JPH09330561A - Recording equipment, reproducing equipment, transmitting equipment and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide recording equipment which superposes a copy protect signal on a main audio signal and records them on a recording medium so that unjust cancellation of the copy protect signal be prevented and that the protect signal can be taken out, with the tone quality of the main audio signal prevented from being deteriorated, at the time of just reproduction thereof and to provide reproducing equipment which can control output of the main audio signal in accordance with the copy protect signal reproduced from a recording medium, transmitting equipment which can transmit the signals and the recording medium. SOLUTION: An adder 3 adds up an analog audio signal in an audio band outputted by a sound source 2 and a copy protect signal of a specific frequency, e.g. 16×44.1kHz, in a band being apart sufficiently from the audio band. A 1-bit ΣΔ converter 5 converts an addition output of the adder 3 into 1-bit digital data. A record processing circuit 6 applies a recording processing to the 1-bit digital data outputted by the 1-bit ΣΔ converter 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium in which a copy protect signal is superimposed on a main signal, a reproducing device for reproducing the recording medium, a recording device for recording the copy protect signal on the recording medium, and a copy protect signal. Relates to a transmission device for transmitting a digital signal superimposed on a main signal.

[0002]

2. Description of the Related Art A method of converting an analog audio signal into a digital signal and recording it on a recording medium, and reproducing and transmitting it from a recording medium is conventionally performed by using an optical disc represented by a compact disc (CD) and a digital audio tape (DAT). Recording and reproducing devices using a typical magnetic tape as a recording medium, and digital broadcasting such as satellite broadcasting are used.

In the conventional digital audio recording or transmitting apparatus as described above, when converting an analog audio signal into a digital signal, the sampling frequency is 48 kHz, 44.1 kHz, etc., and the quantization bit number is 16 bits, 20 bits, etc. Format was specified.

In such a conventional digital audio data format, audio data and sub-data related to the audio data are recorded or transmitted together, and a copy protect signal is recorded in a part of the sub-data. Copy protection is performed by detecting on the reproducing side or the receiving side.

[0005]

As described above, in the method of recording the copy protect signal in a part of the sub data, the copyright is illegally canceled by ignoring the sub data or rewriting the sub data. can do. Moreover, the audio data is not affected at all by the work of releasing the copy protect signal from the sub data.

Further, a method has been considered in which a part of the band of the audio signal is extracted by a steep notch filter and the band extracted by this notch filter is detected to perform copy protection. Since a copy protection signal is included by being superimposed on
Even if the copy protection is normally canceled, the characteristics of the audio signal are changed by the notch filter. Therefore, the copy protection function can be achieved, but the sound quality is greatly affected by the copy protection processing.

The present invention has been made in view of the above circumstances, and it is possible to take out the copy protect signal while preventing the illegal release of the copy protect signal and preventing the sound quality deterioration of the main audio signal during the correct reproduction. A recording device that superimposes the protect signal on the main audio signal so as to record it on a recording medium so that the reproduction device can control the output of the main audio signal according to the copy protect signal reproduced from the recording medium.
An object is to provide a transmission device and a recording medium that can transmit.

[0008]

In order to solve the above problems, a recording apparatus according to the present invention provides a main signal having a first band in a second band sufficiently separated from the first band. Is added by the adding means, and the addition result from this adding means is added to ΣΔ
The modulation means converts the 1-bit digital signal, and the 1-bit digital signal is recorded on the recording medium by the recording means.

Here, since the copy protection signal is converted into a 1-bit digital signal after being superimposed on the main signal, it is difficult to cancel illegally. When it is played back correctly, the copy protection signal is
Since it is included in the band sufficiently separated from the main signal, it does not affect the main signal.

In order to solve the above problems, the reproducing apparatus according to the present invention reproduces from a recording medium a 1-bit digital signal obtained by subjecting the main signal on which the copy protect signal is superimposed to the sigma-delta modulation process. In doing so, the output operation of the output means for the 1-bit digital signal reproduced by the reproduction means is controlled based on the copy protection signal extracted by the second extraction means.

