JP2000175024A - Method and apparatus for superimposing digital watermark information - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To superimpose digital watermark information on image information so as to be inconspicuous on a screen while securing a superimposition amount that can reliably detect digital watermark information. When superimposing digital watermark information on a baseband video signal, an electronic device that superimposes the digital watermark information on the video signal in accordance with the video signal on which the digital watermark information is to be superimposed is assumed. The superimposition level of the watermark information is controlled. For example, in a portion of a video display device where whiteout or blackout is expected to occur, the superimposition level of digital watermark information is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for superimposing additional information such as copy control information and copyright information on image information by performing a digital watermarking process such as spread spectrum. The present invention relates to an apparatus and a method for recording image information using a method.

[0002]

2. Description of the Related Art In recent years, with the spread of digital contents such as the Internet and digital video discs, there has been a problem of copyright infringement due to unauthorized duplication (copy) of the digital contents. In order to cope with this problem, it has been considered that information for copy control is added to digital content and transmitted, and illegal copying is prevented using this additional information.

As a method of adding additional information to image information of digital contents, attention has been paid to a method of adding additional information by digital watermarking because of the difficulty in falsifying the additional information (for example, the magazine "Nikkei Electronics"). No. 683, Feb. 24, 1997).

[0004] This digital watermarking process is a process of embedding additional information as noise directly in the image data in a portion of the image data that is not important to human perception, that is, a portion that is not redundant with the video. is there. The additional information embedded in the image data by such a digital watermarking process is not easily removed from the image data. On the other hand, even after filtering processing and data compression processing are performed on image data, it is possible to detect additional information embedded in the image data from the image data and use it.

[0005]

As described above, when the additional information is superimposed on the image signal by the digital watermarking process, and when the image based on the image signal is displayed on the display, the additional information is not converted from the image signal. However, as described above, the additional information needs to be superimposed on the image signal at a minute level that does not affect the reproduced image of the image signal.

On the other hand, it is important to be able to reliably detect digital watermark information from a main information signal even at a very small level, and it is desired that the probability of erroneous detection be as low as possible.

According to the present invention, in view of the above points, when an image is reproduced and displayed while securing the condition that the digital watermark information can be reliably detected, the digital watermark information is displayed on the displayed image as much as possible. Another object of the present invention is to provide a device and method for superimposing digital watermark information which can be made inconspicuous.

[0008]

According to a first aspect of the present invention, there is provided a method for superimposing digital watermark information upon superimposing digital watermark information on a baseband video signal. Assuming display control in a video display device according to a video signal on which information is to be superimposed, a superposition level of electronic watermark information to be superimposed on the video signal is controlled.

[0009] In a video display device such as a television receiver, display control such as limiting the beam amount or enhancing the contrast is performed, for example, to reduce the amount of X-rays. When such display control is performed, the digital watermark information becomes less noticeable than others or becomes more noticeable depending on the contents of the display control.

Such display control is performed in accordance with the brightness of the entire screen by the video signal and the behavior of the video signal in one screen. Therefore, display control in the video display device can be assumed by detecting the brightness of the entire screen by the video signal and the behavior of the video signal.

Therefore, according to the first aspect of the present invention, the digital watermark information is superimposed on the video signal at a superimposition level higher than the others in the video portion where the digital watermark information becomes less noticeable than the others by the assumed display control. Then, by the assumed display control, the superimposition level of the digital watermark information is set to be smaller than the others in the video portion where the digital watermark information is more conspicuous.

With this configuration, when an image is reproduced and displayed, the digital watermark information is displayed on the displayed image.
This makes it possible to make the electronic watermark information less noticeable and to reliably detect digital watermark information.

According to a second aspect of the present invention, in the method of superimposing digital watermark information according to the first aspect, the superimposing level of the digital watermark information is increased in a portion where it is assumed that whiteout occurs in the video display device. It is characterized by the following.

According to a third aspect of the present invention, in the method for superimposing digital watermark information according to the first aspect, in a video display device, the superimposition level of the digital watermark information is set at a portion where blackout is expected to occur. It is characterized in that it is increased.

The occurrence of underexposure and underexposure as in the second and third aspects of the present invention means that the white level portion and the black level portion of the video signal are not faithfully reproduced. I have. Therefore, the digital watermark information becomes less noticeable in these portions, and the superimposition level can be increased.

According to a fourth aspect of the present invention, in the digital watermark information superimposing method according to the first aspect, the superimposed level of the digital watermark information is reduced in a portion of the video signal near a black level. I do.

