WO2009131424A2 - Randomly distributed watermark unit pattern and ultra high speed track video watermarking algorithm using high speed hvs operation - Google Patents

Abstract

Provided are an apparatus and a method resistant to collusion attack by scattering watermark patterns over successive video frames, and enabling high speed insertion and extraction of watermark patterns.  A unit block of a watermark pattern is created for inserting a watermark pattern into a video frame as a tile structure.  The region of a video frame is divided into (m x n) unit regions having the tile structure.  In a first frame, K positions out of (m x n) positions in the unit region are randomly selected.  In a following frame, K positions that do not overlap with those randomly selected K positions are selected again.  This task is repeated for (m x n/K) successive video frames until all the positions in the (m x n) unit regions having the tile structure are selected.  For the video frame of a decoded video content, an HVS operation is performed on a frame reduced by 4 times the original video frame, to compute NVF.  Only K unit blocks of watermark patterns are inserted at randomly selected K positions of a video frame, according to the NVF.  Since only a few watermark pattern unit blocks are distributed at random positions, the operation speed is minimized, more information about content users can easily be extracted, and high resistance to collusion attack is rendered.

Description

Ultra-fast Tracking Video Watermarking Algorithm Using Randomly Distributed Watermark Unit Patterns and Fast HHS Operations

The present invention relates to an apparatus and method for embedding a digital watermark in video content at high speed or extracting a digital watermark embedded therein. More particularly, the present invention relates to an apparatus and a method for extracting a digital watermark embedded with or embedded with a forensic watermark at high speed and high definition HD video content.

Various media such as video data produced in digital form are easy to store or convert information, and are likely to be copied and distributed without the author's consent, so that the intellectual property of the original author is not protected.

Due to the convenience, mass replication, and circulation of digital information storage and change, the infringement of intellectual property rights through virtual space is becoming more serious, and various watermarking devices and methods for protecting the intellectual property rights of the original authors Is being developed.

Watermarking is a technology that inserts a code such as ID or information that only the user can know into digital content, or inserts a specific code or type into a signal such as video and audio. It is a technology to prevent the illegal copying and effectively protect the copyright and ownership of the data owner by finding the source or the copy path of the original without any obstacle.

Watermarking is classified into Visible Watermarking and Invisible Watermarking depending on whether the watermark is visible or not.In Invisible Watermarking, spatial and watermarking are performed according to the method of inserting a watermark. It is classified as watermarking.

Visible watermarking can be used easily by specifying copyright information by inserting the author's information that can be visually identified in the original image, but has the disadvantage that the original can only be damaged. Therefore, invisible watermarking is mainly used in today's image watermarking technology. Such invisible watermarking is a technique of inserting a watermark so that it cannot be visually detected using the sensory limits of the human visual system (HVS).

In order to insert the watermark invisible, the watermark should be inserted in a large area with low intensity. The spread spectrum method is used as such technology. In the spread spectrum method, a pseudo random sequence is used as a watermark. This random sequence has a uniform distribution function and is evenly distributed over the entire band of frequencies.

Conventional video watermarking has a feature of evenly distributing watermark patterns in all regions of a decoded frame. As described above, the method of inserting the watermark pattern in the entire area of the decoded frame may be vulnerable to a collusion attack. In terms of speed, the higher the video resolution is, the more computation is required, which slows down the insertion and extraction speed. In addition, when several tracking watermarks are inserted into one video content, it is difficult to estimate the inserted tracking watermark patterns, respectively. This is because it is difficult to extract each watermark pattern through a cross-correlation technique because overlapping occurs between a plurality of tracking watermarks inserted in one video content and orthogonality is inferior to each other.

