JPH11146342A - Recording and reproducing method, recording and reproducing device of electronic watermark information and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect electronic watermark information at reproduction by recording a video signal, the electronic watermark information buried in the video signal and a reference signal inserted into a position different from the electronic watermark information in a recording medium. SOLUTION: The video signal reproduced from the recording medium is detected by a synchronization detecting circuit 50 and a position detecting pulse of the electronic watermark information is generated based on a synchronizing signal by a position detecting pulse generating circuit 51 of the watermark information. Furthermore, the position detecting pulse of the reference signal inserted into the video signal and recorded is generated by a position detecting pulse generating circuit 52 of the reference signal. The position detecting pulse is supplied to a sample-and-hold circuit 53 and amplitude of the reference signal is subjected to sample-and-hold. Change of the amplitude of the reference signal supplied to a gain ratio calculating circuit 54 is calculated as the change of a gain of a luminance signal. A gain signal of the corrected luminance signal is supplied to a watermark information detecting circuit 56 and the electronic watermark information is detected by a signal of the information position detecting circuit 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for recording or reproducing image data, especially digital watermark information embedded in a video signal, as a technique for controlling reproduction or recording of an original image or clarifying the source of the image. The present invention relates to a method and apparatus for recording and reproducing digital watermark information and a recording medium.

[0002]

2. Description of the Related Art A digital watermark (water m) is applied to a video signal.
ark, data hiding or embeddi
ng) Several methods have been proposed for embedding information. A typical example is a technical report of the Institute of Image Information and Television Engineers (ITE Technical Report V).
ol 21. No. 31. pp3-8 data hiding technology). As a conventional information embedding technology, Nikkei Electronics (1997) 683 No. 9
It is described on pages 9 to 107. In these prior arts, information different from the information that the original video signal has is embedded in the video signal in part of the video signal by utilizing the statistical properties of the image, and this embedded information is used during playback. It is shown that a control signal for determining the source of the original image and further determining whether or not reproduction is possible is obtained.

[0003]

However, these documents describe recording means in detail, but do not describe in detail the means for detecting digital watermark information during reproduction. In particular, such digital watermark information is V
Once recorded and reproduced by a TR or an optical disk device, the signal level of the information fluctuates depending on the reproduction characteristics of the VTR or the optical disk device. The reproduced waveform also varies depending on the frequency characteristics of the VTR and the optical disk device.

An object of the present invention is to provide a digital watermark information recording / reproducing method, a recording / reproducing apparatus, and a recording medium which can easily detect digital watermark information during reproduction.

Another object of the present invention is to provide a recording / reproducing method, a recording / reproducing apparatus, and a recording medium for digital watermark information capable of easily reproducing embedded digital watermark information even if the reproduction characteristics of the reproducing apparatus fluctuate. Is to do. Still another object of the present invention is to provide a digital watermark information recording / reproducing method, a recording / reproducing apparatus, and a recording medium which can easily detect the digital watermark information even if the signal level of the digital watermark information fluctuates. is there. Still another object of the present invention is to provide a circuit configuration in which detection of digital watermark information contained in a video signal once recorded in a recording device is not so affected by the reproduction level and frequency characteristics of the recording device. .

[0006]

In order to achieve the object of the present invention, a recording medium according to the present invention has a video signal, digital watermark information embedded in the video signal, and inserted at a position different from the digital watermark information. The recorded reference signal is recorded. The method for recording digital watermark information according to the present invention includes a step of embedding the digital watermark information in the video signal while reducing disturbance to the video signal, and inserting and recording a reference signal at a position different from the digital watermark information. ing. Further, the method for recording and reproducing digital watermark information according to the present invention includes the steps of embedding digital watermark information in a video signal, inserting a reference signal in a position different from the digital watermark information, and recording the digital watermark information with less interference with the video signal. Reproducing the reference signal, and correcting the digital watermark information with the reference signal.

Further, in the method for recording digital watermark information according to the present invention, a step of calculating a range that can be visually endured even when a luminance value of a luminance signal included in a video signal is changed,
Changing the luminance value of the luminance signal at a predetermined position within the calculated variable range. A method for recording digital watermark information according to the present invention includes a step of calculating a range that can be visually endured even when a luminance value of a luminance signal included in a video signal is changed, and a luminance signal at a predetermined position. A step of changing the luminance value when the luminance value to be changed is within the calculated variable range.

A method for reproducing digital watermark information according to the present invention reduces a video signal and interference to the video signal,
Detecting a reference signal to detect digital watermark information from a recording medium on which digital watermark information embedded in a video signal and a reference signal inserted at a position different from the digital watermark information are recorded; Correcting the digital watermark information. A method of reproducing digital watermark information according to the present invention includes a video signal, digital watermark information embedded in a video signal by changing a luminance value of a luminance signal included in the video signal, and a position where the digital watermark information is embedded. Comprises a step of detecting a reference signal in order to reproduce digital watermark information from a recording medium on which a reference signal inserted at a different position is recorded, and a step of correcting a luminance value of the digital watermark information using the reference signal. ing. The digital watermark information recording / reproducing method according to the present invention comprises a video signal, digital watermark information embedded in the video signal with less interference with the video signal, and a reference signal inserted at a position different from the digital watermark information. And a step of detecting digital watermark information based on the reference signal. A method for recording digital watermark information according to the present invention includes the steps of: combining a video signal, digital watermark information embedded in the video signal with less disturbance to the video signal, and a reference signal inserted at a position different from the digital watermark information. Recording step. In the method of reproducing digital watermark information according to the present invention, the video signal, the digital watermark information embedded in the video signal with less disturbance to the video signal, and the reference signal inserted at a position different from the digital watermark information are included. In order to reproduce the digital watermark information from the recorded recording medium, a step of detecting the digital watermark information based on the reference signal is provided.

