JP5963636B2 - Digital watermark detection apparatus, digital watermark detection method, and digital watermark detection program - Google Patents

Description

  The present invention relates to a digital watermark detection apparatus, a digital watermark detection method, and a digital watermark detection program for detecting that a digital watermark is included in a video frame.

  Conventionally, as a method for detecting a digital watermark, for example, there is one disclosed in Patent Document 1. In such a conventional detection process, when calculating a correlation value between a frame image and a detection pattern, an average value of pixel values at a predetermined time is calculated for each pixel of the image area, and the average value is calculated in the image area. Time DC component removal processing for subtracting from the pixel value of each pixel, and a spatial DC component for calculating an average value of pixel values at each time for each image region and subtracting the average value from the pixel value of each pixel in the image region Detects the amount of motion of the image area at a predetermined time, and performs DC component removal by spatial DC component removal when the motion amount is greater than a predetermined threshold, and temporal DC component removal when the amount of motion is not greater than the predetermined threshold The DC removal switching is performed to remove the DC component by.

JP 2009-1000029 A

  The purpose of removing the DC component in watermark detection is to remove the influence of the original image signal. Ideally, the DC component to be removed is preferably the luminance value itself of the original image signal, but this is estimated. As a means to do this, in the conventional method as disclosed in Patent Document 1, the average value of pixel blocks (spatial DC component removal) in a certain area of the same frame or the average value of frame pixels (time) within a certain time length. DC component removal) was used.

  However, the average value of the pixel block and the average value of the frame pixel within a certain time length are obtained by calculating the average value from a pixel group having a certain temporal or spatial spread as the DC component, and the luminance value Fluctuations are temporally or spatially dispersed, and may be far from the luminance value of the original image signal to be estimated. That is, there is a problem that it is difficult to efficiently remove the influence of the original image signal from the pixel luminance value.

  The present invention has been made to solve the above-described problems, and is an electronic watermark detection apparatus that can efficiently remove the influence of an original image signal from a pixel luminance value and improve the detection accuracy of a watermark signal. The purpose is to obtain.

  The digital watermark detection apparatus according to the present invention separates the detection target video into an embedding target pixel area that is a pixel area in which the digital watermark is embedded and an embedding prohibited pixel area that is a pixel area in which the digital watermark is not embedded. Area separation means, and for each pixel belonging to the embedding target pixel area, pixel selection means for selecting a pixel belonging to an embedding prohibited pixel area in which luminance fluctuation from the pixel is estimated to be small in the original image signal; For each pixel belonging to the embedding target pixel area, a difference calculating means for calculating a luminance difference value from the pixel selected by the pixel selecting means, and an electron that changes in the time direction for each of the plurality of image areas based on the key information Detection pattern generation means for generating a watermark detection pattern, brightness difference values calculated by the difference calculation means for all pixels belonging to the embedding target pixel area, and detection pattern generation means The correlation value calculating means for calculating the correlation value with the detected detection pattern of the digital watermark, and comparing the correlation value calculated by the correlation value calculation means with a preset threshold value, the digital watermark is detected in the detection target video. It is determined whether or not it is included, and when it is determined that it is included, it includes watermark determination means for outputting detected bit information of the digital watermark.

  The digital watermark detection apparatus according to the present invention selects, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area in which the luminance fluctuation from the pixel is estimated to be small in the original image signal. Since the luminance difference value is obtained and it is determined whether the digital watermark is included based on the correlation value between the difference value and the detection pattern of the digital watermark, the influence of the original image signal is efficiently determined from the pixel luminance value. And the detection accuracy of the watermark signal can be improved.

It is a block diagram which shows the digital watermark detection apparatus by Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the digital watermark detection apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the search of the pixel B of the digital watermark detection apparatus by Embodiment 1 of this invention. It is a block diagram which shows the internal structure of the detection pattern production | generation means of the digital watermark detection apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the video frame of the digital watermark detection apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the waveform corresponding to the watermark waveform number of the digital watermark detection apparatus by Embodiment 1 of this invention. It is explanatory drawing of the watermark determination of the digital watermark detection apparatus by Embodiment 1 of this invention. It is a block diagram which shows the digital watermark detection apparatus by Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the digital watermark detection apparatus by Embodiment 2 of this invention. It is explanatory drawing which shows pixel limitation of the digital watermark detection apparatus by Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a digital watermark detection apparatus according to Embodiment 1 of the present invention.
The digital watermark detection apparatus 100 shown in FIG. 1 includes an area separation unit 101, a pixel selection unit 102, a difference calculation unit 103, a detection pattern generation unit 104, a correlation value calculation unit 105, and a watermark determination unit 106.

