JP2008225235A - Audio signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to hold continuity of signal level between temporally adjacent frames when relative information is added in a frame of audio data, and to perform processing relatively easily so that noise is not included in an audio signal to which the relative information is added. <P>SOLUTION: The audio signal processor includes a frame position specifying means 302 of sectioning audio data by frames and adding information specifying frame positions, a frame extracting means 303 of extracting the sectioned frames, one by one, an additional information switching means 304 of alternating embedding and non-embedding of the relative information associated with the audio data in the extracted frames by the frames, a relative information adding means 305 of adding the relative information in a first frame selected as an object of embedding of the relative information, and a fade adding means 306 of adding fade data in a second frame selected as an object of non-embedding of the relative information so as to keep continuity to the signal level in the first frame temporally adjacent to the second frame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an audio signal processing apparatus, and more particularly to an apparatus that embeds or extracts related information related to audio data, and is used, for example, in a music content distribution system in a stream data format.

  Digitized music content, eg CD quality digital audio data, consists of 44100 16-bit samples per second for each channel. When digital watermark information such as copyright information or other information is added (embedded) to such uncompressed digital audio data, as a basic method of digital signal processing, samples are sampled in a certain length section. A method of extracting and performing individual processing on the extracted sample is often used. Here, each extraction section having a certain length is called a frame. As a typical technique using frame processing, high-speed Fourier transform can be mentioned.

  Conventionally, an information adding device for adding information to digital audio data of CD quality delimits audio data every 2048 samples, for example, extracts samples in the divided frames, and performs a predetermined information adding process. And output as audio data with added information. Then, the information extraction device to which the information-added audio data as described above is input extracts samples in the frame interval for every 2048 samples that is the same as the operation in the information addition device, and performs predetermined signal processing. Extract information embedded in audio data.

  By the way, in the conventional information addition apparatus, it is impossible to maintain the continuity of the audio signal in the adjacent frames depending on the information addition method for the frame of the audio data. There is a problem that noise is included in the signal.

As a technique for reducing noise due to information addition based on frame processing, a technique has been proposed in which the frame length, shape, and processing method for consecutive frames are adaptively changed according to the state. The amount of calculation is large, and it is difficult to apply to inexpensive products. (See Patent Document 1).
JP-T-2004-525429

  The present invention has been made to solve the above-described conventional problems, and when related information is added to a frame of audio data, it is possible to maintain continuity of signal levels in temporally adjacent frames. Therefore, an object of the present invention is to provide an audio signal processing apparatus that can process relatively easily so that noise is not included in an audio signal to which related information is added.

  Further, another object of the present invention is that information related to embedded audio data in which related information is alternately added to each frame of audio data and signal level continuity is maintained between temporally adjacent frames. Another object of the present invention is to provide an audio signal processing apparatus that can extract desired related information relatively easily.

  According to a first aspect of the audio signal processing apparatus of the present invention, a frame position specifying unit that divides the audio data into frames each having a certain length section and specifies a time position of the frame, and the frame position specifying unit Alternately, frame extraction means for extracting a frame for each divided frame and whether to embed related information related to the audio data in the frame for each frame extracted by the frame extraction means Additional information switching means for controlling to switch, and related information adding means for adding the related information in accordance with a predetermined rule in the first frame selected as an embedding target of the related information by the additional information switching means, In the second frame selected as the non-embedding target of the related information by the additional information switching means , Characterized by comprising: a fading adding means for adding the fade data to maintain the continuity of the signal level of the second frame and the temporally first frame adjacent.

  According to the second aspect of the audio signal processing device of the present invention, information is embedded in which related information is alternately added to each frame of audio data and signal level continuity is maintained between temporally adjacent frames. Frame extraction means for extracting the audio data of each frame and extracting data within the frame for each frame, and frame switching for controlling the output destination of the frame alternately for each frame extracted by the frame extraction means Means, related information extracting means for performing a predetermined process on the frame supplied from the frame switching means, and extracting the related information embedded in the frame, a frame output from the related information extracting means, and The frame outputs supplied from the frame switching means are alternately captured and synthesized, and audio data is reproduced and output. Characterized by comprising a reproducing means for outputting the relevant information as well as.