In addition, in the conventional video watermarking, the watermark is distributed through HVS (Human Visual System) estimation of the entire frame so that it is not recognized by human vision. HVS is a model that considers psychological and visual characteristics of humans in order to secure invisibility even after watermark insertion. In particular, HVS applies a cognitive model based on the noise visibility function (NVF) proposed by Voloshynovskiy. Noise Visibility Function NVF is a function that shows the noise level when noise is added to the image. It has a different value depending on the local region of the image and its value is between 0 and 1. In other words, the NVF is 1 in the flat region where there is no change in the image, and is close to 0 in the region where there is much change, such as near the contour or boundary. Such HVS estimation takes the most time when watermark embedding. As the resolution of the video becomes larger, the time taken for HVS estimation and watermark embedding becomes larger.

Therefore, in the conventional watermark embedding technique, when HVS estimation is performed on the original size image of a video frame when watermark is embedded in high definition and high definition HD content, watermark embedding requires a long time.

The present invention has been made to solve the above problems, and relates to an apparatus and method for inserting and extracting watermark at high speed and high definition HD video content at high speed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and method for inserting a watermark at high speed into high-definition and high-definition video content such as HD content and extracting at high speed. In addition, by inserting or extracting a watermark according to the apparatus and method according to the present invention, it is possible to insert or extract a watermark for more content user information in the same video content, and to have a strong characteristic against collusion attacks. It is an object of the invention.

In order to achieve the object of the present invention as described above, the apparatus for embedding a watermark in successive video frames of video content according to an embodiment of the present invention, the decoder to decode the video content, by a watermark modulation technique A message modulation unit for generating a unit block watermark pattern, dividing an area of a video frame into m × n tile structure unit areas, and randomly overlapping K positions among m × n unit area positions in the first frame. Selector, selects K positions so that the randomly selected K positions in the next frame do not overlap with the positions selected in the previous frame, and repeats this position selection process m × n / K times, decoded video An HVS calculator that calculates an NVF by performing an HVS operation on a video frame of content, and a positioning unit According to the NVF calculated from HVS operating section K of the random position is selected as the unit area and comprising a watermark inserting the unit block in the watermark pattern.

The HVS operator performs NVF calculation on the frame reduced by 1/4 times the video frame of the decoded video content, and the watermark inserter calculates the NVF calculated on the video frame reduced by 1/4 times the original video frame size. Map and apply in enlarged form.

In order to achieve the object of the present invention, a method of embedding a watermark in consecutive video frames of video content according to an embodiment of the present invention, decoding the video content, unit block watermark by a watermark modulation technique Generating a pattern, dividing an area of a video frame into m × n tile structure unit areas, randomly selecting K positions from among m × n unit region positions in the first frame so as not to overlap, and then A positioning step that selects K positions so that the randomly selected K positions do not overlap with the positions selected in the previous frame, and repeats this position selection process m × n / K times, for video frames of decoded video content. Performing an HVS operation to calculate the NVF, and the positioning of the randomly selected video frames. And inserting the unit block watermark pattern in K positions according to the NVF.

Computing the NVF by performing an HVS operation includes reducing the video frame of the decoded video content by 1/4 times, and calculating the NVF for the reduced video frame, and inserting a watermark. When inserting the unit block watermark pattern in, the calculated NVF is mapped to the unreduced original video frame size and enlarged form.

In order to achieve the object of the present invention, an apparatus for extracting a watermark according to an embodiment of the present invention is characterized in that in successive video frames of video content, the video frames each consist of m × n unit areas, and a unit block A watermark pattern is a device for extracting a watermark from video content inserted into only K unit region positions randomly selected among m × n unit region positions, and is a decoder for decoding video content, and m × n / K video frames. A watermark estimator for estimating a frequency band in which a watermark exists for each, a summation unit for performing summation on a frequency band in which the estimated watermark exists for m × n / K video frames, and a summation It may also include a watermark extraction unit for extracting a watermark based on the frequency band.