Many consumer television receivers are provided with a circuit for making the level close to black more black in order to make the image look clearer. Therefore, in the level portion close to black, the inclination of the change in luminance is increased by this circuit, and the superimposed digital watermark information becomes conspicuous.

Therefore, according to the present invention, the superimposition level of the digital watermark information is reduced in the level portion of the video signal close to black, so that the digital watermark information is prevented from being conspicuous.

According to a fifth aspect of the present invention, in the method for superimposing digital watermark information according to the first aspect, the average luminance level of the video signal is detected,
The superimposition level of the digital watermark information is increased as the level increases toward the black side.

The farther the video signal level is away from the average luminance level toward the white level, the more easily the underexposure occurs, and the farther the image signal level is toward the black level, the more the overexposure occurs. Therefore, in the invention according to claim 5, the digital watermark information is made less conspicuous on the display image by changing the superimposition level according to the difference between the video signal level and the average luminance level. In addition, it is possible to achieve the object that the digital watermark information can be reliably detected.

According to a sixth aspect of the present invention, in the method for superimposing digital watermark information on a baseband video signal, a relationship between a difference between an average luminance level and a pixel level of the video signal and a superposition level of the digital watermark information is provided. Is prepared, and the table is searched according to the difference between the average luminance level of the input video signal and the level of the input video signal to determine the superimposition level of the digital watermark information. .

According to the sixth aspect of the invention, the superimposition level is changed according to the difference between the video signal level and the average luminance level.
In the table, a correspondence table of the superimposition level of the digital watermark information with respect to the difference between the video signal level and the average luminance level is prepared in advance.

According to the sixth aspect of the present invention, by preparing a table according to the display control characteristics of the video display device in advance, the digital watermark information can be made less noticeable, and It is possible to achieve the object that the detection can be reliably performed.

According to a seventh aspect of the present invention, in the method of superimposing digital watermark information on a baseband video signal, a relationship between a difference between an average luminance level and a pixel level of the video signal and a superposition level of the digital watermark information is provided. A plurality of tables are prepared according to the magnitude of the average luminance level, an average luminance level of the video signal is detected, and the plurality of tables are determined according to the detected average luminance level. And using a table selected from the above, and determining a superimposition level of the digital watermark information on the video signal for each pixel.

According to the seventh aspect of the present invention, the table according to the sixth aspect is changed according to the average luminance level.
By preparing a plurality of digital watermarks, the superimposition level can be controlled more finely, and the digital watermark information can be made less noticeable, and the object of reliably detecting the digital watermark information can be achieved. Can be.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. In the embodiment described below, as one method of digital watermarking, a method is used in which additional information is spectrum-spread and superimposed in a baseband region of image information.

In this system, for example, PN (Pseudorandom Noise) is used as a spreading code.
e) A sequence code (hereinafter referred to as a PN code) is generated at a sufficiently early cycle, and is multiplied with an additional information signal to spread the spectrum, thereby producing a narrow-band, high-level duplication prevention control signal or the like. The additional information signal is converted into a wide-band, minute-level signal that does not affect the image signal. Then, the spectrum-spread additional information signal, that is, the spectrum spread signal is superimposed on the image signal. In this case, the image signal in the baseband region on which the additional information is superimposed may be an analog signal or a digital signal.

In this method, the additional information signal such as the duplication prevention control signal is superimposed on the image signal at the same time and within the same frequency. Is difficult to remove from the image signal. On the other hand, it is possible to detect and use an additional information signal such as a duplication prevention control signal superimposed by inverse spectrum spreading.

[First Embodiment] FIG. 1 is a block diagram showing an example of an image information recording apparatus including an embodiment of a digital watermark information superimposing apparatus according to the present invention. For example, this is a case where a copy protection control signal is superimposed as additional information on a digital signal of a video signal of the NTSC system. In this case, the video signal Vi input to the input terminal 11 is a luminance signal in the case of a color video signal.

As shown in FIG. 1, a video signal Vi input through an input terminal 11 is supplied to an A / D converter 12 and converted into a digital signal.
Supplied to The blocking unit 13 blocks the digital video signal into signals in units of coding blocks for compression coding.

In the case of this example, as shown in FIG. 2, one field (one screen) of the video signal Vi is divided by N in the horizontal direction.
A coding block having a size of a predetermined plurality of pixel regions, for example, a horizontal direction × vertical direction = 8 × 8 = 64 pixel region, assuming that the information includes information for M pixels in the vertical direction. BL.

