JP3926199B2 - Scaling rate detection method, program, receiving apparatus and system using digital watermark - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for detecting a scaling rate representing an enlargement / reduction rate of a video from a video imprinted with a digital watermark, that is, a video embedded with a digital watermark.
[0002]
[Prior art]
For the purpose of copyright protection and the like, it has been proposed to imprint digital watermarks on images. Here, digital watermarking means imprinting noise in a video to conceal information so that it cannot be seen.
[0003]
In this case, it is often necessary to detect the digital watermark on the receiving side that receives the video imprinted with the digital watermark. However, when detecting a digital watermark, for example, if the video itself imprinted with the digital watermark is reduced to, for example, about 80%, the amount of information in the digital watermark also decreases to about 80%. It becomes difficult to detect. As described above, since the detection of the digital watermark depends on the enlargement / reduction ratio of the video, that is, information on how much the video has been scaled (scaling rate), the scaling of the video is performed when the digital watermark is detected. It is important to detect the rate. Thus, the digital watermark becomes difficult to detect as the video is scaled. Further, in this case, it is necessary to consider that the scaling rate is changed in the horizontal direction and the vertical direction of the video.
[0004]
[Problems to be solved by the invention]
2. Description of the Related Art Conventionally, when detecting a scaling rate, a digital watermark is detected at all possible scaling rates, and a full-scaling search method is employed in which the scaling rate at which the digital watermark can be detected is the video scaling rate. When this all-scaling search method is used, if the scaling rate is calculated in a fine order, the combination of the scaling rate in the horizontal direction of the video and the scaling rate in the vertical direction becomes very large. For this reason, the all-scaling search method has the disadvantages that it takes time to detect the scaling rate and the detection accuracy is poor.
[0005]
[Means for Solving the Problems]
An object of the present invention is to provide a scaling rate detection method capable of detecting a scaling rate in an image using a digital watermark with high accuracy in a short time.
[0006]
Another object of the present invention is to provide a scaling rate detection method using a digital watermark that facilitates detection of the scaling rate.
[0007]
Still another object of the present invention is to provide a scaling detector that can accurately calculate a scaling rate even if a video shift or the like occurs.
[0008]
According to the first aspect of the present invention, a step of receiving a video imprinted with a plurality of digital watermarks having different pattern frequencies, and a scaling rate representing an enlargement / reduction rate of the video from the plurality of digital watermarks Detecting a scaling factor using a digital watermark.
[0009]
According to a second aspect of the present invention, in the first aspect, in the step of detecting the scaling rate, an approximate scaling rate in the video is obtained by using a digital watermark having a low frequency among the plurality of digital watermarks. There is obtained a scaling ratio detection method characterized by having a first stage to be obtained, and then a second stage to obtain a scaling ratio of a fine-order video using a high-frequency digital watermark.
[0010]
According to a third aspect of the present invention, in the second aspect, at least one of the steps of obtaining the first and second scaling ratios is embedded in a video and a pixel value included in the video. A scaling rate detection method characterized in that it includes a step of calculating an inner product with the code value of the digital watermark.
[0011]
According to a fourth aspect of the present invention, in the third aspect, in the third aspect, the step of calculating the inner product takes the inner product by shifting the pattern in the horizontal direction and the vertical direction by a pattern taking the inner product in consideration of the shift of the image. A method for detecting a scaling rate, characterized in that it includes a step of calculating.
[0012]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, at least one of the first and second stages includes a step of changing a scaling rate in a predetermined step, and inner product accumulation A scaling rate detection method is characterized in that the scaling rate is determined based on the maximum value obtained by adding the values over a predetermined number of frames.
[0013]
According to a sixth aspect of the present invention, in the computer-readable program, the program receives a video imprinted with a plurality of digital watermarks having different pattern frequencies, and the plurality of digital watermarks. And a step of detecting by a computer a scaling rate that represents the enlargement / reduction rate of the video.
[0014]
According to a seventh aspect of the present invention, there is provided a receiving device that receives a video imprinted with a plurality of digital watermarks having different pattern frequencies, and the receiving device expands the video from the plurality of digital watermarks. A receiving apparatus characterized by comprising a detecting means for detecting a scaling rate representing a reduction rate is obtained.