  The area separating unit 101 is a unit that separates the video frame into an embedding target pixel area composed of pixels in which a digital watermark is embedded and an embedding prohibited pixel area composed of pixels in which the digital watermark is not embedded. For each pixel (referred to as pixel A) belonging to the embedding target pixel area, the pixel selecting unit 102 embeds a pixel B that is estimated to have a small luminance variation from the pixel A in the original image signal. It is means to choose from. The difference calculation unit 103 is a unit that calculates a luminance difference value between the pixel A and the pixel B for each pixel belonging to the embedding target pixel region. The detection pattern generation unit 104 is a unit that generates a digital watermark detection pattern that changes in the time direction for each of a plurality of image areas based on key information given to the digital watermark detection apparatus 100. The correlation value calculation unit 105 correlates the luminance difference value calculated by the difference calculation unit 103 with the detection pattern of the digital watermark generated by the detection pattern generation unit 104 for all pixels belonging to the embedding target pixel region. A means for calculating a value. The watermark determination unit 106 determines whether the digital watermark is included in the detection target video by comparing the correlation value output from the correlation value calculation unit 105 with a preset threshold value. When the determination is made, the digital watermark detection bit information is output.

  The digital watermark detection apparatus 100 is realized by using a computer, and the area separation unit 101 to the watermark determination unit 106 include software corresponding to each unit and hardware such as a CPU and a memory for executing the software. It is configured.

Next, the operation of the digital watermark detection apparatus 100 according to the first embodiment will be described.
FIG. 2 is a flowchart showing the operation of the digital watermark detection apparatus 100.
First, the digital watermark detection apparatus 100 receives a video signal composed of a plurality of frame images as an input, and inputs the image signal I to the area separation unit 101 in units of frame images. As a result, the area separating unit 101 determines whether or not image quality degradation is easily visually recognized for each pixel of the image signal I. If it is determined that the image is easily visually recognized, the pixel is embedded / prohibited for the pixel. 0 is output as the pixel flag (indicating that this is an embedding target pixel), and if it is not determined that the pixel is easily visible, 1 is output as the embedding target / prohibited pixel flag for the pixel ( This indicates an embedding prohibited pixel) (region separation process: step ST1). It should be noted that the embedding target / prohibited pixel flag is output as information combined with the corresponding pixel coordinates to the pixel selection unit 102 that is the actual output destination.

Specifically, as a criterion for determining whether image quality deterioration is likely to be visually recognized, for example, attention is paid to a change in a predetermined pixel value, and visibility when a change in luminance is applied in a flat area with little screen movement As an example, the following formula K = | F (x−2, y, t) −F (x, y, t) | + | F (x−1, y, t) −F (x , Y, t) | + | F (x, y, t) −F (x, y, t−1) | + | F (x + 1, y, t) −F (x, y, t) | + | F (x + 2, y, t) −F (x, y, t) |
If the value K obtained by the above is equal to or less than a preset threshold value ThK, 1 is output as an embedding target / prohibited pixel flag as a flat region with little motion.
Conversely, if the value K is larger than the threshold value ThK, 0 is output as an embedding target / prohibited pixel flag on the assumption that the movement is not small or is not flat.

  The pixel selecting unit 102 receives the embedding target / prohibited pixel flag of each pixel from the region separating unit 101, searches for pixels around which the flag is 0 (referred to as pixel A), and searches for the surrounding pixels, and performs the embedding target The pixel having the closest distance among the pixels having the / prohibited pixel flag of 1 is searched (pixel selection process: step ST2).

  FIG. 3 shows the state of the search. The rectangle in FIG. 3 represents each pixel, the white rectangle indicates an embedding target pixel, that is, a pixel whose embedding target / prohibited pixel flag is 0, and the hatched rectangle indicates an embedding prohibited pixel, that is, an embedding prohibited / prohibited pixel A pixel having a pixel flag of 1 is indicated. With reference to the pixel A in the embedding target pixel area, the pixel B nearest to the pixel A is searched for among the pixels in the embedding prohibited pixel area.

  As a specific search method, for example, first, the embedding target / prohibited pixel flag of the pixel adjacent to the pixel A (pixel S1 in FIG. 3) is sequentially checked. The search ends as a pixel. If there is no pixel whose flag is 1, the search area is expanded to a pixel area (pixel S2 in FIG. 3) that is one pixel outside of the adjacent pixel area, and similarly, there is a pixel whose embedding target / prohibited pixel flag is 1. Check sequentially. In this manner, the process of expanding the search region by one pixel outward is repeated until a pixel having an embedding target / prohibited pixel flag of 1 is found.

