JP2006050043A - Method and apparatus of detecting electronic watermark and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify an electronic watermark detecting operation simultaneously by suppressing the influence of an uncertain factor at a camera photographing when the electronic watermark is detected from the image obtained by inputting the image containing the electronic watermark of a printed matter, etc. by a camera, etc. <P>SOLUTION: The electronic watermark detection is performed to a frame image continuously inputted from an analog input device, such as the camera. A symbol which can be detected with sufficient reliability from the frame image (wherein correlation value more than a threshold A) is stored in a detection symbol buffer. When all the symbols can be detected with sufficient reliability, the detection watermark information is outputted based on the content of a detection symbol buffer. In the case that the electronic watermark detection from one frame image is unreliable, the electronic watermark is detected by synthesizing the detection symbols of a plurality of frames. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital watermark technique which is a technique for embedding other sub information in a content such as an image or video so as not to be perceived and reading the sub information, and in particular, inputs a digital watermark image such as a printed matter with a scanner or a camera. The present invention relates to a digital watermark detection technique for detecting embedded sub-information from an image.

  When distributing content such as images, video, and audio, digital watermark technology that embeds other information so that it cannot be perceived in the content is used for purposes such as content identification / management, copyright protection / management, and related information provision. . Conventionally, in such a digital watermark technology, a printed image of a watermarked image based on the spread spectrum modulation technology for each symbol is input to a scanner or a camera, and the digital watermark is detected from the input image to read related information. There is a method (for example, refer nonpatent literature 1).

  However, there are various uncertain noise factors that occur at the time of shooting, such as camera shake and lighting conditions, and in the conventional technology, such an uncertain noise factor causes a problem that digital watermark detection from an image shot with a camera fails. was there. In addition, after taking a single image with the camera, the user must detect the digital watermark, and if the detection fails, the user must perform the projection again, which makes it difficult for the user to detect the digital watermark. was there.

Nakamura, Katayama, Miyaji, Yamashita, Yamamuro: “Digital watermark detection method for service mediation using mobile phones with cameras”, Information Science and Technology Forum FIT2003, N-020, September 2003

  The present invention provides a digital image embedded with a digital watermark based on a spread spectrum modulation technique for each symbol, which is output as an analog output such as a printed matter or a screen display using an analog input device such as a scanner or a camera. When detecting watermarks, it is possible to suppress the effects of indeterminate noise factors such as camera shake and lighting, which was impossible with conventional technology, and at the same time simplify electronic watermark detection operations. An object of the present invention is to provide a watermark detection method and apparatus, and a program for realizing the method.

  In the present invention, a frame image group of analog images with digital watermarks is continuously input from an analog input device such as a camera in the image input means, and first, one frame image is acquired in the frame image acquisition means. Next, in the digital watermark detection means, detection processing by a digital watermark algorithm based on symbol-by-symbol spread spectrum modulation is performed on the frame image, and symbol values S_k and correlation values X_k (k = 1... K, K) by spread spectrum demodulation. Is obtained as a result of demodulation for symbols having a correlation value X_k greater than or equal to the threshold A as a result of the threshold determination. The symbol value S_k and the correlation value X_k are written as T_k and Y_k respectively in the storage areas corresponding to the k-th symbol position of the detected symbol buffer (the initial value is a value indicating an unwritten state) (that is, T_k ← S_k, Y_k). ← X_k). In some embodiments, only the symbol value S_k can be written and the correlation value X_k can be omitted. If there is a symbol position in which no symbol value or correlation value is written in the detected symbol buffer, the process is repeated from the acquisition of one frame image by the frame image acquisition means. When symbol values and correlation values are written in all symbol positions (1... K) in the detected symbol buffer, all symbol values T_k (k = 1) stored in the detected symbol buffer are obtained. ..., And generates and outputs detected watermark information, and the process ends.

  Further, in the present invention, the number of consecutive cases where the correlation values X_k for each symbol are all less than (1... K) threshold A is counted in the continuous detection failure counter by threshold determination, and this count value When M reaches a predetermined number of times, all values of the detected symbol buffer are initialized.

  In the present invention, as a result of the threshold determination, for a symbol having a correlation value X_k equal to or greater than the threshold A, the storage area corresponding to the k-th symbol position of the detection symbol buffer is in an unwritten state, or k of the detection symbol buffer If the symbol value T_k that has been written matches the symbol value S_k and the written symbol correlation value Y_k is less than the correlation value X_k when the storage area corresponding to the th symbol position is already written, the symbol obtained as a result of demodulation The value S_k and the correlation value X_k are respectively written in the storage area corresponding to the kth symbol position of the detection symbol buffer (ie, T_k ← S_k, Y_k ← X_k), and the storage area corresponding to the kth symbol position of the detection symbol buffer is written Symbol value T that has been written but has been written If k and the symbol value S_k do not match, so as to initialize all the values of detected symbols buffer.

  Furthermore, in the present invention, when there is a symbol having a correlation value X_k equal to or greater than the threshold A as a result of the threshold determination, there is a possibility that digital watermark detection may be performed from the currently input image by screen output or audio output. Notify users.

  Furthermore, in the present invention, as a result of determining whether or not the symbol values and correlation values have been written for all the symbol positions (1... K) in the detected symbol buffer, there is a portion that has not yet been written. In this case, based on the ratio between the number of already written symbol positions and the total number of symbols, the digital watermark detection progress status up to the present time is notified to the user by screen output or voice output.

  Further, in the present invention, the frame image acquisition unit and the digital watermark detection unit are processed in parallel while previewing the frame image group continuously input from the analog input device such as a camera in the image input unit.

