Audio watermark embedding and extracting method and system

Abstract

The invention discloses an audio watermark embedding and extracting method and system, and the method comprises the steps: obtaining audio data, calculating a masking threshold value of each frequency point of the audio data, and carrying out the preprocessing of the audio data; encoding according to the watermark information to generate an audio watermark, and embedding the audio watermark into the audio data according to a masking threshold value of the audio data; and retrieving the position of the audio watermark in the audio data embedded with the audio watermark, and extracting the audio watermark according to the masking threshold value of the original audio data. According to the method, the audio watermarks are embedded according to the masking theory of human ears, the masking threshold value of the audio data is calculated, and the audio watermarks are added to the audio according to the masking threshold value in the frequency domain, so that the audio watermarks can better resist attacks, the robustness of the audio watermarks is ensured, and the detectability can be kept even under severe conditions. The problem that the audio quality is easily affected due to insufficient robustness of the existing audio watermark is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of audio processing, and in particular to an audio watermark embedding and extraction method and system. Background Art

[0002] With the increasing popularity of digitalization and networking of multimedia content, copyright protection has become particularly important. As an effective means of copyright protection, audio watermarking can help confirm the ownership of works and track illegal copying and distribution. However, traditional audio watermarking technology faces many challenges, such as insufficient robustness, impact on audio quality, poor detectability of watermarks, and low processing efficiency.

[0003] Therefore, there is a need for a watermark embedding method that is robust and does not affect the audio quality. Summary of the invention

[0004] To solve the above problems, the present invention provides an audio watermark embedding and extraction method, which calculates the masking threshold of the audio data and adds an audio watermark to the audio in the frequency domain according to the masking threshold, thereby solving the problem that the existing audio watermark is not robust enough and easily affects the quality of the audio itself.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An audio watermark embedding and extraction method comprises the following steps:

[0007] S1. Obtain audio data, calculate the masking threshold of each frequency point of the audio data, and preprocess the audio data;

[0008] S2. Encode the audio watermark according to the watermark information, and embed the audio watermark into the audio data according to the masking threshold of the audio data;

[0009] S3. Retrieve the position of the audio watermark in the audio data in which the audio watermark is embedded, and extract the audio watermark according to the masking threshold of the original audio data.

[0010] Furthermore, in step S1, the preprocessing of the audio data specifically includes: performing fast Fourier transform on the audio data to obtain an audio spectrum.

[0011] Furthermore, in step S2, encoding the watermark information to generate the audio watermark is specifically implemented in the following manner: converting the watermark information into a binary sequence.

[0012] Furthermore, in step S2, encoding according to the watermark information to generate the audio watermark further includes: adding redundant information to the audio watermark.

[0013] Furthermore, the redundant information is a forward error correction code, the encoding algorithm of the forward error correction code is a Reed-Solomon encoding algorithm, and the generation formula of the forward error correction code is:

[0014] g(x)=m(x)*x n-k +r(x)

[0015] Among them, g(x) is the forward error correction code, m(x) is the watermark information polynomial, n is the watermark length, k is the information length, and r(x) is the redundant code polynomial.

[0016] Further, in step S2, the audio watermark is embedded in the audio data according to the masking threshold of the audio data. The specific implementation method is: according to the masking threshold of the audio data, a part whose masking threshold is higher than a preset value is searched, and the part higher than the preset value is the masked part. The audio watermark is divided into several segments according to the distribution of the masked part, and the several segments of audio watermarks are embedded in the masked part in sequence to obtain an audio spectrum embedded with the audio watermark, and the audio data embedded with the audio watermark is subjected to inverse fast Fourier transform to obtain the audio data embedded with the audio watermark.

[0017] Furthermore, in step S3, the specific implementation method is: after performing fast Fourier transform on the audio data embedded with the audio watermark, the masked part is resampled, the resampled masked part is filtered according to the energy size, the embedded audio watermark is screened out, and the embedded audio watermark is decoded to obtain the audio watermark.

[0018] Furthermore, the relationship between the audio watermark strength and the masking threshold of the position where the audio watermark is located is detected, and whether the audio watermark has been modified is determined based on the relationship.

[0019] Furthermore, in step S2, it also includes: embedding the same audio watermark in multiple independent frequency domain positions.

[0020] Through the above technical solution, the present invention has the following beneficial effects: It solves the problem that the existing watermark technology is easily lost when facing various signal processing operations. The audio watermark is embedded according to the masking theory of the human ear, so that the audio watermark can better resist these attacks, ensure the robustness of the audio watermark, and ensure that it can remain detectable even under harsh conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the overall process of an audio watermark embedding and extraction method of the present invention.