The digital video signal from the blocking unit 13 is supplied to the digital watermark information superimposing unit 14, and as described later, in this example, one chip of the PN code corresponds to one encoded block. Are superimposed. And
The digital video signal on which the digital watermark information is superimposed is
The data is supplied to the MPEG compression encoding unit 15, subjected to the MPEG compression encoding, and recorded on a recording medium, for example, a DVD (digital video disk) through the writing unit 16.

The video signal Vi input through the input terminal 11 is also supplied to the synchronization detector 17. In the synchronization detection unit 17, the vertical synchronization signal VD and the horizontal synchronization signal HD
Are detected, and the vertical synchronizing signal VD and the horizontal synchronizing signal HD are supplied to the timing signal generator 18. The timing signal generator 18 generates various timing signals synchronized with the vertical synchronization signal VD and the horizontal synchronization signal HD.

In this example, the digital watermark information generating section 19 includes a PN generating section 191 and an additional information generating section 192.
And a spread spectrum unit 193.

The PN generator 191 synchronizes with the timing signal from the timing signal generator 18 and, in this example,
A PN code sequence reset in synchronization with the synchronization signals VD and HD is generated, and the PN code sequence is spread
Supply 3

The additional information generator 192 generates additional information to be superimposed as digital watermark information on the video signal Vi, in this example, copy control information in synchronization with the timing signal from the timing signal generator 18. , To the spread spectrum unit 193.

In the case of this example, the additional information generator 1
The copy control information as additional information generated from 92 is determined according to the video signal to be transmitted, and is “copyable (Copy Free)”, “copy once (One C
COPY) "Absolute duplication prohibited (Never Copy)"
The information which means etc. is generated. When representing a plurality of states in this way, the additional information has a plurality of bits, and each bit of the plurality of bits is superimposed over one to a plurality of fields, for example, five fields. It is superimposed over the number of fields for bits, and this is repeated.

The spread spectrum section 193 multiplies the additional information from the additional information generation section 192 by the PN code string from the PN generation section 191 to generate a spread spectrum signal which is a signal obtained by spectrum spreading the additional information. .

The spread spectrum signal thus generated is supplied to the superposition level control section 20. The superimposition level control unit 20 controls the superimposition level of the digital watermark information on the video signal to be a superimposition level according to the superimposition level set value from the superimposition level determination setting unit 25, as described later.

As described below, the setting of the superimposition level is performed assuming display control performed by a video display device, in this example, a television receiver.

In a television receiver, as shown in FIG. 4, when a large-amplitude signal such as a telop is input, the beam spot diameter increases, detail cannot be expressed, and the image is overexposed. At a black level having a large difference from the average luminance level, it can be predicted that the black level will be lower than the cutoff level and black will be lost.

In a television receiver, the beam amount is limited so that X-rays are not emitted so much, and this is called an ABL (auto beam limiter).
Among these ABLs, there is a so-called bright ABL that changes the DC level while maintaining the contrast.

This is because, for example, as shown in FIG. 5A, in the case of a signal in which the area on the screen of a white level of a certain value or more becomes a certain size or more, the luminance of the entire screen is reduced. The result of the application of the bright ABL is as shown in FIG. 5 (B). Therefore, at this time, the black level portion below a certain value Lb is below the cutoff level, and blackening occurs.

In a consumer television receiver, a circuit for making the level close to black more black is used in order to show the image clearly. With this circuit, there is a possibility that the inclination of the luminance becomes large and the superimposed digital watermark information becomes conspicuous on the screen.

The superimposition level determination and setting section 25 presupposes the above-described display control on the television receiver side, so that the overexposure and the underexposure occur. It is determined that the superimposition level of the digital watermark information is to be increased and the superimposition level of the digital watermark information is to be lowered in a level portion close to black, and the superimposition level set value to be supplied to the superimposition level control unit 20 at that time is determined. .

For this reason, the digital video signal from the A / D converter 12 is supplied to the average luminance level detector 21, and the average luminance level for each field of the video signal is detected. Then, the detected average luminance level is supplied to the superimposition level determination setting unit 25. The superimposition level determination setting unit 25 predicts a white level and a black level that can be reproduced by the receiver when the contrast is high, based on the value of the average luminance level from the average luminance level detector 21. Then, the predicted white level and black level are supplied to a white level detector 22 and a black level detector 23, respectively.