A digital watermark recording apparatus according to the present invention includes a changeable range detection circuit for calculating a change range of a luminance value according to a luminance value of a luminance signal included in a video signal, and a luminance of a luminance signal at a predetermined position. A digital watermark information embedding processing circuit for embedding digital watermark information by changing a value within the calculated variable range. An electronic watermark recording apparatus according to the present invention includes a changeable range detection circuit that calculates a change range of a luminance value according to a luminance value of a luminance signal included in a video signal, and a luminance signal at a predetermined position. If the calculated brightness value is within the calculated variable range,
A digital watermark information processing circuit for embedding digital watermark information by changing a luminance value. A digital watermark reproducing apparatus according to the present invention records a video signal, digital watermark information embedded in the video signal by reducing interference with the video signal, and a reference signal inserted at a position different from the digital watermark information. Detecting means for detecting the digital watermark information based on the reference signal in order to reproduce the digital watermark information from the recorded recording medium. In the digital watermark reproducing apparatus according to the present invention, the detection means includes a detection signal generation circuit for generating a detection signal for detecting the reference signal from the synchronization signal, a sample and hold circuit for sampling and holding the amplitude of the reference signal by the detection signal, A gain ratio calculation circuit that calculates a gain ratio from the amplitude of the reference signal obtained by the sample and hold circuit, a correction circuit that corrects a luminance signal included in the video signal based on a result calculated from the gain ratio calculation circuit, and a correction circuit. A digital watermark information detecting circuit for detecting digital watermark information from the luminance signal thus obtained by using a detection signal.

In the digital watermark reproducing apparatus according to the present invention, the detecting means includes a detection signal generating circuit for generating a detection signal for detecting the reference signal from the synchronization signal, and a sample for sampling and holding the amplitude of the reference signal by the detection signal. A hold circuit, a gain ratio calculation circuit that calculates a gain ratio from the amplitude of the reference signal obtained by the sample hold circuit, and a detection circuit that detects digital watermark information from a luminance signal included in the video signal using the detection signal And a correction circuit that corrects the amplitude of the detected digital watermark information with the gain ratio calculated by the gain ratio calculation circuit. A digital watermark reproducing apparatus according to the present invention includes a digital watermark information detection circuit that detects a digital watermark signal from a video signal,
A reference signal detection circuit for detecting a reference signal, and a correction circuit for correcting the amplitude of digital watermark information according to a decrease in the amplitude of the reference signal are provided. In the above digital watermark information reproducing apparatus, the correction circuit includes a gain ratio calculation circuit for calculating a gain reduction ratio of the reference signal. In the digital watermark information reproducing apparatus, the digital watermark information detecting circuit includes a digital watermark information position generating circuit for generating a digital watermark information position detecting signal based on the synchronization signal.

In the digital watermark information reproducing apparatus, the reference signal detecting circuit includes a reference signal position detecting circuit for generating a reference signal position detecting signal based on the synchronization signal. In the present invention, a reference signal is added to a specific position of a video signal in advance for detection, and digital watermark information is reproduced based on this signal during reproduction. The reference signal is embedded in a part of the horizontal synchronization signal period, outside the video display period, that is, around the back porch or front porch, or outside the image display area. Then, upon detection, the digital watermark information embedded based on the signal level is reproduced. Here, the recording position of the reference signal may be a vertical synchronization signal period. Further, a timing signal serving as a reference is recorded at the beginning of a video signal, and at the time of reproduction, the recording level and recording position of the digital watermark information are found from the level of the reference signal and the reproduction timing to detect the digital watermark information. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method and apparatus for recording and reproducing digital watermark information according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a reference signal of digital watermark information used in a method and apparatus for recording and reproducing digital watermark information according to the present invention, and a recording position thereof. In the figure, reference numeral 1 denotes a video display area of a display device, for example, a television receiver, and 2 denotes an overscan area, which is a portion obtained by removing the video display area 1 from a region surrounded by a dotted line. Reference numeral 3 denotes an insertion position of the reference signal recorded in the overscan area 2. This reference signal is inserted or added to the video signal over one or more lines. The video signal provided with the reference signal is recorded on a recording medium. This reference signal may be inserted so as to be located in the video display area 1,
Since there is a possibility that the video signal will be disturbed, it is better to insert the signal so that it is located in the overscan area.

FIG. 2 is a schematic diagram showing another embodiment of a method and apparatus for recording and reproducing digital watermark information according to the present invention, a reference signal of digital watermark information used for a recording medium, and a recording position thereof. In FIG. 2, reference signals 4, 5
Are inserted or added to the video signal so as to be located in the upper overscan area and the lower overscan area, respectively. The upper reference signal 4 and the lower reference signal 5 are inserted into the video signal so as to be located over one line or a plurality of lines, respectively. In general, a TV signal sometimes sags at the upper and lower parts of the screen due to the influence of the transmission system. That is, even if a TV signal of the same luminance is transmitted to all the screens, the TV signal changes due to the influence of the transmission system, and when this is reproduced, the phenomenon that the luminance changes between the upper part and the lower part of the screen. Occurs. This is particularly likely to occur in the case of light gray.

Due to this phenomenon, the luminance of the digital watermark information may change asymmetrically. In the embodiment of FIG.
To correct this, reference signals 4 and 5 are inserted in the upper and lower portions of the overscan area. In this arrangement, the upper reference signal 4 is displayed at the upper part of the screen, and the lower reference signal 5 is displayed at the lower part of the screen.
Can be used for correction. Further, this detection level can be corrected by adding the upper reference signal 4 and the lower reference signal 5 and using the average value. Therefore, even if the luminance changes due to the sag, the detection level of the digital watermark information can be corrected.

