JP4155506B2 - Decoding device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, for example , decodes code information when analog information such as an audio signal is analog-digital (A / D) converted with a certain number of quantization bits and recorded on a recording medium or transmitted via a transmission medium. Relates to the device .
[0002]
[Prior art]
Over ten years have passed since the CD (compact disc) as an audio reproducing optical disk was put on the market, and the recording medium for audio information has already surpassed conventional cassette tapes. The physical / logical format of CDs, which are digital discs, has been established as an EFM modulation recording system for 8-bit fixed data length symbols and data formats such as subcode, audio data, CRC, and various application functions. CD players have been developed.
[0003]
The CD is also used as a data CD-ROM by being identified by the control bit (4 bits) of the Q channel in the subcode or by the absence of the TOC. Applications are expanding in the field of electronic publishing by making effective use of capacity and high-speed accessibility. By the way, in the CD-ROM, the sound is compressed by ADPCM, the original sound quality cannot be reproduced by the compression, and recording with higher fidelity has been desired. In other words, it is expected that a disc capable of recording an audio signal equivalent to a band twice that of a normal CD even when compressed will be expected.
[0004]
However, when such a high-quality hi-fi signal is copied in the state of digital information, it is convenient for the user because it does not deteriorate, but there is a problem that it is not desirable from the viewpoint of copyright protection. As methods for solving such problems, there have been proposed methods such as limiting the number of times digital information is copied or not providing a digital output terminal in the device.
[0005]
[Problems to be solved by the invention]
However, there is a problem that it is difficult to achieve both user convenience and copyright protection in a method in which the number of times digital information is copied or a method in which no digital output terminal is provided in the device.
By the way, although copying of high-quality digital data A / D converted with a relatively large number of quantization bits is not permitted, copying of low-quality digital data having a substantially small number of quantization bits is permitted. There is an idea that it is good.
[0006]
In addition, there is an idea that copying may be permitted if the copyright holder can prove that it is a duplicate product by adding copyright data to such an extent that the quality of high-quality digital data is not degraded.
In addition, since analog copy does not include copyright-related information such as copy number limit information included in digital data, there is a possibility that data that has been analog copied once may be copied without limitation. It is not preferable from the viewpoint of protection.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a code information decoding apparatus that can achieve both user convenience and copyright protection.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises the following means .
That is,
A voice generated by A / D converting an analog signal of an audio signal by using a sampling frequency 192 kHz which is approximately four times higher than the sampling frequency of the CD and using a larger quantization bit number than the CD quantization bit number. Modulating and adding copyright data of the analog signal to the digital data and the copyright data managed by the copy number limit information and the ID number related to the analog signal;
The digital data generated by the modulation and addition step is arranged in the user data area of the audio packet of the DVD, and the modulation and addition of the copyright data managed by the copy number limit and the ID number related to the analog signal Is specified in units of audio packets so that each audio packet is stored in a subheader provided in a user data area of the audio packet, and the copyright managed by the copy number limit information is used. Allowing data and an ID number related to the analog signal to be stored in a copyright management information area of the DVD;
A decoding apparatus for code information for decoding a data signal obtained by an encoding method comprising:
Means for deformatting the formatted data signal and retrieving the audio packet;
Means for extracting the digital data from a user data area of the audio packet;
Means for extracting the copyright data from a sub-header provided in a user data area of the audio packet and / or the copyright management information area;
When the copyright data does not have a copy number limit, the extracted digital data is output as a digital signal using a basic sampling frequency and a basic quantization bit number, while the copyright data is copied Is included, the extracted digital data is allowed to be output only as a digital signal together with the copyright data, but the digital data is not D / A converted for an analog signal. Or control means for controlling not to output after D / A conversion;
The decoding apparatus of the code information which consists of.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an encoder for realizing a first reference example of a code information copy prevention method according to the present invention, FIG. 2 is a block diagram showing in detail the signal processing circuit 32 of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing user data packed by the allocation circuit of FIG. 2, and FIG. 5 is a code information copy prevention method applied to the present invention. FIG. 6 is a block diagram showing in detail the signal processing circuit of FIG. 5, and FIG. 7 is an explanatory diagram showing a data string and a sampling period decoded by the decoder of FIG. is there.
