JP5482381B2 - Data transmission apparatus and data transmission method using acoustic signal - Google Patents

Description

  The present invention relates to a data transmission apparatus and a data transmission method for transmitting data using an acoustic signal.

  Various techniques for transmitting or recording a data code superimposed on an acoustic signal have been proposed. The most common technique is a technique of superimposing a modulation signal of a data code on a high frequency band exceeding the human audible frequency (for example, Patent Document 1). However, since the high frequency band of the acoustic signal is greatly affected by the performance and characteristics of the acoustic device and the signal compression, the reliability of data code transmission may be impaired.

  Therefore, a data transmission / recording technique using a low frequency range of an acoustic signal has also been proposed (for example, Patent Document 2). The technique of Patent Document 2 utilizes the fact that the localization of a low-frequency signal is not easily perceived by the listener, and transmits and records data by moving the localization of the low-frequency signal according to the data code.

JP 2010-041695 A

JP 2006-195061 A

  Although the technique of Patent Document 2 described above is difficult for the listener to perceive the localization of the low-frequency signal, the localization of the low-frequency signal is constantly moved, which may give the listener a sense of incongruity. In addition, since it is a technology that uses the low-frequency signal included in the acoustic signal to move its localization, the quality of transmission / recording is such that the characteristics of the low-frequency signal included in the acoustic signal, such as signal level and frequency distribution, etc. When the acoustic signal does not contain a low frequency component, the data code cannot be transmitted / recorded.

  It is an object of the present invention to provide a data transmission apparatus and a data transmission method that use a low frequency range of an acoustic signal and realize reliable data code transmission / recording without a sense of incongruity to a listener.

The first aspect of the present invention is an input unit that inputs a plurality of channels of acoustic signals, a first channel that is at least one of the plurality of channels, and a second channel that does not belong to the first channel. A low- pass filter that extracts a low-frequency component signal of the acoustic signal of the channel, a high- pass filter that extracts a high-frequency component signal that is a higher frequency band than the low frequency range of the first and second channels, and the first adds the bass adder for adding the low-frequency components signals and component signals bass of the second channel of the channel, and a component signal of the summed bass and treble component signals of said first channel A first synthesizing unit that further adds a data code having the low frequency band to the addition signal; With adding the high range component signal component signal and the summed bass of tunnel and the second combining unit for subtracting the data symbols from the sum signal, comprising the.

  The invention of claim 2 is an acoustic signal of a plurality of channels, the first channel and the second channel of which are common to the low frequency range component signals, and in the opposite frequency phase in the low frequency range. An input unit that inputs a signal on which a data code is superimposed, a low-pass filter that extracts the low-frequency component signal from the acoustic signals of the first and second channels, and a low-frequency filter of the extracted first and second channels And a data separation unit that extracts the data code by adding the components of the sound range while inverting the phase of one of the signals.

According to a third aspect of the present invention, in the second aspect of the present invention, in the second aspect of the present invention, a bass adder for adding the low-frequency component signals of the first and second channels extracted by the low-pass filter, and the first and second channel acoustics A high-pass filter that extracts a high-frequency component signal that is a higher frequency band than the low-frequency range of the signal, and a first high-frequency filter that adds the high-frequency component signal of the first channel and the added low-frequency component signal. A synthesis unit; and a second synthesis unit that adds the high-frequency component signal of the second channel and the added low-frequency component signal, and outputs an output of the first and second synthesis units as an acoustic signal It reproduces as.

According to a fourth aspect of the present invention, an acoustic signal of a plurality of channels is input, and an acoustic of a first channel that is at least one of the plurality of channels and an acoustic of a second channel that is at least one channel that does not belong to the first channel. A bass extraction procedure for extracting a low-frequency component signal of a signal, a high-frequency extraction procedure for extracting a high-frequency component signal that is a higher frequency band than the low-frequency range of the first and second channels, and the first channel as well as addition and bass summing procedure for adding the bass component signal and the component signal of the bass region of the second channel, the component signal of the summed bass and treble component signals of said first channel , A first synthesis procedure for further adding a data code having the low frequency band to the added signal, and a high tone of the second channel While adding the component signal and the component signal of the summed bass of, characterized in that from the addition signal and a second synthesis procedure for subtracting the data code.

