JP4736794B2 - Digital watermark encoding apparatus, digital watermark decoding apparatus, digital watermark encoding method, digital watermark decoding method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic watermark encoding device etc., for effectively protecting speech data while freely providing data representing speeches. <P>SOLUTION: A speech data input unit E1 of the electronic watermark encoding device E acquires the speech data representing a speech, and a pitch specifying unit E2 specifies the frequency of a pitch component of the speech; and a BPFE 3 extracts a pitch component having a frequency near the frequency, and a BRFE 4 shifts the frequency. A switching unit E5 processes the frequency-shifted pitch component so that the pitch component has a pattern of intermittence representing a value of data to be embedded as an electronic watermark, and an adding unit E6 adds it to the original speech data. The electronic watermark decoding device acquires electronically watermarked speech data and extracts a pitch component similarly to the electronic watermark encoding device E, and a pitch array extracting unit specifies embedded data from a pattern of multiplexing of the pitch component. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a digital watermark encoding apparatus, a digital watermark decoding apparatus, a digital watermark encoding method, a digital watermark decoding method, and a program.

As a technique for synthesizing speech, there is a technique called a recording editing system. The recording / editing system is used in a station voice guidance system, an in-vehicle navigation system, and the like.
The recording and editing method associates a word with voice data representing a voice that reads out the word, divides a sentence to be synthesized into words, and acquires voice data associated with these words. This is a technique of joining them together (for example, see Patent Document 1).
JP 10-49193 A

  As a technique for making it possible to change the speaker of the synthesized speech obtained by the recording and editing method, or to diversify the synthesized speech obtained, record the speech data on removable media (portable recording media). As one to use, a plurality of removable media in which different audio data are recorded may be replaced as necessary. However, there is a problem that the audio data recorded on the removable medium is likely to be illegally copied, falsified or otherwise illegally used.

  The present invention has been made in view of the above circumstances, and is an electronic watermark encoding apparatus, electronic watermark decoding apparatus, electronic watermark encoding for effectively protecting audio data while freely supplying data representing sound. It is an object to provide a method, a digital watermark decoding method, and a program.

In order to achieve the above object, a digital watermark encoding apparatus according to the first aspect of the present invention provides:
An audio signal acquisition means for acquiring an audio signal representing the audio;
Subject distribution on the time axis of the multiplexed portion by superimposing pitch component obtained by shifting the frequency of the pitch component of the speech represented by the audio signal on the obtained audio signal is embedded as a digital watermark to represent the value of the data, by processing the acquired voice signal, a voice signal processing means for generating an audio signal subjected to digital watermark,
Characterized the Ruco equipped with.

The audio signal processing means is, for example,
Pitch component extraction means for extracting a pitch component signal representing the pitch component of the voice represented by the voice signal from the acquired voice signal;
Pitch component frequency shifting means for shifting the frequency of the pitch signal;
Pitch component processing means for acquiring the pitch component signal whose frequency has been shifted and processing the pitch component signal so as to have an intermittent pattern on the time axis representing the value of data to be embedded as a digital watermark;
What is necessary is just to include an adding means for generating the digital watermarked audio signal by adding the processed pitch component signal and the audio signal to each other.

The pitch component extraction means is, for example,
Pitch frequency specifying means for specifying the frequency of the pitch component of the voice represented by the voice signal;
What is necessary is just to be provided with the band pass filter which extracts the component of the said frequency vicinity specified as said pitch component among the said audio | voice signals.

A digital watermark decoding apparatus according to the second aspect of the present invention provides:
An audio signal acquisition means for acquiring an audio signal to which a digital watermark is applied, which represents audio;
Pitch component extraction means for extracting a pitch component signal representing the pitch component of the voice represented by the voice signal from the acquired voice signal;
Of the extracted pitch component signal, the distribution of the portion on the time axis of the portion that is multiplexed by superimposing the pitch component of the voice and the pitch component obtained by shifting the frequency of the pitch component. Specifying means for specifying a pattern, and specifying data embedded as a digital watermark in the audio signal based on the specified pattern;
It is characterized by providing.

