2 shows a pattern which is alternately changed for each embedding unit block.
[0019]
In the sample value direct operation type, the most watermark information is embedded in a rather complicated block, and in the frequency component operation type, the most watermark information is embedded in the middle frequency region of the frequency component. For example, when a discrete cosine transform (DCT) with 8 × 8 pixels is used as a frequency transform method, embedding is performed in the middle frequency region shown in FIG.
FIG. 3 is a diagram cited for explaining the embedding position of the digital watermark in the DCT component. The low-frequency region is a region mainly used in the conventional method, and the high-frequency region is irreversible such as JPEG or MPEG. This is an area where information is deleted by compression. Therefore, the medium frequency region is defined as a region used in the present invention.
[0020]
Hereinafter, the operation of the embodiment of the present invention shown in FIG. 1 will be described in detail with reference to the flowchart shown in FIG. Specifically, the flowchart shown here shows the processing procedure of the multiple digital watermark embedding program of the present invention.
First, the image input unit 11 captures image data to be embedded with a watermark from an image storage unit (not shown) (S41) and supplies the image data to the unit block dividing unit 13.
The unit block dividing unit 13 divides the content data to be embedded with the electronic watermark into the embedding unit blocks and supplies them to the identifying unit 14 (S42). The identification unit 14 calculates the feature amount for each block, identifies the block type (contour, high-frequency portion, flat portion, attentional portion), calculates the embedding strength for each block, and supplies it to the digital watermark embedding unit 15. (S43). Further, the embedding method is selected in accordance with an embedding rule defined in advance based on the identified block type, and an instruction is given to the digital watermark embedding unit 15 (S44).
[0021]
As shown in FIGS. 2 and 3, the digital watermark embedding unit 15 embeds a digital watermark embedded according to a sample value direct operation type when embedding a digital watermark in an upper layer of a content to be embedded with a digital watermark. A digital watermark to be embedded according to the operation type is switched and embedded by the embedding unit block specified by the unit block dividing unit 13.
Specifically, in the case of the sample value direct operation type, the embedding strength of the digital watermark is set high for the contour, the embedding strength of the digital watermark is set for the high frequency part, and the embedding strength of the digital watermark is set for the flat part and the attention part. Embedding is performed with the embedding strength being low (S45, S46). In the case of the frequency component operation type, first, frequency conversion is performed (S45, S47), embedding is performed in the middle frequency region as shown in FIG. 3, and inverse conversion is performed (S48, S49).
[0022]
In the area where the digital watermark is not embedded, no operation is performed, and the digital content in which the multiple digital watermark is embedded is output to a display or an image storage unit (not shown) via the image output unit 16 (S50). .
Here, in the block type, the high-frequency portion refers to a region in which the luminance between adjacent pixels greatly changes, the flat portion refers to a small region, and the attention portion refers to a case where a human recognizes a shape of an object. It refers to a conspicuous portion on the conscious outline (for example, a portion where corners, line segments, or curves are connected).
[0023]
As described above, according to the present invention, when a digital watermark is embedded in the upper layer of the content to be embedded, for example, a digital watermark embedded according to a sample value direct operation type digital watermark and a frequency component operation type digital watermark are embedded. By embedding a digital watermark to be switched between them in an embedding unit block, interference between the upper watermark and the lower watermark is avoided as much as possible, and the detection accuracy of the lower watermark is ensured.
Note that a program for realizing the functions of the image input unit 11, the unit block division unit 13, the identification unit 14, the digital watermark embedding unit 15, and the image output unit 16 shown in FIG. The program is recorded on a medium, and the program recorded on the recording medium is read by a computer, and the computer sequentially reads and executes the program, whereby the multiple digital watermark embedding device of the present invention is constructed. The computer system referred to here includes an OS and hardware such as peripheral devices.
[0024]
The “computer system” also includes a homepage providing environment (or a display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) inside a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, programs that hold programs for a certain period of time are also included.
[0025]
Further, the above program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting a program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
Further, the program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.
[0026]
As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes a design and the like within a range not departing from the gist of the present invention.
[0027]
【The invention's effect】
As described above, according to the present invention, when embedding a digital watermark in the upper layer of digital content to be embedded with a digital watermark, for example, a digital watermark embedded according to a sample value direct operation type digital watermark and a frequency component operation type electronic watermark By embedding a digital watermark to be embedded according to the watermark in a switching unit block, the interference between the upper watermark and the lower watermark can be avoided as much as possible, and the detection accuracy of the lower watermark can be ensured.
[0028]
Digital watermarks are used to prevent unauthorized use of digital contents and manage copyrights. However, there are various types of systems for each company, and it is not possible to specify the type of watermark embedded only from digital contents. Therefore, there was also the problem that it is difficult to detect the watermark information embedded with non have or not embedded in advance which method the information, by using multiple electronic watermark of the present invention described above, With respect to digital content in which an existing digital watermark is embedded, it is possible to realize a model of embedding, as information, a method in which the content is embedded, and it is also possible to solve this problem.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the internal configuration of a multiple digital watermark embedding device according to the present invention by developing its function;
FIG. 2 is a diagram cited for describing an example of a digital watermark embedding pattern according to the present invention.
FIG. 3 is a diagram cited for explaining an embedding position of a digital watermark in a DCT component.
FIG. 4 is a flowchart cited for explaining the operation of the embodiment of the present invention shown in FIG. 1;
FIG. 5 is a diagram cited for explaining the concept of multiple digital watermarking.
[Explanation of symbols]
11 image input unit, 13 unit block division unit, 14 identification unit, 15 digital watermark embedding unit, 16 image output unit