Finally, the pixel selection unit 102 outputs the coordinates and pixel value of the pixel A and the pixel value of the embedding prohibited pixel B obtained as a search result to the difference calculation unit 103.
In general, the closer the pixels are to each other, the smaller the luminance variation in the original image signal tends to be seen as a whole pixel, so searching for the nearest embedding prohibited pixel when viewed from the embedding target pixel is This is effective as a method for searching for a pixel estimated to have a small luminance variation in the original image signal. However, the search method of the embedding prohibited area pixel in the pixel selecting unit 102 is not necessarily limited to searching for the nearest pixel of the embedding target area pixel, and the luminance variation from the pixel A in the original image signal is small. Any search method other than the nearest neighbor may be used as long as it is a method for searching the estimated embedding prohibited area pixel.

  The difference calculation unit 103 calculates the difference between the pixel values of the pixel A and the pixel B output from the pixel selection unit 102, and outputs the difference together with the coordinates of the pixel A to the correlation value calculation unit 105 (difference calculation process: step ST3). .

The detection pattern generation means 104 generates a digital watermark detection pattern that changes in the time direction for each of a plurality of image areas based on the key information (detection pattern generation processing: step ST4). FIG. 4 shows its internal configuration.
The detection pattern generation unit 104 shown in FIG. 4 has a function of generating a detection pattern according to time information and outputting the detection pattern to the correlation value calculation unit 105. The detection pattern generation unit 104 includes a number generation unit 1041 and a detection waveform generation unit 1042. . The number generation means 1041 refers to the random number initial value, which is key information, and time information, and uses, for example, the same method as the watermark waveform number generation in the watermark embedding process disclosed in Patent Document 1, for each predetermined time. In addition, a watermark waveform number assigned to each area (hereinafter referred to as a block set) obtained by dividing the image frame shown in FIG. The detection waveform generation means 1042 generates and outputs a watermark waveform determined by the watermark waveform number for each pixel of each block set. Specifically, the detection waveform generation unit 1042 has a function of generating, for example, a normal phase waveform and a reverse phase waveform of a watermark waveform having a different phase corresponding to the watermark waveform number illustrated in FIG. Normal phase waveforms are used for the pixels in the upper left and lower right blocks (X1 and X4 in FIG. 5), and negative phase waveforms are used for the pixels in the upper right and lower left blocks (X2 and X3 in FIG. 5). Output as detection pattern.

  The correlation value calculation means 105 is a waveform pattern having the same coordinates as the pixel A in the difference value corresponding to the pixel A in the embedding target area calculated by the difference calculation means 103 and the detection pattern output from the detection pattern generation means 104. The correlation with the value is calculated for each block set as an integrated correlation value for all the pixels in the embedding target pixel region (correlation value calculation process: step ST5). Note that the integrated correlation value may be integrated for a plurality of image frames instead of only for a single image frame.

The watermark determination unit 106 determines whether the digital watermark is included in the input image I by comparing the integrated correlation value output from the correlation value calculation unit 105 with a preset threshold (watermark determination process). : Step ST6).
FIG. 7 shows a state of determination by the watermark determination means 106. The integrated correlation value output from the correlation value calculation means 105 is a real value that can take a range of [−1, +1]. On the other hand, a threshold T having a positive real value is set in advance. If the integrated correlation value is larger than the threshold value + T, it is determined that bit information “0” has been detected, and if it is smaller than the threshold value −T, it is determined that bit information “1” has been detected, and the detected bit information is output. When the integrated correlation value is not larger than the threshold value + T and smaller than the threshold value −T, it is determined that the bit information is not detected, and is output as undetected bit information.

  As described above, in the first embodiment, by extracting a difference from neighboring embedding prohibited pixels, “temporal DC component removal” that subtracts a temporal average value of pixels, or an average value in an image region is obtained. Compared with “spatial DC component removal” to be subtracted, pixel luminance components are compared more locally. Therefore, when viewed as the whole pixel in the image frame, the influence of the original video signal can be more efficiently removed, and the influence of the relatively remaining watermark signal is more likely to exceed the influence of the original video signal. The accuracy of detection is improved.

  As described above, according to the digital watermark detection apparatus of the first embodiment, the detection target video is an embedding target pixel area that is a pixel area in which the digital watermark is embedded and a pixel area in which the digital watermark is not embedded. An area separating unit that separates into an embedding prohibited pixel area and an embedding prohibited pixel area in which, for each pixel belonging to the embedding target pixel area, the luminance variation from the pixel is estimated to be small in the original image signal A pixel selecting unit that selects a pixel, a difference calculating unit that calculates a luminance difference value between each pixel belonging to the embedding target pixel region and the pixel selected by the pixel selecting unit, and a plurality of images based on the key information Detection pattern generation means for generating a detection pattern of a digital watermark that changes in the time direction for each region, and a luminance difference value calculated by the difference calculation means for all pixels belonging to the embedding target pixel area Correlation value calculation means for calculating a correlation value with the detection pattern of the digital watermark generated by the detection pattern generation means, and comparing the correlation value calculated by the correlation value calculation means with a preset threshold value Is included in the detection target video, and when it is determined to be included, a watermark determination unit that outputs detection bit information of the digital watermark is provided. The influence of the signal can be removed, and the detection accuracy of the watermark signal can be improved.