[0010]
An analog signal such as an audio signal is input to the input terminal IN shown in FIG. 1, and the input signal is input to the A / D converter 31 by a sufficiently high sampling frequency (sampling period shown in FIG. 3) worth prohibiting copying. Δt), which is sampled at, for example, 192 kHz and converted into a high-resolution PCM signal of, for example, 24 bits, and as shown in FIG. .., xbi, x2i-1, xai, x2i, ...
Is converted to
[0011]
This data string (xbi, x2i-1, xai, x2i) is encoded by the signal processing circuit 32 and the memory 33 shown in detail in FIG. 2 and then packed by the DVD encoding circuit 34. The packing data is output to the output terminal OUT1, or is modulated by the modulation circuit 35 by a modulation method corresponding to the medium and output to the output terminal OUT2.
[0012]
The configuration of the signal processing circuit 32 will be described in detail with reference to FIG. First, the data string (xbi, x2i-1, xai, x2i) corresponding to the curve [alpha] shown in FIG. 3 is converted into a band-limited curve [beta] by a low pass filter 36 that passes a half band, for example, an FIR filter. Corresponding data string xc1, *, *, *, xc2, *, *, *, xc3, *, *, *, ..., xci, *, *, *, ...
Next, by thinning out the data “*” of the data string by the thinning circuit 37, the data string xc1, xc2, xc3,..., Xci,.
Is generated. Further, the data string xb1, xa1, xb2, xa2,..., Xbi, xai,...
Is generated.
[0013]
Then, a difference xbi−xci = Δ1i is calculated by a difference calculation unit 39 constituted by an adder based on these data strings xci, xbi, xai.
xai-xci = Δ2i
Is calculated. Here, the difference data Δ1i and Δ2i is, for example, 24 bits or less, and the number of bits may be fixed or variable. As shown in FIG. 4, the allocation circuit 40 packs the data string xci and the difference data Δ1i and Δ2i as user data, and outputs the user data to record the data on a recording medium such as a DVD (digital video disk). And transmitted to the transmission line. When the user data is 2034 bytes as in a DVD, the data xci and the difference data Δ1i and Δ2i are both 225, and the subheader is 9 bytes.
Here, the data string xci is a data string in which the sampling frequency is reduced to ¼ by limiting the band of the digital data A / D converted by the A / D converter 31.
[0014]
Next, the decoder will be described with reference to FIG. The input signal is first demodulated by the demodulation circuit 41 in accordance with the modulation method of the modulation circuit 35 on the encoder side, then decoded by the DVD decoding circuit 42, and the decoded data (data string xci and difference data Δ1i, Δ2i) is shown in FIG. This is applied to the signal processing circuit 43 (and memory 44) and the switch 51 shown in detail. In the signal processing circuit 43, first, as shown in FIG. 6, the adder 46 makes Δ1i + xci = xbi.
Δ2i + xci = xai
Is calculated, and the data strings xbi and xai are restored. Here, the data strings xbi and xai are the original 24 bits.
[0015]
Next, the interpolation processing circuit 47 interpolates the data string xi between them using a plurality of data of the data strings xai and xbi as shown in FIG. Note that the interpolation processing circuit 47 can obtain the interpolation data string xi by using, for example, an upsampling method and filling each of them with zero data and passing through a low-pass filter. The interpolation data string xi may also be obtained by curve approximation or prediction approximation. In this case, the degree of approximation can be increased by adding approximate auxiliary data for transmission.
[0016]
Data interpolated in this way is
xb1, x1, xa1, x2, xb2, x3, xa2,..., xbi, x2i-1, xai, x2i,.
And are applied to the D / A converter 45 and the adder 56. In the D / A converter 45, input data is converted into an analog signal at a sampling frequency of 192 kHz and output through an analog output terminal 55.
[0017]
On the other hand, the dither noise is dither generator 57 as random noise for limiting the number of quantization bits (24 bits) of each data of the data string (xbi, x2i-1, xai, x2i) to substantially 16 bits, for example. Generated from. The adder 56 adds the dither noise and the data string (xbi, x2i-1, xai, x2i) and outputs the result via the output terminal 53. Instead of simply adding the dither noise and the data string (xbi, x2i-1, xai, x2i), the lower 17 bits of the 24-bit data of the data string (xbi, x2i-1, xai, x2i) were truncated. Dither noise may be added later. Further, white noise or pink noise may be added instead of dither noise to degrade the S / N ratio of the data string (xbi, x2i-1, xai, x2i).