The digital video signal is supplied to a white level detector 22. As described above, the white level detector 22 detects whether or not the level of the digital video signal is higher than the white level predicted by the superimposition level determination setting unit 25, and outputs the detection output to the superimposition level determination. It is supplied to the setting unit 25. The superimposition level determination and setting unit 25 determines that the white level portion larger than the predicted white level causes whitening loss on the receiver side, and determines that the superimposition level of the digital watermark information can be increased. The superimposition level setting value to be supplied is supplied to the superimposition level controller 20.

The white level detector 22 also detects whether the area on the screen occupied by the white level portion larger than the preset level is larger than the preset area, and superimposes the detection output. It is supplied to the level judgment setting unit 25.

Further, the digital video signal is supplied to the black level detector 23, and as described above, it is determined whether or not the level of the digital video signal is lower than the black level predicted by the superimposition level determination setting section 25. The detection output is supplied to the superimposition level determination setting unit 25. The superimposition level determination setting unit 25 determines that the black level portion lower than the predicted black level causes black loss on the receiver side, and sets a superimposition level for increasing the superimposition level of the digital watermark information. , Superimposed level control unit 20.

The black level detector 23 also detects whether or not the level of the digital video signal is equal to or lower than the certain level Lb (different from the predicted black level). It is supplied to the judgment setting unit 25. In the superimposition level determination setting section 25, the white level detector 2
2, it is determined that the area on the screen occupied by the white level portion larger than the preset level is equal to or larger than the preset area, and the digital video signal is output from the black level detector 23. As described above, when the detection output arrives that the black level is equal to or lower than the level Lb, the receiver side determines that the black level will be lost because the bright ABL is applied. A superimposition level setting value for increasing the superimposition amount of the digital watermark information in the portion is supplied to the superimposition level control unit 20.

The digital video signal is further supplied to a near black level detector 24. The near black level detector 24 detects a level portion near the black level, and supplies a detection output to a superimposed level determination setting unit 25. Upon receiving the detection output of the level portion near the black level, the superimposition level determination setting section 25 controls the near black level on the receiver side so that the near black level becomes a higher black level, and the inclination of the luminance change is reduced. When it is determined that the superimposition level becomes larger, the superimposition level set value for lowering the superimposition level in the near black level portion is supplied to the superimposition level controller 20.

Next, a method of superimposition level control in superimposition level control section 20 in this embodiment will be described.

In this embodiment, from the spread spectrum section 193, for one of the coding blocks BL shown in FIG. 2, a spread spectrum signal corresponding to one chip of the PN code corresponds to the superposition level control section. 20. In the superposition level control unit 20, one encoded block B
Whether or not to superimpose digital watermark information, that is, a spread spectrum signal, on each of the 64 pixels constituting L is determined based on a setting value from the superimposition level determination setting unit 25.

In the case of this embodiment, 6 of the block BL
At the superimposition level where superimposition is performed on all four pixels, the superimposition amount Strength = 1. FIG.
In FIG. 3, if a portion filled with black indicates a pixel portion on which digital watermark information is not superimposed, the state of the superimposition amount Strength = 1 is the state of FIG.

Then, as the amount of superimposition decreases, the number of non-superimposed pixel portions filled with black increases. For example, a pattern with a superimposition amount of Strength = 0.75 in which digital watermark information is superimposed on 75% of the pixels in the block area BL is as shown in FIG. 3B, for example. Further, a pattern with a superimposition amount of Strength = 0.50 in which digital watermark information is superimposed on 50% of the pixels in the block area BL is represented by:
For example, the pattern as shown in FIG. 3C, and a pattern with a superimposition amount of Strength = 0.25 in which the digital watermark information is superimposed only on 25% of the pixels in the block area BL is as shown in FIG. become.

In the case of this embodiment, such superposition amount control is performed as follows.

An effective pixel in the field is defined as V (x, y). Here, x indicates a pixel position in the horizontal direction, and y indicates a pixel position in the vertical direction. For example, it is assumed that 0 ≦ x ≦ 719; 0 ≦ y ≦ 239. The superimposition level determination setting unit 25 includes a 16-bit PN generator that transitions the state for each pixel, and uses the value PN (x, y) of the upper 8 bits. Here, 0 ≦ PN (x, y) ≦ 255.

In the superimposition level judgment setting section 25, the value P
Threshold value th (x, y) for each pixel to be compared with N (x, y)
The value of y) is set based on the detectors 21, 22, 23, and 24. Then, the superimposition level judgment setting unit 25
Then, the following operation is performed to determine whether to superimpose digital watermark information on each pixel.