  In addition, according to the digital watermark detection apparatus of the first embodiment, the pixel selecting unit determines, for each pixel belonging to the embedding target pixel area, a pixel nearest to each pixel in the embedding prohibited pixel area. Since the selection is made, it is possible to efficiently select the pixel to which the embedding prohibited region estimated to have a small luminance variation belongs.

  Further, according to the digital watermark detection method of the first embodiment, the detection target video is embedded in a pixel area to be embedded, which is a pixel area in which the digital watermark is embedded, and an embedding prohibited pixel, which is a pixel area in which the digital watermark is not embedded. A region separation step for separating the region into pixels, and for each pixel belonging to the embedding target pixel region, a pixel belonging to an embedding prohibited pixel region in which luminance fluctuation from the pixel is estimated to be small in the original image signal is selected. A pixel selection step, a difference calculation step for calculating a luminance difference value from the pixel selected in the pixel selection step for each pixel belonging to the embedding target pixel region, and a time for each of the plurality of image regions based on the key information A detection pattern generation step for generating a detection pattern of a digital watermark that changes in direction, and a luminance difference calculated in a difference calculation step for all pixels belonging to the embedding target pixel A correlation value calculation step for calculating a correlation value between the value and the detection pattern of the digital watermark generated in the detection pattern generation step, and comparing the correlation value calculated in the correlation value calculation step with a preset threshold value And a watermark determination step for outputting the detected bit information of the digital watermark when it is determined that the digital watermark is included in the detection target video. In addition, the influence of the original image signal can be removed, and the detection accuracy of the watermark signal can be improved.

  Further, according to the digital watermark detection program of the first embodiment, the detection target video is embedded in the computer that determines whether the detection target video includes a predetermined digital watermark, which is an area of a pixel in which the digital watermark is embedded. An area separation step for separating the target pixel area from an embedding prohibited pixel area that is a pixel area in which the digital watermark is not embedded, and the luminance from the pixel in the original image signal for each pixel belonging to the embedding target pixel area The pixel selection step for selecting a pixel belonging to the embedding prohibited pixel region estimated to have a small variation, and the luminance difference value between the pixel selected in the pixel selection step for each pixel belonging to the embedding target pixel region A difference calculation step to be calculated, and a detection pattern generation step for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image areas based on the key information. And a correlation value calculation that calculates a correlation value between the luminance difference value calculated in the difference calculation step and the detection pattern of the digital watermark generated in the detection pattern generation step for all pixels belonging to the embedding target pixel When it is determined that the digital watermark is included in the detection target video by comparing the step and the correlation value calculated in the correlation value calculation step with a preset threshold value, The watermark determination step for outputting the detection bit information of the digital watermark is executed, so that the influence of the original image signal can be efficiently removed from the pixel luminance value and the detection accuracy of the watermark signal can be improved. The detection method can be executed on a computer.

Embodiment 2. FIG.
In the second embodiment, for each pixel belonging to the embedding target pixel region, only the pixel A that satisfies a certain level of selection criteria in the pixel selection means is extracted.

  FIG. 8 is a configuration diagram illustrating the digital watermark detection apparatus according to the second embodiment. The illustrated digital watermark detection apparatus 100a includes an area separation unit 101, a pixel selection unit 102, a difference calculation unit 103, a detection pattern generation unit 104, a correlation value calculation unit 105, a watermark determination unit 106, and a pixel limitation unit 107. In the digital watermark detection apparatus 100a according to the second embodiment, the region separation is performed except that the output of the pixel selection unit 102 is input to the pixel limitation unit 107 and the difference calculation unit 103 is input to the output of the pixel limitation unit 107. The basic configuration of means 101 to watermark determination means 106 is the same as that of the first embodiment. Further, the pixel limiting means 107 is a means for limiting and extracting only the pixels A that satisfy the selection criteria in the pixel selection means 102 for each pixel belonging to the embedding target pixel area.