  According to the audio signal processing device of the present invention, when related information is added in a frame of audio data, processing is performed so as to maintain continuity of signal levels in temporally adjacent frames, and information is added. The audio signal can be processed relatively easily so as not to include noise.

  Further, according to the audio signal processing device of the present invention, desired information can be obtained from audio data in which related information is alternately added for each frame and the continuity of the signal level between temporally adjacent frames is maintained. Information can be extracted relatively easily.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this description, common parts are denoted by common reference numerals throughout the drawings.

<First Embodiment>
FIG. 1 schematically shows the configuration of an audio content distribution system according to the first embodiment of the audio signal processing apparatus of the present invention. On the transmission side 10 of this audio content distribution system, audio data of the audio content distribution system is input, an information adding device 30 for adding predetermined information, and a transmission for sending the output of this information adding device 30 to some transmission path 40 Circuit 20. On the receiving side 50 of the audio content distribution system, a receiving circuit 60 that receives an input from the transmission path 40, an information extracting device 70 that extracts predetermined information from the output of the receiving circuit 60, and extracts audio data; It comprises. The information adding device 30 and the information extracting device 70 can be realized by software or hardware. In this example, the information adding device 30 and the information extracting device 70 are realized by using a CPU and a program.

  FIG. 2 is a block diagram showing an example of a processing flow (step) focusing on the processing function in the information adding device 30 in FIG. The information adding device 30 includes frame position specifying means 302, frame extracting means 303, additional information switching means 304, related information adding means 305, and fade adding means 306.

  The frame position specifying unit 302 receives audio data (audio data) of the audio content distribution system, for example, CD quality audio data, and divides the audio data into frames (for example, 2048 samples) that are constant length sections. It has a function of specifying the frame position. The frame extraction unit 303 has a function of extracting a sample in the frame for each frame delimited by the frame position specifying unit 302.

  In this example, the additional information switching unit 304 includes a first frame switching unit 3041 and a second frame switching unit 3042. The function of the additional information switching unit 304 controls to alternately switch whether or not to embed related information related to audio data in the frame for each frame extracted by the frame extracting unit 303. is there.

  The related information adding unit 305 has a function of adding related information in accordance with a predetermined rule in the first frame selected as the related information embedding target by the additional information switching unit 304. Here, the related information related to the audio data is, for example, text information such as lyrics, copyright information, performance information such as a score or rhythm, performance control information of a performance robot or toy, for example, a MIDI standard Added in data format.

  The fade adding means 306 determines the continuity between the signal level in the first frame temporally adjacent to the second frame in the second frame selected as the non-embedding target of the related information by the additional information switching means 304. It has a function of adding fade data to keep it.

  The first frame switching unit 3041 has a function of alternately switching and supplying the frame output to the related information adding unit 305 and the fade adding unit 306 for each frame extracted by the frame extracting unit 303. When the first frame switching unit 3041 supplies, for example, an odd-numbered frame to the related information adding unit 305, the odd-numbered frame signal to which the related information is added is continuous with the adjacent even-numbered intra-frame signal. There is a risk of losing. In order to compensate for this continuity, the signal of the even-numbered frame is supplied to the fade adding means 306 by the first frame switching means 3041, and the continuity of the waveform with the signal of the odd-numbered frame adjacent in time is maintained. Processing is performed as follows.

  The second frame switching means 3042 operates in synchronism with the first frame switching means 3041, and alternately captures and synthesizes the output of the information adding means 305 and the output of the fade adding means 306, and the information-added audio data As an output function.

  Next, a processing example in the information adding device 30 in FIG. 2 will be described. FIG. 3 shows an example of the signal waveform of the audio data input to the frame position specifying means 302 in FIG. Here, taking the CD quality audio data input in which the sampling value of the amplitude of the audio signal is digitally expressed as an example, the sampling value is expressed by a continuous waveform, and the three frame sections N1, N2, An example is shown that is divided into N3. The odd-numbered frames N1 and N3 are supplied to the related information adding means 305 by the first frame switching means 304, and the even-numbered frame N2 is supplied to the fade adding means 306 by the first frame switching means 304.