That is, assuming that a variable for superimposing each pixel in the block BL is diz (x, y), if PN (x, y) ≦ th (x, y), diz (x, y)
y) = 1 If PN (x, y)> th (x, y), diz (x,
y) = 0. Here, when the variable diz (x, y) = 1, superposition is performed, and the variable diz (x, y) = 0 means that superposition is not performed.

Therefore, for example, when the superimposition level is set to the superimposition amount of Strength = 1 when viewed in units of the block BL, the threshold value th (x, y) for all the pixels in the block BL is 255. Also, the block BL
Threshold value th (x, y) = 192 for all pixels in
If, the superposition amount Streng for the block
th = 0.75. Note that, as described above, the block B
It is not necessary to make the thresholds th (x, y) equal for all pixels in L.

In the superimposition level control unit 20, the variable diz obtained by the superimposition level
(X, y) is multiplied by the digital watermark information WMO from the spread spectrum unit 193 to calculate final digital watermark information WME to be superimposed on the video signal. Here, WMO (x, y) = 1; digital watermark information embedding area WMO (x, y) = 0; area other than the above, WME (x, y) = WMO (x, y) × diz (x ,
y)

Accordingly, the output data Vwm (x, y) represented by Vwm (x, y) = V (x, y) + WME (x, y) is obtained from the digital watermark information superimposing unit 14.

FIG. 6 shows the relationship between additional information to be superimposed as a spread spectrum signal and a video signal in a spectrum. The additional information is a signal having a small bit rate and a low bit rate, and is a narrow-band signal as shown in FIG. 6A. When this is subjected to spectrum spreading, a signal having a wide bandwidth as shown in FIG. 6B is obtained. At this time, the spread spectrum signal level decreases in inverse proportion to the band expansion ratio.

The spread spectrum signal is superimposed on the digital video signal Vi by the additional information superimposing section 12. In this case, as shown in FIG. 6C, the dynamic range of the video signal as the information signal is reduced. At small levels, the spread spectrum signal becomes superimposed.

On the other hand, as will be described later, in order to detect SS duplication control information, when inverse spread spectrum is performed, FIG.
As shown in (d), the SS duplication control information is restored again as a narrowband signal. By giving a sufficient band spreading factor, the power of the duplication control information after despreading exceeds the information signal and becomes detectable.

In particular, in the configuration of the above-described embodiment, the spread spectrum is performed using the PN code string of the vertical cycle using the vertical synchronization signal as the reference signal.
The PN code sequence for inverse spectrum spreading required for detecting the spread spectrum signal from the video signal can be easily generated based on a signal synchronized with the vertical synchronization signal detected from the video signal.

In the case of this embodiment, FIG.
By performing dither processing on the spread spectrum signals in the states of (b) and (c), the superimposition level is changed as shown in FIGS.
The level is lower than that of the spread spectrum signal in the state (c). Further, by adding high-frequency random noise, the high-frequency side of the spread spectrum signal in the state of FIGS. 6B and 6C is extended, and becomes closer to the frequency range of the video signal band. This makes the additional information superimposed on the video signal less noticeable on the playback screen.

[Second Embodiment] In the above-described first embodiment, the superimposition level determination setting unit 25 includes the average luminance level detector 21, the white level detector 22, and the black level detector 2.
3. Based on the detection output of the near black level detector 24, the superimposition level of the digital watermark information is determined on the assumption that display control is performed on a television receiver as an example of an image display device.

On the other hand, in the second embodiment, the superimposition level of the digital watermark information is determined according to the difference between the average luminance level and each pixel value. This is because the characteristics of the image are taken into consideration, and the fact that when the image is farther away from the average luminance level toward the white side or the black side than the average luminance level, the underexposure and underexposure occur.

FIG. 7 shows an example of an image information recording apparatus including a digital watermark information superimposing apparatus according to the second embodiment. Unlike the first embodiment shown in FIG. 1, the white level detector 22, the black level detector 23, and the near black level detector 24 are not provided.

The superimposition level determination setting section 25 of the second embodiment comprises a superposition level setting section 251 and a conversion table ROM 252. Conversion table RO
As shown in FIG. 8, for example, a correspondence table of the threshold value th for each value that can be taken as the difference DIFF between the average luminance value per field and the pixel value is written in M252.

In the second embodiment, the difference DIFF (x, y) between the average luminance level from the average luminance level detector 21 and each pixel value V (x, y) is subtracted by the subtracter 3.
1 and supplies the calculated difference DIFF (x, y) to the superimposition level determination setting unit 25. In this example, as the average luminance level, the difference DIFF (x,
y).