[0018]
Accordingly, the S / N ratio of the data string (xbi, x2i-1, xai, x2i) that has been A / D converted with the number of quantization bits of 24 bits, encoded, recorded on the recording medium, and degraded is deteriorated. Therefore, it is possible to prevent copying with high quality quantization bit number. Further, the output data strings xci, Δ1i, Δ2i of the DVD decoding circuit 42 are output to the digital output terminal 52 through the switch 51, and are also input through the terminal 49 and the terminal 49 for inputting the personal identification number. A decryption section 50 is provided for turning on the switch 51 when the personal identification number is decrypted. Therefore, only the specific person can copy the encrypted data string (xci, Δ1i, Δ2i), but cannot copy the high-quality data string (xbi, x2i-1, xai, x2i).
[0019]
FIG. 8 is a block diagram showing a signal processing circuit of a decoder that realizes a second reference example of the code information copy preventing method applied to the present invention, and FIG. 9 is an S / N ratio deterioration process of the signal processing circuit of FIG. It is explanatory drawing which shows. The encoder is the same as in the first reference example, and the circuit shown in FIG. 8 differs only in the circuit that degrades the high-quality data string (xbi, x2i-1, xai, x2i), and the other configurations are the same. is there.
[0020]
Here, the ID number is recorded on the DVD together with video and audio. Therefore, the ID number (AB... Z in the figure) and the character code “COPY” decoded by the DVD decoding circuit 42 are converted into, for example, an ASCII code by the pattern generator 58, and this is converted into noise and copy evidence data in FIG. As shown in the figure, it is replaced with the lower 8 bits of a high-quality data string (xbi, x2i-1, xai, x2i) and output as digital data.
[0021]
Therefore, when the user copies this data and performs D / A conversion, the quality of the audio signal is deteriorated, so that it can be prevented from being copied with a high-quality quantization bit number, and the copyright holder can record the recording medium. Can be detected to identify whether the recording medium is a copy. Further, instead of the ID number, the current time data (data output time) of the clock 59 may be converted into, for example, an ASCII code, which may be used for copy determination while deteriorating the quality of the audio signal.
[0022]
In the above reference example, the data string xci is a data string in which the digital data A / D converted by the A / D converter 31 is band-limited and the sampling frequency is lowered to ¼, and the difference data is the data string xci. The data string xci is a data string obtained by limiting the bandwidth of the digital data A / D converted by the A / D converter 31 and reducing the sampling frequency to ½, and the difference data May be calculated based on this data string xci. In the above embodiment, the data string xci reduces the sampling frequency of the digital data A / D converted by the A / D converter 31 to ¼. The interpolation data may not be calculated as a data string having the same sampling frequency as the D-converted digital data.
[0023]
Next, a third reference example will be described with reference to FIGS. 10 is a block diagram showing an encoder that realizes a code information copy prevention method according to the reference example, FIG. 11 is a block diagram showing the signal processing circuit of FIG. 10 in detail, and FIG. 12 is a sampling of the A / D converter of FIG. FIG. 13 is a block diagram showing a decoder for realizing the first embodiment of the code information copy prevention method according to the present invention, and FIG. 14 is a block diagram showing the signal processing circuit of FIG. 13 in detail. FIG. Further, the user data packed by the allocation circuit of FIG. 11 is the same as that shown in FIG. 4, and the data string and the sampling period decoded by the decoder of FIG. 13 are the same as those shown in FIG.
[0024]
In the encoder shown in FIG. 10, a copyright identification signal supply unit 100 is added to the configuration shown in FIG. 1, and the signal processing circuit 32 performs processing as shown in FIGS. 11 and 12. First, as in the first and second reference examples, a sufficiently high sampling frequency (sampling period Δt) that is worthy to prohibit the analog signal input via the input terminal IN from being copied by the A / D converter 31; For example, it is sampled at 192 kHz and converted into a high resolution PCM signal of, for example, 24 bits, and converted into a data string (xbi, x2i-1, xai, x2i) corresponding to the curve α as shown in FIG.