FIG. 3 is a schematic diagram showing still another embodiment of a recording / reproducing method and a recording / reproducing apparatus for digital watermark information, a reference signal of digital watermark information used for a recording medium and a recording position thereof according to the present invention. In the present embodiment, the reference signals 6 and 7 are inserted so as to be located at an upper part and a lower part of the overscan area 2. In this embodiment, 1
When the reference signals 6 and 7 are added to all the lines, the signals 6 and 7 disturb the video signal during the video display period, so that the reference signal 6 and 7 are positioned at the edge of the screen in order to prevent the screen from being difficult to see. , 7 are additionally recorded. In this embodiment, the reference signals 6 and 7 are inserted so that the reference signals 6 and 7 are located in the upper part and the lower part of the overscan area 2. May be recorded. In VTR,
Since the head is switched under the tape and the gap between the tapes is small, the reference signal 6 can be recorded in a place where the recording space of the tape is located compared to the reference signal 7, so that the VT
For R, it is more advantageous to use the reference signal 6. As the reference signals 6 and 7, a signal representing the white peak level of the luminance signal is added to the video signal. Therefore, when the luminance of a video signal is changed in order to embed digital watermark information, correct digital watermark information can be obtained by correcting the luminance of the video signal using the reference signal 6 or 7. That is, the digital watermark information is embedded in the video signal so as to change the brightness of the video signal as described later, and the brightness level changes in the transmission system. Since the luminance level of the signal can be corrected, digital watermark information can be easily detected.

FIG. 4 is a schematic diagram showing still another embodiment of the recording / reproducing method and the recording / reproducing apparatus of the digital watermark information, the reference signal of the digital watermark information used for the recording medium and the recording position according to the present invention. In FIG. 4, the reference signals 8, 9
Is the overscan area 2 immediately before and after the horizontal synchronization signal.
In the example shown in FIG. That is, the reference signals 8 and 9
Are added to the video signal and recorded on the recording device at the beginning and end of the horizontal synchronization signal period. In this embodiment, the reference signals 8 and 9 are added at the beginning and end of the horizontal synchronizing signal period. However, the luminance level of the video signal can be corrected by inserting only at the beginning or end of the horizontal synchronizing signal. .

FIG. 5 is a schematic diagram showing still another embodiment of the recording / reproducing method and recording / reproducing apparatus for digital watermark information, the reference signal of the digital watermark information used for the recording medium and the recording position according to the present invention. In this embodiment, the first to third reference signals 11, 12, and 13 having different luminance levels are provided.
Are provided in the overscan area 2. In FIG. 5, the reference signals 11 to 13 are provided for each block, but may be provided for each line. 6 (a) to 6 (c) show FIG.
FIG. 5 is a waveform chart showing an example of first, second, and third reference signals, timing signals, and sample-held waveforms shown in FIG. FIG. 6A is a waveform diagram of the first to third reference signals. The first to third reference signals 11 to 13 are inserted between the horizontal synchronization signals 15 and 16 in the overscan area 2. . The amplitudes of the first to third reference signals 11 to 13 are different from each other. For example, the first reference signal 11 has a white level peak amplitude (IRE100 level), and the second reference signal 12 has a half of the white peak (IR
E50 level), and the third reference signal 13 is a signal having the level of IRE10.

FIG. 6B is a waveform diagram showing a timing pulse, and shows sampling timing signals T1, T2, and T3 of the first to third reference signals 11 to 13. The timing signals T1 to T3 are generated at a predetermined time based on the horizontal synchronization signal 15. Timing signal T
1 samples and holds the first reference signal 11, and the timing signals T2 and T3 sample and hold the second and third reference signals, respectively. These timing signals T1 to T3
May be added to the beginning of the video signal. in this case,
It can be used as a timing signal when detecting digital watermark information. Alternatively, it can be used as a signal for correcting a timing signal obtained from a synchronization signal.

FIG. 6C is a waveform diagram of the sampled and held reference signal. The sampled and held first to third reference signals 11a to 13a have amplitudes A1 and A1, respectively, as shown in FIG. 6C. I have A2 and A3. By using the first to third reference signals 11a to 13a having different amplitudes, the first to third reference signals 11a to 13a
Can be confirmed whether the change in the luminance level is linear or non-linear. When the change in luminance changes at a fixed rate regardless of the magnitude of the luminance, that is, when the luminance changes linearly, one of the first to third reference signals 11a to 13a is used to generate digital watermark information. The luminance of the video signal at the point where is embedded can be corrected. When the rate of change of the luminance level changes according to the first to third reference signals,
When the luminance level changes non-linearly, the ratio of the change in luminance to the magnitude of the luminance is approximately obtained from the amplitudes of the first to third reference signals 11a to 13a, and the luminance of the digital watermark information to be detected is determined. The luminance of the digital watermark information is corrected depending on the size of the digital watermark information. By doing so, the luminance of the digital watermark information can be accurately corrected.

Further, the first to third reference signals 11
To 13 are synchronized with the position where the digital watermark information is recorded, so that the timing signals T1, T
2. A reference clock is created based on T3, and the position where the digital watermark information is recorded can be specified by this clock.

As described in the prior art, the digital watermark information is obtained by decomposing an image of an 8 × 8 matrix block at a predetermined position into pixel units, taking the sum of the luminance of each pixel, and embedding in block units. It is carried out. In this case, it is important to accurately synchronize with this block in order to extract digital watermark information during reproduction. Synchronizing the timing signals T1 to T3 with the position where the digital watermark information is embedded and recording this timing signal in synchronization with an 8 × 8 block during recording minimizes the influence on the phase change of the timing signal in the transmission system. It becomes possible. In addition, the first to third amplitude reference signals 11 to 11 taken out simultaneously.
13 are taken into the sample-and-hold circuit, and the digital watermark information embedded in the video signal is detected using this level as a reference level signal, so that the influence of a luminance change in the transmission system can be corrected.