Next, the operation of the digital watermark detection apparatus according to the second embodiment will be described.
FIG. 9 is a flowchart illustrating the operation of the digital watermark detection apparatus 100a according to the second embodiment. Here, the region separation processing (step ST1) to watermark determination processing (step ST6) by the region separation means 101, the pixel selection means 102, the detection pattern generation means 104, the correlation value calculation means 105, and the watermark determination means 106 are basically described. The same as in the first embodiment. However, the pixel selection unit 102 sets the data output destination as the pixel limiting unit 107 and outputs not only the coordinate value of the coordinate A but also the coordinate value of the coordinate B to the pixel limiting unit 107.

  The pixel limiting unit 107 uses the coordinates and pixel values of the pixel A and the coordinates and pixel values of the embedding prohibited pixel B received from the pixel selecting unit 102 to determine whether the selection criterion in the pixel selecting unit 102 satisfies a certain level. As a determination criterion, for example, the coordinates of the pixel A and the coordinates of the pixel B are compared, and it is determined whether or not they are in adjacent positions (pixel limiting process; step ST7). This corresponds to, for example, the relationship between the pixel A and the pixel B in FIG. Similarly, the pixel A ′ (plurality) shown in FIG. 10 exists as a pixel in the embedding target pixel region in which the pixels in the embedding prohibited pixel region are adjacent to each other. For these pixels A or A ′, the coordinates and pixel values of each pixel and the pixel values of the corresponding embedding prohibited pixels are output to the difference calculation means 103.

  Note that the determination criterion in the pixel limiting unit 107 is not necessarily limited to that the pixel A and the pixel B are adjacent to each other. For example, the pixel A and the pixel B may be located at a distance equal to or smaller than a preset distance threshold. good. Further, the method is not limited to the method using the distance between the pixel A and the pixel B, and any method can be used as long as it can be determined that the selection criterion in the pixel selection unit 102 satisfies a certain level.

  The difference calculation unit 103 calculates a difference between each pixel value of the pixel A extracted by the pixel limiting unit 107 and the corresponding pixel B, and outputs the difference together with the coordinates of the pixel A to the correlation value calculation unit 105 (difference calculation processing: Step ST3). The correlation value calculation means 105 is a waveform pattern having the same coordinates as the pixel A in the difference value corresponding to the pixel A in the embedding target area calculated by the difference calculation means 103 and the detection pattern output from the detection pattern generation means 104. The correlation with the value is calculated for each block set as an integrated correlation value for the pixels in the embedding target pixel area extracted by the pixel limiting means 107 (correlation value calculation processing: step ST5). Note that the integrated correlation value may be integrated for a plurality of image frames instead of only for a single image frame. Further, the detection pattern generation process in step ST4 and the watermark determination process in step ST6 are the same as those in the first embodiment.

  As described above, in the second embodiment, the entire embedding target pixel is not subjected to correlation value calculation as in the first embodiment, but is embedded in an embedding prohibited pixel adjacent to or within a certain distance from the embedding prohibited pixel. By limiting to pixels only, the correlation value target is limited to only those obtained from coordinates closer to each other than the luminance value difference, and the influence of the original image signal is less affected by the correlation value calculation.

  As described above, according to the digital watermark detection apparatus of the second embodiment, the detection target video is an embedding target pixel region that is a pixel region in which the digital watermark is embedded and a pixel region in which the digital watermark is not embedded. An area separating unit that separates into an embedding prohibited pixel area and an embedding prohibited pixel area in which, for each pixel belonging to the embedding target pixel area, the luminance variation from the pixel is estimated to be small in the original image signal Pixel selecting means for selecting pixels, pixel limiting means for limiting and extracting only pixels satisfying a certain level of selection criteria in the pixel selecting means for each pixel belonging to the embedding target pixel area, and pixel limiting means A difference calculation unit that calculates a luminance difference value between the pixel output from the pixel selected by the pixel selection unit and a digital watermark that changes in a time direction for each of a plurality of image areas based on the key information. A detection pattern generation unit that generates an outgoing pattern, a luminance difference value calculated by the difference calculation unit for a pixel extracted by the pixel limitation unit, and a detection pattern of the digital watermark generated by the detection pattern generation unit Correlation value calculating means for calculating a correlation value, and determining whether the digital watermark is included in the detection target video by comparing the correlation value calculated by the correlation value calculating means with a preset threshold If it is determined that the signal is detected, a watermark determination unit that outputs digital watermark detection bit information is provided, so that the influence of the original image signal can be efficiently removed from the pixel luminance value, and the detection accuracy of the watermark signal Can be improved.

  In addition, according to the digital watermark detection apparatus of the second embodiment, the pixel selecting unit determines, for each pixel belonging to the embedding target pixel area, a pixel nearest to each pixel in the embedding prohibited pixel area. Since the selection is made, it is possible to efficiently select the pixel to which the embedding prohibited region estimated to have a small luminance variation belongs.