  In the present invention, digital watermark detection is performed on a frame image continuously input from an analog input device such as a camera, and a symbol that has been detected from the frame image with sufficient reliability (correlation value equal to or greater than a threshold A) is detected symbol. When all the symbols are accumulated in the buffer and detected with sufficient reliability, detection watermark information is output based on the contents of the detected symbol buffer. As a result, when the digital watermark can be completely detected from one frame image, the detection result can be output as usual. Further, when the digital watermark detection from one frame image is uncertain, the digital watermark is detected by synthesizing the detection symbols of a plurality of frames. Here, since various uncertain noise factors such as camera shake and lighting conditions are different for each frame, uncertain noise factors can be reduced by combining detection symbols of multiple frames. The digital watermark can be successfully detected with a smaller number of detection trials than the simple method of independently detecting the digital watermark from one frame image.

  In the present invention, when detection results are low (all correlation values X_k are less than the threshold A) and detection results are continuous, it is determined that digital watermark detection has been interrupted, and the detection symbol buffer is initialized. Turn into. As a result, for example, when there is a printed matter B and B with different digital watermark information embedded, and the detection symbol buffer has been partially written after the detection from the first halfway, the user switches the camera. In case of moving and re-photographing the second party, by initializing the detection symbol buffer before the second frame is taken out and the second party is photographed, different digital watermark information is mixed in the detection symbol buffer. It is possible to prevent erroneous detection (outputting incorrect detection watermark information as a result).

  In the present invention, the detected symbol buffer is initialized when a symbol value different from the symbol value already stored in the detected symbol buffer is detected with sufficient reliability. This is an example of the above-mentioned printed materials of Party A and Party B. When the detection from the Party A is performed halfway and the detection symbol buffer is partially written, the user moves the camera and photographs the Party B. When the symbol value detected with sufficient reliability from B is different from the detection value on the detection symbol buffer read from the former, the detected symbol buffer is initialized, so that different digital watermark information can be obtained. It is possible to prevent erroneous detection (incorrect detection watermark information is output as a result) due to mixing in the detection symbol buffer.

  Furthermore, according to the present invention, in the case of shooting conditions that facilitate detection of digital watermarks, the user can interactively feed back to the user how to perform shooting that is easy to detect digital watermarks by outputting a screen or audio to the user. It is possible to provide the user with a further reduction in the number of detection attempts and an excellent user interphase.

  Furthermore, according to the present invention, the progress of detection of digital watermarks up to the present can be interactively fed back to the user by performing screen or audio output to the user, further reducing the number of detection attempts and An excellent user interface phase can be provided to the user.

  Furthermore, according to the present invention, by performing digital watermark detection in parallel while previewing a frame image group, the preview frame rewriting time is generally shorter than the trial processing time of the digital watermark detection process. On the other hand, it is possible to make it appear that the digital watermark is detected from the frame in real time, and when combined with the digital watermark detection progress screen or audio output as described above, for example, like a mobile phone with a camera When shooting while looking at the camera preview screen, it is possible to provide the user with a more intuitive user interface phase, such as outputting a message on the preview display screen when the digital watermark detection possibility is high. .

  Hereinafter, some examples as the best mode of the present invention will be described with reference to the drawings.

  FIG. 1-1 shows the overall configuration of the digital watermark detection apparatus in the first embodiment of the present invention. The digital watermark detection apparatus 100 includes a camera input unit 110, a frame image acquisition unit 120, and a digital watermark detection unit 130 as image input means. The digital watermark detection analog image 101 is input, and detected watermark information 131 is output. . The analog image 100 with a digital watermark is an analog output of a digital image in which a digital watermark is embedded by printing on paper or displaying on a screen.

  In the present invention, a digital watermark applying a symbol-by-symbol spread spectrum modulation technique is assumed as a digital watermark embedding and detection algorithm. In digital watermarking based on symbol-by-symbol spread spectrum modulation, watermark information is converted into a sequence of symbols, and for each symbol, symbol information is spread with a sufficiently large random number sequence (pseudo-random number sequence) by applying communication spread spectrum modulation ( Modulation) and embedding the spreading sequence by adding it to the original image according to the embedding intensity parameter. When embedding the original image in a DCT frequency matrix image obtained by frequency conversion, the diffusion sequence is similarly frequency-converted to obtain a DCT frequency matrix, and this is embedded by adding it to the system value of the DCT frequency matrix image. In the digital watermark detection, a detection target sequence is extracted from a detection target image with a digital watermark, and a symbol is detected by performing spread spectrum demodulation (despreading) for each symbol using a spreading sequence (random number sequence) used at the time of embedding. A column is detected as watermark information. Here, the symbol is a symbol that can take a value in a predetermined range. For example, a symbol that takes 256 values can be represented by 8-bit information. In the digital watermark based on the spread spectrum modulation for each symbol, for example, when the watermark information is 32-bit information “ABCD” (ASCII notation), 8-bit symbols “A”, “B”, “C”, “D” Each of the four symbols is embedded with a digital watermark based on spread spectrum modulation. In the same manner, spread spectrum demodulation is performed for each symbol to detect four symbols “A”, “B”, “C”, and “D”, and detection watermark information is 32 bits based on a sequence of four symbols. Information "ABCD" is output. If the value that a symbol can take is binary, 1 symbol = 1 bit. In this case, a digital watermark based on bit-by-bit spread spectrum modulation is used.