A digital watermark encoding method according to a third aspect of the present invention is a digital watermark encoding method executed in an apparatus having an audio signal acquisition unit and an audio signal processing unit,
An audio signal acquisition step in which the audio signal acquisition unit acquires an audio signal representing the audio;
The audio signal processing unit, the distribution on the time axis of the multiplexed portion by superimposing pitch component obtained by shifting the frequency of the pitch component of the speech represented by the audio signal on the obtained audio signal Is a voice signal processing step of generating a digital watermarked voice signal by processing the acquired voice signal so as to represent the value of data to be embedded as a digital watermark ;
It is characterized by providing .

A digital watermark decoding method according to a fourth aspect of the present invention is a digital watermark decoding method executed in an apparatus having an audio signal acquisition unit, a pitch component extraction unit, and a specification unit,
An audio signal acquisition step in which the audio signal acquisition unit acquires an audio signal to which a digital watermark is applied, which represents audio;
A pitch component extraction step in which the pitch component extraction unit extracts a pitch component signal representing a pitch component of the voice represented by the voice signal from the acquired voice signal;
Of the extracted pitch component signal, the time of the portion multiplexed by superimposing the pitch component obtained by shifting the frequency of the pitch component and the pitch component obtained by shifting the frequency of the pitch component in the extracted pitch component signal A specifying step of specifying a pattern of distribution on the axis and specifying data embedded as a digital watermark in the audio signal based on the specified pattern;
It is characterized by providing.

A program according to the fifth aspect of the present invention is
Computer
An audio signal acquisition means for acquiring an audio signal representing the audio ;
Subject distribution on the time axis of the multiplexed portion by superimposing pitch component obtained by shifting the frequency of the pitch component of the speech represented by the audio signal on the obtained audio signal is embedded as a digital watermark of to represent the value of the data, by processing the acquired voice signal, audio signal processing means for generating an audio signal subjected to digital watermark,
Characterized in that it is intended to function as a.

A program according to the sixth aspect of the present invention is
Computer
An audio signal acquisition means for acquiring an audio signal to which an electronic watermark has been applied, representing the audio;
Pitch component extraction means for extracting a pitch component signal representing the pitch component of the voice represented by the voice signal from the acquired voice signal;
Of the extracted pitch component signal, the distribution of the portion on the time axis of the portion that is multiplexed by superimposing the pitch component of the voice and the pitch component obtained by shifting the frequency of the pitch component. Means for identifying a pattern and identifying data embedded as a digital watermark in the audio signal based on the identified pattern;
It is for making it function as.

  According to the present invention, there are provided a digital watermark encoding device, a digital watermark decoding device, a digital watermark encoding method, a digital watermark decoding method, and a program for effectively protecting audio data while freely providing data representing audio. Realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking a digital watermark encoding apparatus and a digital watermark decoding apparatus as examples.

(Digital watermark encoding device)
FIG. 1 is a diagram showing a configuration of a digital watermark encoding apparatus E according to an embodiment of the present invention. As shown in the figure, the digital watermark encoding apparatus E includes an audio data input unit E1, a pitch specifying unit E2, a BPF (band pass filter) E3, a pitch shift unit E4, a switching unit E5, and an adding unit E6. It is configured.

The audio data input unit E1, the pitch identification unit E2, the BPFE3, the pitch shift unit E4, the switching unit E5, and the addition unit E6 store, for example, a processor such as a CPU (central processing unit) and a program to be executed by the processor. It consists of memory etc.
A single processor may perform a part or all of the functions of the audio data input unit E1, the pitch specifying unit E2, the BPFE3, the pitch shift unit E4, the switching unit E5, and the adding unit E6.

  The voice data input unit E1 obtains input voice data in a digital format (for example, PCM (pulse code modulation) format) representing a voice waveform from the outside, and supplies the input voice data to the pitch specifying unit E2, BPFE3, and the adding unit E6. .

  Note that the voice data input unit E1 may acquire any input voice data. For example, the voice data input unit E1 may acquire the voice data from an external device (for example, a hard disk device) or a network via an interface circuit (not shown). You may read from the recording medium (for example, a flexible disk, CD-ROM, etc.) set to the recording medium drive device which does not carry out via this recording medium drive device.