[0015]
According to an eighth aspect of the present invention, in the seventh aspect, the detection means uses a first digital watermark having a high frequency among the plurality of digital watermarks to obtain a rough scaling rate in the video. And a second means for obtaining a scaling rate of a fine-order video using a digital watermark with a low frequency thereafter.
[0016]
According to a ninth aspect of the present invention, in the seventh or eighth aspect, the system includes a digital recording device that receives an image from a satellite, and the receiving device serves as a scaling rate detector in the digital recording device. A system characterized by being incorporated is obtained.
[0017]
According to a tenth aspect of the present invention, in the seventh or eighth aspect, the system includes a DVD, and the receiving device is incorporated as a scaling factor detector in a digital recording device that records video from the DVD. A system characterized by the above is obtained.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIGS. 1A and 1B, a digital watermark printed on a video in the present invention will be described. First, in the present invention, two types of digital watermarks as shown in FIGS. 1A and 1B are imprinted on a video to be imprinted with digital watermarks. The digital watermark shown in FIG. 1A divides a video area into four blocks, and a digital watermark represented by A and B is inserted into each block. In this example, two blocks of digital watermark A and two blocks of digital watermark B are provided. In other words, the digital watermark A having the same value is inserted in the digital watermark A block, and the digital watermark B having the same value is similarly inserted in the digital watermark B block. As described above, when the video area is roughly divided into four blocks, the frequency of the code pattern constituting each of the digital watermarks A and B is low.
[0019]
On the other hand, the digital watermark shown in FIG. 1B divides the video area into 40 blocks, and the digital watermark A or B is inserted into the video of each block. For this reason, the code pattern constituting the digital watermark A or B is inverted at a higher frequency than in the case of FIG. As described above, the present invention is characterized in that a plurality of digital watermarks A and B having different pattern frequencies are inserted and used for scaling. Here, A and B have values that cancel each other when taking the inner product, for example, 0 and (+ 1 / −1). In this way, a plurality of digital watermarks having different frequencies are inserted or imprinted in the video by adding each corresponding code, for example. Here, it is assumed that scaling has been performed on the video after insertion of the digital watermarks A and B.
[0020]
Next, referring to FIG. 2, as described above, when a video imprinted with a plurality of digital watermarks A and B having different frequencies is received, the receiving apparatus side performs scaling according to an embodiment of the present invention. A rate detection method is executed. In this example, the period of a digital watermark with a high pattern frequency (FIG. 1B) is M in both the horizontal and vertical directions, and the period of a digital watermark with a low pattern frequency (FIG. 1A) is in the horizontal and vertical directions. Both are N (N> M). The scaling rate detection method according to the present invention can be realized by using a software program incorporated in the receiving apparatus and a CPU that executes the program.
[0021]
First, in step S1 of FIG. 2, the pattern is scaled at a scaling rate of 10% by using a digital watermark pattern having a low pattern frequency. This means an operation of expanding / contracting the pattern with N / 10 width. When the scaling rate is determined, the inner product is calculated in each block.
[0022]
Here, referring also to FIG. 3, the pixel values P11. . . P16 and the digital watermark pattern code value C11. . . . . A method for calculating the inner product with C16 will be described. The inner product is P11 · C11 + P12 · C12 + P13 · C13 + P14 · C14 +. . . . Given in.
[0023]
In step S1 shown in FIG. 2, the inner product is independently taken even when the digital watermark pattern is shifted to the width and height of the pattern in consideration of the blur of the video. The calculation of the inner product is performed over the number of frames that can extract the digital watermark, the inner product values over these frames are accumulated, and the inner product accumulation value is obtained for each block.
[0024]
In step S2, it is determined whether or not there is a negative inner product accumulated value in the block. If a negative inner product accumulated value exists, the process returns to step S1 (step S1: Yes). On the other hand, if all the inner product accumulation values are positive, the inner product accumulation values are added over all the blocks in the frame, and the maximum addition result is obtained among the addition results. Subsequently, the digital watermark pattern corresponding to the maximum addition result is determined as a pattern having a close scaling rate. Thus, in step S3, a pattern close to the scaling rate is roughly determined.
[0025]
Next, the process proceeds to step S4 in which an inner product is calculated using a digital watermark pattern having a high frequency. In step S4, the inner product of each block is calculated at a scaling rate of M / 10 width in both the horizontal and vertical directions using a digital watermark pattern with a high frequency. Also in step S4, in the same way as in step S1, considering the image shift, the inner product is calculated for the pattern in which the pattern is shifted independently up to the pattern width and height. The inner product is performed in the same manner as in FIG.