  The essence of spread spectrum demodulation is a correlation calculation between a detection target sequence and a spread sequence, and a highly reliable digital watermark is detected by detecting a peak of a superior correlation value. In the present invention, the digital watermark algorithm is arbitrary as long as it is based on the symbol-by-symbol spread spectrum modulation technique. For example, the algorithm described in Japanese Patent Laid-Open No. 2003-219148 can be used.

FIG. 1-2 shows the overall processing flow of the digital watermark detection apparatus in the first embodiment of the present invention. Hereinafter, the operation of the present embodiment will be described with reference to FIG.
In the digital watermark detection apparatus 100, first, the camera input unit 110 continuously captures and inputs an analog image 101 with a digital watermark and outputs the input image as a frame image group 111 (S1). That is, it is assumed that the camera operates like a video camera, not a still camera.

  Next, the frame image acquisition unit 120 picks up one frame image 121 from the frame image group 111 and sends it to the digital watermark detection unit 130 (S2). As a method of selecting one frame image, for example, as shown in FIG. 1C, the moment the frame image acquisition unit 120 tries to acquire the frame image group obtained by continuous capture input in real time. It is assumed that a frame image obtained by capture is selected (time to in FIG. 1-3).

  Next, the digital watermark detection unit 130 attempts to detect a digital watermark from the frame image 121. 1-4 shows a detailed configuration of the digital watermark detection unit 130 in the present embodiment. The digital watermark detection unit 130 includes a detection target sequence extraction unit 1310, a spread spectrum demodulation unit 1320, a buffer writing unit 1330, a detection symbol buffer 1340, and an output determination unit 1350. In FIG. 1-2, steps S3 to S11 indicate processing of the digital watermark detection unit 130.

  First, the detection target sequence extraction unit 130 extracts the detection target sequence 1311 from the frame image 121 (S3). The specific extraction method varies depending on the digital watermark algorithm. For example, in Japanese Patent Laid-Open No. 2003-219148, each element of the frequency component matrix obtained by discrete Fourier transform of an image is determined by the key of the digital watermark. A sequence to be detected is a one-dimensional rearrangement using a random number sequence.

  Next, the spread spectrum demodulator 1320 performs spread spectrum demodulation for each symbol using the spread sequence (random number sequence) used for embedding the digital watermark, and detects the detected symbol value S_k and the correlation value X_k (k = 1... K and K are predetermined digital watermark embedding / detection symbol string lengths) (S4). The specific demodulation method also varies depending on the digital watermark algorithm. For example, in Japanese Patent Laid-Open No. 2003-219148, the cross correlation between the detection target sequence and the spread sequence is calculated for each symbol position k on the symbol sequence. The detected symbol value S_k and the correlation value X_k at that time are output as the shift amount when the maximum correlation value is calculated by shifting the position of the first term one by one. Further, as a simpler spread spectrum demodulation, for example, when a symbol is binary, that is, a 1-bit symbol, a correlation value between a detection target sequence and a spread sequence is obtained for each bit position. There may be a method in which “0” is positive and “1” is detected symbol value S_k and output together with correlation value X_k. In correlation calculation, the detection target sequence is, for example, average 0, norm 1 It is assumed that the normalization method may be different.

  Next, the buffer writing unit 1330 performs threshold determination for each of the correlation values X_k (k = 1... K) using a predetermined threshold (hereinafter referred to as threshold A), and the correlation value X_k is greater than or equal to the threshold A. For k, the detected symbol value S_k and the correlation value X_k are written in the kth storage area of the detected symbol buffer 1340 (S5 to S9). In the present embodiment and the next embodiment 2, the writing of the correlation value X_k may be omitted.

  FIG. 1-5 shows the configuration of the detected symbol buffer 1340. The detection symbol buffer 1340 is a storage device capable of storing K symbol value / correlation value pairs, and the symbol value / correlation value pairs are assigned k = 1... The values (detected symbol value T_k and correlation value Y_k) of all storage areas of the detected symbol buffer 1340 are initialized to values representing “unwritten”. As examples of values indicating unwritten values, T_k is a value outside the range of values that a symbol can take (for example, “−1” in the case of a non-negative symbol value), and Y_k is a correlation value “0”, for example. is there.

  Here, the meaning of the threshold A will be described. In general, it can be said that the larger the correlation value (or the absolute value of the correlation value) obtained at the time of spread spectrum demodulation, the higher the probability that the demodulated information is correct and the higher the reliability of the demodulated information. There is also a digital watermark method that can quantitatively guarantee the reliability probability for the correlation value by a statistical method, as described in Japanese Patent Laid-Open No. 2003-219148, for example. For example, the threshold A can be set so that the false positive determination rate (probability of erroneously demodulating wrong information) is equal to or less than 10 to the negative sixth power. That the correlation value X_k passes the threshold determination (YES in S6) means that the detected symbol value S_k has been detected with sufficient reliability.

  FIG. 1-6 shows how the buffer writing unit 1330 writes to the detected symbol buffer 1340 by threshold determination for each symbol position k. The upper side of FIG. 1-6 shows the detected symbol value S_k and the correlation value X_k obtained from the current frame image. A threshold value determination is performed for each correlation value X-k using the threshold value A (S6), and k for which the correlation value X_k is greater than or equal to the threshold value A is shown in the lower side of FIG. S_k and X_k are respectively written in the symbol value T_k and the correlation value Y_k in the kth storage area (S7). That is, T_k ← S_k, Y_k ← X_k. On the other hand, for k for which the correlation value X_k is less than the threshold A, the storage area in the detection symbol buffer 1340 (for example, k = 2, k = K in FIGS. 1-6) is not particularly operated.

