JP4754204B2 - Digital watermark embedding device - Google Patents

Description

  The present invention relates to a digital watermark embedding apparatus that maintains a detection level of a digital watermark embedded in a video and maintains a good image quality of the video signal.

  As a method of embedding a digital watermark, there is a method of embedding a digital watermark by changing, as a parameter, one or more values of moving image data or numerical values obtained from the moving image data, or a numerical value for calculating those values. is there. When an electronic watermark is embedded in a moving image by such a method, moving image data before embedding the electronic watermark is output from a camera or a digital VTR tape. In addition, when using data embedded with a digital watermark in a moving image for broadcasting, distribution, medium recording, etc., the digital watermark is embedded in the moving image of the video signal source, and then encoded for direct broadcasting or distribution. Alternatively, it is common to use a method of recording again on a video signal source such as a recording medium using a hard disk, an optical disk, etc., and decoding and reproducing the encoded data as necessary. At that time, in order to reduce the amount of data necessary for broadcasting, distributing, and recording a moving image, the moving image data is often encoded and compressed by some method. In that case, the original moving image data and the moving image data decoded and reproduced after encoding have different image quality. For this reason, the digital watermark embedded in the input moving image is affected by the encoding method, and depending on the characteristics of each frame constituting the moving image and the characteristics of each area within the frame, From the decoded moving image data, it is sometimes impossible to detect the correct embedded data of the digital watermark.

  On the other hand, in order to ensure that the digital watermark can be detected, it is only necessary to set the parameter so that the digital watermark is strongly embedded. However, since the digital watermark is embedded more than necessary, this time the image quality is unnecessarily degraded. There is a problem of letting you. In many digital watermarks, there is a trade-off between the “strength” when embedding a digital watermark and the image quality, and the “strength” when embedding a digital watermark is more optimal to balance that. It needs to be adjusted. However, if this adjustment is performed artificially, it is difficult to complete it by a single operation, which is extremely inefficient. Therefore, it has been required to automatically detect an electronic watermark and obtain a satisfactory embedding strength that the image quality is within an allowable range. In order to solve this problem, after embedding the digital watermark by the digital watermark embedding unit, the moving image data before recording obtained through the signal processing of coding compression is decoded, and the decoded data is embedded. A system has been proposed in which a digital watermark is detected, a parameter for determining an embedding strength is changed based on the detection result, and embedded in subsequent input moving image data (for example, see Patent Document 1). ).

JP 2003-219376 A

  As described above, the original moving image is encoded after the digital watermark is embedded. At this time, the amount of data is reduced by performing encoding compression using the MPEG method or the like for the use of the moving image. Since then, it has been broadcasting, distributing and recording. In that case, it is known that image quality degradation caused by encoding varies greatly depending on the scene. However, the method according to Patent Document 1 determines the embedding strength with an emphasis on the detection rate of the digital watermark, and does not perform processing that directly considers image quality degradation due to encoding. That is, it is not possible to perform control that changes the embedding strength that predicts the variation in the watermark detection rate in accordance with the deterioration of the image quality. For example, for one scene, the state of the digital watermark is detected for each successive frame, and the embedding strength is determined by adjusting the embedding strength step by step according to the state, so a scene change occurs and the image quality deteriorates When there was a large variation in the image quality, it was impossible to determine the optimum embedding strength according to the image quality degradation. Also, depending on the degree of image quality degradation, even if the embedding strength is set to be the same, it may not be possible to control the digital watermark detection rate to the same value.

  The present invention has been made in order to solve the above-described problems. By controlling the embedding strength to be fed back in addition to the degree of image quality degradation or the detection rate of the digital watermark, a more suitable digital watermark is provided according to the image quality. An object of the present invention is to obtain a digital watermark embedding apparatus capable of determining the embedding strength of the image.

The digital watermark embedding device according to the present invention includes a digital watermark embedding unit that embeds an arbitrarily set embedding strength digital watermark in the input video data, and encodes the video data in which the digital watermark is embedded. The image quality deterioration detection unit for extracting the degree of image quality deterioration of the original moving image data from the converted moving image data, and the electronic image embedded from the moving image data encoded and decoded from the moving image data embedded with the digital watermark A digital watermark detection unit that detects a watermark and extracts a detection rate of the digital watermark, and a predetermined relationship between the degree of image quality degradation, the detection rate of the digital watermark, and the embedding strength that provides the predetermined detection rate of the digital watermark based on, Umakomikyo the predetermined detection rate of the digital watermark corresponding to the rate of detection of electronic watermark extracted in image quality degradation degree and the digital watermark detection unit extracted by the image quality deterioration detection unit is obtained It determines, at a determined value that a embedding strength determination unit for outputting a set value for updating the embedded intensity of the digital watermark embedding unit.