  The invention of claim 5 is an acoustic signal of a plurality of channels, the first channel and the second channel of which are common to the low frequency range component signals, and in the opposite frequency phase in the low frequency range. An input procedure for inputting a signal on which a data code is superimposed, a bass extraction procedure for extracting the low-frequency component signal from the acoustic signals of the first and second channels, and the extracted first and second channels A data separation procedure for extracting the data code by inverting the phase of any one of the signals of the components of the low sound range and adding them.

According to the present invention, it is possible to transmit a data code with high reliability by superimposing a data code on a low frequency range of an acoustic signal without feeling uncomfortable for the listener.

The figure which shows the structure of the acoustic communication system containing the data transmission apparatus (transmission apparatus, reception apparatus) which is embodiment of this invention. Block diagram of a data superimposing unit of the transmission device The figure which illustrates the signal spectrum of each part of a data superposition part Diagram showing actual signal spectrum Block diagram of a data separator of the receiver The figure which shows the signal waveform of each part of the said data separation part

  FIG. 1 is a diagram showing a configuration of a data transmission system using a low frequency band of an audio signal according to an embodiment of the present invention.

  A transmission device 1 that is a device that superimposes and outputs a data code on a stereo acoustic signal includes a data superimposing unit 10 and an output unit 11. A stereo sound signal S and a data code D are input to the data superimposing unit 10. The data superimposing unit 10 superimposes the data code D on the low frequency range of the stereo acoustic signal S. The output unit 11 is a functional unit that outputs the stereo sound signal S ′ on which the data code D is superimposed to the receiving device 2. Here, to output means to transmit to the receiving device 2 by wire or wireless, for example, or to write on a medium (such as a CD) readable by the receiving device 2.

  The reception side device (reception device) 2 includes an input unit 20, a data separation unit 21, a data decoding unit 22, and an acoustic reproduction unit 23. The input unit 20 is a functional unit that receives the stereo sound signal S ′ transmitted from the transmission device 1 or reads a medium on which the stereo sound signal S ′ is recorded. The stereo sound signal S ′ received or reproduced by the input unit 20 is input to the data separation unit 21 and the sound reproduction unit 22. The data separation unit 21 separates and extracts the component of the data code D superimposed on the low sound range of the stereo acoustic signal S ′ and inputs it to the data decoding unit 22. The data decoding unit 22 shapes the component waveform of the input data code D, decodes the data code D, and outputs it. If the data code D is a signal that has undergone some modulation, the data decoding unit 22 may demodulate it into a baseband signal.

  The sound reproducing unit 23 is a functional unit that reproduces and outputs the stereo sound signal S as sound. The reproduced stereo sound signal is output from the speaker 24 or the line output unit 25. The output stereo sound signal may be either the stereo sound signal S ′ with the data code D superimposed or the original stereo sound signal S with the data code D separated.

  The reception device 2 in FIG. 1 includes an acoustic reproduction unit 23 that reproduces a stereo sound signal. However, the reception device 2 includes only a data separation unit 21 and a data decoding unit 22 that separate and output data codes. Also good.

  FIG. 2 is a configuration diagram of the data superimposing unit 10 of the transmission device 1. 3 is a diagram showing the distribution of frequency components of the acoustic signal S and data code D processed in the data superimposing unit 10, and FIG. 4 is a diagram showing the frequency spectrum of the actual acoustic signal and data code.

  A stereo sound signal S is input from the signal input terminal 30. The stereo sound signal S has frequency components distributed over the entire range from a low sound range to a high sound range as shown in FIG. The acoustic signal S is input to the low pass filter 31 and the high pass filter 35. That is, the left channel acoustic signal is input to the low pass filter 31L and the high pass filter 35L via the input terminal 30L, and the right channel acoustic signal is input to the low pass filter 31R and the high pass filter 35R via the input terminal 30R. .