  In addition, according to the digital watermark detection apparatus of the second embodiment, the pixel limiting unit only detects a pixel in which each pixel and the pixel selected by the pixel selection unit are adjacent to each pixel belonging to the embedding target pixel region. Since extraction is performed in a limited manner, the influence of the original image signal can be made less susceptible to correlation value calculation.

  In addition, according to the digital watermark detection apparatus of the second embodiment, the pixel limiting unit has a certain distance between each pixel belonging to the embedding target pixel region and the pixel selected by the pixel selection unit. Since only certain ones are extracted, the influence of the original image signal can be made less susceptible to correlation value calculation.

  In addition, according to the digital watermark detection method of the second embodiment, the detection target image is embedded in a pixel area to be embedded, which is a pixel area in which the digital watermark is embedded, and an embedding prohibited pixel, which is a pixel area in which the digital watermark is not embedded. A region separation step for separating the region into pixels, and for each pixel belonging to the embedding target pixel region, a pixel belonging to an embedding prohibited pixel region in which luminance fluctuation from the pixel is estimated to be small in the original image signal is selected. A pixel selection step, a difference calculation step for calculating a luminance difference value from the pixel selected in the pixel selection step for each pixel belonging to the embedding target pixel region, and a time for each of the plurality of image regions based on the key information A detection pattern generation step for generating a detection pattern of a digital watermark that changes in direction, and a luminance difference calculated in a difference calculation step for all pixels belonging to the embedding target pixel A correlation value calculation step for calculating a correlation value between the value and the detection pattern of the digital watermark generated in the detection pattern generation step, and comparing the correlation value calculated in the correlation value calculation step with a preset threshold value And a watermark determination step for outputting the detected bit information of the digital watermark when it is determined that the digital watermark is included in the detection target video. In addition, the influence of the original image signal can be removed, and the detection accuracy of the watermark signal can be improved.

  Further, according to the digital watermark detection program of the second embodiment, the detection target video is embedded in the computer that determines whether the detection target video includes a predetermined digital watermark, which is an area of a pixel in which the digital watermark is embedded. An area separation step for separating the target pixel area from an embedding prohibited pixel area that is a pixel area in which the digital watermark is not embedded, and the luminance from the pixel in the original image signal for each pixel belonging to the embedding target pixel area The pixel selection step for selecting a pixel belonging to the embedding prohibited pixel region estimated to have a small variation, and the luminance difference value between the pixel selected in the pixel selection step for each pixel belonging to the embedding target pixel region A difference calculation step to be calculated, and a detection pattern generation step for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image areas based on the key information. And a correlation value calculation that calculates a correlation value between the luminance difference value calculated in the difference calculation step and the detection pattern of the digital watermark generated in the detection pattern generation step for all pixels belonging to the embedding target pixel When it is determined that the digital watermark is included in the detection target video by comparing the step and the correlation value calculated in the correlation value calculation step with a preset threshold value, The watermark determination step for outputting the detection bit information of the digital watermark is executed, so that the influence of the original image signal can be efficiently removed from the pixel luminance value and the detection accuracy of the watermark signal can be improved. The detection method can be executed on a computer.

Embodiment 3 FIG.
In the third embodiment, the luminance difference value that is a correlation value calculation target is multiplied by a weighting coefficient corresponding to the distance between the pixel A and the pixel B. Since the configuration on the drawing is the same as that of the second embodiment shown in FIG. 8, description will be made with reference to FIG.

  In addition to the function of the difference calculation unit 103 according to the second embodiment, the difference calculation unit 103 according to the third embodiment selects each pixel belonging to the embedding target pixel region by using these pixels and the pixel selection unit 102. The luminance difference value is multiplied by a weighting coefficient corresponding to the distance from the pixel. Since other configurations are the same as those of the second embodiment, description thereof is omitted here.

Next, the operation of the digital watermark detection apparatus according to the third embodiment will be described.
The pixel limiting unit 107 in the third embodiment performs the same processing as in the second embodiment, but outputs not only the coordinate A but also the coordinate value of the coordinate B to the difference calculation unit 103. The difference calculating unit 103 calculates the inter-pixel distance from the coordinates of the pixel A and the pixel B received from the pixel limiting unit 107. On the other hand, the difference between the pixel values of the pixel A and the pixel B is calculated, and as the weighting coefficient according to the distance between the pixel A and the pixel B, for example, the calculated pixel value difference is multiplied by the reciprocal of the inter-pixel distance. The closer the inter-pixel distance is, the larger the weighting coefficient is, and the farther the distance is, the smaller the weighting coefficient is.
As a general tendency, the luminance variation of the original image signal becomes smaller as the distance between the pixels is shorter. Therefore, by multiplying the weight according to the proximity of the distance between the pixels, the original image signal is more effectively used in the correlation value calculation. It becomes possible to weaken the influence.