  Next, the output determination unit 1350 determines whether or not the detected symbol values have been written in all the storage areas 1 to k for the current detected symbol buffer 1340 (S10). If there is no storage area where the detected symbol value remains the initial value), the digital watermark information is demodulated and output based on the detected symbol value sequence in the detected symbol buffer 1340, and the digital watermark detection process is terminated (S11). ). On the other hand, if an unwritten storage area remains in the detected symbol buffer 1340 (that is, if there is at least one storage area where the detected symbol value remains the initial value), the process returns to the process of the frame image acquisition unit 120, and the frame After a new frame image is acquired by the image acquisition unit 120 (S2), the digital watermark detection unit 130 repeats the processing from step S3 onward.

  Whether or not the detection symbol values have been written in all the storage areas (1... K) of the detection symbol buffer 1340 is determined by using a K-bit flag register corresponding to each storage area of the detection symbol buffer 1340. For example, when all the initial values are set to “0” and the detected symbol value S_k and the correlation value X−k are written in the detected symbol buffer 1340 in step S7 in FIG. It is also possible to set “1” and then determine whether or not all the bits of the flag register are “1” in step S10. Further, the detection symbol buffer 1340 may include the same flag bit.

  FIG. 1-7 shows a state of processing in the output determination unit 135. In FIG. 1-7, the shaded area indicates “written” and the white background indicates “unwritten” storage area. As shown in FIG. 1-7, when the read / write storage area still remains in the detected symbol buffer 1340, the output determination unit 1350 determines to return to the processing of the frame image acquisition unit 120, and again the frame image The acquisition unit 120 repeats the process from acquisition of a new frame image. On the other hand, as shown in the lower part of FIG. 1-7, when all the storage areas of the detection symbol buffer 1340 have been written, the output determination unit 1350 detects the sequence of detection symbol values (T_l, Based on T_2, T_3,..., T_K), detection watermark information is configured (in the above example, four symbol values “A”, “B”, “C”, “D” are 32-bit information) Output as “ABCD”), and the digital watermark detection process ends.

  Next, the function and effect of this embodiment will be described with reference to FIGS. In this embodiment, digital watermark detection is performed on a frame image continuously input from an analog input device such as a camera to obtain a detected symbol value and a correlation value, and a threshold value determination for the correlation value is performed for each detected symbol value. It is determined whether or not to hold in the detection symbol buffer. As shown in FIG. 1-8, even when a detected symbol value detected from each frame and having a correlation value equal to or greater than the threshold A cannot form complete detection watermark information and has only a partial symbol, As described above, when the digital watermark detection process from a new frame image is repeated one after another, the value of the detected symbol buffer gradually fills in the written state, and finally when the detected symbol buffer is completely written. The detection watermark information is constructed and output based on the symbol value in the detection symbol buffer. As a result, when the digital watermark can be completely detected from one frame image (corresponding to the case where all the correlation values X_k are equal to or greater than the threshold value A), the detection result can be output as usual. On the other hand, even if various indeterminate noise factors such as camera shake and lighting conditions are different for each frame, the detection symbol value buffering as described above enables detection of a digital watermark from one frame image. The digital watermark can be successfully detected with a smaller number of detection trials than the simple method of repeating the above independently.

  The entire configuration of the digital watermark detection apparatus according to the second embodiment of the present invention is the same as that of FIG. FIG. 2A shows a detailed configuration of the digital watermark detection unit 130 in the present embodiment. In this embodiment, the digital watermark detection unit 130 includes a continuous detection failure number counter 1360. Other than that, the configuration is the same as that of the digital watermark detection unit 130 of FIG. The initial value of the continuous detection failure counter 1360 is zero.

FIG. 2-2 shows the overall processing flow of the digital watermark detection apparatus in this embodiment. Hereinafter, only the processing of the part different from FIG.
As shown in FIG. 2-2, when the correlation value X_k obtained from the detection target sequence is less than the threshold A for all k of k = 1... K, the continuous detection failure number counter 1360 is incremented (S31, S32). . If there is at least one k at which the correlation value X_k is equal to or greater than the threshold A at a certain time, the count value c of the continuous detection failure counter 1360 is reset to 0 (S28).

  If all the correlation values X_k are less than the threshold value A, the continuous detection failure frequency counter 1360 is incremented and then compared with the threshold value M for the predetermined continuous detection failure frequency (S33), and the count value c is less than the threshold value M In this case, the processing is immediately repeated again from the acquisition of the frame image by the frame image acquisition unit 120. When the count value c is equal to or greater than the threshold value M, the detection symbol buffer 1340 is initialized (S34), and the continuous detection failure counter 1360 Is reset (S35), and the process is repeated from the acquisition of the frame image by the frame image acquisition unit 120 again.

  As described above, in this embodiment, in addition to the processing of the first embodiment, when the detection result is low (all the phase threshold values X_k are equivalent to less than the threshold value A) and the detection result is continuous, the digital watermark detection is performed. Is detected, the detected symbol buffer 1340 is initialized. As a result, for example, as shown in FIG. 2-3, there are printed matter A and B with different digital watermark information embedded therein, and detection from the former is performed halfway, and the detection symbol buffer 1340 is partially written. Sometimes, when the user moves the camera and re-photographs the second image, the detection symbol buffer 1340 is initialized before the second image is taken out of the frame, and different digital watermark information is obtained. It is possible to prevent the detection symbol buffer 1340 from being mixed and causing an unnecessary increase in the number of trials until erroneous detection or successful detection. In the example of FIG. 2-3, if the processing as in the present embodiment is not performed, erroneous information “123D” is detected.