Claims (5)

A multiple digital watermark embedding device that embeds a digital watermark in a lower layer of the same content, further embeds a digital watermark in an upper layer, and can independently detect the digital watermark,
Unit block dividing means for dividing the content data to be embedded in the digital watermark into embedded unit blocks,
When embedding a digital watermark in the upper layer of the content to be embedded with the digital watermark, the digital watermark embedded according to the first method and the digital watermark embedded according to the second method are switched and embedded by the embedding unit block. Embedding means,
A multiplex digital watermark embedding device, comprising: The first method comprises:
A sample value direct operation type in which an electronic watermark is embedded by operating information obtained by sampling a luminance value or an RGB value for each pixel of the content to be embedded with the electronic watermark,
2. The multiple digital watermark embedding device according to claim 1, wherein when embedding a digital watermark in the upper layer, a characteristic portion in which the lower layer digital watermark is likely to be embedded is avoided. 3. The second method comprises:
Using a frequency transform method such as Fourier transform, discrete cosine transform, or wavelet transform, the luminance value of each pixel of the content to be embedded with the digital watermark or the amplitude value of the frequency component obtained from information obtained by sampling the RGB values is manipulated. In this way, a digital watermark is embedded as a frequency component operation type digital watermark.
2. The multiple digital watermark embedding apparatus according to claim 1, wherein when embedding the digital watermark in the upper layer, a frequency band in which the lower layer electronic watermark is likely to be embedded is avoided. A digital watermark embedding program used in a multiple digital watermark embedding apparatus capable of embedding a digital watermark in a lower layer of the same content and further embedding a digital watermark in an upper layer, and independently detecting the digital watermark,
Dividing the content data to be embedded with the digital watermark into embedding unit blocks;
A step of embedding a digital watermark to be embedded according to a first method and a digital watermark to be embedded according to a second method by embedding the electronic watermark in the upper layer of the content to be embedded with the electronic watermark by switching the two in the embedding unit block When,
Watermark embedding program that causes a computer to execute Obtaining a block type based on the characteristics of the pixels in the embedding unit block, and selecting an embedding method according to an embedding rule defined based on the block type;
The digital watermark embedding program according to claim 4, further comprising: causing the computer to execute.

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