In order to achieve the object of the present invention, a method for extracting a watermark according to an embodiment of the present invention includes: in successive video frames of video content, the video frames each consist of m × n unit areas, and a unit block The watermark pattern is a method of extracting a watermark from video content inserted only at randomly selected K unit region positions among m × n unit region positions, and decoding the video content, m × n / K video frames. Estimating frequency bands in which watermarks exist for each, summing frequency bands in which estimated watermarks exist for m × n / K video frames, and water based on the summed frequency bands It may also include extracting the mark.

According to the present invention, the watermark pattern of the unit block is not evenly distributed and inserted in the entire video frame in one video frame, and only a few watermark pattern unit blocks are distributed at random positions, thereby minimizing the computation speed. have. Since the pattern unit blocks are distributed and distributed among a plurality of video frames, selecting and combining them constitutes a single tile structure frame which is finally evenly distributed over the entire area of the video frame size. In addition, since only a few are distributed at random positions in one frame, it is difficult to externally estimate the location of the watermark pattern, and the location of the watermark pattern unit blocks distributed in the video sequence according to the secret key. The number of branches is infinitely large, which increases the probability of not overlapping each other. Therefore, even if a plurality of tracking watermarks are inserted in a video, the probability of overlapping is reduced, and thus, more content user information is easier to extract than the conventional watermark embedding method. In addition, since the calculation amount is small, the insertion and extraction speed is also increased. In addition, when the averaging attack among collusion attacks, the video quality is worse, so it has a strong characteristic against the collusion attack.

In addition, according to the present invention, a method of obtaining an HVS estimation part from a region reduced by 1/4 times the original size of a video frame (area ratio, 2 times horizontally and vertically), and applying the same to the original image size and enlarged form When the watermark is inserted, the calculation speed in the HVS estimation part, which is the most time-consuming part, is 4 times faster than the existing calculation speed.

In addition, since watermark extraction is attempted once after accumulating (m × n) / K frames without performing a process of extracting a watermark every frame, (m × n) / K− The time cost of extracting the watermark once is saved. Here, when accumulating (m × n) / K frames, since the inserted random position is selected by the secret key, the insertion position can be known by the secret key when extracting. Therefore, only the pattern of the corresponding position is selected and accumulated.

1 is an overall configuration diagram of an apparatus for embedding a watermark according to an embodiment of the present invention.

2 illustrates a method of randomly distributing a unit block watermark pattern without overlapping on successive frames, and distributing only K randomly within one frame.

3 is a diagram illustrating a process of applying to a video frame reduced by 1/4 times in a process of calculating HVS at high speed according to an embodiment of the present invention.

4 is a flowchart of a method for embedding a watermark according to an embodiment of the present invention.

5 is an overall configuration diagram of an apparatus for extracting a watermark according to an embodiment of the present invention.

6 is a flowchart of a method of extracting a watermark according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

In the present invention, the watermark has a method of inserting a unit block watermark pattern into a frame in a tiling structure. The video frame area is divided into horizontal and vertical (1 / m) x (1 / n) rectangular areas, where m≥4 and n≥4. The size of one area divided by the square area of (1 / m) × (1 / n) has the size of M and N.

1 is an overall configuration diagram of an apparatus for embedding a watermark according to an embodiment of the present invention. As shown in FIG. 1, an apparatus for embedding a watermark on consecutive frames of video content according to an embodiment of the present invention includes a decoder (1) for decoding video content, a unit block watermark by a watermark modulation technique. In the message modulation unit (2) for generating a pattern, a video frame composed of m × n unit regions, K positions are selected so as not to overlap at random among m × n unit region positions, and the selected K positions are the previous frame. (3) a HVS operation unit that performs HVS operation on the video frame of the decoded video content and calculates the NVF by repeating the K position selection processes m × n / K times so as not to overlap with the positions selected at (4) and a watermark inserter for inserting a watermark according to the NVF calculated by the HVS calculating section 4 at K positions randomly selected by the positioning section 3; And a portion (5).

Decoder 1 first decodes the video content to which the watermark is to be inserted.