That is, from among the effective pixels V (x, y) in the field described above, for example, 75 ≦ x ≦ 644,4
The sum Z of 131100 luminances satisfying ≦ y ≦ 233 is obtained. Then, the average brightness value avr is calculated as avr = [Z / 131072]. [] Means a Gaussian symbol.

Next, the average luminance value avr of the previous field
Is used to calculate the difference DIFF (x,
y), DIFF (x, y) = [{V (x, y) -avr} / 1
6] It is determined by the following arithmetic expression. The value of each DIFF in FIG. 8 corresponds to the result of this arithmetic expression.

The difference DIFF from the subtracter 31 is stored in the conversion table ROM 252 of the superimposition level judgment setting unit 25.
(X, y) is supplied as an argument, and the threshold value th corresponding thereto is obtained from the conversion table 1 ROM 252 by the threshold value t.
Output as h (x, y).

The threshold value th (x, y) output from the conversion table ROM 252 is supplied to the superimposition level setting unit 251. As described above, the superimposition level setting unit 251 includes a 16-bit PN generator that changes the state for each pixel, and a value PN (x, y) of the upper 8 bits and a threshold th (x, y). ), A variable diz (x, y) for each pixel is determined in the same manner as described above. Then, the obtained variable diz (x, y) is supplied to the superimposition level control unit 20,
The superimposition level control is executed in the same manner as described above.

As is apparent from FIG. 8, when the difference DIFF is smaller than zero in the conversion table ROM 252, that is, when the pixel value is on the black level side and when the difference is larger than zero, that is, when the pixel value is The difference in the setting value of the superimposition level between the white level side and the white level side is in consideration of video characteristics such as a gamma characteristic.

As described above, in the case of the second embodiment, by using the table ROM 252, the configuration of the superposition level judgment setting section 25 can be simplified, and the first embodiment can be implemented. The various detectors 22, 23, 24 as in the embodiment described above can be dispensed with.

[Third Embodiment] The third embodiment corresponds to a modification of the second embodiment. In the second embodiment, since there is only one conversion table ROM, the superimposition level on the black level side of the pixel level is not so much higher than the average luminance level. But,
As described above, in the case of an image in which the average luminance level in the field unit is high and the area of the white level portion is large, the blackout occurs on the television receiver side due to the bright ABL. When it is high, the superimposition amount can be further increased on the black level side.

Therefore, in the third embodiment, the amount of electronic watermark information superimposed on pixels on the black side of the average luminance level is changed according to the average luminance level.

FIG. 9 is a block diagram showing an example of an image information recording apparatus including the digital watermark information superimposing apparatus according to the third embodiment. The internal configuration of the superimposition level determination setting unit 25 is different from the block diagram of the recording device including the digital watermark information superimposition device of the second embodiment shown in FIG.

That is, in this example, the average luminance level is assumed to be three levels of “large”, “medium”, and “small”, and conversion tables for the respective average luminance levels are created.
ROMs 253 and 254 in which the conversion table is written,
255 is provided in the superimposition level determination setting unit 25.

In this case, when the average luminance level per field of the input video signal is “large”, the conversion table is as follows.
As shown in FIG. 10A, the superimposition level on the black level side from the average luminance level is set higher than in the case of the above-described second embodiment.

As shown in FIG. 10B, the conversion table for the case where the average luminance level is “medium” indicates the superimposed level on the black level side of the average luminance level as described in the second embodiment. Same as for the form.

Further, as shown in FIG. 10C, the conversion table in the case where the average luminance level is “small” indicates that the superimposed level on the black level side of the average luminance level is the same as that in the second embodiment. Make smaller than in case of form.

These three conversion table ROMs 253,
The difference DIFF (x, y) between the average luminance level from the subtractor 31 and each pixel value is stored in the second
In the same manner as in the embodiment, the thresholds th (x, y) are supplied as arguments and output.

The three conversion table ROMs 253,
Each of the threshold values th (x, y) output from 254 and 255 is supplied to the selection switch circuit 256. The selection switch circuit 256 includes three conversion tables RO
One of the threshold values th (x, y) from M253 to 255 is selected and supplied to the superimposition level setting unit 251.

The average luminance level detected by the average luminance level detector 21 is supplied to the switching signal generator 32, and the detected average luminance levels are classified into three levels of “large”, “medium” and “small”. Is determined, a switching signal for switching the selection switch circuit 256 is generated, and the generated switching signal is supplied to the selection switch circuit 256.