[0025]
This data string (xbi, x2i-1, xai, x2i) is encoded by the signal processing circuit 32 and the memory 33 shown in detail in FIG. 11, and then this data is a copyright identification signal from the copyright identification signal supply unit 100. Are packed by the DVD encoding circuit 34 together with the copyright data. This packing data is output to the output terminal OUT1, or is modulated by the modulation circuit 35 by the modulation method according to the medium and output to the output terminal OUT2, and information for identifying the copyright is output to the output terminal OUT3. Is output. The output terminal OUT3 is also used as an input terminal when searching from an external device.
[0026]
In the signal processing circuit 32, as shown in detail in FIGS. 11 and 12, as in the first and second reference examples, the data string (xbi, x2i-1, xai, x2i) is first in a 1/4 band. The signal is divided into low frequencies by the low-pass filter 36 to be divided and down-sampled to a quarter band, and the low-frequency signal (xci) therein is extracted by the thinning circuit 37 and applied to the allocation circuit 40. A data string (xbi, xai) is extracted by the thinning circuit 38, and the difference Δ1i is extracted by the subtractor 39.
xbi-xci = Δ1i
Is calculated and applied to the allocation circuit 40.
[0027]
In the third reference example, for example, the predictor 101 calculates the predicted value xdi ′ of the curve β at the time of the sample (xai) of the curve α using the second-order prediction method, and then the subtractor 102 calculates the predicted value. Difference Δ2i between xdi 'and actual sample value xai
xai−xdi ′ = Δ2i
Is calculated and applied to the allocation circuit 40. As shown in FIG. 4, the allocation circuit 40 packs these low-frequency components xci, two types of prediction differences Δ2i, Δ1i, and copyright identification signals in different channels in a predetermined arrangement, and the DVD encoding circuit 34 To supply.
[0028]
Here, when one user data (packet) is 2034 bytes as in the case of DVD, the low frequency data xci is packed with 334 pieces of 3 bytes, and the difference data Δ2i and Δ1i are 167 pieces each having an average of 1.5 bytes. In addition, 33 bytes are allocated to the subheader. Data from the copyright identification signal supply unit 100 is recorded in the sub-header.
-Disc serial number (16 bytes), which is information for managing the copy status to identify copyright
-Player identifier code (4 bytes)
・ Recording date (3 bytes)
・ Number of recordings (3 bytes)
・ Number of duplicates (4 bytes) and ・ Number of duplicates to manage copyright status (3 bytes)
Is recorded. In addition to the sub-header, a DVD has a copyright management information area (CMI area) provided on the inner periphery of the disc so as to correspond to a TOC area defined by a CDR disc or the like for identifying these copyrights. Are recorded in more detail.
[0029]
Next, the decoder will be described with reference to FIGS. In the decoder shown in FIG. 13, instead of the adder 56, the dither generator 57, and the digital output terminal 53 shown in FIG. 5, for example, LSB of PCM data of a high-quality data string (xbi, x2i-1, xai, x2i). Is provided with a digital output terminal 90 for adding and outputting copyright information.
[0030]
The signal processing circuit 43 will be described with reference to FIG. 14. In the circuit shown in the upper part, xbi = Δ1i + xci is calculated by the adder 46, and xai = Δ2i + xdi ′ is calculated by the predictor 111 and the adder 112. A high-quality data string (xbi, x2i-1, xai, x2i) is restored by calculating xi by the interpolation processing circuit 47 based on xai and xbi. This data string (xbi, x2i-1, xai, x2i) is output as an analog signal through the D / A converter 45 and the analog output terminal 55, and in the circuit shown in the lower stage, a high quality data string (xbi, Digital data obtained by adding the copyright data (adder 118) to the multi-value data of x2i-1, xai, x2i) is output via the digital output terminal 90.
[0031]
More specifically, the copyright data reproduced from the sub-header is modulated by the FM modulator 114 at a frequency of, for example, 5 kHz from the oscillator 113, and this modulated signal is then spread by the spread modulator 116 using the spread code 115. The frequency spectrum is spread widely to a low level. Furthermore, it is converted into 1 bit (192 kHz) by the Δ modulator 117 and applied to the adder 118, and added to the LSB of the data of the high quality data string (xbi, x2i-1, xai, x2i) by the adder 118. Later, it is output as digital data.