[0022] Figure 2 The figure is a schematic diagram of the structure of an audio watermark embedding and extraction system in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] See also Figure 1 , an audio watermark embedding and extraction method, comprising the following steps:

[0027] S1. Obtain audio data, calculate the masking threshold of each frequency point of the audio data, and preprocess the audio data;

[0028] S2. Encode the audio watermark according to the watermark information, and embed the audio watermark into the audio data according to the masking threshold of the audio data;

[0029] S3. Retrieve the position of the audio watermark in the audio data in which the audio watermark is embedded, and extract the audio watermark according to the masking threshold of the original audio data.

[0030] Masking is a common psychoacoustic phenomenon, which is determined by the frequency discrimination mechanism of the human ear. It means that a relatively weak sound near a stronger sound will not be perceived by the human ear, that is, it will be masked by the strong sound. The stronger sound is called the masker, and the weak sound is called the masked. In the auditory area, the response of the human ear to sound varies with the frequency, and the most sensitive frequency range is 2 to 4kHz. Outside this frequency range, the hearing sensitivity of the human ear gradually decreases. The lowest sound pressure level that the human ear can just hear is called the hearing threshold, which is a function of the sound frequency. The human ear cannot hear sounds with a sound pressure level lower than the hearing threshold. For example, if a pure tone signal is used as a target, if its sound pressure level is lower than the hearing threshold (that is, the threshold in silence), the human ear cannot hear it. Therefore, we can use this feature to embed the audio watermark signal at a position with a stronger threshold, so as to achieve the goal of hiding information in the audio without affecting the user's normal listening to the audio.

[0031] In an optional embodiment, in step S1, the preprocessing of the audio data specifically includes: performing a fast Fourier transform on the audio data to obtain an audio spectrum.

[0032] The time domain signal is converted into a frequency domain signal through Fourier transform, so as to facilitate embedding the watermark signal in the frequency domain.

[0033] In an optional embodiment, in step S2, encoding the watermark information to generate the audio watermark is specifically implemented by: converting the watermark information into a binary sequence.

[0034] In an optional embodiment, in step S2, encoding according to the watermark information to generate the audio watermark further includes: adding redundant information to the audio watermark.

[0035] Redundant information is used to add verification information to the audio watermark to improve the robustness of the audio watermark.

[0036] The watermark information is a binary sequence. In order to enhance robustness, we need to add an error correction code to it. Reed-Solomon code is a commonly used forward error correction code that can be used to increase the anti-interference ability of the watermark.

[0037] The present invention applies the Reed-Solomon coding algorithm and uses the RS (255, 239) coding scheme, where 255 is the codeword length and 239 is the information length, meaning that every 239 bits of information will generate a 255-bit coding block, including 16 bits of redundant code for error correction.

[0038] In an optional embodiment, the redundant information is a forward error correction code, the encoding algorithm of the forward error correction code is a Reed-Solomon encoding algorithm, and the generation formula of the forward error correction code is:

[0039] g(x)=m(x)*x n-k +r(x)

[0040] Among them, g(x) is the forward error correction code, m(x) is the watermark information polynomial, n is the watermark length, k is the information length, and r(x) is the redundant code polynomial.

[0041] In an optional embodiment, in step S2, the audio watermark is embedded in the audio data according to the masking threshold of the audio data. The specific implementation method is: according to the masking threshold of the audio data, a part whose masking threshold is higher than a preset value is searched, and the part higher than the preset value is the masked part. The audio watermark is divided into several segments according to the distribution of the masked part, and the several segments of audio watermarks are embedded in the masked part in sequence to obtain an audio spectrum embedded with the audio watermark, and the audio data embedded with the audio watermark is subjected to inverse fast Fourier transform to obtain the audio data embedded with the audio watermark.

[0042] Select the area in the frequency domain that is protected by the masking effect to embed the watermark, avoid the important audio feature area, and reduce the impact on the audio quality. Specifically, the following steps are included:

[0043] Using the masking threshold M(f) and a predefined factor α, the watermark embedding strength W(f) = α*M(f) is calculated, where α represents the expansion factor of the embedding area;

[0044] The encoded watermark information is added to the selected spectral component in proportion β, where β is the embedding strength (0-1), that is, S'(f) = S(f) + β*W(f), where S(f) is the original spectrum and S'(f) is the spectrum after embedding the watermark.

[0045] In an optional embodiment, in step S3, the specific implementation method is: after performing fast Fourier transform on the audio data embedded with the audio watermark, the masked part is resampled, the resampled masked part is filtered according to the energy size, the embedded audio watermark is screened out, and the embedded audio watermark is decoded to obtain the audio watermark.

[0046] In an optional embodiment, the relationship between the audio watermark strength and the masking threshold of the position where the audio watermark is located is detected, and whether the audio watermark has been modified is determined based on the relationship.