Meanwhile, the message modulation unit 2 uses the watermark modulation technique to convert the unit block watermark pattern having the M × N size so that the unit block watermark pattern may correspond to one unit area among the plurality of unit areas of the video frame. Create

The position determiner 3 selects only a few unit region positions among the plurality of unit region positions of the video frame so as not to overlap at random and determines a position for inserting the unit block watermark pattern. In the conventional tiling structure, a watermark embedding apparatus inserts a watermark pattern in all regions of a video frame. However, in the watermark embedding apparatus according to the present invention, K unit region positions are randomly selected instead of the entire region of a video frame. Since only the unit block watermark pattern is inserted, the positioning unit 3 determines the position where the unit block watermark pattern is to be inserted. The random specific positioning method has a structure for determining a random pattern position of a random pattern by a secret key.

FIG. 2 illustrates a method of randomly distributing a unit block watermark pattern without overlapping any number of K on several frames.

The positioning unit 3 first selects K positions randomly among the m × n unit region positions of the video frame. At this time, (m × n) C (K) pieces exist which can be selected as a random position. Here, C (·) represents a combination. For example, if a video frame has 4 × 4 unit areas and four of them are randomly selected to insert a unit block watermark pattern, (4 × 4) C (4) = 1,820 random The location exists. If K unit region positions are selected for the first video frame, the next video frame (second frame) selects K regions other than the K unit region positions selected in the first frame, so that the position of the selected unit block is selected. Do not overlap each other. At this time, there are (m × n−K) C (K) pieces of random positions that can be selected. Therefore, after four of the 4x4 unit regions are selected, there are (4x4-4) C (4) = 495 random positions that can be selected in the second video frame.

The positioning unit 3 repeats the above process until all unit region positions of the video frame are selected. That is, the process of selecting K positions as described above is repeated m × n / K−1 times. For example, in the case of randomly selecting four unit region positions among the 4 × 4 unit regions, after the selection is repeated three times, only the positions of the four unit regions will automatically remain.

By the above method, the number of branches of a pattern randomly distributed in several frames may be calculated as in Equation (1) below.

[Equation 1]

If P (i) = P (i-1) × (m × n) C (K), i == 1,

    = P (i-1) × (m × n-K) C (K), in other cases i = 2, ..., (m × n) / K, P (0) = 1

The larger m and n are, the more number of branches that can not be randomly overlapped.

In addition, since only a few are distributed at random positions, it is difficult to externally estimate the location of the watermark pattern, and the number of positions of the watermark pattern unit blocks distributed in the video sequence according to the secret key is It is infinitely large, increasing the probability of not overlapping each other. Therefore, even if a plurality of tracking watermarks are inserted in a video, the probability of overlapping is reduced, and thus, more content user information is easier to extract than the conventional watermark embedding method.

1, the HVS calculation unit 4 of the apparatus for embedding a watermark according to an embodiment of the present invention will be described.

The HVS operator 4 performs an HVS operation on the video frame of the decoded video content to calculate the NVF. HVS operation is a method for finding parts that are difficult to recognize by considering human visual characteristics so that the watermark pattern is not recognized by human vision. The Noise Visibility Function (NVF) is a function that indicates the degree of noise when noise is added to an image, and has a different value depending on a local region of the image, and the value is between 0 and 1. In other words, the NVF is 1 in the flat region where there is no change in the image, and is close to 0 in the region where there is much change, such as near the contour or boundary.

Such calculation of NVF may be performed on video frames of the original size as in the conventional HVS computational model.

Further, in the watermark embedding apparatus according to an embodiment of the present invention, the HVS calculator 4 makes the decoded video frame 1/4 to perform high-speed operation while making the flat portion more flat and the edge portion stronger. It can be done after being scaled down.

3 illustrates a video frame reduced by one-fourth in the process of calculating HVS at high speed according to an embodiment of the present invention.