[0032]
Therefore, in the case of outputting in the state of digital data, since the copyright data is included in the data, the copy state can be managed even if copied, and as a result, unlimited copying can be prevented. it can. In this example, since the copyright data is transmitted through the medium, the decryption unit 50 decrypts the password and only the specific person copies the encrypted data string (xci, Δ1i, Δ2i). Since copyright data is included, the copy status can be managed.
[0033]
Next, an embodiment applied to the present invention will be described with reference to FIGS. 15 and 16. FIG. 15 is a block diagram showing in detail the signal processing circuit of the encoder that implements the first embodiment of the code information copy prevention method applied to the present invention. FIG. 16 shows the code information copy prevention method applied to the present invention. It is a block diagram which shows the signal processing circuit of the decoder which implement | achieves 1st Embodiment of this in detail. The first embodiment is a modification of the third reference example, and FIGS. 15 and 16 correspond to FIGS. 11 and 14, respectively.
[0034]
As shown in FIGS. 15 and 16, an oscillator 113, an FM modulator 114, a spread modulator 116 for modulating a copyright identification signal and adding it to a data string (xbi, x2i-1, xai, x2i), The Δ modulator 117 and the adder 118 are provided not on the decoder side but on the encoder side. That is, as shown in FIG. 15, the data obtained by adding the copyright data to the LSB of the multi-value data of the high-quality data string (xbi, x2i-1, xai, x2i) on the encoder side is the low pass of the signal processing circuit 32. The data is input to the filter 36, compressed, and transmitted.
[0035]
Then, as shown in FIG. 16, on the decoder side, data in which copyright data is added to the LSB of multi-value data of a high-quality data string (xbi, x2i-1, xai, x2i) can be output in a digital state. Allow digital copy. In other words, the copyright data is copied at the time of digital copying and not copied at the time of analog copying in the third reference example, whereas it is copied both at the time of digital copying and at the time of analog copying in the first embodiment. Further, when the decryption unit 50 decrypts the code number and only a specific person copies the encrypted data string (xci, Δ1i, Δ2i), the copyright data recorded in the subheader of the recording medium is damaged or restricted. Can be copied completely without being interrupted.
[0036]
Next, a second embodiment will be described with reference to FIG. This embodiment is a modification of the decoder of the first reference example shown in FIG. 5. A control unit 126 responding to the copy number limit information output from the decryption unit 50 is provided, and copy number limit information exists. In some cases, the digital signal is output from the digital signal output terminal 53, but the D / A converter 45 is disabled, and the analog signal is not output from the analog signal output terminal 55. This prevents unlimited copying of analog data that does not include copyright data.
[0037]
FIG. 18 is a block diagram showing the third embodiment, which is a modification of the decoder of FIG. Similar to the fifth embodiment, the control unit 126 responding to the copyright data to the copy number limit information output from the decryption unit 50 disables the D / A converter 45 when copy number limit information exists. The analog signal is controlled not to be output from the analog signal output terminal 55. Instead, the output signal of the signal processing circuit 43 is output via the digital signal output terminal 90, and the digital signal with the copyright data added is output. This prevents unlimited copying of analog data that does not include copyright data. In the third and fourth embodiments, the operation of the D / A converter 45 is stopped when there is copy number limit information. However, the present invention is not limited to this, and the D / A converter is not limited to this. A switch can be provided before and after 45 so that an analog signal is not output from the analog signal output terminal.
[0038]
【The invention's effect】
As described above, according to the present invention, in particular, copying is permitted in the state of digital data in which data indicating copyright is added to high-quality digital data. It is possible to achieve both protection.
In addition, if there is a limit on the number of copies for a digital signal, the digital signal is allowed to be output only, and the analog signal is not output, enabling unlimited copying as an analog signal. Can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an encoder that implements a first reference example of a code information copy prevention method according to the present invention;
FIG. 2 is a block diagram showing in detail the signal processing circuit of FIG. 1;
3 is an explanatory diagram showing a sampling period and a data string of the A / D converter of FIG. 1. FIG.
4 is an explanatory diagram showing user data packed by the allocation circuit of FIG. 1; FIG.