  The pitch specifying unit E2 specifies the time change of the frequency of the pitch component of the voice represented by the input voice data supplied from the voice data input unit E1, and represents the specified time change (hereinafter referred to as pitch frequency data). Is continuously supplied to BPFE3.

  Specifically, the pitch specifying unit E2 may specify the time change of the frequency of the pitch component, for example, by performing cepstrum analysis on the input voice data. That is, for example, the waveform represented by the input voice data is divided into a number of small parts on the time axis, and the intensity of each obtained small part is substantially equal to the logarithm of the original value (the base of the logarithm is arbitrary). Convert this value into a value, and then convert this small portion of the spectrum (ie, the cepstrum) to a Fast Fourier Transform technique (or any other technique that produces data representing the result of Fourier transforming a discrete variable) ) Then, the minimum value among the frequencies giving the maximum value of the cepstrum is specified as the frequency of the pitch component in this small portion.

  The time change of the frequency of the pitch component is specified based on the pitch waveform data after converting the input voice data into the pitch waveform data according to the method disclosed in Japanese Patent Laid-Open No. 2003-108172, for example. A good result can be expected. Specifically, the input voice data is filtered to extract a pitch signal, and based on the extracted pitch signal, the waveform represented by the input voice data is divided into sections of unit pitch length. The input speech data may be converted into a pitch waveform signal by identifying the phase shift based on the correlation between the two and aligning the phases of the sections. Then, the obtained pitch waveform signal is handled as input voice data, and a cepstrum analysis is performed, for example, so that the time change of the frequency of the pitch component may be specified.

The BPFE 3 performs filtering so as to pass components of its own center frequency and frequencies in the vicinity thereof among signals input to the BPFE 3 and substantially block other components.
Specifically, the self center frequency is set to be substantially equal to the value indicated by the pitch frequency data supplied from the pitch specifying unit E2 (that is, the current value of the frequency of the pitch component of the input audio data). . Then, the input voice data supplied from the voice data input unit E1 is filtered, and the filtered input voice data (hereinafter referred to as pitch component) is supplied to the pitch shift unit E4. Note that the pitch components are all composed of data in the same format, for example, digital data having a sampling interval substantially the same as the sampling interval of the input audio data.

  The pitch shift unit E4 acquires the pitch component from the BPFE 3, shifts the frequency of the pitch component by a certain width (the width shown as “Δf” in FIG. 2), as shown in FIG. 2, and then goes to the switching unit E5. Supply. Specifically, for example, the pitch shift unit E4 generates a local oscillation signal having a frequency equal to the value Δf, mixes the local oscillation signal and the pitch component, filters the obtained signal, The frequency of the pitch component may be shifted by extracting a component having a frequency corresponding to the sum or difference between the frequency of the local oscillation signal and the frequency of the pitch signal.

  The switching unit E5 provides a path through which the frequency-shifted pitch component passes from the pitch shift unit E4 to the addition unit E6, while the binary bit string (for example, input) to be embedded in the form of a digital watermark from the outside. Data representing the name of the creator of the audio data as a binary bit string). Then, the pitch component is encoded so as to include information represented by the bit string by interrupting the path according to each bit value in the bit string.

  Specifically, as shown in FIG. 3, for example, the switching unit E5 determines the value of each bit in order from the beginning of the bit string, and if the value of the bit is “1”, the switching unit E5 determines a certain time (in FIG. The operation of allowing the pitch component to pass through the adding unit E6 only for the time (ΔT) and blocking the pitch component for the time ΔT if the value is “0” until the last bit of the bit string is reached. You can continue.

  Note that the method by which the switching unit E5 acquires the bit string is arbitrary, and for example, the bit string may be acquired by a method substantially the same as the method by which the audio data input unit E1 acquires the input audio data. In addition, the processor that performs the process of realizing the function of the switching unit E5 moves to the process of realizing the function of the switching unit E5 by using the bit string generated by the other process performed by itself as a bit string embedded in the form of a digital watermark. You may make it deliver.

  The adder E6 acquires the input audio data supplied from the audio data input unit E1, and also acquires this pitch component while the pitch component is supplied from the BPFE 3. The output audio data having a value corresponding to the sum of the values of the input audio data and the pitch component acquired at the same time (provided that the value of the pitch component is 0 while the pitch component is not supplied). Is generated and output. The output audio data is assumed to be composed of data in the same format as the input audio data acquired by the audio data input unit E1.