According to the present invention, it is possible to embed an optimum embedding strength that maintains detection of a predetermined digital watermark against image quality degradation by controlling the embedding strength by feeding back the image quality degradation degree and the digital watermark detection rate. There is an effect to.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a digital watermark embedding apparatus according to Embodiment 1 of the present invention.
In the figure, reference numeral 10 denotes a video signal source such as a digital VTR reproducing apparatus, and 20 denotes a digital watermark embedding apparatus. Reference numeral 30 denotes a utilization device that uses a video signal embedded with a digital watermark output from the digital watermark embedding device 20 and uses image data obtained by encoding the video signal, and corresponds to a digital VTR, DVD recorder, transmission or distribution device. To do. The utilization device 30 is configured so that the encoded image data can be branched and decoded and taken out as a monitor output.

  The digital watermark embedding device 20 includes a digital watermark embedding unit 21, an image quality deterioration detection unit 22, and an embedding strength determination unit 24 as a configuration. The image quality deterioration detection unit 22 is a means for extracting the image quality deterioration degree of the decoded moving image data with respect to the original moving image data in units of frames after the digital watermark is embedded and encoded. The embedding strength determination unit 24 calculates the embedding strength corresponding to the predetermined detection rate requested for the digital watermark based on the image quality degradation degree extracted by the image quality degradation detection unit 22, and the calculated value is embedded in the digital watermark embedding. It is a means to output as a setting value of the embedding strength of the embedding part. The digital watermark embedding unit 21 is a unit that embeds the digital watermark of the embedding strength calculated by the embedding strength determining unit 24 in the moving image data output from the video signal source 10.

  FIG. 2 is an explanatory diagram showing the relationship between the image quality degradation level and the digital watermark detection rate when the embedding strength of the digital watermark is fixed. The digital watermark detection rate is obtained from the moving image data output from the decoding unit 32 in the configuration of FIG. As can be seen from FIG. 2, the detection rate of the digital watermark that can be expected when a certain embedding strength is set can be known for each degree of image quality degradation. Therefore, it is possible to determine the next embedding strength value when the image quality deteriorates and the detection rate decreases or when a decrease can be assumed during the operation of the system.

Next, the operation will be described.
The moving image data output from the video signal source 10 is input to the digital watermark embedding unit 21 and the image quality deterioration detection unit 22 of the digital watermark embedding device 20. The embedding strength determination unit 24 can select a plurality of levels of embedding strength, and operates to set a predetermined standard embedding strength for the first moving image data. Therefore, the digital watermark embedding unit 21 embeds a digital watermark with a standard embedding strength in the first moving image data. The moving image data in which the digital watermark is embedded is encoded in the use device 30 by, for example, an encoding unit 31 using an MPEG2 encoding method. The encoded data is decoded by the decoding unit 32 and output to the image quality deterioration detection unit 22 as a monitor output. The image quality deterioration detection unit 22 extracts the degree of image quality deterioration indicating how much the decoded moving image data has deteriorated from the moving image data directly input from the video signal source 10 in units of frames, and embeds them. Output to the strength determination unit 24.

  The embedding strength determination unit 24 calculates an embedding strength appropriate for the extracted image quality degradation level. For example, as shown in FIG. 2, a processing formula for a plurality of embedding strengths is prepared in advance, and the current detection rate for the extracted current image quality degradation degree is calculated using the formula for the current embedding strength. When the current detection rate is equal to or less than a value requested in advance, an embedding strength having a value slightly larger than the current value is selected and output to the digital watermark embedding unit 21 as a setting value for the next embedding strength. As a result, if the detection rate is not improved at the image quality degradation level extracted next time, the same processing is repeated again. In this process, the embedding strength of the first equation that makes the detection rate equal to or higher than the value requested in advance for the current image quality degradation degree may be selected.

  As another processing example of the embedding strength determination unit 24, there is a method using a table illustrated in FIG. This table is divided into a plurality of ranges occupied by the degree of image quality degradation, and an optimum embedding strength for obtaining a predetermined detection rate of digital watermark is set in advance corresponding to each range. The embedding strength determination unit 24 refers to this table using the current image quality degradation level detected by the image quality degradation detection unit 22, determines the optimum embedding strength, and uses the determined new embedding strength as a digital watermark. This is given to the embedding part 21. The digital watermark embedding unit 21 embeds a digital watermark of this embedding strength in the subsequent moving image data until the image quality deterioration degree changes due to a change in video or the like. Therefore, it is possible to set the embedding strength of the detection rate estimated according to the degree of image quality degradation.