  Since other operations are the same as those in the second embodiment, description thereof is omitted here.

  As described above, according to the digital watermark detection apparatus of the third embodiment, the difference calculation means calculates the difference between these pixels and the pixel selected by the pixel selection means for each pixel belonging to the embedding target pixel area. Since the luminance difference value is multiplied by the weighting coefficient corresponding to the distance, the influence of the original image signal can be more efficiently removed from the pixel luminance value, and the watermark signal detection accuracy can be improved.

  In addition, according to the digital watermark detection method of the third embodiment, the difference calculation step includes, for each pixel belonging to the embedding target pixel region, a weighting factor corresponding to the distance between the pixel and the pixel selected in the pixel selection step. Therefore, the influence of the original image signal can be more efficiently removed from the pixel luminance value, and the detection accuracy of the watermark signal can be improved.

  In addition, according to the digital watermark detection program of the third embodiment, the difference calculation step includes, for each pixel belonging to the embedding target pixel region, a weighting factor corresponding to the distance between the pixel and the pixel selected in the pixel selection step. Since the luminance difference value is multiplied by the digital watermark detection method, the influence of the original image signal can be more efficiently removed from the pixel luminance value, and the watermark signal detection accuracy can be improved by a computer. Can be made.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  100, 100a Digital watermark detection apparatus, 101 area separation means, 102 pixel selection means, 103 difference calculation means, 104 detection pattern generation means, 105 correlation value calculation means, 106 watermark determination means, 107 pixel limitation means, 1041 number generation means, 1042 Detection waveform generation means.

Claims (13)