Therefore, the variable diz (x, y) is obtained from the superimposition level setting unit 251 so that the superimposition amount on the black level side becomes larger than the average luminance level as the average luminance level of the field increases. It is supplied to the superposition level control unit 20.

According to the third embodiment, according to the third embodiment, the superimposition amount on the black level side of the average luminance level is further larger than that of the second embodiment in accordance with the average luminance level of the field. It is properly controlled.

In the above-described embodiment, a case has been described in which one block of a spread spectrum signal is superimposed on a coding block of MPEG coding, but the superimposing mode is limited to this. It goes without saying that it is not.

Further, the additional information to be superimposed on the image information as the digital watermark information is not limited to the spread spectrum signal in each of the above-described embodiments, and various digital watermarking schemes can be used. For example, when additional information is superimposed on a digital signal at a very small level, or when compression using orthogonal transformation such as MPEG compression is performed on data, a component converted on the frequency axis may be so small that it does not stand out as noise. The case where the additional information of the level is superimposed may be adopted.

Further, one screen is divided into small areas of a predetermined size, and a unit digital watermark pattern is
A digital watermarking process for superimposing the video information on the video information may be used.

[0094]

As described above, according to the present invention, while ensuring a superimposed amount that can reliably detect digital watermark information, the image information is not discriminated on the screen and is not noticeable. Can be superimposed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a recording device to which a first embodiment of a digital watermark information superimposing device according to the present invention is applied.

FIG. 2 is a diagram for explaining an embodiment of the present invention.

FIG. 3 is a diagram for describing superposition amount control in the embodiment of the present invention.

FIG. 4 is a diagram for explaining display control in a television receiver.

FIG. 5 is a diagram for explaining display control in the television receiver.

FIG. 6 is a diagram for explaining characteristics of a spread spectrum process as a digital watermark process used in the embodiment of the present invention;

FIG. 7 is a block diagram showing an example of a recording apparatus to which a second embodiment of the digital watermark information superimposing apparatus according to the present invention is applied.

FIG. 8 is a diagram used to explain a main part of the second embodiment.

FIG. 9 is a block diagram showing an example of a recording apparatus to which a second embodiment of the digital watermark information superimposing apparatus according to the present invention is applied.

FIG. 10 is a diagram used to explain a third embodiment of a digital watermark information superimposing device according to the present invention.

[Explanation of symbols]

11: input terminal of video signal Vi, 12: A / D converter, 13: blocking unit, 14: digital watermark information superimposing unit, 15: MPEG compression encoding unit, 16: writing unit,
17: synchronization detector, 18: timing signal generator, 19
... Electronic watermark information generator, 191 ... PN generator, 192
... Additional information generating section, 193... Spread spectrum section, 20
... superimposition level control unit, 21 ... average luminance level detector, 2
2 white level detector, 23 black level detector, 24 near black level detector, 25 superimposed level control unit, 251 superimposed level setting unit, 252, 253, 254, 255 conversion table ROM, 31 Subtractor, 256: selection switch circuit, 32: switching signal generator

Continued on front page F term (reference) 5C063 AB03 CA36 DA20 DB09 5C076 AA40 5D044 AB07 DE17 EF05 FG18 GK17 HL04 5J104 AA14 PA14 9A001 BB02 BB03 EE03 EE04 EE05 GG01 HH27 HH31 LL03

Claims (16)