The output audio data corresponds to the input audio data acquired by the audio data input unit E1 and is digitally watermarked, in which information represented by the bit string acquired by the pitch shift unit E4 is embedded. It can be said that there is.
Specifically, for example, the pitch component of the input audio data is extracted by BPFE3, processed by the processing shown in FIGS. 2 and 3, and then added to the original input audio data by the adder E6. If data is generated, the time change of the pitch component included in the output audio data is as shown in FIG. That is, this output audio data is substantially the same as the input audio data for the section in which the bit of value “0” is embedded, while the input audio data for the section in which the bit of value “1” is embedded. In addition, another pitch component whose frequency is shifted by Δf from the original pitch component is superposed, so that the pitch component is multiplexed.

  Note that the adding unit E6 can output the output audio data in any manner. For example, the adding unit E6 may store the output audio data in a storage area of an external device (for example, a hard disk device) via an interface circuit (not shown) or to a network. May be sent. Further, the recording medium may be written to a recording medium set in a recording medium drive device (not shown) via the recording medium drive device.

(Digital watermark decoding device)
FIG. 5 is a diagram showing the configuration of the digital watermark decoding apparatus D according to the embodiment of the present invention. As shown in the figure, the digital watermark decoding apparatus D is composed of an audio data input unit D1, a pitch specifying unit D2, a BPFD 3, and a bit string extraction unit D4.

  The audio data input unit D1, the pitch identification unit D2, the BPFD 3, and the bit string extraction unit D4 are configured by, for example, a processor such as a CPU and a memory that stores a program to be executed by the processor. Note that a single processor may perform a part or all of the functions of the audio data input unit D1, the pitch identification unit D2, the BPFD 3, and the bit string extraction unit D4.

  The audio data input unit D1 obtains, from the outside, digital audio data (hereinafter referred to as decoding target audio data) to which digital watermarking is applied, corresponding to the output audio data described above, and the pitch specifying unit D2 and Supply to BPFD3. The method by which the audio data input unit D1 acquires the decoding target audio data is arbitrary. For example, the audio data input unit E1 of the digital watermark encoding device E described above is substantially the same as the method by which the input audio data is acquired. Get it.

  The pitch specifying unit D2 is substantially the same as the technique in which the pitch specifying unit E2 of the digital watermark encoding apparatus E performs the time change of the frequency of the pitch component of the voice represented by the decoding target audio data supplied from the audio data input unit D1. Specify by the same method. And the pitch frequency data showing the specified said time change is continuously supplied to BPFD3.

  Note that the pitch specifying unit D2 interpolates a portion corresponding to a section of the audio data to be decoded that does not include a pitch component in the pitch frequency data by a method such as Lagrange interpolation or linear interpolation, for example. do it.

The BPFD 3 performs substantially the same function as the BPFE 3 of the digital watermark encoding apparatus E, for example, and passes the center frequency of the signal input to itself and components in the vicinity thereof, Filtering is performed so as to substantially block the components.
The filtered decoding target audio data (hereinafter referred to as a decoding pitch component) is supplied to the bit string extraction unit D4.

  The bit string extraction unit D4 acquires the decoding pitch component supplied from the BPFD 3, and extracts the bit string embedded in the decoding target audio data based on the frequency shift pattern of the decoding pitch component. Then, the extracted bit string is output to the outside.

  Specifically, for example, when the time change of the frequency of the pitch component of the audio data to be decoded is as shown in FIG. 4, the bit string extraction unit D4 performs time from the beginning of the decoding pitch component as shown in FIG. Determines whether or not the pitch component is multiplexed by ΔT, generates a bit with a value of “1” when it is determined that the pitch component is multiplexed, and determines that the pitch component is not multiplexed In this case, the bit string may be extracted by sequentially performing a process of generating a bit having a value of “0”.

  Note that the bit string extraction unit D4 can output the bit string in any manner. For example, the bit string extraction unit D4 may store the bit string in a storage area of an external device via an interface circuit (not shown) or send the bit string to a network. Further, the recording medium may be written to a recording medium set in a recording medium drive device (not shown) via the recording medium drive device.