The conventional HVS model calculates the NVF for the original video image and uses it for watermark insertion. In contrast, the HVS model according to an embodiment of the present invention reduces NVF to 1/4 times the decoded video frame and calculates the NVF. By applying the mapping in the form, the computation speed of the HVS estimation portion, which is the most time-consuming part when inserting the watermark, is performed four times faster than the existing computation speed.

Returning to Fig. 1, the watermark embedding section 5 of the apparatus for embedding a watermark according to an embodiment of the present invention will be described.

The watermark inserting section 5 inserts a watermark in accordance with the NVF calculated by the HVS calculating section 4 at the K unit region positions of the video frame selected not to be randomly overlapped by the positioning section 3. The watermark inserting section 5 inserts a unit block watermark pattern at the K unit region positions selected so as not to overlap with the positioning section 3 for the first video frame. Next, for the second video frame, the unit block watermark pattern is applied to the K unit region positions selected not to be randomly overlapped by the positioning unit 3 among the remaining region except for the K unit regions selected in the first video frame. Insert it.

The watermark inserting unit 5 repeats the above process until the unit block watermark pattern is inserted at all unit region positions of the video frame. For example, if four unit region positions are randomly selected among 4 × 4 unit regions, the above process is repeated for four video frames. In a video frame including 4 × 4 unit areas, the total number of frames in which four unit blocks can be selected so as not to overlap each other is four, so when a unit block watermark pattern is inserted into each of the four video frames, All of the plurality of unit regions of the frame may be selected.

4 is an overall flowchart of a method for embedding a watermark in video content according to an embodiment of the present invention.

The watermark embedding method according to the present invention has a method of inserting a unit block watermark pattern into a video frame using a tiling structure. The video frame area is divided into horizontal and vertical (1 / m) x (1 / n) rectangular areas, where m≥4 and n≥4. The size of one area divided by the square area of (1 / m) × (1 / n) has the size of M and N.

As shown in FIG. 4, in the method of embedding a watermark into consecutive video frames of video content according to an embodiment of the present invention, generating a unit block watermark pattern by a watermark modulation technique (S1), m In a video frame consisting of × n unit regions, selecting K positions so as not to be randomly overlapped among m × n unit region positions (S2), and performing an HVS operation on the video frame of the decoded video content to perform NVF Calculating (S3), and inserting the unit block watermark pattern according to the NVF in the K unit region positions of the video frame randomly selected in the positioning step (S4).

In generating a unit block watermark pattern (S1), the unit block watermark pattern may correspond to a position of one of a plurality of unit region positions of a video frame by using a watermark modulation technique. Create a watermark pattern.

In the step S2 of randomly selecting the K unit region positions so as not to overlap, only a few positions of the plurality of unit region positions of the video frame are randomly selected to determine a position for inserting the unit block watermark pattern. In the conventional method of inserting a watermark with a tiling structure, the watermark pattern is inserted into the entire area of the video frame. However, in the watermark embedding method according to the present invention, K unit area positions are randomly selected instead of the entire area of the video frame. Since the unit block watermark pattern is inserted only at step S, randomly selecting the K unit region positions in step S2 determines the K unit region positions into which the unit block watermark pattern is to be inserted. The random specific positioning method has a structure for determining a random pattern position of a random pattern by a secret key.

In step S2, first, K positions are randomly selected among m × n unit region positions of a video frame. At this time, (m × n) C (K) pieces exist which can be selected as a random position. Here, C (·) represents a combination. If K unit region positions are selected for the first video frame, the next video frame (second frame) selects K regions other than the K unit region positions selected in the first frame, so that the position of the selected unit block is selected. Do not overlap each other. At this time, there are (m × n−K) C (K) pieces of random positions that can be selected. Step S2 repeats the above process until all unit region positions of the video frame are selected. That is, the process of selecting K positions as described above is repeated m × n / K−1 times. For example, in the case of randomly selecting four unit region positions among the 4 × 4 unit regions, after the selection is repeated three times, only the positions of the four unit regions will automatically remain. In addition, the number of branches of the pattern randomly distributed in several frames by the above method can be calculated as shown in Equation (1).