[0047] When an audio watermark is embedded, due to the existence of the embedding strength, there is a certain coefficient relationship between it and the masking threshold of the audio watermark location. We can judge whether the audio watermark has been tampered with during the transmission process by the weakening of the audio watermark strength.

[0048] In an optional embodiment, in step S2, the method further includes: embedding the same audio watermark in multiple independent frequency domain positions.

[0049] By embedding multiple identical watermarks, it is ensured that even if the audio is partially damaged due to compression or other reasons during audio transmission, the audio watermark can be retained in different locations to ensure the integrity of copyright protection.

[0050] Example 2

[0051] See also Figure 2 , an audio watermark embedding and extraction system, comprising:

[0052] An audio processing module is used to obtain audio data, calculate the masking threshold of each frequency point of the audio data, and pre-process the audio data;

[0053] A watermark embedding module, used to encode the watermark information to generate an audio watermark, and embed the audio watermark into the audio data according to a masking threshold of the audio data;

[0054] The watermark extraction module is used to retrieve the position of the audio watermark in the audio data embedded with the audio watermark, and extract the audio watermark according to the masking threshold of the original audio data.

[0055] The embodiment disclosed in this specification is only an example of a unilateral feature of the present invention, and the protection scope of the present invention is not limited to this embodiment, and any other functionally equivalent embodiments fall within the protection scope of the present invention. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. An audio watermark embedding and extraction method, characterized in that: The following steps are involved: S1. Obtain audio data, calculate the masking threshold of each frequency point of the audio data, and pre-process the audio data; S2. Encode the audio watermark according to the watermark information, and embed the audio watermark into the audio data according to the masking threshold of the audio data; S3. Retrieve the position of the audio watermark in the audio data in which the audio watermark is embedded, and extract the audio watermark according to the masking threshold of the original audio data.

2. The method for embedding and extracting an audio watermark according to claim 1, characterized in that: In step S1, the preprocessing of the audio data specifically includes: performing fast Fourier transform on the audio data to obtain an audio spectrum.

3. The audio watermark embedding and extraction method according to claim 2, characterized in that: In step S2, the audio watermark is generated by encoding according to the watermark information, and its specific implementation method includes: converting the watermark information into a binary sequence.

4. The audio watermark embedding and extraction method according to claim 3, characterized in that: In step S2, encoding the audio watermark according to the watermark information further includes: adding redundant information to the audio watermark.

5. The method for embedding and extracting an audio watermark according to claim 4, characterized in that: The redundant information is a forward error correction code, the encoding algorithm of the forward error correction code is a Reed-Solomon encoding algorithm, and the generation formula of the forward error correction code is: g(x)=m(x)*x n-k +r(x) Among them, g(x) is the forward error correction code, m(x) is the watermark information polynomial, n is the watermark length, k is the information length, and r(x) is the redundant code polynomial.

6. The method for embedding and extracting an audio watermark according to claim 2, characterized in that: In step S2, the audio watermark is embedded in the audio data according to the masking threshold of the audio data. The specific implementation method is: according to the masking threshold of the audio data, the part whose masking threshold is higher than the preset value is searched, and the part higher than the preset value is the masked part. The audio watermark is divided into several segments according to the distribution of the masked part, and the several segments of audio watermarks are embedded in the masked part in sequence to obtain the audio spectrum embedded with the audio watermark, and the audio data embedded with the audio watermark is subjected to inverse fast Fourier transform to obtain the audio data embedded with the audio watermark.

7. The method for embedding and extracting an audio watermark according to claim 6, characterized in that: In step S3, the specific implementation method is: after performing fast Fourier transform on the audio data embedded with the audio watermark, the masked part is resampled, the resampled masked part is filtered according to the energy size to screen out the embedded audio watermark, and the embedded audio watermark is decoded to obtain the audio watermark.

8. The method for embedding and extracting an audio watermark according to claim 7, characterized in that: The relationship between the audio watermark strength and the masking threshold of the position where the audio watermark is located is detected, and whether the audio watermark has been modified is determined based on the relationship.

9. The audio watermark embedding and extraction method according to claim 1, characterized in that: In step S2, it also includes: embedding the same audio watermark in multiple independent frequency domain positions.

10. An audio watermark embedding and extraction system, characterized in that: include: An audio processing module is used to obtain audio data, calculate the masking threshold of each frequency point of the audio data, and pre-process the audio data; A watermark embedding module, used to encode the watermark information to generate an audio watermark, and embed the audio watermark into the audio data according to a masking threshold of the audio data; The watermark extraction module is used to retrieve the position of the audio watermark in the audio data embedded with the audio watermark, and extract the audio watermark according to the masking threshold of the original audio data.

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