FIG. 7 is a schematic diagram showing still another embodiment of the recording / reproducing method and the recording / reproducing apparatus of the digital watermark information, the reference signal of the digital watermark information used for the recording medium and the recording position according to the present invention. In FIG. 7, the reference signal 21 is inserted in a horizontal blanking period outside the overscan area 2. This position is schematically shown in FIG.
Can be displayed as if it were inserted at the upper right position in the drawing as shown in FIG.

FIG. 8 is a schematic diagram showing still another embodiment of a recording / reproducing method and a recording / reproducing apparatus of digital watermark information, a reference signal of digital watermark information used for a recording medium and a recording position thereof according to the present invention. In FIG. 8, the reference signal 22 is inserted in a vertical blanking period outside the overscan area 2. This position is schematically shown in FIG.
Can be displayed as if it were inserted at the lower right position in the drawing as shown in FIG.

FIG. 9 is a schematic diagram showing the positional relationship between the reference signal shown in FIG. 7 and the horizontal synchronization period, the video display area and the overscan area, and FIG. 10 is a diagram showing the reference signal shown in FIG. FIG. 3 is a schematic diagram illustrating a positional relationship between a display area and an overscan area. As is clear from FIG. 9, the horizontal synchronization period P1 is divided into a video signal period P2, horizontal blanking periods P3 and P4, and a synchronization signal period P5.
The video signal period P2 is divided into a video display period P6 and overscan periods P7 and P8. And the video period P2
Is generally designed to be wider than the screen size P6 in order to avoid chipping on the screen. In this embodiment, the reference signal 21 is inserted and recorded so as to be located outside the video display period P6. In the figure, reference numerals 15 and 16 denote horizontal synchronization signals, and reference numeral 23 denotes a video signal. Although the reference signal 21 is provided after the video signal 23 in FIG. 9, there is no problem if it is provided before the video signal 23.

FIG. 10 is a schematic diagram showing the positional relationship between the reference signal shown in FIG. 8 and the vertical synchronizing period, the video display area and the overscan area. As is clear from FIG. The period is divided into a period P12, vertical blanking periods P13 and P14, and a vertical synchronization signal period P15. The video signal period P12 is divided into a video display period P16 and overscan periods P17 and P18. The video period P12 is generally designed to be generally wider than the screen size P16 in order to avoid any chipping on the screen. In this embodiment, the reference signal 22 is inserted so as to be located outside the video signal period P12 and recorded on the recording medium. In the figure, reference numerals 25 and 26 denote vertical synchronization signals, and reference numeral 27 denotes a video signal between the vertical synchronization signals 25 and 26.

Next, a configuration for processing and reproducing information in which digital watermark information embedded in a recording medium is embedded will be described with reference to FIGS. FIG. 11 (a),
FIG. 11B is a block diagram showing an embodiment of the recording / reproducing apparatus according to the present invention. In FIG. 11A, a recording medium, for example, a disk 31, has a video signal, digital watermark information embedded in the video signal, and a reference signal for correcting an amplitude change when reproducing the digital watermark information. Is recorded. This disc 31 is reproduced by a video player 32. If copying is not prohibited based on the reproduced digital watermark information, the video signal recorded on the disc 31 can be recorded on the VTR 33.

FIG. 11B shows a case where the copied tape 34 is reproduced by the VTR 33. When the tape 34 is duly copied, the tape 34 is reproduced,
If illegally copied, the tape 34 is not reproduced by the VTR 33. Here, the digital watermark information may be used for two purposes. The first is used to check whether the disc 31 has been created legally or illegally. The second is used to check whether the tape copied by the VTR has been copied properly.

Next, when the disc on which the digital watermark information is recorded is reproduced by a regular player, the player reads the digital watermark information to find out that the disc has been properly manufactured. Let's talk about getting started. FIG. 12 is a block diagram showing one embodiment of the reproducing apparatus according to the present invention.

In the drawing, reference numeral 40 denotes a mechanism for reproducing a disk, 41 is a signal processing circuit for processing a reproduced signal, and 42 is an output control circuit for controlling whether or not to output a reproduced output to a player output terminal. And 43 are digital watermark information detecting circuits for detecting digital watermark information. FIG.
As shown in FIG. 2, the information recorded on the disc is reproduced by the reproduction mechanism 40 and output to the signal processing circuit 41. For example, CGMS (Copy Generator
on Management System), SCM
S (Serial Copy Management)
If digital watermark information such as System) is recorded on the disc, this digital watermark information is supplied to the digital watermark information detection circuit 43. The detection circuit 43 decodes the digital watermark information and supplies the decoding result to the output control circuit 42. The output control circuit 42 controls on / off of the reproduction output based on the digital watermark information. When it is detected from the digital watermark information detected by the detection circuit 43 that copying is prohibited, the output control circuit 42 is controlled so as not to output a reproduction output. In FIG. 12, the output of the detection circuit 13 can be supplied to the signal processing circuit 41 to stop the operation of the signal processing circuit 41. In the digital watermark information, the CGMS is 2-bit information, and is composed of information indicating that copying is permitted, that copying is permitted once, and that copying is not permitted. The SCMS is composed of information on whether copying is possible or not. In such a digital watermark information detecting circuit 43, the video signal or information undergoes distortion due to the characteristics of the transmission system during recording and reproduction, and the amplitude changes, and accordingly, the video signal or information is embedded in the video signal or information. There is a problem that the amplitude of the recorded digital watermark information also changes, and the digital watermark information cannot be read.