Therefore, the control means can prohibit the output of the 1-bit digital signal from the output means according to the contents of the copy protect signal.

In order to solve the above-mentioned problems, the transmission apparatus according to the present invention has a predetermined signal included in the main signal having the first band and the second band sufficiently separated from the first band. The copy protection signal having the frequency is added by the addition means, the addition result from the addition means is converted into a 1-bit digital signal by the ΣΔ modulation means, and the 1-bit digital signal is transmitted by the transmission means.

Here, since the copy protection signal is converted into a 1-bit digital signal after being superimposed on the main signal, it is difficult to cancel illegally. When it is played back correctly, the copy protection signal is
Since it is included in the band sufficiently separated from the main signal, it does not affect the main signal.

In order to solve the above problems, the recording medium according to the present invention has, in the main signal having the first band, a predetermined frequency contained in the second band sufficiently separated from the first band. After superimposing a copy protect signal, a 1-bit digital signal obtained by subjecting this signal to ΣΔ modulation processing is recorded. Therefore, it is difficult to illegally cancel the copy protect signal. Further, at the time of correct reproduction, it is possible to suppress the influence of the copy protect signal on the main signal.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a recording device, a reproducing device, a transmission device and a recording medium according to the present invention will be described below with reference to the drawings.

First, as a first embodiment, FIG. 1 shows an audio data recording apparatus 1 for converting an analog audio signal into 1-bit digital audio data by a sigma-delta (ΣΔ) conversion process and recording it on a magnetic tape. .

The audio data recording apparatus 1 includes an analog audio signal in the audible band output from the sound source 2 and a signal in a band sufficiently separated from the audible band, for example, 16 × 44.
An adder 3 for adding the copy protection signal from the input terminal 4 modulated at a specific frequency of 1 KHz, a 1-bit ΣΔ converter 5 for converting the addition output of the adder 3 into 1-bit digital data, and 1 A recording processing circuit 6 for performing recording processing on the 1-bit digital data output from the bit ΣΔ converter 5 is provided.

Usually, the 1-bit ΣΔ converter 5 samples the analog audio signal at a very high sampling frequency with respect to the frequency band (audible frequency band) of the analog audio signal and quantizes it into 1 bit. Here, the current CD sampling frequency f _s (= 44.1)
KHz) of 64 times the sampling frequency (= 64f _S)
Sample the analog audio signal.

The 1-bit ΣΔ converter 5 has a structure as shown in FIG. The analog input signal input from the input terminal 11 is supplied to the integrator 13 via the adder 12. The integrated output from the integrator 13 is supplied to the comparator 14, is compared with the midpoint potential of the input signal, and is subjected to 1-bit quantization processing for each sample period and output as 1-bit digital audio data.

The 1-bit digital audio data which is the quantized data is supplied to the 1-sample delay unit 15 and delayed by 1 sample period. This delay data is converted into an analog signal by a 1-bit D / A (Digital to Analog Converter) converter 16 and supplied to the adder 12 to be added to the input signal from the input terminal 11.

1 output from the 1-bit ΣΔ converter 5 in FIG.
Audit frequency characteristics of bit digital audio data
o Show as signal. By the ΣΔ conversion processing in the 1-bit ΣΔ converter 5, a noise component (illustrated as a noise floor) can be shifted to a band higher than the audible band. 1
In the case of 1-bit digital audio data output from the bit ΣΔ converter 5, a pass band of 100 KHz is secured, and a Nyquist frequency of 3 is used to prevent aliasing.
Even to have a moderate attenuation characteristic up to 2f _S, although the dynamic range is not so large as shown in FIG. 3, the Nyquist frequency of 3 from nearby frequencies 16f _S
A wide unused band remains up to 2f _S.
This band is usually removed by an analog low-pass filter when the signal is converted into an analog signal by a D / A converter on the reproducing apparatus and reproduced.