  The overall configuration of the digital watermark detection apparatus in the third embodiment of the present invention is the same as that of FIG. The configuration of the digital watermark detection unit 130 is the same as that shown in FIGS. The difference is basically only the processing in the buffer writing unit 1330 in the digital watermark detection unit 130.

FIG. 3A shows an overall processing flow of the digital watermark detection apparatus according to the first embodiment to which the present embodiment is applied. Only the processing of the parts different from the first embodiment will be described below.
As shown in FIG. 3A, in the digital watermark detection unit 130 in the digital watermark detection apparatus according to the present embodiment, the correlation value X_k (k = 1... K) obtained from the detection target sequence is first set to a threshold value based on the threshold value A. A determination is made (S46), and for k that is equal to or greater than the threshold A, it is next determined whether or not the k-th storage area of the detection symbol buffer 1340 has been written (S47). The detected symbol value S_k and the correlation value X_k are written in the area (S50). On the other hand, if it has been written in the determination of whether or not it has been written in S47, the k-th correlation value Y_k and X_k in the detected symbol buffer 1340 are further compared (S48), and Y_k is less than X_k. If there is a match, the k-th symbol value T_k in the detected symbol buffer 1340 is compared with the detected symbol value S_k (S49). If they match, the k-th storage area of the detected symbol buffer 1340 is stored. S_k and X_k are written (S50). That is, T_k ← S_k, Y_k ← X_k. If there is no match in the match comparison between T_k and S_k in S49, the detected symbol buffer 1340 is initialized (S53), and the process returns to the process of the frame image acquisition unit 120.

It is obvious that the present embodiment is not limited to the application to the first embodiment but can be easily applied to the second embodiment.
In this embodiment, it is determined that the symbol value held in the detected symbol buffer 1340 has been detected reliably (correlation value X_k is equal to or greater than the threshold value A), and it is determined that the symbol value held in the detected symbol buffer 1340 has also been reliably detected. If the symbol values are different, it is determined that detection has been performed across images embedded with different digital watermarks, and the detection symbol buffer 1340 is initialized. Thus, for example, as shown in FIG. 3-2, when there is a printed material A and a B in which different digital watermark information is embedded, detection from the A is performed halfway, and the detection symbol buffer is partially written. When the user moves the camera and re-photographs the image, the symbol value in the detection symbol buffer 1340 and the symbol detected reliably in this trial when the image of the image is taken out Since the values (“1” and “A” in FIG. 3-2) are different, by initializing the detection symbol buffer 1340, different digital watermark information is mixed in the detection symbol buffer, and erroneous detection or It is possible to prevent an unnecessary increase in the number of trials until the detection is successful. In the example of FIG. 3B, if the processing as in the present embodiment is not performed, erroneous information “AB3D” will be detected.

  The overall configuration of the digital watermark detection apparatus according to the fourth embodiment of the present invention is the same as that shown in FIG. FIG. 4A shows the configuration of the digital watermark detection unit 130 based on the first embodiment to which this embodiment is applied, and FIG. 4B shows the overall processing of the digital watermark detection apparatus based on the first embodiment to which this embodiment is applied. An example of the flow is shown. Only the parts different from the first embodiment will be described below.

  Assume that the digital watermark detection apparatus in this embodiment is an apparatus capable of outputting a screen or audio. In the buffer writing unit 1330 of the digital watermark detection unit 130, if there is one or more k that is equal to or greater than the threshold A among the correlation values X_k (k = 1... K) obtained from the detection target sequence, the currently processed frame A sound or screen display indicating that there is a possibility of digital watermark detection from the image is performed (S68). Specifically, it emits a beep, displays a message such as “Capturing a detectable image, so continue shooting”, or outputs a beep with the pitch or volume changed according to the correlation value X_k. Or

It is obvious that the present embodiment is not limited to the application to the first embodiment but can be easily applied to the second and third embodiments.
According to the present embodiment, when an analog image capable of detecting a digital watermark is being shot, a shooting method that can detect a digital watermark is used by outputting a screen or audio to the user. The user can be interactively fed back, and the number of detection trials can be further reduced and an excellent user interface can be provided to the user. Specifically, for example, if the subject and the camera are extremely far away or too close, there is no output because there is no possibility of detecting the watermark, but the camera position is moved little by little to detect the watermark. When there is a possibility (correlation value X_k is greater than or equal to threshold A), audio or screen output occurs. As a result, the user can know that the method of shooting when sound or screen output occurs is highly likely to detect digital watermarks, and feed back to the shooting method so as to continue the shooting method with high detection possibility. It takes. As a result, the number of detection trials can be further reduced, and by providing feedback in real time for the user, an excellent user interface can be provided to the user in the sense that it is easy to perform digital watermark detection.

  The overall configuration of the digital watermark detection apparatus according to the fifth embodiment of the present invention is the same as that shown in FIG. The configuration of the digital watermark detection unit 130 is the same as in FIG. FIG. 5A shows an example of the overall processing flow of the digital watermark detection apparatus based on the first embodiment to which the present embodiment is applied. Only the parts different from the first embodiment will be described below.

  In this embodiment, the digital watermark detection unit 130 determines whether or not the symbol values and correlation values have been written for all the symbol positions 1 to K in the detection symbol buffer 1340. If there is a part that has not been written yet, based on the ratio of the number of already written symbol positions to the total number of symbols, the progress of digital watermark detection up to now can be displayed to the user by screen output or audio output. Notification is made (S92).

Specifically, when performing screen / audio output, the output method is changed according to the detection progress rate α given by the following equation.
α = a / K (1)
In the above equation (1), a is the number of written storage areas in the detected symbol buffer, and K is a predetermined number of digital watermark symbols. The detection progress rate α clearly takes a value between 0 and 1.