  The digital watermark encoding apparatus E described above extracts the pitch component from the input audio data, shifts the frequency, and adds the pitch component to the original input audio data after being intermittent according to the value of the bit string to be embedded. The information represented by the bit string is embedded in the audio data (that is, the audio data is digitally watermarked). Then, the digital watermark decoding device D extracts the bit string embedded in the audio data by the digital watermark encoding device E from the audio data.

  In general, the frequency of the pitch component of the voice uttered by human beings is around 200 [Hz], while the human audible range is in the range of about 20 to 20000 [Hz], but the frequency around 200 [Hz]. The sensitivity of the component is low, and even if a change is caused in such a component, it is difficult to distinguish this change. Therefore, the difference between the audio reproduced using the audio data that has been digitally watermarked by the digital watermark encoding apparatus E and the audio reproduced using the audio data before the digital watermarking is Is difficult to identify. In other words, the influence of the digital watermark by the digital watermark encoding apparatus E on the sound is suppressed to a negligible level.

The digital watermark encoding apparatus E applies digital watermarking by partially multiplexing the pitch component of the audio data. Therefore, a person who does not know which of the multiplexed pitch components is the original pitch component can use the audio data before being subjected to the digital watermark from the audio data subjected to the digital watermark by the digital watermark encoding device E. Cannot be completely restored.
Also, it is possible to extract an embedded bit string from data obtained by analog copying audio data that has been digitally watermarked by the digital watermark encoding device E.

The configurations of the digital watermark encoding device E and the digital watermark decoding device D are not limited to those described above.
For example, the audio data input unit E1 may include a microphone, an amplifier, a sampling circuit, an A / D (Analog-to-Digital) converter, a PCM encoder, and the like. In this case, the audio data input unit E1 amplifies the audio signal representing the audio collected by its own microphone, performs sampling and A / D conversion, and then performs PCM modulation on the sampled audio signal, thereby generating audio. Data may be created.

  Although the embodiment of the present invention has been described above, the digital watermark encoding apparatus and the digital watermark decoding apparatus according to the present invention can be realized using a normal computer system, not a dedicated system.

  For example, a recording medium (CD-ROM, which stores a program for causing a personal computer to execute the operations of the audio data input unit E1, the pitch identification unit E2, BPFE3, the pitch shift unit E4, the switching unit E5, and the addition unit E6 described above. By installing the program from a flexible disk or the like, the digital watermark encoding apparatus E that executes the above-described processing can be configured.

  Further, the program is stored from a recording medium (CD-ROM, flexible disk, etc.) that stores a program for causing the personal computer to execute the operations of the audio data input unit D1, pitch identification unit D2, BPFD3, and bit string extraction unit D4. By installing, it is possible to configure the digital watermark decoding apparatus D that executes the above-described processing.

Note that a program for causing a personal computer to perform the function of the digital watermark encoding device E or the digital watermark decoding device D may be uploaded to a bulletin board (BBS) of a communication line and distributed via the communication line, for example. Further, the carrier wave may be modulated with a signal representing these programs, the obtained modulated wave may be transmitted, and the apparatus that receives the modulated wave may demodulate the modulated wave to restore these programs.
The above-described processing can be executed by starting up these programs and executing them under the control of the OS in the same manner as other application programs.

  When the OS shares a part of the processing, or when the OS constitutes a part of one component of the present invention, a program excluding the part is stored in the recording medium. May be. Also in this case, in the present invention, it is assumed that the recording medium stores a program for executing each function or step executed by the computer.

It is a block diagram which shows the structure of the digital watermark encoding apparatus which concerns on embodiment of this invention. It is a graph which shows the aspect by which the frequency of a pitch component is shifted. It is a graph which shows the aspect by which the pitch component shifted in frequency is intermittent. It is a graph which shows the time change of the frequency of the pitch component of output audio | voice data. It is a block diagram which shows the structure of the digital watermark decoding apparatus concerning embodiment of this invention.

