KR100574766B1 - Apparatus for preventing from distorion of watermark signal and method of the same - Google Patents

Abstract

An apparatus and method for preventing distortion of a watermark signal are disclosed. The watermark robustness measurement unit sets a parameter value of a conversion function to be performed on the content, and checks whether the watermark signal is detected from the converted content based on the set parameter value and measures the robustness of the watermark signal. The metadata generating unit generates metadata on a condition under which the watermark signal is to be detected after the content is converted, based on the robustness of the watermark signal measured for the content converting function. The watermark survival confirmation unit converts the content according to the predetermined conversion parameter value based on the metadata and checks whether or not the watermark signal can be detected and outputs the confirmation result. The content conversion unit provides the conversion parameter value to the watermark survival confirmation unit and performs content conversion based on the confirmation result input from the watermark survival confirmation unit. According to the present invention, it is possible to detect a watermark inserted in the converted content even in an environment in which the content is converted and serviced according to the content consumer's environment.

Watermark, transformation, content, distortion, metadata

Description

Apparatus for preventing from distorion of watermark signal and method of the same}

1 is a block diagram showing the configuration of a preferred embodiment of an apparatus for preventing distortion of a watermark signal according to the present invention;

FIG. 2 is a flowchart illustrating a process of generating metadata by measuring the robustness of a watermark embedded in content when converting content in the method for preventing distortion of a watermark signal according to the present invention; FIG.

3 is a diagram showing the structure of metadata for a still image;

4 is a diagram illustrating a structure of metadata about a video, and

FIG. 5 is a flowchart illustrating a process of controlling content conversion to be performed in a range in which a watermark embedded in content is detectable using metadata about a watermark in the method for preventing distortion of a watermark signal according to the present invention.

The present invention relates to an apparatus and method for preventing distortion of a watermark signal, and more particularly, to a multimedia content in which a watermark signal is inserted in a digital rights management (DRM) system considering a multimedia content conversion function. An apparatus and method for preventing distortion of a watermark signal generated when content conversion such as image signal processing and encoding are performed.

With the advent of the ubiquitous computing environment, users can be provided with various kinds of services regardless of time and place. In the ubiquitous environment, multimedia content is transmitted through various channels such as ADSL, wireless LAN, and mobile network. In addition, various types of devices such as PDAs, mobile phones, and HDTVs are used as user terminals. In order to satisfy various consumption environments of users under such ubiquitous computing environments, researches on content adaptation and transformation have been conducted. However, content adaptation serves as a watermark attack that makes it difficult to detect watermark signals.

Digital watermarking is a technology that enables ownership verification and tracking of contents distributed in a DRM system developed for copyright protection in distribution of contents, and may be used to track illegal distribution of contents inside the DRM system. However, in the process of adapting and converting the digital content according to the user's consumption environment, distortion of the watermark signal embedded in the digital content may occur. Therefore, in the DRM system using watermarking as a means of protecting intellectual property rights, the distortion of the watermark signal generated when the content is converted must be considered. To date, there have been many studies on watermarking algorithms that are robust to video signal processing and image compression, such as image size conversion corresponding to content adaptive conversion. However, the conventional watermarking algorithms have a strong characteristic against a specific watermark attack and thus are not robust to all content adaptation conversion functions, and have a limitation in robustness against a specific watermark attack. Therefore, there is a problem in that it is not possible to guarantee the detection of the inserted watermark signal using the conventional watermarking algorithm from the content that has passed the adaptive conversion.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an apparatus and method for preventing distortion of a watermark signal such that a watermark signal embedded in the content can be detected even after the content is converted.

The technical problem to be achieved by the present invention can be read by a computer that records a program for executing a method of preventing distortion of a watermark signal on a computer so that a watermark signal inserted in the content can be detected even after the content is converted. To provide a record carrier.