In the watermark embedding method according to an embodiment of the present invention, step (S2) of randomly selecting non-overlapping K unit regions selects K positions randomly among m × n unit region positions of a video frame. A first step (S21) and a second step (S22) of randomly selecting non-overlapping K positions among the remaining positions other than the K positions selected in the preceding video frame in the next frame of video; Step S22 is repeated until all unit region positions of the video frame are selected.

In a first step S21, first, K positions are randomly selected among m × n unit region positions of a video frame. At this time, (m × n) C (K) pieces exist which can be selected as a random position. Here, C (·) represents a combination. For example, if a video frame has 4 × 4 unit areas and four of them are randomly selected to insert a unit block watermark pattern, (4 × 4) C (4) = 1,820 random The location exists.

The second step S22 selects K positions randomly from the remaining positions except the K positions already selected. If K unit blocks are selected for the first video frame, the next video frame (second frame) selects K of the remaining areas except the selected K unit block positions in the first frame, so that the positions of the selected unit blocks Do not overlap. At this time, there are (m × n−K) C (K) pieces of random positions that can be selected. Therefore, after four of the 4x4 unit regions are selected, there are (4x4-4) C (4) = 495 random positions that can be selected in the second video frame. On the other hand, the second step (S22) repeats the above process until all the unit region of the video frame is selected. Therefore, the second step S22 is repeated m × n / K−1 times. After the second step S22 is repeated m × n / K−1 times, the number of unselected areas among the unit areas of the video frame is K, so that the K unit area positions remain without a separate positioning process. Will be.

In step S3, an HVS operation is performed on the video frame of the decoded video content to calculate the NVF.

Such calculation of NVF may be performed on video frames of the original size as in the conventional HVS computational model.

In addition, in the watermark embedding method according to an embodiment of the present invention, the step (S3) of calculating the NVF by performing the HVS operation is performed to perform the high speed operation while making the flat portion more flat and the edge portion stronger. It may be performed after reducing the decoded video frame by 1/4 times.

Computing the NVF by performing the HVS operation (S3) includes reducing the video frame by 1/4 times (S31), and calculating the NVF for the reduced video frame (S32).

In this case, when inserting the unit block watermark pattern in the step S4 of inserting the watermark, the NVF calculated for the video frame reduced by 1/4 times is enlarged with the original video frame size which has not been reduced. Mapping can be applied. The conventional HVS model calculates the NVF for the original video image and uses it for watermark insertion. In contrast, the HVS model according to an embodiment of the present invention reduces NVX to 1/4 times the decoded video frame, calculates the NVF, and applies the mapping to the original video frame size and the enlarged form when the watermark is inserted. Through the method, the computation speed of the HVS estimation portion, which is the most time-consuming part when inserting a watermark, can be performed four times faster than the existing computation speed.

In step S4, a watermark is inserted in accordance with the NVF calculated in step S3 at K unit region positions of the video frame randomly selected in step S2. Step S4 inserts a unit block watermark pattern at the K unit region positions selected in step S2 for the first video frame. Next, for the second video frame, the unit block watermark pattern is inserted at the position of the K unit region randomly selected in step S2 among the remaining regions except for the K unit regions selected in the first video frame. Step S4 repeats the above process until the unit block watermark pattern is inserted in all unit region positions of the video frame. For example, if four unit region positions are randomly selected among 4 × 4 unit regions, the above process is repeated for four video frames. In a video frame including 4 × 4 unit areas, the total number of frames in which four unit blocks can be selected so as not to overlap each other is four, so when a unit block watermark pattern is inserted into each of the four video frames, All of the plurality of unit regions of the frame may be selected.