  FIG. 5-2 shows an example of screen / audio output using the detection progress rate α in the present embodiment. FIG. 5-2 (a) is for directly drawing the numerical value of α on the screen. FIG. 5-2 (b) shows α displayed as a bar graph. There can be various other output methods such as changing the screen background color depending on α. Further, FIG. 5-2 (c) is an example in which the sound volume at the time of sound output is changed according to α. Further, FIG. 5-2 (d) is an example in which the timbre of the audio output is changed according to α. There can be various other output methods such as changing the pitch of a beep sound and switching and playing several kinds of music.

It is obvious that the present embodiment is not limited to application to the first embodiment but can be easily applied to the second to fourth embodiments.
According to the present embodiment, the progress of detection of digital watermarks up to now can be screened or output to the user, and the progress can be interactively fed back to the user. User interface can be provided to users.

  The overall configuration of the digital watermark detection apparatus according to the sixth embodiment of the present invention is the same as that shown in FIG. The configuration of the digital watermark detection unit 130 is the same as in FIG. FIG. 6A shows an overall processing flow of the digital watermark detection apparatus according to the first embodiment to which the present embodiment is applied. Only the parts different from the first embodiment will be described below.

  It is assumed that the digital watermark detection apparatus in this embodiment is an apparatus capable of screen output. For example, this is a camera-equipped mobile phone. The digital watermark detection apparatus captures continuous frames at the camera input unit 110, displays the captured frame image group on the display screen as a preview (S112), and in parallel, the frame image acquisition unit 120 and the digital watermark detection unit 130. The digital watermark detection process is performed according to (S101 to S111).

It is obvious that this embodiment is not limited to the application to the first embodiment but can be easily applied to the second and fifth embodiments.
According to the present embodiment, since the frame rewriting time of the preview is generally shorter than the trial processing time of the digital watermark detection process, it is possible to make the user seem to detect the digital watermark from the frame in real time. In addition, in combination with the fourth or fifth embodiment, for example, when shooting while looking at the camera preview screen, such as a camera-equipped mobile phone, when the digital watermark detection possibility is high, it is displayed on the preview display screen. It is possible to provide a user with a more intuitive user interface such as outputting a message to that effect.

  FIG. 6-2 shows an example when this embodiment is applied to a camera-equipped mobile phone. On the display screen of the camera-equipped telephone, an analog image with a digital watermark being captured by the camera is previewed in real time, and the detection progress is displayed on the screen according to the fifth embodiment. As a result, the user can interactively feed back the method of shooting an analog image with a digital watermark as a shooting target according to the detection progress display while viewing only the display screen.

  Note that the present invention can be realized by configuring a part or all of the processing functions of each unit in the digital watermark detection apparatus shown in FIG. 1-1 and the like by a computer program and executing the program using the computer. Alternatively, the processing procedure shown in FIG. 1-2, FIG. 2-2, FIG. 3-1, FIG. 4-2, FIG. 5-1, and FIG. It goes without saying that it can be executed. In addition, a computer-readable recording medium such as an FD, MO, ROM, memory card, CD, or the like is stored in the computer. In addition, the program can be recorded and stored on a DVD, a removable disk, etc., and the program can be distributed through a network such as the Internet.

1 is an overall configuration diagram of a digital watermark detection apparatus of the present invention. It is a whole processing flow figure of Example 1 of the present invention. It is a figure explaining the process of a frame image acquisition part. It is a block diagram of the digital watermark detection part of Example 1 of this invention. It is a figure explaining the structure of a detection symbol buffer. It is a figure explaining the writing to a detection symbol buffer. It is a figure explaining the process of an output determination part. It is a figure explaining the effect of Example 1 of this invention. It is a block diagram of the digital watermark detection part of Example 2 of this invention. It is a whole process flowchart of Example 2 of this invention. It is a figure explaining the effect of Example 2 of this invention. It is a whole processing flow figure of Example 3 of the present invention. It is a figure explaining the effect of Example 3 of this invention. It is a block diagram of the digital watermark detection part of Example 4 of this invention. It is a whole process flowchart of Example 4 of this invention. It is a whole processing flow figure of Example 5 of the present invention. It is a figure explaining the audio | voice / screen output method by Example 5 of this invention. It is a whole process flowchart of Example 6 of this invention. It is a figure which shows the example of a screen display of Example 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Digital watermark detection apparatus 110 Camera input part 120 Frame image acquisition part 130 Digital watermark detection part 1310 Detection target series extraction part 1320 Spread spectrum demodulation part 1330 Buffer writing part 1340 Detection symbol buffer 1350 Output determination part 1360 Continuous detection failure frequency counter

Claims (13)