  As described above, according to the first embodiment, the degree of image quality degradation caused by embedding and encoding of the digital watermark is extracted, and a predetermined digital watermark detection rate is obtained based on the extracted degree of image quality degradation. The embedding strength to be determined is determined as a set value, and is embedded in the subsequent moving image data. Therefore, by controlling the embedding strength by feeding back the image quality degradation degree, an effect of enabling embedding with the optimum embedding strength that maintains detection of a predetermined digital watermark against the image quality degradation can be obtained. That is, it is possible to predict the fluctuation of the detection rate according to the deterioration of the image quality and change the embedding strength. For example, it is possible to perform embedding that maintains detection of a predetermined digital watermark against image quality degradation that varies greatly depending on the scene. Even if the detection rate of the digital watermark is the same, the embedding strength can be changed to a more suitable one according to the deterioration of the image quality.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing a configuration of a digital watermark embedding apparatus according to Embodiment 2 of the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted in principle.
In the first embodiment, the moving image data of the video signal source 10 is used as the original signal used as the evaluation reference by the image quality deterioration detection unit 22. In the second embodiment, the digital watermark embedding unit 21 The data after embedding was used. Therefore, the image quality deterioration detection unit 22 extracts the image quality deterioration degree of the decoded moving image data after encoding the data with reference to the moving image data in which the digital watermark is embedded. In this case, when the embedding strength determination unit 24 determines the embedding strength, the embedding strength determination unit 24 determines the embedding strength without considering the image quality degradation due to the digital watermark. For example, when a table as shown in FIG. 3 is used, the table data is created in advance obtained under the same conditions.

  As described above, according to the second embodiment, only the degree of image quality degradation caused by encoding is extracted, and a setting value for updating the optimum embedding strength is determined based on the extracted degree of image quality degradation. It is embedded in subsequent moving image data. Therefore, by controlling the embedding strength by feeding back the image quality degradation degree, an effect of enabling embedding with the optimum embedding strength that maintains detection of a predetermined digital watermark against the image quality degradation can be obtained. That is, even if the detection rate of the digital watermark does not change, the change in the detection rate can be predicted according to the deterioration of the image quality, and the embedding strength can be changed. For example, it is possible to perform embedding that maintains detection of a predetermined digital watermark against image quality degradation that varies greatly depending on the scene. Even if the detection rate of the digital watermark is the same, the embedding strength can be changed to a more suitable one according to the deterioration of the image quality.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing a configuration of a digital watermark embedding apparatus according to Embodiment 3 of the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted in principle.
The third embodiment is different from the first embodiment in that a digital watermark detection unit 23 is newly provided. The digital watermark detection unit 23 is a means for detecting a digital watermark embedded from the encoded and decoded moving image data, which is the monitor output of the utilization device 30, and extracting the detection rate. Also, the difference from the first embodiment is that the embedding strength determination unit 24 embeds the image using the image quality degradation level extracted by the image quality degradation detection unit 22 and the digital watermark detection rate detected by the digital watermark detection unit 23. This is to determine the strength.

Next, the operation will be described.
Assume that the digital watermark embedding unit 21 embeds a digital watermark with a standard embedding strength in the first moving image data. The image quality deterioration detection unit 22 extracts the image quality deterioration degree of the decoded moving image data in units of frames. On the other hand, the digital watermark detection unit 23 detects an embedded digital watermark from the decoded moving image data, and extracts the detection rate. The extracted image quality degradation level and digital watermark detection rate are given to the embedding strength determination unit 24, and the optimum embedding strength is determined based on these.

For example, as shown in FIG. 2, a processing formula for a plurality of embedding strengths is prepared in advance, and the current image quality deterioration degree and detection rate extracted for the current embedding strength are used to request in advance. An expression that provides a predetermined value for the detection rate is selected. There is no problem if the current image quality degradation level and detection rate are approximately satisfied in the formula corresponding to the current embedding strength, and the detection rate is equal to or higher than the predetermined value, but in other cases Is processed as follows.
When the current detection rate is less than or equal to a predetermined value, an expression is selected so that the detection rate is greater than or equal to the predetermined value at the current image quality degradation level, and the embedding strength corresponding to the expression is set to the next embedding in the digital watermark embedding unit 21. Determined as the strength setting.