  The low-pass filter 31 and the high-pass filter 35 are set so as to have symmetrical characteristics on the frequency axis. That is, the pass band, the transition band, and the stop band of the low-pass filter 31 and the stop band, the transition band, and the pass band of the high-pass filter 35 are common, and the transition band of the low-pass filter 31 and the transition band of the high-pass filter 35 are cross-faded. It has become. The cut-off frequency of the low-pass filter 31 is set to a frequency (for example, 200 Hz) that makes it difficult for the listener (human) to feel the localization of the sound image when the frequency is lower than that. The cut-off frequency of the high-pass filter 35 is set to approximately 1 kHz and is set to be completely blocked (-100 dB attenuation) at 200 Hz. Hereinafter, the frequency component filtered and extracted by the low-pass filter 31 is referred to as a low-frequency component signal, and the frequency component filtered and extracted by the high-pass filter 35 is referred to as a high-frequency component signal.

  The low-frequency component signals of the left and right channels extracted by the low-pass filters 31L and 31R are signals having frequency components equal to or lower than the cut-off frequency as shown in FIG. 3B and FIG. It is synthesized and made monaural. At this time, the level adjuster 32L, 32R limits the level of the low frequency component signal of the left and right channels to ½ (0.5) before the addition so that the signal level after the addition is not saturated. . The low frequency range component signals added and monauralized by the adder 33 are input to the adders 36L and 36R.

  Further, the high-frequency component signals of the left and right channels extracted by the high-pass filters 35L and 35R are signals having frequency components equal to or higher than the cutoff frequency as shown in FIGS. 3C and 4B, respectively. Input individually to the adders 36L and 36R.

  The data code D (see FIG. 3D) is input to the level adjuster 38 via the data input terminal 37. The level adjuster 38 adjusts the level so that the signal level of the data code D is excessive compared to the low sound component signal and cannot be heard as noise. The level ratio between the level of the data code D and the low frequency range component signal is set to a component as shown in FIG. 3 (E) and FIG. The level-adjusted data code D is input to the inverter 39 that inverts the phase of the waveform (shifts 180 degrees) and the right channel adder 36R. Further, the data code -D inverted by the inverter 39 is input to the adder 36L of the left channel.

  Therefore, the left channel addition unit 36L adds and synthesizes the high-frequency component signal of the left channel, the monaural low-frequency component signal, and the inverted data code. In addition, the right channel adding unit 36R adds and synthesizes the high-frequency component signal of the right channel, the monaural low-frequency component signal, and the data code (not inverted).

  As a result, since the bass signal is a monaural signal, the acoustic signal S ′ is synthesized in which the difference between the left and right channel waveforms in the bass (bass frequency band) is only the component of the data code D. Is done. The acoustic signal S ′ is a signal having a frequency component as shown in FIG. Note that the data code added to the left channel is inverted, but the frequency characteristics are the same as before the inversion.

  In this way, the data code D is superimposed on the acoustic signal S ′, and it is possible to extract only the data code D by subtracting the low-frequency signal components of the left and right channels.

  FIG. 5 is a diagram illustrating a configuration of the data separation unit 21 of the reception device 2. FIG. 4A is a diagram showing a configuration of only the data separation unit 21, and FIG. 4B is a diagram showing a configuration in which the data separation unit 21 and the sound reproduction unit 23 are combined. The data separator 21 having these configurations can separate and extract the data code D from the acoustic signal S ′ on which the data code D is superimposed.

  First, in FIG. 5A, a stereo sound signal S ′ received or reproduced by the input unit 20 is input from a signal input terminal 40. This stereo sound signal S ′ is a stereo signal, but the low sound range is made monaural, and the data code D is superimposed on the low frequency band as shown in FIG. This acoustic signal S ′ is input to the low-pass filter 41. That is, the left-channel acoustic signal is input to the low-pass filter 41L via the input terminal 40L, and the right-channel acoustic signal is input to the low-pass filter 41R via the input terminal 40R.

  The low-pass filter 41 has the same cutoff characteristics as the low-pass filter 31 of the data superimposing unit 10 of the transmission device 1. By filtering the acoustic signal S ′ with this low-pass filter, the low-frequency component shown in FIG. 3E, that is, the monaural low-frequency component signal and the data code D that is inverted and superimposed on the left and right channels are superimposed. Can be taken out.