In order to solve this problem, in the present invention, the reference signal described with reference to FIGS. 1 to 10 is inserted into a video signal (or information). Therefore, FIG.
Also in the block diagram shown in FIG. 2, the detection accuracy is improved by correcting the amplitude of the video signal in which the digital watermark information is embedded using the reference signal. Hereinafter, an example will be described with reference to FIG. 13 in which the detection circuit is calibrated with a reference signal embedded at a specific position of a video signal to increase the detection accuracy of the detection circuit.

FIG. 13 is a block diagram showing an embodiment of a reference signal detecting circuit provided in the reproducing apparatus according to the present invention. In FIG. 13, a video signal reproduced from a recording medium is supplied to a synchronization detection circuit 50, which detects a horizontal synchronization signal or a vertical synchronization signal. Based on the synchronization signal detected by the synchronization detection circuit 50, the watermark information position detection pulse generation circuit 51 generates a pulse for detecting the position of the digital watermark information. Further, a pulse for detecting the position of the reference signal (see FIGS. 1 to 10 and its description) inserted into the video signal and recorded is generated by the reference signal position detection pulse generation circuit 52 based on the synchronization signal. Let it.
The position detection pulse generated by the reference signal position detection pulse generation circuit 52 is supplied to a sample and hold circuit that holds the level of the reference signal. Sample hold circuit 53
Is supplied with a video signal, and the position detection pulse samples and holds the amplitude of a reference signal inserted into the video signal. The amplitude of the sampled and held reference signal is supplied to the gain ratio calculation circuit 54. Since the amplitude of the recorded reference signal is predetermined, the gain ratio calculation circuit 54 can calculate the change in the amplitude of the reference signal, that is, the change in the gain of the luminance signal by the transmission system. The gain ratio of the luminance signal calculated by the gain ratio calculation circuit 54 is supplied to a gain correction circuit 55. The video signal is supplied to the gain correction circuit 55, and the gain of the luminance signal of the video signal is corrected. The video signal in which the gain of the luminance signal has been corrected is supplied to a watermark information detecting circuit 56, and this circuit 5
At 6, the digital watermark information is detected by the pulse supplied from the watermark information position detection circuit 51.

In this embodiment, the gain change in the transmission system of the luminance signal is calculated using the level (amplitude value) of the reference signal included in the reproduced signal, and thereby the gain of the luminance signal of the video signal is calculated. After the correction, the digital watermark information is detected. Even if the luminance signal is distorted in the transmission system, the reference signal is also distorted and transmitted in the same way. By correcting the level fluctuation of the luminance signal with this reference signal, the level fluctuation of the luminance signal due to the transmission system is corrected. Digital watermark information can be reproduced without being affected or with less influence of level fluctuation.

FIG. 14 is a block diagram showing another embodiment of the reference signal detecting circuit provided in the reproducing apparatus according to the present invention. In the embodiment shown in FIG.
5, the gain of the luminance signal is corrected. As shown in FIG. 14, the output of the gain ratio calculation circuit 54 and the video signal are directly supplied to the watermark information detection circuit 56, and the watermark information detection circuit 56 First, the watermark information may be detected, and the luminance gain of the detected watermark information may be corrected using the calculation result of the gain ratio calculation circuit 54. Further, instead of providing a circuit for detecting the position of the reference signal from the synchronization signal, a timing signal detection circuit 57 is provided to detect the timing signals T1 to T3 shown in FIG. The amplitude of the signal may be held. Further, in the present embodiment, the amplitude level of the reference signal has been described. However, as shown in FIG. 6, if the reference signal is inserted and recorded at a predetermined position from the synchronization signal, the reproduction of the digital watermark information is performed. The timing can be corrected, and the digital watermark information can be detected more easily.

FIG. 15 is a block diagram showing an embodiment of a digital watermark information recording apparatus according to the present invention. In this embodiment, the digital watermark information is embedded by changing the luminance of the pixel. In FIG. 15, a video signal is input to an input circuit 61. A luminance signal is extracted from the input circuit 61 and supplied to a changeable range calculation circuit 63. Based on the luminance signal, a range that does not significantly affect the luminance signal even when the luminance signal is changed is calculated. In a part where the luminance change is large, even if the luminance signal is largely changed, the luminance signal does not change much. However, in a part where the luminance change is small, the luminance change amount is visually conspicuous unless the amount of change in luminance is small. Then, the changeable range is calculated in consideration of this. This changeable range calculation circuit 63 can be realized by a CPU of a computer. The calculation result from the changeable range calculation circuit 63 is supplied to the information embedding processing circuit 65, and when the calculation result is within the changeable range, a process of changing the luminance of the video signal and embedding the digital watermark information in the luminance signal is performed. The video signal in which the luminance signal is processed and the digital watermark information is embedded is stored in the memory of the output circuit 67 and output until processing for one screen is completed. In this circuit, the calculation process in the changeable range calculation circuit 63 is performed as follows.

(1) In a place where the change of the edge of the image is large, even if the amplitude of the edge signal is largely changed, there is not much change visually. Conversely, if the change in the edge of the image is small, if the amplitude of the edge signal is greatly changed, the image visually changes greatly. (2) The change range of the image is limited to a range where the image does not visually change or a range where the image does not hinder viewing even if the image changes visually. When the digital watermark information is embedded in this way, an image having a luminance different from that of the original image but not visually changing is obtained. In addition, the changeable range calculation circuit 63 calculates, for each pixel,
The luminance before application of the image processing and the luminance after application are stored, it is confirmed whether or not the luminance is within a changeable range, and the luminance signal is changed only when the luminance falls within the changeable range.