A region separating means for separating the detection target video into an embedding target pixel region that is a region of a pixel in which a digital watermark is embedded, and an embedding prohibited pixel region that is a region of a pixel in which the digital watermark is not embedded;
Pixel selecting means for selecting, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area that is estimated to have a small luminance variation from the pixel in the original image signal;
Difference calculation means for calculating a luminance difference value between each pixel belonging to the embedding target pixel area and the pixel selected by the pixel selection means;
A detection pattern generating means for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image areas based on key information;
Correlation value for calculating the correlation value between the luminance difference value calculated by the difference calculation means and the detection pattern of the digital watermark generated by the detection pattern generation means for all pixels belonging to the embedding target pixel area A calculation means;
By comparing the correlation value calculated by the correlation value calculating means with a preset threshold value, it is determined whether the digital watermark is included in the detection target video. An electronic watermark detection apparatus comprising: watermark determination means for outputting watermark detection bit information. Pixel selection means
2. The digital watermark detection apparatus according to claim 1, wherein, for each pixel belonging to the embedding target pixel area, a pixel nearest to the pixel in the embedding prohibited pixel area is selected. A region separating means for separating the detection target video into an embedding target pixel region that is a region of a pixel in which a digital watermark is embedded, and an embedding prohibited pixel region that is a region of a pixel in which the digital watermark is not embedded;
Pixel selecting means for selecting, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area that is estimated to have a small luminance variation from the pixel in the original image signal;
For each pixel belonging to the embedding target pixel area, pixel limiting means for limiting and extracting only pixels that satisfy a certain level of selection criteria in the pixel selecting means;
A difference calculating means for calculating a luminance difference value between the pixel output from the pixel limiting means and the pixel selected by the pixel selecting means;
A detection pattern generating means for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image areas based on key information;
Correlation value calculation for calculating a correlation value between the luminance difference value calculated by the difference calculation unit and the detection pattern of the digital watermark generated by the detection pattern generation unit for the pixel extracted by the pixel limiting unit Means,
By comparing the correlation value calculated by the correlation value calculating means with a preset threshold value, it is determined whether the digital watermark is included in the detection target video. An electronic watermark detection apparatus comprising: watermark determination means for outputting watermark detection bit information. Pixel selection means
4. The digital watermark detection apparatus according to claim 3, wherein for each pixel belonging to the embedding target pixel area, a pixel nearest to the pixel in the embedding prohibited pixel area is selected. Pixel limiting means
4. The digital watermark detection apparatus according to claim 3, wherein, for each pixel belonging to the embedding target pixel area, only the pixels adjacent to the pixel selected by the pixel selection means are extracted. Pixel limiting means
4. The electron according to claim 3, wherein, for each pixel belonging to the embedding target pixel region, only those pixels within a certain distance from the pixel and the pixel selected by the pixel selection means are extracted. Watermark detection device. The difference calculation means is
7. The luminance difference value is multiplied by a weighting coefficient corresponding to a distance between the pixel and a pixel selected by a pixel selection unit for each pixel belonging to the embedding target pixel region. The electronic watermark detection apparatus according to any one of the above. An area separation step of separating the detection target video into an embedding target pixel area that is an area of a pixel in which a digital watermark is embedded, and an embedding prohibited pixel area that is an area of a pixel in which the electronic watermark is not embedded;
A pixel selection step of selecting, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area that is estimated to have a small luminance variation from the pixel in the original image signal;
A difference calculation step for calculating a luminance difference value with respect to each pixel belonging to the embedding target pixel region with the pixel selected in the pixel selection step;
A detection pattern generation step for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image regions based on key information;
Correlation value calculation for calculating a correlation value between the luminance difference value calculated in the difference calculation step and the detection pattern of the digital watermark generated in the detection pattern generation step for all pixels belonging to the embedding target pixel Steps,
It is determined whether a digital watermark is included in the detection target video by comparing the correlation value calculated in the correlation value calculating step with a preset threshold value. And a watermark determination step of outputting watermark detection bit information. An area separation step of separating the detection target video into an embedding target pixel area that is an area of a pixel in which a digital watermark is embedded, and an embedding prohibited pixel area that is an area of a pixel in which the electronic watermark is not embedded;
A pixel selection step of selecting, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area that is estimated to have a small luminance variation from the pixel in the original image signal;
For each pixel belonging to the embedding target pixel area, a pixel limiting step for limiting and extracting only pixels satisfying a selection standard in the pixel selection step;
A difference calculating step for calculating a luminance difference value between the pixel extracted in the pixel limiting step and the pixel selected in the pixel selecting step;
A detection pattern generation step for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image regions based on key information;
Correlation value calculation for calculating the correlation value between the luminance difference value calculated in the difference calculation step and the detection pattern of the digital watermark generated in the detection pattern generation step for the pixels extracted in the pixel limiting step Steps,
It is determined whether a digital watermark is included in the detection target video by comparing the correlation value calculated in the correlation value calculating step with a preset threshold value. And a watermark determination step of outputting watermark detection bit information. The difference calculation step is
10. The luminance difference value is multiplied by a weighting coefficient corresponding to the distance between the pixel and the pixel selected in the pixel selection step for each pixel belonging to the embedding target pixel region. Digital watermark detection method. A computer that determines whether the detection target video includes a predetermined digital watermark,
A region separation step of separating the detection target image into an embedding target pixel region that is a region of a pixel in which a digital watermark is embedded and an embedding prohibited pixel region that is a region of a pixel in which the digital watermark is not embedded;
A pixel selection step of selecting, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area that is estimated to have a small luminance variation from the pixel in the original image signal;
A difference calculation step for calculating a luminance difference value with respect to each pixel belonging to the embedding target pixel region with the pixel selected in the pixel selection step;
A detection pattern generation step for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image regions based on key information;
Correlation value calculation for calculating a correlation value between the luminance difference value calculated in the difference calculation step and the detection pattern of the digital watermark generated in the detection pattern generation step for all pixels belonging to the embedding target pixel Steps,
It is determined whether a digital watermark is included in the detection target video by comparing the correlation value calculated in the correlation value calculating step with a preset threshold value. An electronic watermark detection program for executing a watermark determination step for outputting watermark detection bit information. A computer that determines whether the detection target video includes a predetermined digital watermark,
A region separation step of separating the detection target image into an embedding target pixel region that is a region of a pixel in which a digital watermark is embedded and an embedding prohibited pixel region that is a region of a pixel in which the digital watermark is not embedded;
A pixel selection step of selecting, for each pixel belonging to the embedding target pixel area, a pixel belonging to the embedding prohibited pixel area that is estimated to have a small luminance variation from the pixel in the original image signal;
For each pixel belonging to the embedding target pixel area, a pixel limiting step for limiting and extracting only pixels satisfying a selection standard in the pixel selection step;
A difference calculating step for calculating a luminance difference value between the pixel extracted in the pixel limiting step and the pixel selected in the pixel selecting step;
A detection pattern generation step for generating a detection pattern of a digital watermark that changes in the time direction for each of a plurality of image regions based on key information;
Correlation value calculation for calculating the correlation value between the luminance difference value calculated in the difference calculation step and the detection pattern of the digital watermark generated in the detection pattern generation step for the pixels extracted in the pixel limiting step Steps,
It is determined whether a digital watermark is included in the detection target video by comparing the correlation value calculated in the correlation value calculating step with a preset threshold value. An electronic watermark detection program for executing a watermark determination step for outputting watermark detection bit information. The difference calculation step is
13. The luminance difference value is multiplied by a weight coefficient corresponding to the distance between the pixel and the pixel selected in the pixel selection step for each pixel belonging to the embedding target pixel region. Digital watermark detection program.

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