5 is an overall configuration diagram of an apparatus for extracting a watermark according to an embodiment of the present invention.

As shown in FIG. 5, in video frames where video content is continuous according to an embodiment of the present invention, the video frames each consist of m × n unit areas, and the unit block watermark pattern is one of m × n unit area positions. An apparatus for extracting a watermark from video content, which is inserted only at randomly selected K unit region positions, includes a decoder 6 for decoding video content and a watermark for each of m × n / K video frames. A watermark estimator 7 for estimating a frequency band, an adder 8 for performing summation on a frequency band in which an estimated watermark exists for m × n / K video frames, and a summed frequency band And a watermark extractor 9 for extracting the watermark on the basis of.

In the watermark estimator 7 estimating the frequency band in which the watermark exists, the band in which the watermark exists and the F _band may estimate the band in which the watermark exists through a filter such as a Wiener filter. This estimation of the frequency band is performed for each of m × n / K sequential video frames.

The adder 8 sums up the frequency bands performed for each of m × n / K sequential video frames. The summation of such frequency bands may be performed by the following equation (2).

[Equation 2]

From here,

Denotes the result of summing the frequency bands from the first frame to the jth frame. For example, looking at the total sum of frequency bands for each of 4 × 4/4 sequential video frames,

= F _band (0) + F _band (1) + F _band (2) + F _band (3). When m × n / K frames are accumulated, the inserted random position is selected by the secret key, so the insertion position can be known by the secret key when extracting. Therefore, only the pattern of the corresponding position is selected and accumulated.

A frequency band in which the unit block watermark pattern exists is accumulated for m × n / K frames.

Since the watermark pattern unit block U _idx (i, j) is distributed in a tile structure,

U _idx (i, j) in the stack is accumulated by overlapping as shown in Equation (3) below.

[Equation 3]

The watermark extracting section 9 extracts a watermark based on the summation result of the adding section 8. If a watermark pattern is inserted into a video frame using a spread spectrum method, the watermark may be extracted through a cross correlation technique.

The message modulation unit 10 of the watermark extraction structure finds the synchronization information (Sync) of the watermark pattern, restores the original video image when the RST (Rotation, Scale, Translation) attack is received, and then inserts the inserted watermark. It is used to extract

As described above, the watermark extraction apparatus performs a watermark extraction once after accumulating m × n / K frames, unlike performing a process of extracting a watermark every frame in the conventional watermark extraction apparatus. Therefore, the time cost of extracting the water mark m × n / K−1 times is saved compared with the conventional apparatus. Therefore, it is possible to have a high speed watermark extraction speed.

6 is a flowchart of a method of extracting a watermark according to an embodiment of the present invention.

As shown in FIG. 6, in video content according to an embodiment of the present invention, video frames are each divided into m × n unit areas in a tile structure, and a unit block watermark pattern is randomly selected among m × n unit area positions. The method of extracting a watermark from video content inserted only at selected K unit region positions may include estimating a frequency band in which a watermark exists for each of m × n / K sequential video frames (S10); summing up frequency bands each having an estimated watermark for m × n / K sequential video frames, and extracting a watermark based on the summed frequency bands (S30). .

Band, _band F of the watermark is present the watermark exists in the step (S10) for estimating a frequency band that can estimate the bandwidth of the watermark present over the filter, such as a Wiener Filter. This estimation of the frequency band is performed for each of m × n / K sequential video frames.

In the step of adding the frequency bands (S20), the frequency bands performed on each of the m × n / K sequential video frames are accumulated. The summation of such frequency bands may be performed by Equation (2) described above.

From here,

Denotes the result of summing the frequency bands from the first frame to the jth frame. For example, looking at the total sum of frequency bands for each of 4 × 4/4 sequential video frames,

= F _band (0) + F _band (1) + F _band (2) + F _band (3). When accumulating m × n / K frames, since the inserted random position is selected by the secret key, the insertion position can be known by the secret key when extracting. Therefore, only the pattern of the corresponding position is selected and accumulated.