The information embedding circuit 65 first selects a pixel whose luminance is to be changed from the pixels constituting the image. Next, information is embedded by changing the luminance to a specific value for a pixel of which luminance is not within a changeable range among the selected pixels. As a result, a video signal in which digital watermark information is embedded is obtained. This video signal is output from an output circuit 67.
Output to the outside through

In FIG. 15, the reference signal generator 6
The reference signal generated from the generator 68 is supplied to an adder 69, which is added to a video signal in which digital watermark information supplied from an information embedding processing circuit 65 is embedded, and an output circuit 67 is provided. Through a recording medium (not shown).

Next, a method of changing the luminance in the information embedding circuit 65 will be described with reference to FIG. FIG.
6 is a schematic diagram in which the luminance values of the pixels are displayed in a straight line. In the figure, it is assumed that the luminance value of one pixel ranges from 0 to 255. In the present embodiment, the value of the white circle on this number line is a luminance corresponding to a multiple of 16, and corresponds to the embedded information “0”. The value of the black point is a point corresponding to the value of (multiple of 16 + 8), and corresponds to the embedding information “1”. First, the basic operation of the information embedding circuit 65 will be described.
In order to obtain digital watermark information, it is necessary to change the luminance corresponding to the pixel of the image to the nearest white or black circle. That is, when the information to be embedded in the pixel is "0", the information is changed to a white circle, and when the information is "1", the information is changed to a black circle. For example, when the luminance of a pixel is the value of △ in the figure, that is, 30 and the information to be embedded is “0”, the luminance of the pixel is changed to 32, and the information to be embedded is “1”. , The luminance is changed to 24.

Next, the use of the changeable range calculation circuit 63 will be described. When embedding digital watermark information, there is a case where an image visually changes due to a change in luminance of a pixel being too large. In order to prevent this, the range in which the pixel value can be changed must be set within the changeable range. For example, FIG.
In 6, it is assumed that the value of the luminance of the pixel is 30 and the changeable range of the luminance of the pixel is 26 to 33. In this case, if the information to be embedded is “0”, the luminance of the pixel may be changed to 32 as in the above basic operation. However, when the information to be embedded is “1”, the luminance 24 at the change destination is not included in the changeable range, and in this case, the luminance 26 is changed to a value 26 closest to 24.
Or, giving up changing the brightness of this pixel,
The luminance of another predetermined pixel is changed.

Further, a method of extracting digital watermark information from a watermark inserted image, that is, a video signal in which digital watermark information is embedded will be described. First, a pixel whose luminance value has been changed is selected. Since the position of the pixel whose luminance is to be changed is predetermined, it can be selected by a pulse obtained based on the horizontal synchronization signal. That is, the pixel whose luminance has been changed is selected in accordance with the same rule as the pixel selection in the information embedding processing circuit 65.

Next, for each selected pixel, its luminance signal is extracted, and depending on whether the value is a multiple of 16 or a multiple of 16 + 8, the embedded information is “0” or “0”. 1 "is determined. As described above, since the information embedding processing circuit 65 changes the luminance within a changeable range, the luminance may not be accurately changed to a multiple of 16 or (multiple of 16 + 8). Therefore, an error occurs at a certain probability in information extraction. However, this problem can be solved by overlappingly embedding the same information in a plurality of pixels and performing a majority decision in extraction. When detecting the digital watermark information recorded in this way, it is important to correct the level fluctuation of the luminance signal. Therefore, in the present invention, correction is performed using a reference signal recorded in advance in a video signal signal. FIG. 17 shows this state.

FIG. 17 is a schematic diagram showing the situation of luminance correction according to the present invention. In the figure, 70 and 71 indicate the positions of the luminance values of the reference signal recorded in the video signal. That is,
This is the position of the luminance value of the first and second reference signals described with reference to FIG. In the figure, a position 72 is a position of a luminance value of digital watermark information having a luminance value of 128 in which the luminance value of a predetermined pixel is changed. When the amplitude of the luminance signal included in the video signal decreases, the luminance value level of the digital watermark information embedded in the luminance signal also decreases as shown in FIG. 17 and moves to the luminance value position 72a. Similarly, the positions 70 and 71 of the luminance value of the reference signal also move to the positions 70a and 71a. Since the magnitude of the luminance value 256 is known and the luminance value of the reference signal is also known, the luminance value at the position 72a can be changed to the luminance value at the position 72.

If the reproduction side attempts to detect the digital watermark information at the same level as the recording side, the detection may be erroneously made due to a level change. However, in the present invention, since the luminance level on the reproduction side can be corrected by the reference signal recorded in the video signal, the digital watermark information can be detected efficiently.

[0044]

According to the present invention, the luminance level of the digital watermark information is corrected by the reference signal recorded at another position even if the digital watermark information recorded in the video signal is detected, even if the distortion occurs in the transmission system. Therefore, digital watermark information can be detected more accurately.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a digital watermark information recording / reproducing method and recording / reproducing apparatus, a digital watermark information reference signal used in a recording medium, and a recording position thereof according to the present invention.

FIG. 2 is a schematic diagram showing another embodiment of a recording / reproducing method and a recording / reproducing apparatus for digital watermark information, a reference signal of digital watermark information used for a recording medium, and a recording position thereof according to the present invention.

FIG. 3 is a schematic diagram showing still another embodiment of a digital watermark information recording / reproducing method, a recording / reproducing apparatus, a digital watermark information reference signal used in a recording medium, and a recording position thereof according to the present invention.

FIG. 4 is a schematic diagram showing still another embodiment of a recording / reproducing method and a recording / reproducing apparatus for digital watermark information, a reference signal of digital watermark information used for a recording medium and a recording position thereof according to the present invention.

FIG. 5 is a schematic diagram showing still another embodiment of a recording / reproducing method and a recording / reproducing apparatus for digital watermark information, a reference signal of digital watermark information used for a recording medium, and a recording position thereof according to the present invention.

FIG. 6 shows first, second, and third reference signals shown in FIG. 5,
FIG. 4 is a waveform chart showing an example of a timing signal and a sample-held waveform.