This is a digital watermark detection method for capturing an analog image with a digital watermark that is an analog output of a digital image embedded with a digital watermark based on spread spectrum modulation for each symbol, and detecting the digital watermark from the captured image. And
Continuously inputting a group of frame images from an analog input device;
Obtaining one frame image from the frame image group;
Extracting a detection target sequence from the frame image;
Performing symbol spread spectrum demodulation of the detection target sequence to obtain a symbol value S_k and a correlation value X_k (k = 1... K, K is a symbol length);
For each of the correlation values X_k, a threshold value is determined based on a predetermined threshold value A. As a result of the threshold value determination, the symbol value S_k obtained as a result of the demodulation or the symbol for the symbol having the correlation value X_k equal to or greater than the threshold value A Writing each of the value S_k and the correlation value X_k into a storage area corresponding to the k-th symbol position of the detection symbol buffer whose initial value is a value representing an unwritten state;
When symbol values or symbol values and correlation values have been written for all symbol positions (1... K) in the detected symbol buffer, based on all symbol values stored in the detected symbol buffer. Generating and outputting detected watermark information and ending the process;
If there remains a symbol position in which no symbol value or correlation value is written in the detected symbol buffer, repeating the process of obtaining one frame image from the frame image group again;
A digital watermark detection method comprising: This is a digital watermark detection method for capturing an analog image with a digital watermark that is an analog output of a digital image embedded with a digital watermark based on spread spectrum modulation for each symbol, and detecting the digital watermark from the captured image. And
Continuously inputting a group of frame images from an analog input device;
Obtaining one frame image from the frame image group;
Extracting a detection target sequence from the frame image;
Performing symbol spread spectrum demodulation of the detection target sequence to obtain a symbol value S_k and a correlation value X_k (k = 1... K, K is a symbol length);
For each of the correlation values X_k, a threshold value is determined based on a predetermined threshold value A. As a result of the threshold value determination, the symbol value S_k obtained as a result of the demodulation or the symbol for the symbol having the correlation value X_k equal to or greater than the threshold value A Writing each of the value S_k and the correlation value X_k into a storage area corresponding to the k-th symbol position of the detection symbol buffer whose initial value is a value representing an unwritten state;
The number of consecutive cases in which the correlation value X_k for each symbol is less than the threshold A by the threshold determination is counted in a continuous detection failure counter, and the count value of the counter becomes a predetermined number M. And initializing all values of the detected symbol buffer;
When symbol values or symbol values and correlation values have been written for all symbol positions (1... K) in the detected symbol buffer, based on all symbol values stored in the detected symbol buffer. Generating and outputting detected watermark information and ending the process;
If there remains a symbol position in which no symbol value or correlation value is written in the detected symbol buffer, repeating the process of obtaining one frame image from the frame image group again;
A digital watermark detection method comprising: This is a digital watermark detection method for capturing an analog image with a digital watermark that is an analog output of a digital image embedded with a digital watermark based on spread spectrum modulation for each symbol, and detecting the digital watermark from the captured image. And
Continuously inputting a group of frame images from an analog input device;
Obtaining one frame image from the frame image group;
Extracting a detection target sequence from the frame image;
Performing symbol spread spectrum demodulation of the detection target sequence to obtain a symbol value S_k and a correlation value X_k (k = 1... K, K is a symbol length);
For each correlation value X_k, a threshold value is determined based on a predetermined threshold value A. As a result of the threshold value determination, a symbol having a correlation value X_k that is equal to or greater than the threshold value A, and an initial value is a value indicating an unwritten state. When the storage area corresponding to the k-th symbol position of the detection symbol buffer to be taken is in an unwritten state, or the storage area corresponding to the k-th symbol position of the detection symbol buffer is in a written state and written symbol value T_k When the symbol values S_k match and the written symbol correlation value Y_k is less than the correlation value X_k, the symbol value S_k and the correlation value X_k obtained as a result of the demodulation are used as the k-th symbol position of the detection symbol buffer. Writing to the corresponding storage areas respectively to T_k, Y_k;
As a result of the threshold determination, the symbol having a correlation value X_k equal to or greater than the threshold A, the storage area corresponding to the k-th symbol position of the detection symbol buffer is in a written state, and the written symbol value If T_k and the symbol value S_k do not match, initializing all values of the detected symbol buffer;
When symbol values and correlation values are written in all symbol positions (1... K) in the detected symbol buffer, all symbol values T_k (k = 1...) Stored in the detected symbol buffer. Generating and outputting detected watermark information based on K) and ending the process;
If there remains a symbol position in which no symbol value and correlation value are written in the detected symbol buffer, repeating the process of acquiring one frame image from the frame image group again;
A digital watermark detection method comprising: The digital watermark detection method according to any one of claims 1 to 3,
As a result of the threshold determination, if there is a symbol having a correlation value X_k that is equal to or higher than the threshold A, the user is informed that there is a possibility of digital watermark detection from the currently input image by screen output or audio output. And a step of notifying the electronic watermark detection method. The digital watermark detection method according to any one of claims 1 to 4,
When it is determined whether or not the symbol values or the correlation values with the symbol values have been written for all symbol positions (1... K) of the detected symbol buffer, there is a portion that has not yet been written. The electronic system further comprises a step of notifying a user of a digital watermark detection progress up to the present by screen output or voice output based on a ratio between the number of already written symbol positions and the total number of symbols. Watermark detection method. The digital watermark detection method according to any one of claims 1 to 5,
A step of displaying a preview of a group of frame images continuously input from the analog input device;
A digital watermark detection method, wherein a digital watermark detection process is performed in parallel with the preview display step. A digital watermark detection apparatus that captures an analog image with a digital watermark, which is an analog output of a digital image embedded with a digital watermark based on spread spectrum modulation for each symbol, using an analog input device, and detects the digital watermark from the captured image. And
Image input means for continuously inputting a frame image group from an analog image with digital watermark, frame image acquisition means for acquiring one frame image from the frame image group, and digital watermark detection means for detecting digital watermark information With
The digital watermark detection means includes