A frequency band in which the unit block watermark pattern exists is accumulated for m × n / K frames.

Since the watermark pattern unit block U _idx (i, j) is distributed in a tile structure,

U _idx (i, j) in the stack is accumulated by overlapping as in the above expression (3).

In step S30 of extracting the watermark, the watermark is extracted based on the result of step S20. If a watermark pattern is inserted into a video frame using a spread spectrum method, the watermark may be extracted through a cross correlation technique.

This method is different from the conventional method for extracting a watermark every frame in the conventional watermark extraction method. Since the watermark extraction is performed once after accumulating m × n / K frames, the conventional method is used. The time cost of extracting the watermark m × n / K−1 times is further saved. Therefore, it is possible to have a high speed watermark extraction speed.

Claims (6)

1. An apparatus for embedding a watermark in consecutive video frames of video content, the apparatus comprising:

   A decoder for decoding video content,

   A message modulation unit for generating a unit block watermark pattern by a watermark modulation technique;

   Divides an area of a video frame into m × n tile structure unit areas, randomly selects K positions among m × n unit region positions in the first frame so as not to overlap, and randomly selected K positions in the next frame. Selects K positions so that does not overlap with the positions selected in the previous frame, and the positioning unit repeats this position selection process m × n / K times,

   An HVS calculator which performs an HVS operation on a video frame of the decoded video content to calculate an NVF, and

   And a watermark inserting unit inserting a watermark according to the NVF calculated by the HVS calculating unit in K unit areas of the video frame randomly selected by the positioning unit.
2. The method of claim 1,

   The HVS calculator performs calculation of NVF on a frame reduced by one-fourth the video frame of the decoded video content.

   And the watermark inserting unit maps and applies the NVF calculated for the video frame reduced by 1/4 times to the original video frame size and the enlarged form.
3. A method of embedding a watermark in successive video frames of video content, the method comprising:

   Decoding the video content,

   Generating a unit block watermark pattern by a watermark modulation technique;

   The video frame is divided into m × n tile unit areas, randomly selected K positions among m × n unit region positions in the first frame are not overlapped, and K positions randomly selected in the next frame. Selects K positions so that does not overlap with the positions selected in the previous frame, and repeats this position selection process m × n / K times,

   Calculating an NVF by performing an HVS operation on the video frame of the decoded video content, and

   And inserting a unit block watermark pattern according to NVF into K unit regions of the video frame randomly selected in the positioning step.
4. The method of claim 3, wherein

   Computing the NVF by performing an HVS operation,

   Reducing the video frame of the decoded video content by one quarter times, and

   Calculating an NVF for the reduced video frame,

   When inserting the unit block watermark pattern in the step of inserting the watermark, the watermark is inserted into the video content, wherein the calculated NVF is mapped to the unreduced original video frame size in an enlarged form. Way.
5. In successive video frames of video content, the video frames each consist of m × n unit areas, and the unit block watermark pattern is inserted only at randomly selected K unit area locations among the m × n unit area locations. An apparatus for extracting a watermark from video content,

   A decoder for decoding video content,

   a watermark estimator for estimating a frequency band in which a watermark exists for each of m × n / K video frames;

   a summation unit for performing summation on a frequency band in which an estimated watermark exists for m × n / K video frames, and

   And a watermark extractor for extracting a watermark based on the summed frequency bands.
6. In successive video frames of video content, the video frames each consist of m × n unit areas, and the unit block watermark pattern is inserted only in K unit areas randomly selected from the m × n unit areas. A method of extracting a watermark from content,

   Decoding the video content,

   estimating a frequency band in which a watermark exists for each m × n / K video frames,

   summing frequency bands each having an estimated watermark for m × n / K video frames, and

   Extracting a watermark based on the summed frequency bands.

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