FIG. 7 is a schematic diagram showing still another embodiment of a recording / reproducing method and a recording / reproducing apparatus of digital watermark information, a reference signal of digital watermark information used for a recording medium and a recording position thereof according to the present invention.

FIG. 8 is a schematic diagram showing still another embodiment of a digital watermark information recording / reproducing method and recording / reproducing apparatus, a digital watermark information reference signal used in a recording medium, and a recording position thereof according to the present invention.

FIG. 9 is a schematic diagram showing a positional relationship between the reference signal shown in FIG. 7 and a horizontal synchronization period, a video display area, and an overscan area.

FIG. 10 is a schematic diagram showing a positional relationship among a reference signal shown in FIG. 8, a vertical synchronization period, a video display area, and an overscan area.

FIG. 11 is a block diagram showing an embodiment of a digital watermark information reproducing apparatus according to the present invention.

FIG. 12 is a block diagram showing an embodiment of a digital watermark information reproducing apparatus according to the present invention.

FIG. 13 is a block diagram showing an embodiment of a reference signal detection circuit provided in the digital watermark information reproducing apparatus according to the present invention.

FIG. 14 is a block diagram showing an embodiment of a reference signal detection circuit provided in the digital watermark information reproducing apparatus according to the present invention.

FIG. 15 is a block diagram showing an embodiment of a digital watermark information recording apparatus according to the present invention.

FIG. 16 is a schematic diagram in which luminance values of pixels are displayed in a straight line.

FIG. 17 is a schematic diagram showing a situation of luminance correction according to the present invention.

[Explanation of symbols]

3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 2,
Reference numerals 1, 22: reference signal, 50: synchronization detection circuit, 51: watermark information position detection pulse generation circuit, 52: reference signal position detection pulse generation circuit, 53: sample hold circuit, 54
... Gain ratio calculation circuit, 55 ... Gain correction circuit, 56 ... Watermark information detection circuit, 57 ... Timing signal detection circuit, 6
DESCRIPTION OF SYMBOLS 1 ... Input circuit, 63 ... Changeable range calculation circuit, 65 ... Information embedding processing circuit, 67 ... Output circuit, 68 ... Reference signal generator, 69 ... Adder.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshifumi Takeuchi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Multimedia Systems Development Division of Hitachi, Ltd. Address Co., Ltd.System Development Laboratory, Hitachi, Ltd.

Claims (41)