[0026]
In this case, as in step S1, the inner product is calculated over the number of frames from which the digital watermark can be extracted, and the inner product value over these frames is calculated as the inner product integrated value.
[0027]
In step S5, it is determined whether there is a negative inner product accumulated value in the block. If there is an inner product accumulated value having a negative value (step S5: Yes), the process returns to step S4.
[0028]
If there is no negative inner product accumulation value (step S5: No), in step S6, the inner product accumulation value is added over all the blocks in the frame, and the pattern corresponding to the maximum addition value is imprinted with the digital watermark pattern. And the scaling rate of the video is determined.
[0029]
As described above, in the present invention, the scaling rate is roughly determined using the digital watermark pattern having a low pattern frequency, and then the fine scaling rate is determined using the digital watermark pattern having a high pattern frequency. In this scaling rate detection method, the scaling rate detection time can be shortened, and further, a fine order scaling rate can be calculated. In the above-described embodiment, in steps S1, S2, and S3 (first stage) for roughly determining the scaling rate, the inner product is calculated, and further, the scaling rate in a fine order is determined in step S4. In S5 and S6 (second stage), the inner product is calculated, but the inner product may be calculated in one of the stages, or the scaling rate may be determined by another method.
[0030]
With reference to FIG. 4, a system using the method for detecting the scaling rate of video and digital watermark according to the present invention will be described. The system shown in FIG. 4 is a system for receiving a digital image with the above-described digital watermark inserted from a satellite, and includes a BS antenna 11, a BS digital broadcast receiver 12, DVD recording devices 13 and 16, and a DVD reproducing device 14. And a VTR editing device 15. Here, the DVD recording devices 13 and 16 include a detector / inserter that detects and inserts a write-once digital watermark including copy control information, and a scaling rate detector that executes the scaling detection method according to the present invention. Suppose that The illustrated VTR editing apparatus 15 is capable of enlarging / reducing video.
[0031]
In the above-described system, the above-described digital video is received by the BS antenna 11 and scaled in the BS digital tuner 12. This digital video is recorded together with electronic watermark information by the DVD recording device 13. The digital image on which the digital watermark information is imprinted is scaled by the VR editing device 15 and recorded again on the DVD recording device 16.
[0032]
Here, the write-once type digital watermark detector for copyright protection provided in the DVD recording devices 13 and 16 receives N-bit information, and from the N-bit information, for example, “copy once” “copy prohibited Copy control information such as “,” “copy free”, etc. can be acquired / added.
[0033]
The BS digital tuner 12 receives digital video from the satellite. The image received from the satellite is imprinted with a pattern with a high frequency for detecting the scaling factor and a digital watermark with a low frequency. In this video, a digital watermark for detecting the scaling rate and a digital watermark for write-once copyright protection are imprinted as “one copy is possible” and scaled by the BS digital tuner 12.
[0034]
When this video is recorded on the DVD recording devices 13 and 16, the scaling rate detector performs the operation described with reference to FIG. That is, the scaling detector takes an inner product with a scaled digital watermark pattern for detecting a scaling factor having a low frequency, obtains 10 integrated values, and calculates a sum of the integrated values. Here, considering the horizontal / vertical deviation of the video signal, the inner product is calculated for those obtained by shifting the pattern in the horizontal / vertical directions, and the integrated value is calculated. The pattern that is the largest among the sums of the integrated values is determined as the pattern that is closest to the scaled pattern of the low frequency pattern.
[0035]
Next, a finer scaling rate is obtained by taking an inner product with a scaled digital watermark pattern for detecting a scaling rate having a high frequency. Thus, the electronic watermark is accurately detected, and the illustrated DVD recording apparatus 16 detects that copy prohibition is imprinted as the copy control information, and stops recording.