In order to achieve the above technical problem, an apparatus for preventing distortion of a watermark signal according to the present invention sets a parameter value of a conversion function to be performed on a content, and sets a watermark from the converted content based on the set parameter value. A watermark stiffness measurement unit which checks whether the signal is detected and measures the stiffness of the watermark signal; A metadata generator for generating metadata on a condition under which the watermark signal is to be detected after the content is converted based on the robustness of the watermark signal measured for the content conversion function; A watermark survival confirmation unit for converting content by a predetermined conversion parameter value based on the metadata and checking whether a watermark signal can be detected and outputting a confirmation result; And a content conversion unit providing the conversion parameter value to the watermark survival confirmation unit, and performing content conversion based on a confirmation result input from the watermark survival confirmation unit.

According to another aspect of the present invention, there is provided a method for preventing distortion of a watermark signal, the method comprising: (a) setting a parameter value of a conversion function to be performed on content, and based on the set parameter value; Measuring the robustness of the watermark signal by confirming whether the watermark signal is detected after the conversion; (b) generating metadata on a condition under which the watermark signal is to be detected after content conversion based on the robustness of the watermark signal measured for the content conversion function; And (c) converting the content by a predetermined conversion parameter value based on the metadata and checking whether the watermark signal can be detected, and performing content conversion based on the confirmation result. do.

As a result, the watermarking embedded in the converted content can be detected even in an environment in which the content is converted and serviced according to the content consumer's environment.

Hereinafter, exemplary embodiments of an apparatus and method for preventing distortion of a watermark signal according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a preferred embodiment of an apparatus for preventing distortion of a watermark signal according to the present invention.

Referring to FIG. 1, the apparatus 100 for preventing distortion of a watermark signal according to the present invention includes a watermark inserting unit 110, a watermark toughness measuring unit 120, a metadata generating unit 130, and metadata survival. The identification unit 140 and the content conversion unit 150 are provided.

The watermark inserting unit 110 inserts a watermark signal into the content, and provides the watermark stiffness measuring unit 120 with the type of the watermarking algorithm and the embedding signal used to insert the watermark.

The watermark toughness measurement unit 120 receives the watermark-embedded content, the watermarking algorithm, and the embedding signal from the watermark inserting unit 110, and sets initial parameter values for each content conversion function to be applied to the content. Set to the smallest value. In addition, the watermark toughness measurement unit 120 checks whether the watermark signal is detected from the content converted by the content conversion unit 150. The watermark toughness measuring unit 120 repeatedly detects the watermark signal from the content converted by each parameter value while increasing the parameter value. When the process of checking the watermark signal for all parameter values is completed, the watermark toughness measuring unit 120 provides the measurement result to the metadata generating unit 130.

The metadata generating unit 130 generates metadata on the condition under which the watermark signal is to be detected after the content conversion, based on the robustness of the watermark signal measured for each content conversion function. The metadata generated by the metadata generator 130 includes boundary condition and linearity information corresponding to each content conversion function. The boundary condition means a parameter corresponding to a detectable area and an undetectable area of the watermark signal. In addition, the linearity information means information on whether or not the watermark detection rate increases as the parameter value increases.

The watermark survival confirmation unit 140 converts the content by the parameter value input from the content conversion unit 150 based on the metadata regarding the robustness of the watermark signal provided from the metadata generation unit 130. It is checked whether the watermark signal can be detected, and the verification result is provided to the content converting unit 150.

The content converter 150 converts the content. The content conversion unit 150 provides the parameter value of the conversion function to the watermark survival confirmation unit 140 and performs a content conversion operation according to the verification result input from the watermark survival confirmation unit 140. First, upon receiving the confirmation result indicating that the watermark signal can be detected after the content conversion from the watermark survival confirmation unit 140, the content conversion unit 150 notifies the watermark survival confirmation unit 140 of the parameter value. Perform content conversion using. On the contrary, when receiving the confirmation result indicating that the watermark signal cannot be detected after the content conversion from the watermark survival confirmation unit 140, the content conversion unit 150 may determine the parameter value according to the linearity information of the parameter of the metadata. After adjusting the content conversion. That is, the content conversion unit 150 increases the parameter value if the linearity of the parameter of the metadata is True, decreases the parameter value if the parameter is true, and then notifies the watermark survival confirmation unit 150 of the adjusted parameter value. Ask for confirmation. In this case, if the parameter value cannot be adjusted, the content converter 150 does not perform content conversion.