As another processing example of the embedding strength determination unit 24 of the third embodiment, there is a method using a table illustrated in FIG. In the table of FIG. 7, the relationship between the range of the image quality degradation level, the embedding strength of the digital watermark, and the detection rate is set in advance. Explanation of terms in this table is as follows.
Embedding strength A: Standard embedding strength embedding strength B for a certain image quality degradation level B: Maximum embedding strength detection rate a for a certain image quality degradation level a: Lower limit detection rate c to be maintained in normal operation c: Upper limit of detection rate where embedding strength may be reduced considering image quality

FIG. 6 shows a processing algorithm of the digital watermark embedding apparatus in this processing example.
First, the digital watermark embedding unit 21 embeds a digital watermark having a standard embedding strength A in the input original moving image data (step ST1). With respect to moving image data encoded and decoded after embedding a digital watermark of embedding strength A, the image quality deterioration detection unit 22 acquires the image quality deterioration degree with respect to the original moving image data, and the digital watermark detection unit The detection rate of digital watermark is acquired (step ST2). The embedding strength determination unit 24 determines whether or not the corresponding acquisition detection rate is equal to or higher than the lower limit value a within the range of the acquired image quality degradation level (step ST3). If it is less than or equal to the lower limit value a, the embedding strength is set to the maximum embedding strength B and the digital watermark embedding unit 21 performs processing (step ST6), and the processing of step ST2 is performed again. On the other hand, when the detection rate is equal to or greater than the lower limit value a in the determination of step ST3, the detection rate in the case of the embedding strength A is a value above the upper limit value c of the detection rate that may reduce the embedding strength. It is determined whether it has (step ST4). In this determination, when the expected detection rate is equal to or lower than the upper limit value c, the current embedding strength A is not changed (step ST7), and the digital watermark embedding unit 21 applies the same embedding strength A to the subsequent moving image data. Embed the digital watermark. On the other hand, when the detection rate is equal to or higher than the upper limit value c, the standard embedding strength A is set (step ST5), and the digital watermark having the same embedding strength A is embedded in the subsequent moving image data. As a result, when the image quality degradation level is large, the method for increasing the embedding strength of the digital watermark can be increased compared to when the degradation level is small.
Note that there may be fluctuations in the original image quality degradation level due to encoding. The cause is due to a processing path such as a buffer used for processing by the encoding unit 31 and the decoding unit 32. In such a case, it is preferable to create a table in consideration of the variation.

As still another processing example of the third embodiment, there is a method of using the table illustrated in FIG. Here, the embedding strength of the digital watermark can be switched in four stages. The standard embedding strength of the digital watermark to be embedded first is assumed to be strength 1, for example, and the table of FIG. 8 is referred to using the image quality deterioration level and detection rate acquired at that time, and an appropriate embedding strength considering the image quality deterioration level is Set up.
As another example of processing, there is a method of using the table illustrated in FIG. Here, the condition of the detection rate is subdivided as compared with the case of FIG. 8 to enhance the embedding strength.

  As described above, according to the third embodiment, the image quality degradation level and the digital watermark detection rate generated by embedding and encoding the digital watermark are extracted, and the extracted image quality degradation level, digital watermark detection rate, and Based on the current embedding strength, when changing the embedding strength according to the detection rate of the digital watermark, determine a setting value to update the embedding strength by changing the amount of adjustment of the embedding strength according to the degree of image quality degradation, It is embedded in subsequent moving image data. Therefore, by controlling the embedding strength by feeding back the image quality degradation level and the digital watermark detection rate, it is possible to embed an optimum embedding strength that maintains the detection of a predetermined digital watermark against the image quality degradation. It is done. That is, it is possible to predict the fluctuation of the detection rate according to the deterioration of the image quality and change the embedding strength. For example, it is possible to perform embedding that maintains detection of a predetermined digital watermark against image quality degradation that varies greatly depending on the scene. Even if the detection rate of the digital watermark is the same, the embedding strength can be changed to a more suitable one according to the deterioration of the image quality.

Embodiment 4 FIG.
FIG. 10 is a block diagram showing the configuration of a digital watermark embedding apparatus according to Embodiment 4 of the present invention. In the figure, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted in principle.
In the third embodiment shown in FIG. 5, the moving image data of the video signal source 10 is used as the original signal used as the evaluation reference by the image quality deterioration detection unit 22. In the fourth embodiment, the digital watermark embedding is performed. The data after the embedding of the part 21 is used. Therefore, the image quality deterioration detection unit 22 extracts the image quality deterioration degree of the moving image data obtained by encoding and decoding the data with reference to the moving image data in which the digital watermark is embedded. Also in the case of the fourth embodiment, processing is performed with the same algorithm as in FIG. 6, and when the embedding strength determining unit 24 determines the embedding strength, it is the same as in FIG. 7, FIG. 8, or FIG. A table is used. However, it is assumed that the image quality deterioration degree set in the table in this case is determined in advance with a value that does not consider the image quality deterioration due to the digital watermark.