Means for inputting a frame image acquired by the frame image acquisition means and extracting a detection target sequence;
Means for obtaining a symbol value S_k and a correlation value X_k (k = 1... K, K is a symbol length) by performing spread spectrum demodulation for each symbol on the detection target sequence;
For each of the correlation values X_k, a threshold value is determined based on a predetermined threshold value A. As a result of the threshold value determination, a symbol value S_k obtained as a result of the demodulation or the symbol value S_k or the Means for writing the symbol value S_k and the correlation value X_k respectively into a storage area corresponding to the k-th symbol position of the detection symbol buffer whose initial value is a value representing an unwritten state;
When symbol values or symbol values and correlation values have been written for all symbol positions (1... K) in the detected symbol buffer, based on all symbol values stored in the detected symbol buffer. Means for generating and outputting detected watermark information and terminating the process;
Means for repeating digital watermark detection by inputting a single frame image from the frame image acquisition means again when a symbol position in which no symbol value or correlation value is written is left in the detected symbol buffer When,
A digital watermark detection apparatus comprising: A digital watermark detection apparatus that captures an analog image with a digital watermark, which is an analog output of a digital image embedded with a digital watermark based on spread spectrum modulation for each symbol, using an analog input device, and detects the digital watermark from the captured image. And
Image input means for continuously inputting a frame image group from an analog image with digital watermark, frame image acquisition means for acquiring one frame image from the frame image group, and digital watermark detection means for detecting digital watermark information With
The digital watermark detection means includes
Means for inputting a frame image acquired by the frame image acquisition means and extracting a detection target sequence;
Means for obtaining a symbol value S_k and a correlation value X_k (k = 1... K, K is a symbol length) by performing spread spectrum demodulation for each symbol on the detection target sequence;
For each of the correlation values X_k, a threshold value is determined based on a predetermined threshold value A. As a result of the threshold value determination, the symbol value S_k obtained as a result of the demodulation or the symbol for the symbol having the correlation value X_k equal to or greater than the threshold value A Means for writing the value S_k and the correlation value X_k respectively in a storage area corresponding to the k-th symbol position of the detection symbol buffer whose initial value is a value indicating an unwritten state;
As a result of the threshold determination, the number of consecutive cases where the correlation value X_k for each symbol is less than the threshold A is counted in the continuous detection failure counter, and the count value of the counter becomes a predetermined number of times M. Sometimes means for initializing all values of the detected symbol buffer;
When symbol values or symbol values and correlation values have been written for all symbol positions (1... K) in the detected symbol buffer, based on all symbol values stored in the detected symbol buffer. Means for generating and outputting detected watermark information and terminating the process;
Means for repeating digital watermark detection by inputting a single frame image from the frame image acquisition means again when a symbol position in which no symbol value or correlation value is written is left in the detected symbol buffer When,
A digital watermark detection apparatus comprising: A digital watermark detection apparatus that captures an analog image with a digital watermark, which is an analog output of a digital image embedded with a digital watermark based on spread spectrum modulation for each symbol, using an analog input device, and detects the digital watermark from the captured image. And
Image input means for continuously inputting a frame image group from an analog image with digital watermark, frame image acquisition means for acquiring one frame image from the frame image group, and digital watermark detection means for detecting digital watermark information With
The digital watermark detection means includes
Means for inputting a frame image acquired by the frame image acquisition means and extracting a detection target sequence;
Means for obtaining a symbol value S_k and a correlation value X_k (k = 1... K, K is a symbol length) by performing spread spectrum demodulation for each symbol on the detection target sequence;
For each correlation value X_k, a threshold value is determined based on a predetermined threshold value A. As a result of the threshold value determination, a symbol having a correlation value X_k that is equal to or greater than the threshold value A, and an initial value is a value indicating an unwritten state. When the storage area corresponding to the k-th symbol position of the detection symbol buffer to be taken is in an unwritten state, or the storage area corresponding to the k-th symbol position of the detection symbol buffer is in a written state and written symbol value T_k When the symbol values S_k match and the written symbol correlation value Y_k is less than the correlation value X_k, the symbol value S_k and the correlation value X_k obtained as a result of the demodulation are used as the k-th symbol position of the detection symbol buffer. Means for writing to the corresponding storage areas respectively to be T_k, Y_k;
As a result of the threshold determination, the symbol having a correlation value X_k equal to or greater than the threshold A, the storage area corresponding to the k-th symbol position of the detection symbol buffer is in a written state, and the written symbol value Means for initializing all values of the detected symbol buffer if T_k and the symbol value S_k do not match;
When symbol values and correlation values are written in all symbol positions (1... K) in the detected symbol buffer, all symbol values T_k (k = 1...) Stored in the detected symbol buffer. Means for generating and outputting detected watermark information based on K) and terminating the process;
Means for repeating the digital watermark detection by inputting a single frame image from the frame image acquisition means again when there remains a symbol position in which no symbol value and correlation value are written in the detection symbol buffer;
A digital watermark detection apparatus comprising: The digital watermark detection apparatus according to any one of claims 7 to 9,
If the result of the threshold determination is that there is a symbol having a correlation value X_k greater than or equal to the threshold A, the digital watermark detection means may detect the digital watermark from the currently input image by screen output or audio output. An electronic watermark detection apparatus, further comprising means for notifying a user that there is an image. The digital watermark detection apparatus according to any one of claims 7 to 10,
The digital watermark detection means determines whether or not the symbol value or the symbol value and the correlation value have been written for all the symbol positions (1... K) of the detected symbol buffer. In the case where there is no part, there is further provided means for notifying the user of the digital watermark detection progress up to the present by screen output or audio output based on the ratio of the number of already written symbol positions to the total number of symbols. An electronic watermark detection apparatus comprising: The digital watermark detection apparatus according to any one of claims 7 to 11,
An electronic watermark detection apparatus further comprising means for displaying a preview of a group of frame images continuously input from the image input means, and performing digital watermark detection processing in parallel with the preview display step.   A program for causing a computer to execute the digital watermark detection method according to claim 1.

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