2 is a flowchart illustrating a process of generating metadata by measuring the robustness of a watermark embedded in content when converting content in the method for preventing distortion of a watermark signal according to the present invention.

Referring to FIG. 2, the watermark toughness measurement unit 120 sets a parameter value for a conversion function that is expected to be applied to the content in which the watermark is inserted (S200). The content conversion unit 150 converts the content by the parameter value set by the watermark toughness measurement unit 120 (S210). The watermark toughness measurement unit 120 checks whether a watermark signal is detected from the converted content (S220). The watermark toughness measuring unit 120 checks whether the watermark signal is detected for all parameter values while increasing the parameter value for the content conversion function (S230). By performing steps S200 to S230, the watermark toughness measuring unit 120 finds parameter values indicating a boundary between a detectable area and a non-detectable area of the watermark signal.

On the other hand, a conversion function performed when the content is a still image may include size conversion and image quality conversion, and parameters corresponding to each conversion function are a scale ratio and a quality value. At this time, the watermark toughness measuring unit 120 finds a boundary dividing the two-dimensional area composed of the enlargement and consumption ratio and the image quality improvement value into the watermark detectable area and the non-detectable area within a range of a given parameter value. In contrast, the conversion function performed when the content is a video may include size conversion and video encoding. The parameter corresponding to the size conversion function is a scale ratio and the parameter corresponding to the video encoding function is an encoder type. , Target Bitrate, and Frame Ratio. At this time, the watermark toughness measurement unit 120 finds a boundary divided into a watermark detectable region and an undetectable region within a range of a given parameter value. The watermark toughness measuring unit 120 finds a boundary line or a boundary area by whether or not the watermark from the content converted by each parameter value is detectable.

 The watermark toughness measuring unit 120 provides the measured result to the metadata generating unit 130 (S240). The measurement result provided from the watermark toughness measuring unit 120 to the metadata generating unit 130 is based on the robustness (eg, watermark detection rate) and watermark signal detection of the watermark corresponding to each parameter value. It includes a boundary area. The metadata generating unit 130 generates metadata based on the measurement result received from the watermark toughness measuring unit 120 (S250).

The metadata generated by the metadata generator 130 includes a name of a content transformation function, respective parameters related to the transformation function, and detectable boundary region information. The boundary region information includes a parameter name, a linearity pair corresponding to the parameter name, and a parameter value indicating the boundary region. In the case where there are a plurality of parameters, the boundary area information is expressed as follows.

<< parameter name 1, linearity>, <parameter name 2, linearity>,... , <Parameter name k, linearity >>

Parameter name 1: parameter value,

Parameter name2: parameter value,

… ,

Parameter name k: parameter value

Here, linearity is a value indicating a trend of change in the watermark detection rate according to the change of the parameter value. If the watermark detection rate increases as the parameter value increases, the linearity is true. If the watermark detection rate decreases as the parameter value increases, the linearity is False. If there is no correspondence between them, the linearity is None. Each parameter value representing a boundary region may take one of a number, a string, and a boolean value (True, False). If there are two or more parameters, the boundary area is represented in the form of fixing one parameter value and expressing the boundary area for the remaining parameters.

3 is a diagram illustrating the structure of metadata for a still image, and FIG. 4 is a diagram illustrating the structure of metadata for a video.

3 and 4, in the case of a still image, the linearity of the scaling factor and the image quality improvement value are both true, and the parameter values corresponding to the scaling factor and the image quality improvement value are (1, 75), ( 0.5, 75), and (0.25, 80). In addition, in the case of a video, the type of the encoder, the scaling ratio, the format target bit rate, and the frame rate may be set as parameters. In this case, "format", which means the type of encoder, indicates the actual encoding format and may be "MPEG1", "MPEG4", "H.263", "H.264", etc., and linearity of the type of encoder is defined. It doesn't work. On the other hand, the linearity of the remaining parameters, the scaling ratio, the format target bit rate, and the frame rate, are all given True. In addition, a_a, a_b, a_z, b_a, b_b, b_z, f_a, f_b, f_z, etc., which are given values corresponding to each parameter, represent parameter values.