  As described above, according to the fourth embodiment, the degree of image quality degradation that is substantially caused only by encoding and the digital watermark detection rate of moving image data that has been embedded and encoded and decoded are extracted. Based on the extracted image quality degradation level, digital watermark detection rate, and current embedding strength, when the embedding strength is changed according to the digital watermark detection rate, the adjustment amount of the embedding strength is changed depending on the image quality degradation level. Then, a setting value for updating the embedding strength is determined and embedded in the subsequent moving image data. Therefore, by controlling the embedding strength by feeding back the image quality degradation level and the digital watermark detection rate, it is possible to embed an optimum embedding strength that maintains the detection of a predetermined digital watermark against the image quality degradation. It is done. That is, even if the detection rate of the digital watermark does not change, the change in the detection rate can be predicted according to the deterioration of the image quality, and the embedding strength can be changed. For example, it is possible to perform embedding that maintains detection of a predetermined digital watermark against image quality degradation that varies greatly depending on the scene. Even if the image quality is the same, the embedding strength can be changed according to the detection rate of the digital watermark.

It is a block diagram which shows the structure of the digital watermark embedding apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the image quality degradation degree at the time of fixing the embedding strength of a digital watermark, and the detection rate of a digital watermark. It is explanatory drawing which shows the example of a table which the embedding strength determination part which concerns on Embodiment 1 of this invention uses. It is a block diagram which shows the structure of the digital watermark embedding apparatus by Embodiment 2 of this invention. It is a block diagram which shows the structure of the digital watermark embedding apparatus by Embodiment 3 of this invention. It is a flowchart which shows the algorithm of the digital watermark embedding process based on Embodiment 3 of this invention. It is explanatory drawing which shows the example of a table used for the process which concerns on Embodiment 3 of this invention. It is explanatory drawing which shows the other example of a table used for the process which concerns on Embodiment 3 of this invention. It is explanatory drawing which shows the other example of a table used for the process which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the digital watermark embedding apparatus by Embodiment 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Image | video signal source, 20 Digital watermark embedding apparatus, 21 Digital watermark embedding part, 22 Image quality degradation detection part, 23 Digital watermark detection part, 24 Embedding strength determination part, 30 Utilization apparatus, 31 Encoding part, 32 Decoding part .

Claims (2)

A digital watermark embedding unit that embeds a digital watermark with an arbitrarily set embedding strength in the input video data;
An image quality deterioration detection unit that extracts an image quality deterioration degree of the moving image data obtained by encoding and decoding the moving image data in which the digital watermark is embedded;
A digital watermark detection unit for detecting the digital watermark embedded from the video data encoded and decoded from the video data embedded with the digital watermark, and extracting the detection rate of the digital watermark;
Based on a predetermined relationship between the degree of image quality degradation, the detection rate of the digital watermark, and the embedding strength for obtaining the predetermined detection rate of the digital watermark, the image quality degradation level extracted by the image quality degradation detection unit and the digital watermark detection Determining an embedding strength at which a predetermined detection rate of the digital watermark corresponding to the detection rate of the digital watermark extracted by the unit is obtained, and using the determined value as a setting value for updating the embedding strength of the digital watermark embedding unit An electronic watermark embedding device comprising an embedding strength determining unit for outputting. A digital watermark embedding unit that embeds a digital watermark with an arbitrarily set embedding strength in the input video data;
An image quality deterioration detection unit that extracts the image quality deterioration degree of the moving image data encoded and decoded from the moving image data embedded with the electronic watermark by the electronic watermark embedding unit ;
A digital watermark detection unit for detecting the digital watermark embedded from the video data encoded and decoded from the video data embedded with the digital watermark, and extracting the detection rate of the digital watermark;
Based on a predetermined relationship between the degree of image quality degradation, the detection rate of the digital watermark, and the embedding strength for obtaining the predetermined detection rate of the digital watermark, the image quality degradation level extracted by the image quality degradation detection unit and the digital watermark detection Determining an embedding strength at which a predetermined detection rate of the digital watermark corresponding to the detection rate of the digital watermark extracted by the unit is obtained, and using the determined value as a setting value for updating the embedding strength of the digital watermark embedding unit An electronic watermark embedding device comprising an embedding strength determining unit for outputting.

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