  FIG. 4 shows an example of the signal waveform of the audio data to which information has been added in which related information related to the audio data is added to the frame of the audio data based on the related information adding means 305 in FIG. Here, as a result of processing the odd-numbered frames N1 and N3 by the related information adding means 305 and changing the waveform, the trailing edge (right end in the figure) of the frame N1 and the leading edge of the subsequent frame N2 (see FIG. In the figure, the continuity of the signal waveform is lost at the left edge) and at the trailing edge of the frame N2 and the leading edge of the subsequent frame N3.

  FIG. 5 shows an example of fade data added to the frame N2 to be faded, which is input to the fade adding means 306 in FIG. FIG. 6 shows an example of a signal waveform of data x ′ (n) after fade addition in which fade data is added to the frame N2 to be faded by the fade adding means 306 in FIG.

  In this example, when the set value of the frame length is N samples, the signals x (N) to x (2N-1) of the frame N2 are expressed by the following (Expression 1) and (Expression 2) by the fade adding means 306. Is replaced with the signal x ′ (n).

(When N ≤ n <N + N / 2)
x '(n) = x (n) + {x (N-1)-x (N)} x (3N / 2-n) / (N / 2) (Formula 1)
(N + N / 2 ≤ n <2N)
x '(n) = x (n) + {x (2N)-x (2N-1)} x (n-3N / 2) / (N / 2) (Formula 2)
That is, the fade adding means 306 detects the correlation of the signal amplitude between adjacent frames, and adds a fade signal to the frame N2 to be faded. In this example, the value of the fade signal is obtained by proportionally changing the difference value between adjacent frames according to the distance (time) from the center position (temporal center position) of the frame N2.

  At this time, the fade adding means 306 adds the fade signal after detecting the correlation of the signal amplitude between the adjacent frames for the signals of the plurality of temporally adjacent frames, so that a slight delay corresponding to this processing is required. Even if this occurs, it is hardly a problem as compared with the speed of the audio data, and the fade addition can be processed in real time.

  As a method for changing the fade signal value, various characteristics such as a secondary change, a curve by a trigonometric function, and the like can be used in addition to the primary change with respect to the time axis as described above.

  As described above, the continuity of the signal waveforms of the temporally adjacent frames is corrected by performing the fade addition on the frame N2 to be faded. Further, the signals of the frames N1 and N3 that are not subject to fade addition are not affected by the fade process, and do not interfere with the additional information extraction process in a later processing stage.

  According to the information adding device 30 described above, when information is added in a frame of audio data, processing is performed so as to maintain the continuity of the audio signal in temporally adjacent frames, and the audio signal to which information is added is processed. Processing can be performed relatively easily so as not to include noise. The information adding device 30 described above can be provided not only on the transmission side of the audio content distribution system as described above but also in any audio signal processing system.

  FIG. 7 is a block diagram showing an example of a processing flow (step) focusing on the processing function in the information extracting device 70 in FIG. This information extraction apparatus includes a frame extraction unit 402, a frame switching unit 403, a related information extraction unit 404, and a reproduction unit 405.

  The frame extraction unit 402 receives the voice data with information embedded therein as described above, and extracts a sample in the frame for each frame (every 2048 samples, which is the same as when the information adding device is operating).

  The frame switching unit 403 has a function of alternately switching and supplying the frame output to the related information extracting unit 404 and the audio reproducing unit 405 for each frame extracted by the frame extracting unit 402. In this example, only the odd-numbered frames are supplied to the related information extracting means 404, and the even-numbered frames are not supplied.

  The related information extracting unit 404 has a function of performing a predetermined process on the odd-numbered frame supplied by the frame switching unit 403 and extracting related information embedded in the frame. In this example, information extraction is performed only from odd-numbered frames supplied by the frame switching means 403, and information extraction is not performed from even-numbered frames.