[Claims] 1. A recording medium for recording a video signal, digital watermark information embedded in the video signal, and a reference signal inserted at a position different from the digital watermark information. 2. The recording medium according to claim 1, wherein said digital watermark information is a signal obtained by changing a luminance value of a luminance signal at a predetermined position of said video signal. 3. The recording medium according to claim 1, wherein said reference signal is recorded by being inserted into an overscan area of said video signal. 4. The recording medium according to claim 1, wherein said reference signal is inserted and recorded during a blanking period of a synchronization signal. 5. The recording medium according to claim 1, wherein said reference signal has an amplitude of a white peak value. 6. The recording medium according to claim 1, wherein said reference signal comprises first and second reference signals,
Wherein the reference signal has an amplitude of a white peak, and the second reference signal has an amplitude smaller than that of the first reference signal. 7. The recording medium according to claim 2, wherein said luminance change value of said luminance signal is within a changeable range. 8. An electronic apparatus comprising: a step of embedding digital watermark information in said video signal while reducing interference with a video signal, and inserting and recording a reference signal at a position different from said digital watermark information. How to record watermark information. 9. The method according to claim 8, wherein the reference signal is inserted in an overscan area of the video signal. 10. A recording method according to claim 8, wherein said reference signal is inserted in a blanking period of a synchronization signal. 11. A recording method according to claim 8, wherein said reference signal has an amplitude of a white peak value. 12. A recording method according to claim 8, wherein said reference signal comprises first and second reference signals, wherein said first reference signal has a white peak amplitude, The recording method according to claim 1, wherein the reference signal has an amplitude smaller than an amplitude of the first reference signal. 13. A method of embedding digital watermark information in said video signal by reducing interference to a video signal, inserting and recording a reference signal at a position different from said digital watermark information, and reproducing said reference signal. Correcting the digital watermark information with the reference signal. 14. The method for recording and reproducing digital watermark information according to claim 13, wherein said digital watermark information is a signal in which a luminance value of a luminance signal at a predetermined position of said video signal is changed. Method for recording and reproducing digital watermark information. 15. The digital watermark information recording / reproducing method according to claim 13, wherein said correcting step corrects a luminance value of said digital watermark information by a luminance value of said reference signal. Recording and playback method. 16. A step of calculating a range in which the luminance value of a luminance signal included in a video signal is visually permissible even when the luminance value of the luminance signal is changed, and calculating the luminance value of the luminance signal at a predetermined position in the calculated variable range Recording the digital watermark information. 17. The method for recording digital watermark information according to claim 16, further comprising a step of inserting a reference signal outside a video display area of said video signal. 18. A step of calculating a range in which the luminance value of a luminance signal included in a video signal can be visually perceived even when the luminance value is changed, and wherein the luminance signal at a predetermined position is changed. When it is within the calculated variable range,
Changing the luminance value. 19. The method for recording digital watermark information according to claim 18, further comprising a step of inserting a reference signal outside a video display area of said video signal. 20. Recording in which a video signal, digital watermark information embedded in the video signal, and a reference signal inserted at a position different from the digital watermark information are recorded by reducing interference to the video signal. A method for reproducing digital watermark information, comprising: detecting the reference signal to detect the digital watermark information from a medium; and correcting the digital watermark information with the reference signal. 21. A video signal, digital watermark information embedded in the video signal by changing a luminance value of a luminance signal included in the video signal, and a position different from the position where the digital watermark information is embedded. Detecting the reference signal in order to reproduce the digital watermark information from the recording medium on which the reference signal inserted into the digital signal is recorded, and correcting the luminance value of the digital watermark information with the reference signal. A method for reproducing digital watermark information. 22. A method of reproducing digital watermark information according to claim 21, wherein a step of calculating a gain ratio from said reference signal, a step of correcting a luminance value of said luminance signal with said calculated gain ratio, Detecting the digital watermark information from the luminance signal whose luminance value has been corrected. 23. The digital watermark information reproducing method according to claim 21, wherein a step of calculating a gain ratio from the reference signal, a step of detecting the digital watermark signal from the luminance signal, and a step of detecting the digital watermark are performed. Correcting the amplitude of the information with the calculated gain ratio. 24. A step of recording a video signal, digital watermark information embedded in the video signal by reducing interference with the video signal, and a reference signal inserted at a position different from the digital watermark information. And a step of detecting the digital watermark information based on the reference signal. 25. A recording method comprising the steps of: recording a video signal, digital watermark information embedded in the video signal by reducing interference with the video signal, and a reference signal inserted at a position different from the digital watermark information. A method of recording digital watermark information as a feature. 26. A recording medium in which a video signal, digital watermark information embedded in the video signal by reducing interference to the video signal, and a reference signal inserted at a position different from the digital watermark information are recorded. A method for reproducing digital watermark information, comprising detecting the digital watermark information based on the reference signal in order to reproduce the digital watermark information. 27. A changeable range detecting circuit for calculating a change range of the luminance value according to a luminance value of a luminance signal included in a video signal, and a luminance value of a luminance signal at a predetermined position is calculated. An electronic watermark recording device, comprising: a digital watermark information embedding processing circuit for embedding electronic watermark information by changing within a variable range. 28. A digital watermark recording apparatus according to claim 27, wherein a reference signal generator and an adder for adding a reference signal generated from said reference signal generator to a position outside a video display area of a video signal. An electronic watermark recording device comprising: 29. A changeable range detection circuit for calculating a change range of the luminance value according to a luminance value of a luminance signal included in a video signal, and a luminance signal at a predetermined position, the luminance being changed. A digital watermark recording device, comprising: a digital watermark information processing circuit for changing the luminance value and embedding digital watermark information when a value is within the calculated variable range. 30. A digital watermark recording apparatus according to claim 29, wherein a reference signal generator and said reference signal generated by said reference signal generator are added to a position of said video signal outside a video display area. An electronic watermark recording device comprising an adder. 31. A recording apparatus according to claim 29, wherein said reference signal has an amplitude of a white peak value. 32. A recording apparatus according to claim 29, wherein said reference signal comprises first and second reference signals, wherein said first reference signal has a white peak amplitude and said second reference signal has a white peak amplitude. The recording apparatus according to claim 1, wherein the reference signal has an amplitude smaller than an amplitude of the first reference signal. 33. A video signal, digital watermark information embedded in the video signal by reducing interference to the video signal, and a reference signal inserted at a position different from the digital watermark information are recorded. An apparatus for reproducing digital watermark information, comprising: detecting means for detecting the digital watermark information based on the reference signal in order to reproduce the digital watermark information from a recording medium. 34. An apparatus for reproducing digital watermark information according to claim 33, wherein said detecting means generates a detection signal for detecting said reference signal from a synchronization signal, and said detection means generates said detection signal based on said detection signal. A sample and hold circuit that samples and holds the amplitude of a reference signal, a gain ratio calculation circuit that calculates a gain ratio from the amplitude of the reference signal obtained by the sample and hold circuit, and a result calculated from the gain ratio calculation circuit. An electronic device comprising: a correction circuit that corrects a luminance signal included in a video signal; and a digital watermark information detection circuit that detects the digital watermark information from the corrected luminance signal using the detection signal. A reproduction device for watermark information. 35. An apparatus for reproducing digital watermark information according to claim 33, wherein said detecting means generates a signal for detecting said reference signal from a synchronization signal, and said reference signal is generated by said detection signal. A sample and hold circuit that samples and holds the amplitude of the reference signal; a gain ratio calculation circuit that calculates a gain ratio from the amplitude of the reference signal obtained by the sample and hold circuit; Digital watermark information, comprising: a detection circuit that detects the digital watermark information from a signal; and a correction circuit that corrects the amplitude of the detected digital watermark information based on the gain ratio calculated by the gain ratio calculation circuit. Playback device. 36. A digital watermark information detection circuit for detecting a digital watermark signal from a video signal, a reference signal detection circuit for detecting a reference signal, and a correction circuit for correcting the amplitude of the digital watermark information based on the amplitude of the reference signal. An electronic watermark information reproducing apparatus, comprising: 37. An apparatus for reproducing digital watermark information according to claim 36, wherein said correction circuit has a gain ratio calculating circuit for calculating a gain reduction ratio of said reference signal. 38. A digital watermark information reproducing apparatus according to claim 36, wherein said digital watermark information detecting circuit has a digital watermark information position generating circuit for generating a digital watermark information position detecting signal based on a synchronization signal. A digital watermark information reproducing apparatus. 39. The digital watermark information reproducing apparatus according to claim 36, wherein said reference signal detection circuit has a reference signal position detection circuit for generating a reference signal position detection signal based on said synchronization signal. Digital watermark information playback device. 40. A digital watermark information reproducing apparatus according to claim 36, wherein said reference signal detecting circuit has a timing signal detecting circuit provided for a video signal for detecting a timing signal. apparatus. 41. A video signal, digital watermark information embedded in the video signal, a reference signal inserted at a position different from the electronic watermark information, and a timing signal provided at the head of the video signal. A recording medium characterized by being recorded.