[0036]
Referring to FIG. 5, another system capable of performing the scaling rate detection method according to the present invention is shown. As shown in FIG. 5, the scaling rate detection digital watermark may be recorded on the DVD 21 and input from the DVD 21, not by satellite broadcasting. Here, a DVD 21 printed with a scaling ratio detection digital watermark and a write-once type digital watermark “capable of one copy” is scaled by a VTR or the like and recorded on a video tape, and recorded on a video tape. Use to zoom in / out. In this example, the DVD recording device 23 is used to record again on the DVD. In this case, the DVD recording device 23 includes a scaling ratio detector, detects the scaling ratio using the above-described digital watermark, and inserts the above-described write-once digital watermark information. After that, it is played back by the DVD playback device 24 and is also stored on the magnetic tape in an enlarged and reduced state as an analog signal by the VTR editing device 25. When an analog video signal stored in the VTR editing device 25 is recorded on the DVD recording device 26 again, the digital watermark is detected by the scaling rate detector provided in the DVD recording device 26 and copy prohibition is performed. After recording the digital watermark, the recording is stopped.
[0037]
【The invention's effect】
Conventionally, when obtaining a video scaling rate, digital watermarks are detected at any scaling rate, and the detected scaling rate is used as the video scaling rate. However, according to the present invention, it is possible to obtain a fine scaling rate with a low-frequency digital watermark after obtaining a rough scaling rate with a high digital watermark among digital watermark patterns having two types of pattern frequencies. , The time to detect the scaling rate has been shortened, and the scaling rate on a fine order has been required.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams for explaining a digital watermark pattern used in the present invention in association with a pattern frequency.
FIG. 2 is a flowchart for explaining a scaling rate detection method according to the present invention.
FIG. 3 is a diagram for explaining an inner product calculation method used in the scaling rate detection method according to the present invention;
FIG. 4 is a diagram illustrating an example of a system to which a scaling rate detection method according to the present invention can be applied.
FIG. 5 is a diagram showing another example of a system to which the scaling rate detection method according to the present invention can be applied.
[Explanation of symbols]
A, B Digital watermarks 11 different from each other 11 BS antenna 12 BS digital broadcast receiver 13, 16 DVD recording device 14 DVD playback device 15 VTR editing device 21 DVD
22 VTR editing device 23 DVD recording device 24 DVD playback device 25 VTR editing device 26 DVD recording device

Claims (8)

A first electronic watermark having a low pattern frequency, the steps of the second electronic watermark with a high pattern frequency than the first watermark, receives an image imprinted on top, the first and second Detecting a scaling rate representing an enlargement / reduction rate of the video from a video imprinted with the electronic watermark of
The step of detecting the scaling rate includes a first step of obtaining a rough scaling rate in the video using the first digital watermark, and then a scaling rate of a fine order video using the second digital watermark. And a second stage for obtaining the scaling rate.   2. The method of claim 1, wherein at least one of the first and second stages includes a step of calculating an inner product of a pixel value included in the video and a code value of a digital watermark embedded in the video. A scaling rate detecting method characterized by the above.   3. The step of calculating an inner product according to claim 2, wherein the step of calculating the inner product includes a step of calculating the inner product by shifting the pattern in which the inner product is taken in the horizontal direction and the vertical direction in consideration of a video shift. Scaling rate detection method. In any one of Claims 1-3,
At least one of the first and second stages includes a step of changing the scaling rate in a predetermined step, and the scaling rate is determined by a maximum value of values obtained by adding the inner product accumulated values over a predetermined number of frames. A scaling rate detection method characterized by In a computer readable program,
The program includes a first watermark having a low pattern frequency, the steps of the second electronic watermark with a high pattern frequency than the first watermark, receives an image imprinted on top, the received A scaling rate detection step of detecting a scaling rate representing the enlargement / reduction rate of the video from a captured image by a computer,
In the scaling rate detection step, a first step of obtaining a rough scaling rate in the video using the first digital watermark, and then a scaling rate of a fine-order video using a second digital watermark are obtained. And a second stage. Comprising a first digital watermark having a low pattern frequency, and a second electronic watermark with a high pattern frequency than the first watermark, a receiving apparatus for receiving an image imprinted on top,
The receiving device includes detection means for detecting a scaling rate representing an enlargement / reduction rate of the video from the received video,
The detection means uses a first step of obtaining a rough scaling rate in the video using the first digital watermark, and then uses a second digital watermark to obtain a scaling rate of a fine order video. And a receiving device.   7. The system according to claim 6, further comprising a DVD recording device that receives video from a satellite, wherein the receiving device is incorporated in the DVD recording device as a scaling factor detector.   7. The system according to claim 6, wherein the receiving device is incorporated as a scaling detector in a DVD recording device that records video from the DVD.

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