  The reproduction means 405 alternately captures and synthesizes odd-numbered frames output from the related information extraction means 404 and even-numbered frame outputs output from the frame switching means 403, reproduces and outputs the audio data, and Has a function of outputting.

  According to the information extraction device 70 described above, the embedded information of the audio data in which the related information is alternately added for each frame of the audio data and the continuity of the signal level between the temporally adjacent frames is maintained. Even when input, desired related information can be extracted relatively easily.

  The present invention is applicable to the field of using an audio portion of a video signal such as a DVD or a movie file and embedding an auxiliary signal such as a control signal in the audio portion. In addition, audio data recorded on CDs or uncompressed audio such as wave formats handled by personal computers, audio compression / decompression technologies such as MP-3 and AAC, such as DVD and music distribution, portable digital music players, and Chaku-Uta It is applicable to the field of transmitting and distributing audio signals such as package and file format using file, or file distribution and streaming. For example, sales of music contents with lyrics (comments and artist messages) such as Chaku-Uta, karaoke service using audio compression / decompression technology such as MP-3 / AAC, music distribution service for displaying lyrics, commercialization of musical instrument playing robot toys, It can be applied to fields such as sales of music content with performance information and sales of music content with beat timing.

1 is a block diagram schematically showing the configuration of an audio content distribution system according to a first embodiment of an audio signal processing device of the present invention. The block diagram shown according to an example of a processing flow (step) paying attention to the processing function in the information addition apparatus in FIG. FIG. 3 is a signal waveform diagram showing an example of audio data input to the frame position specifying means in FIG. 2. FIG. 3 is a signal waveform diagram showing an example of audio data with information added to which related information related to audio data is added in a frame of audio data by the related information adding means in FIG. FIG. 3 is a signal waveform diagram showing an example of fade data added to a frame N2 to be faded, which is input to the fade adding means in FIG. FIG. 3 is a signal waveform diagram showing an example of data x ′ (n) after fade addition in which fade data is added to a frame N2 to be faded by the fade adding means in FIG. 2; The block diagram shown according to an example of a processing flow (step) paying attention to the processing function in the information extraction device in FIG.

Explanation of symbols

302 ... Frame position specifying means, 303 ... Frame extracting means, 304 ... Additional information switching means, 3041 ... First frame switching means, 3042 ... Second frame switching means, 305 ... Related information adding means, 306 ... Fade adding means .

Claims (3)

A frame position specifying unit that divides the audio data into frames that are sections of a certain length and specifies the time position of the frame;
Frame extracting means for extracting a frame for each frame delimited by the frame position specifying means;
Additional information switching means for controlling to alternately switch whether or not to embed related information related to the audio data in the frame for each frame extracted by the frame extraction means;
Related information adding means for adding the related information in accordance with a predetermined rule in the first frame selected as an embedding target of the related information by the additional information switching means;
The second frame selected as the non-embedding target of the related information by the additional information switching means is faded so as to maintain continuity with the signal level in the first frame temporally adjacent to the second frame. A fade adding means for adding data;
An audio signal processing device comprising: The additional information switching means includes
First frame switching means for controlling each frame extracted by the frame extracting means to alternately switch and supply a signal of the frame to the related information adding means or the fade adding means;
Audio data with information added, which operates in synchronism with the first frame switching means, alternately captures the output frame of the information adding means and the output frame of the fade adding means, and synthesizes the frames continuously in time. Second frame switching means for outputting as:
The audio signal processing apparatus according to claim 1, further comprising: Relevant information is alternately added to each frame of audio data, and embedded audio data in which signal level continuity is maintained between temporally adjacent frames is input. Frame extraction means for extracting data;
Frame switching means for controlling to alternately switch the output destination of the frame for each frame extracted by the frame extraction means;
Related information extracting means for performing predetermined processing on the frame supplied from the frame switching means and extracting the related information embedded in the frame;
A reproduction unit that alternately captures and synthesizes the frame output from the related information extraction unit and the frame output supplied from the frame switching unit, reproduces and outputs audio data, and outputs related information;
An audio signal processing device comprising:

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