FIG. 5 is a flowchart illustrating a process of controlling content conversion to be performed in a range in which a watermark embedded in content is detectable using metadata about a watermark in the method for preventing distortion of a watermark signal according to the present invention. .

Referring to FIG. 5, the content conversion unit 150 provides a parameter value of a conversion function to be performed to the watermark survival confirmation unit 140 (S500). The watermark survival confirmation unit 140 converts the content by the parameter value input from the content conversion unit 150 based on the metadata regarding the robustness of the watermark signal provided from the metadata generation unit 130. In step S510, the controller determines whether the watermark signal is detectable and provides the verification result to the content converter 150. That is, the watermark survival confirmation unit 140 detects the watermark signal when the content is converted by the parameter value according to whether the parameter value is included in the detectable area of the boundary area recorded in the metadata. Or check if it is impossible. When the watermark survival confirmation unit 140 receives the confirmation result indicating that the watermark signal can be detected after converting the content by the corresponding parameter (S520), the content conversion unit 150 receives the watermark survival confirmation unit. Content conversion is performed using the parameter value notified to 140 (S530).

On the contrary, if the watermark survival confirmation unit 140 receives the confirmation result indicating that the watermark signal cannot be detected after converting the content by the corresponding parameter (S520), the content conversion unit 150 receives the confirmation. Check whether the variable value is adjustable (S540). If it is confirmed that the parameter value can be adjusted, the content conversion unit 150 checks the linearity information of the parameter of the metadata (S550). If the linearity of the parameter of the metadata is True (S560), the content conversion unit 150 increases the parameter value and then notifies the watermark survival confirmation unit 140 of the adjusted parameter value to request confirmation. (S570). On the contrary, if the linearity of the parameter of the metadata is False (S560), the content conversion unit 150 decreases the parameter value and then notifies the watermark survival confirmation unit 150 of the adjusted parameter value to confirm. Request (S580). When the content conversion unit 150 receives a confirmation result indicating that the watermark signal can be detected from the watermark survival confirmation unit 140, the content conversion unit 150 uses the adjusted parameter value notified to the watermark survival confirmation unit 140. To perform content conversion. On the other hand, if it is determined that the parameter value cannot be adjusted, the content conversion unit 150 does not perform content conversion (S590).

In the above-described embodiment, the watermark stiffness measurement unit 120 performs only a process of checking whether the watermark signal is detected from the changed parameter and the converted content, and the content conversion is performed by the content conversion unit 150. do. However, the watermark toughness measurement unit 120 may be provided with a component for performing content conversion. In this case, the watermark toughness measurement unit 120 may change a parameter without the intervention of the content conversion unit 150. The process of converting the content by the changed parameters and checking whether the watermark signal is detected from the converted content is performed.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

According to the apparatus and method for preventing distortion of a watermark signal according to the present invention, by converting the multimedia content using the robustness information of the watermark signal inserted into the content as the metadata, the content is converted to suit the environment of the content consumer, so that the service Even in such an environment, watermarking embedded in the content can be detected.

Claims (14)