  Among the low-frequency components of the left and right channels extracted by the low-pass filters 41L and 41R, the signal of one channel (the left channel in FIG. 5) is inverted using the inverter 42. The adding unit 43 adds and synthesizes the inverted left channel signal and the non-inverted right channel signal. By this addition and synthesis, the low-frequency component, that is, the low-frequency component signal of the monaural sound signal is canceled and deleted. On the other hand, since the data code D is superimposed with the phase inverted in the left and right channels, the data code D is emphasized and extracted by this addition synthesis. The extracted signal of the data code D is input to the data decoding unit 22.

  FIG. 6 is a diagram illustrating an example of signal waveforms of each unit of the data separation unit 21 illustrated in FIG. In the figure, the left figure shows a time axis waveform of a relatively long range (about 250 ms), and the right figure shows a partially enlarged (about 25 ms) time axis waveform. FIG. 4A shows the signal waveform of the low-frequency component of the left channel that has passed through the low-pass filter 41L, and FIG. 4B shows the signal waveform of the low-frequency component of the right channel that has passed through the low-pass filter 41R. Since it is a monaural signal component, the data codes D are superimposed in a mutually inverted state, but the waveforms are almost the same. Even if this waveform is emitted as sound, the listener can hardly hear the data code D.

  On the other hand, FIG. 6C shows an output waveform of the adding unit 43. The scale of the vertical axis in this figure is enlarged about 100 times from FIGS. By inverting one of the signal waveforms in FIGS. 4A and 4B and adding them, the component of the acoustic signal (low-frequency component signal) is almost completely canceled, and only the waveform of the data code D is extracted. By inputting this signal waveform to the data decoding unit 22, the data decoding unit 22 outputs a data code D that has been waveform-shaped or decoded and decoded.

  In FIG. 1, the sound reproduction unit 23 may reproduce and output the sound signal S ′ received or reproduced by the input unit 20 as sound as it is. However, the sound reproduction unit 23 should reproduce and output the superimposed data code D component. It may be preferable.

  FIG. 5 (B) is combined with the data separation unit 21 to efficiently remove the component of the data code D from the acoustic signal S ′ and reproduce the signal returned to the original signal (acoustic signal S). FIG. 4 is a diagram illustrating a configuration of a unit 23. In the configuration of this figure, the same components as those of the data separation unit 21 shown in FIG.

  The acoustic signal S ′ input from the signal input terminal 40 is input to the low-pass filter 41 of the data separation unit 21 and also input to the high-pass filter 46 of the sound reproduction unit 23. That is, the left channel acoustic signal is input to the low pass filter 41L and the high pass filter 46L via the input terminal 40L, and the right channel acoustic signal is input to the low pass filter 41R and the high pass filter 46R via the input terminal 40R. . The high pass filter 46 is set to the same cut-off characteristics as the high pass filter 35 of the data superimposing unit 10 of the transmission apparatus 1. The high-frequency component signals of the left and right channels extracted by the high-pass filters 46L and 46R are individually input to the adders 36L and R, respectively.

  The low-frequency component signals of the left and right channels extracted by the low-pass filters 41L and R of the data separation unit 21 are taken out by the sound reproduction unit 23 and added by the addition unit 45 to remove the data code D component. That is, since the data code D is superimposed on the left and right channels with the phases reversed, the components of the data code D can be removed by adding the signals of the left and right channels as they are. At this time, the level adjusters 44L and 44R limit the low-frequency component low-frequency component signal level to 1/2 (0.5) before the addition so that the signal level after the addition is not saturated. . The low frequency range component signals added and monauralized by the adder 33 are input to the adders 47L and 47R.

  As a result, the left channel adder 47L adds and synthesizes the high-frequency component signal of the left channel and the monaural low-frequency component signal from which the data code D component has been removed. In addition, the right channel adder 47R adds and synthesizes the high-frequency component signal of the right channel and the monaural low-frequency component signal from which the component of the data code D is removed.

  In this way, with the configuration shown in FIG. 5B, the signal component in the low sound range is monauralized, but the sound signal restored to the original sound signal S can be output. The acoustic signals synthesized by the adders 47L and R are analogized and amplified and output from the speaker 24 and the like.