FIG. 5 is a block diagram showing a decoder that implements a first reference example of a code information copy prevention method according to the present invention;
6 is a block diagram showing in detail the signal processing circuit of FIG. 5;
7 is an explanatory diagram showing a data string and a sampling period decoded by the decoder of FIG.
FIG. 8 is a block diagram showing a signal processing circuit of a decoder for realizing a second reference example of the code information copy prevention method according to the present invention;
9 is an explanatory diagram showing S / N ratio deterioration processing of the signal processing circuit of FIG. 8;
FIG. 10 is a block diagram showing an encoder that implements a first embodiment of a code information copy prevention method according to the present invention;
11 is a block diagram showing in detail the signal processing circuit of FIG. 10;
12 is an explanatory diagram showing a sampling cycle and a data string of the A / D converter of FIG. 1. FIG.
FIG. 13 is a block diagram illustrating a decoder that implements a first embodiment of a code information copy prevention method according to the present invention;
14 is a block diagram showing in detail the signal processing circuit of FIG. 13;
FIG. 15 is a block diagram showing in detail a signal processing circuit of an encoder that implements a second embodiment of the code information copy prevention method according to the present invention;
FIG. 16 is a block diagram showing in detail a signal processing circuit of a decoder that implements a second embodiment of the code information copy prevention method according to the present invention;
FIG. 17 is a block diagram illustrating a decoder that implements a third embodiment of the code information copy prevention method according to the present invention;
FIG. 18 is a block diagram showing a decoder that implements a fourth embodiment of the code information copy prevention method according to the present invention;
[Explanation of symbols]
31 A / D converter (A / D conversion means)
32, 43 Signal processing circuit 33, 44 Memory 34 DVD encoding circuit 35 Modulation circuit 36 Low pass filter 37, 38 Decimation circuit 39 Adder (difference calculation unit)
40 Allocation circuit (output means)
41 Demodulation circuit 42 DVD decoding circuit 45 D / A converter (D / A conversion means)
46 Adder (configures restoration means together with the interpolation processing circuit 47)
47 Interpolation processing circuit 49 Terminal 50 Cryptographic decryption unit 51 Switch 52, 53, 90 Digital output terminal 55, 132 Analog output terminal 56 Adder (dither generator 57, pattern generator 58, clock 59 and S / N ratio deterioration means Constitute)
57 Dither generator 58 Pattern generator 59 Clock 100 Copyright identification signal supply unit 101, 111 Predictor 102, 112 Adder 113 Oscillator (with FM modulator 114, spread code 115, spread modulator 116, Δ modulator 117) Configure modulation means)
114 FM modulator 115 spreading code 116 spreading modulator 117 Δ modulator 118 adder (addition means)
126 Control unit (control means)

Claims (1)

A voice generated by A / D converting an analog signal of an audio signal by using a sampling frequency 192 kHz which is approximately four times higher than the sampling frequency of the CD and using a larger quantization bit number than the CD quantization bit number. Modulating and adding copyright data of the analog signal to the digital data and the copyright data managed by the copy number limit information and the ID number related to the analog signal;
The digital data generated by the modulation and addition step is arranged in the user data area of the audio packet of the DVD, and the modulation and addition of the copyright data managed by the copy number limit and the ID number related to the analog signal Is specified in units of audio packets so that each audio packet is stored in a subheader provided in a user data area of the audio packet, and the copyright managed by the copy number limit information is used. Allowing data and an ID number related to the analog signal to be stored in a copyright management information area of the DVD;
A decoding apparatus for code information for decoding a data signal obtained by an encoding method comprising:
Means for deformatting the formatted data signal and retrieving the audio packet;
Means for extracting the digital data from a user data area of the audio packet;
Means for extracting the copyright data from a sub-header provided in a user data area of the audio packet and / or the copyright management information area;
When the copyright data does not have a copy number limit, the extracted digital data is output as a digital signal using a basic sampling frequency and a basic quantization bit number, while the copyright data is copied Is included, the extracted digital data is allowed to be output only as a digital signal together with the copyright data, but the digital data is not D / A converted for an analog signal. Or control means for controlling not to output after D / A conversion;
The decoding apparatus of the code information which consists of.

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