A watermark stiffness measurement unit for setting a parameter value of a conversion function to be performed on the content, and checking whether the watermark signal is detected from the converted content based on the set parameter value and measuring the robustness of the watermark signal; A metadata generator for generating metadata on a condition under which the watermark signal is to be detected after the content is converted based on the robustness of the watermark signal measured for the content conversion function; A watermark survival confirmation unit for converting content by a predetermined conversion parameter value based on the metadata and checking whether a watermark signal can be detected and outputting a confirmation result; And And a content conversion unit providing the conversion parameter value to the watermark survival confirmation unit, and performing content conversion based on a confirmation result input from the watermark survival confirmation unit. Anti-distortion device. The method of claim 1, The watermark stiffness measurement unit sets a minimum value among the values that the parameter value can take as an initial value of the parameter value, and then sequentially increases the parameter value and detects a watermark signal corresponding to each parameter value. Anti-distortion device of the watermark signal, characterized in that for checking whether or not. The method of claim 1, The metadata includes boundary condition and linearity information corresponding to each content conversion function. The boundary condition includes a parameter corresponding to a detectable area and an undetectable area of a watermark signal, and the linearity information indicates information on whether the watermark detection rate increases with increasing parameter value. Distortion prevention device for watermark signal. The method of claim 3, wherein When the content conversion unit receives a confirmation result indicating that the watermark signal cannot be detected when the content is converted based on the conversion parameter from the watermark survival confirmation unit, the conversion parameter included in the metadata is included. The apparatus for preventing distortion of a watermark signal, characterized in that the content conversion is performed after adjusting the parameter value of the conversion according to the linearity information of the parameter corresponding to. The method of claim 4, wherein If the linearity of the parameter corresponding to the conversion parameter is true, the content conversion unit increases the conversion parameter value; if false, decreases the conversion parameter value; Requesting confirmation of whether a watermark signal has been detected by notifying a parameter value for the watermark signal. The method according to claim 1 or 3, The content conversion unit notifying the watermark survival confirmation unit of the watermark survival confirmation unit when receiving the confirmation result indicating that the watermark signal can be detected when the content is converted based on the conversion parameter from the watermark survival confirmation unit. An apparatus for preventing distortion of a watermark signal, wherein the content is converted using a variable value. The method of claim 1, And the parameter corresponding to each conversion is an enlargement reduction ratio and an image quality improvement value when the content is still image content and the conversion function is size conversion and image quality conversion. The method of claim 1, And the parameter includes a type of encoder, an enlargement / reduction ratio, a format target bit rate, and a frame rate when the content is moving picture content and the conversion function is encoding. (a) setting a parameter value of a conversion function to be performed on the content, converting the content on the basis of the set parameter value, and checking whether the watermark signal is detected to measure the robustness of the watermark signal; (b) generating metadata on a condition under which the watermark signal is to be detected after content conversion based on the robustness of the watermark signal measured for the content conversion function; And (c) converting the content by a predetermined conversion parameter value based on the metadata and checking whether the watermark signal can be detected, and performing the content conversion based on the confirmation result; The distortion prevention method of the watermark signal, characterized in that. The method of claim 9, In step (a), (a1) The minimum value among the values that can be taken by the parameter value is set as an initial value of the parameter value, the content is converted based on the set initial parameter value, and the watermark is checked by detecting whether the watermark signal is detected. Measuring the robustness of the signal; And (a2) The parameter value is changed by adding a predetermined increment to the set initial parameter value, the content is converted based on the changed parameter value, and then the watermark signal is confirmed by detecting whether the watermark signal is detected. It comprises; measuring, And repeating step (a2) until the parameter value reaches a maximum value that can be taken. The method of claim 9, The metadata includes boundary condition and linearity information corresponding to each content conversion function. The boundary condition includes a parameter corresponding to a detectable area and an undetectable area of a watermark signal, and the linearity information indicates information on whether the watermark detection rate increases with increasing parameter value. To prevent distortion of the watermark signal. The method of claim 11, Step (c) is, (c1) checking the linearity information of a parameter corresponding to the conversion parameter included in the metadata when it is determined that the watermark signal cannot be detected from the converted content; (c2) if the linearity of the parameter corresponding to the conversion parameter is true, the conversion parameter value is increased; if false, the conversion parameter value is decreased and the conversion is performed based on the adjusted conversion parameter value. Checking whether a watermark signal is detected from the extracted content; And (c3) converting the content using the adjusted conversion parameter value when it is determined that the watermark signal can be detected when the content is converted based on the adjusted conversion parameter value. To prevent distortion of the watermark signal. The method of claim 9, If it is determined in step (c) that the watermark signal can be detected when the content is converted based on the conversion parameter value, the watermark signal distortion is characterized in that the content is converted using the conversion parameter value. Prevention method. (a) setting a parameter value of a conversion function to be performed on the content, converting the content on the basis of the set parameter value, and checking whether the watermark signal is detected to measure the robustness of the watermark signal; (b) generating metadata on a condition under which the watermark signal is to be detected after content conversion based on the robustness of the watermark signal measured for the content conversion function; And (c) converting the content by a predetermined conversion parameter value based on the metadata and checking whether the watermark signal can be detected, and performing the content conversion based on the confirmation result; A computer-readable recording medium having recorded thereon a program for executing a method of preventing distortion of a watermark signal on a computer.

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