  In this way, by removing the data code D from the acoustic signal output from the receiving device 2, even if it is heard as the same acoustic signal, whether the signal is output from the transmitting device 1 or the receiving device 2 once Whether the received signal is received or not can be identified, and the data code D can be used as a so-called watermark. In addition, so-called generation management can be performed by superimposing another new data code D in the receiving apparatus 2.

  In this embodiment, the data superimposing unit 10 adds the inverted data code D to the left channel, and the data separating unit 21 inverts the left channel bass band signal to obtain the right channel bass band signal. Although addition is performed, it is arbitrary which channel is added with the data code D inverted at the time of data superimposition, and which channel signal is inverted at the time of data separation.

  In the above embodiment, the acoustic signal S is described as a two-channel stereo signal, but the acoustic signal S is not limited to two channels. In the case of a multi-channel acoustic signal having more channels, two channels (for example, surround left and surround right) may be taken out and the above-described processing may be performed. Further, the above processing may be performed by dividing the multi-channel into two channel groups.

DESCRIPTION OF SYMBOLS 1 Transmission apparatus 2 Reception apparatus 10 Data superimposition part 21 Data separation part

Claims (5)

An input unit for inputting multi-channel acoustic signals;
A low-pass filter that extracts a low-frequency component signal of an acoustic signal of a first channel that is at least one of the plurality of channels and a second channel that is at least one channel that does not belong to the first channel;
A high-pass filter for extracting a high-frequency component signal that is a frequency band higher than the low-frequency range of the first and second channels;
Bass adder for adding the component signals bass bass component signal and the second channel of the first channel,
A first synthesis unit that adds the high frequency component signal of the first channel and the added low frequency component signal, and further adds a data code having the low frequency band to the added signal;
A second synthesizing unit that adds the high-frequency component signal of the second channel and the added low-frequency component signal, and subtracts the data code from the added signal;
A data transmission device using an acoustic signal. It is a multi-channel acoustic signal, the first and second channels of which are common to the low frequency range component signals, and the data code is superimposed on the low frequency range in opposite phases. An input for inputting a signal;
A low-pass filter for extracting the low-frequency component signal from the acoustic signals of the first and second channels;
A data separation unit for extracting the data code by adding the extracted low-frequency component signals of the first and second channels while inverting the phase of one of the signals;
A data transmission device using an acoustic signal. A bass adder for adding the low-frequency component signals of the first and second channels extracted by the low-pass filter;
A high-pass filter that extracts a high-frequency component signal that is a frequency band higher than the low-frequency range of the acoustic signals of the first and second channels;
A first synthesizing unit that adds the high frequency component signal of the first channel and the added low frequency component signal;
A second synthesis unit for adding the high frequency component signal of the second channel and the added low frequency component signal;
The data transmission device using an acoustic signal according to claim 2, wherein the output of the first and second combining units is reproduced as an acoustic signal. Enter the acoustic signals of a plurality of channels, at least one first channel and the low frequency range component signal for the second channel of the audio signal is at least one channel first does not belong to the channel is a channel among said plural channels A bass extraction procedure to extract
A high sound extraction procedure for extracting a high frequency component signal that is a frequency band higher than the low frequency range of the first and second channels;
A bass summing procedure for adding the component signals bass bass component signal and the second channel of the first channel,
Adding a high frequency component signal of the first channel and the added low frequency component signal, and further adding a data code having the low frequency band to the added signal;
A second synthesis procedure for adding the high-frequency component signal of the second channel and the added low-frequency component signal and subtracting the data code from the added signal;
A data transmission method using an acoustic signal including It is a multi-channel acoustic signal, the first and second channels of which are common to the low frequency range component signals, and the data code is superimposed on the low frequency range in opposite phases. Input procedure for inputting signals,
A bass extraction procedure for extracting the low-frequency component signal from the first and second channel acoustic signals;
A data separation procedure for extracting the data code by inverting the phase of one of the signals and adding the extracted low-frequency component signals of the first and second channels;
A data transmission method using an acoustic signal including

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