Explanation of symbols

E Digital watermark encoding device E1 Audio data input unit E2 Pitch identification unit E3 BPF
E4 Pitch shift section E5 Switching section E6 Addition section D Digital watermark decoding device D1 Audio data input section D2 Pitch identification section D3 BPF
D4 Bit string extraction unit

Claims (8)

An audio signal acquisition means for acquiring an audio signal representing the audio;
The distribution on the time axis of the portion multiplexed by superimposing the pitch component obtained by shifting the frequency of the pitch component of the voice represented by the voice signal on the acquired voice signal is the target of embedding as a digital watermark. Audio signal processing means for generating a digital watermarked audio signal by processing the acquired audio signal so as to represent a data value;
An electronic watermark encoding apparatus comprising: The voice signal processing means is
Pitch component extraction means for extracting a pitch component signal representing the pitch component of the voice represented by the voice signal from the acquired voice signal;
Pitch component frequency shifting means for shifting the frequency of the pitch signal;
Pitch component processing means for acquiring the pitch component signal whose frequency has been shifted and processing the pitch component signal so as to have an intermittent pattern on the time axis representing the value of data to be embedded as a digital watermark;
Adding means for generating the digital watermarked audio signal by adding the processed pitch component signal and the audio signal to each other;
The digital watermark encoding apparatus according to claim 1. The pitch component extraction means includes
Pitch frequency specifying means for specifying the frequency of the pitch component of the voice represented by the voice signal;
A band pass filter that extracts a component in the vicinity of the identified frequency as the pitch component of the audio signal,
The digital watermark encoding apparatus according to claim 2. An audio signal acquisition means for acquiring an audio signal to which a digital watermark is applied, which represents audio;
Pitch component extraction means for extracting a pitch component signal representing the pitch component of the voice represented by the voice signal from the acquired voice signal;
Of the extracted pitch component signal, the distribution of the portion on the time axis of the portion that is multiplexed by superimposing the pitch component of the voice and the pitch component obtained by shifting the frequency of the pitch component. Specifying means for specifying a pattern, and specifying data embedded as a digital watermark in the audio signal based on the specified pattern;
An electronic watermark decoding apparatus comprising: An electronic watermark encoding method executed in an apparatus having an audio signal acquisition unit and an audio signal processing unit,
An audio signal acquisition step in which the audio signal acquisition unit acquires an audio signal representing the audio;
A distribution on the time axis of a portion multiplexed by the audio signal processing unit superimposing a pitch component obtained by shifting the frequency of the pitch component of the audio represented by the audio signal on the acquired audio signal An audio signal processing step for generating a digital watermarked audio signal by processing the acquired audio signal so as to represent a value of data to be embedded as a digital watermark;
An electronic watermark encoding method comprising: An electronic watermark decoding method executed in an apparatus having an audio signal acquisition unit, a pitch component extraction unit, and a specification unit,
An audio signal acquisition step in which the audio signal acquisition unit acquires an audio signal to which a digital watermark is applied, which represents audio;
A pitch component extraction step in which the pitch component extraction unit extracts a pitch component signal representing a pitch component of the voice represented by the voice signal from the acquired voice signal;
Of the extracted pitch component signal, the time of the portion multiplexed by superimposing the pitch component obtained by shifting the frequency of the pitch component and the pitch component obtained by shifting the frequency of the pitch component in the extracted pitch component signal A specifying step of specifying a pattern of distribution on the axis and specifying data embedded as a digital watermark in the audio signal based on the specified pattern;
An electronic watermark decoding method comprising: Computer
An audio signal acquisition means for acquiring an audio signal representing the audio;
The distribution on the time axis of the portion multiplexed by superimposing the pitch component obtained by shifting the frequency of the pitch component of the voice represented by the voice signal on the acquired voice signal is the target of embedding as a digital watermark. A voice signal processing means for generating a digital watermarked voice signal by processing the acquired voice signal so as to represent a data value;
Program to function as. Computer
An audio signal acquisition means for acquiring an audio signal to which an electronic watermark has been applied, representing the audio;
Pitch component extraction means for extracting a pitch component signal representing the pitch component of the voice represented by the voice signal from the acquired voice signal;
Of the extracted pitch component signal, the distribution of the portion on the time axis of the portion that is multiplexed by superimposing the pitch component of the voice and the pitch component obtained by shifting the frequency of the pitch component. Means for identifying a pattern and identifying data embedded as a digital watermark in the audio signal based on the identified pattern;
Program to function as.

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