[Claims] When superimposing digital watermark information on a baseband video signal, display control in a video display device is assumed in accordance with the video signal on which the digital watermark information is to be superimposed. A method for superimposing digital watermark information, comprising controlling a superimposition level of digital watermark information to be superimposed. 2. The method of superimposing digital watermark information according to claim 1, wherein the superimposing level of the digital watermark information is increased in a portion of the video display device where whiteout is expected to occur. A method for superimposing digital watermark information. 3. The method for superimposing digital watermark information according to claim 1, wherein the superimposition level of the digital watermark information is increased in a portion where blackout is expected to occur in the video display device. A method for superimposing digital watermark information. 4. The method of superimposing digital watermark information according to claim 1, wherein the superimposing level of the digital watermark information is reduced in a portion of the video signal near black. . 5. The method of superimposing digital watermark information according to claim 1, wherein an average luminance level of the video signal is detected, and as the level becomes further away from the average luminance level toward the white side and the black side, the digital watermark becomes higher. A method for superimposing digital watermark information, comprising increasing a superimposition level of information. 6. A method for superimposing digital watermark information on a baseband video signal, comprising: a difference between an average luminance level and a pixel level of the video signal;
A table representing the relationship between the digital watermark information and the superimposed level is prepared, and the table is searched based on the difference between the average luminance level of the input video signal and the level of the input video signal. A method for superimposing digital watermark information, comprising determining a superimposition level. 7. A method for superimposing digital watermark information on a baseband video signal, comprising: a difference between an average luminance level and a pixel level of the video signal;
A table representing the relationship between the superimposition level of the digital watermark information and a plurality of tables is provided according to the average luminance level.
In preparation, an average luminance level of the video signal is detected, and a table selected from the plurality of tables is used in accordance with the detected average luminance level. Determining a superimposition level of said digital watermark information. 8. Digital watermark information generating means, superimposing means for superimposing digital watermark information from the digital watermark information generating means on a baseband video signal, said superimposing means, and said digital watermark information generating means. , A superimposition level control means for controlling a superimposition level of the digital watermark information, a level detection means for detecting a level of an input video signal, and a display control according to a video signal in a video display device. Based on the detection level from the level detection means,
A superimposition level judging unit for judging a superimposition level of the digital watermark information, wherein the superimposition level control unit controls the superimposition level according to a judgment result by the superimposition level judgment unit. Digital watermark information superimposing device. 9. The electronic watermark information superimposing device according to claim 8, wherein the superimposition level determining means is arranged such that, in the video display device, a portion of a video signal in which it is assumed that whiteout occurs, is compared with other portions. An electronic watermark information superimposing device, wherein the electronic watermark information superimposing level is determined to be increased. 10. The digital watermark information superimposing device according to claim 8, wherein the superimposition level determining means is arranged such that, in the video display device, a portion of a video signal in which it is assumed that blackouts occur is more than other portions. An electronic watermark information superimposing device, wherein the electronic watermark information superimposing level is determined to be increased. 11. The electronic watermark information superimposing apparatus according to claim 8, wherein the superimposition level judging means sets the superimposition level of the electronic watermark information in a portion of the video signal having a level closer to black than in other portions. A device for superimposing digital watermark information, characterized in that it is determined to lower it. 12. The digital watermark information superimposing apparatus according to claim 8, wherein the superimposition level determining means sets the digital watermark information as the level becomes farther from the average luminance level of the video signal to the white side and the black side. A digital watermark information superimposing device, wherein the superimposing level of the digital watermark information is increased. 13. Digital watermark information generating means, superimposing means for superimposing digital watermark information from said digital watermark information generating means on a baseband video signal, said superimposing means, and said digital watermark information generating means. , A superimposition level control means for controlling a superimposition level of the digital watermark information, a difference detection means for detecting a difference between a level of an input video signal and an average luminance level of the input video signal, The difference between the average luminance level of the signal and the pixel level,
A superimposition level determination unit that includes a table representing a relationship between the digital watermark information and the superimposition level, and searches the table based on the difference detected by the difference detection unit to determine the superimposition level of the digital watermark information; Wherein the superimposition level control means controls the superimposition level according to the result of the judgment made by the superimposition level judgment means. 14. Digital watermark information generating means, superimposing means for superposing digital watermark information from said digital watermark information generating means on a baseband video signal, said superimposing means, and said digital watermark information generating means. And a superimposition level control means for controlling a superimposition level of the digital watermark information; an average luminance level detection means for detecting an average luminance level of the input video signal; a level of the input video signal; Difference detection means for detecting a difference between the average luminance level detected by the luminance level detection means, and a difference between the average luminance level and the pixel level of the video signal,
A plurality of tables representing the relationship between the digital watermark information and the superimposition level are provided in accordance with the average luminance level, and the plurality of tables are displayed based on the average luminance level detected by the average luminance level detection means. Selecting one of the tables, searching the selected table according to the difference detected by the difference detecting means, and determining a superimposing level of the digital watermark information. A superimposition device for superimposing digital watermark information, wherein the superimposition level control means controls the superimposition level in accordance with the result of the judgment by the superimposition level judgment means. 15. An image information recording method, comprising the step of recording image information on which digital watermark information has been superimposed by the digital watermark information superimposing method according to any one of claims 1 to 7. 16. An image information recording apparatus comprising the electronic watermark information superimposing device according to claim 7, wherein the image information on which the electronic watermark information is superimposed is recorded.