The audio data recording apparatus 1 according to the first embodiment is a copy having a specific frequency 16f _S in a band from a frequency around 16f _S which is a frequency that does not affect 1-bit digital data to a Nyquist frequency 32f _S. Protect signal is superimposed (added) and the addition output is 1
The bit ΣΔ converter 5 performs ΣΔ conversion. The 1-bit digital data from the 1-bit ΣΔ converter 5 is subjected to recording processing by the recording processing circuit 6, and then recorded on the magnetic tape 8 via the recording head 7 as 1-bit digital data.

The copy protect signal is a signal for preventing audio data recorded or transmitted together from being illegally copied. In this case, the copy protect signal is a sine wave supplied from the input terminal 4, and is 16 times (= 16 × 4) the sampling frequency (f _S = 44.1 KHz) of the current compact disc (CD).
It is a high frequency sine wave of 4.1 KHz.

Since the spectrum of this copy protect signal is as shown in FIG. 4 (illustrated as copy protect signal), the spectrum of 1-bit digital audio data on which this copy protect signal is superimposed is as shown in FIG. As shown in FIG. 5, the copy protect signal is a 1-bit digital audio data (audio signal) masked by a noise floor.
It exists in a band higher than the band of, which is removed by the analog low-pass filter when reproducing.

Therefore, in the audio data recording apparatus 1, the copy protect signal can be superimposed on the main audio data, and an illegal copy protect function releasing operation on the reproducing side can be prevented. Also, since the frequency band that does not affect the audio band is used as the band for superimposing the copy protection signal,
There is no adverse effect on the main audio data.

Next, as a second embodiment, an audio data reproducing device 20 for reproducing the 1-bit digital data recorded on the magnetic tape 8 by the audio data recording device 1 of the first embodiment is illustrated. 6 shows.

The audio data reproducing apparatus 20 has a reproduction processing circuit 22 for reproducing the 1-bit digital data extracted by the reproduction head 21 and 1-bit digital data from the reproduction processing circuit 22 as a copy protection signal. and 4-tap analog FIR filter 23 for D / a conversion while sufficiently attenuating the frequency of the sine wave of the 16f _s that is, the analog FIR filter 23
An analog low-pass filter 24 that uses the filter output of the above as an analog audio signal, a band-pass filter (BPF) 26 that passes a copy protect signal from the above 1-bit digital data, and the level of the filter output of this BPF 26 are compared at a predetermined reference level. Level detector 27 for detecting the presence or absence of the copy protect signal,
When the level detector 27 detects a copy protect signal, the switch 29 is turned off to inhibit the output of 1-bit digital data from the reproduction processing circuit 22 from the output terminal 30, and a controller 28. Here, the analog BPF 26 and the level detector 27 constitute a copy protection extraction unit that extracts a copy protection signal.

As shown in FIG. 7, the analog FIR filter 23 includes four D flip-flops D-FF ₁ , D-FF ₂ , D-FF ₃ and D-FF ₄ connected in cascade and this D flip-flop. D-FF ₁ , D-FF ₂ , D-FF ₃ , D
-FF ₄ connected to four resistors R ₁ , R ₂ , R
₃ and R ₄ are provided. These four resistors R ₁ , R ₂ , R
By adding the currents from ₃ and R ₄ , the analog F
An IR filter is formed, the output of the FIR filter is smoothed by the capacitor C, and the result is derived from the output terminal 33.

[0029] The input terminal 31 of one bit digital data is supplied to connected to the data input terminal D of the D flip-flop D-FF _1, the output terminal Q of the D flip-flop D-FF ₁ D flip-flop D-FF connected to _second data input terminal D, connected to the output terminal Q of the D flip-flop D-FF ₂ to the data input terminal D of the D flip-flop D-FF _3, the output terminal of the D flip-flop D-FF ₃ Q is the data input terminal D of the D flip-flop D-FF _4.
Connected to

The clock input terminal 32 to which the clock CK is supplied is connected to the D flip-flops D-FF ₁ , D-FF ₂ and D.
-Connect to each clock terminal of FF ₃ and D-FF ₄ , respectively.

Output terminal Q of D flip-flop D-FF ₁
Connect one end of resistor R ₁ to D flip-flop DF
The output terminal Q of F ₂ is connected to one end of the resistor R ₂ , the output terminal Q of the D flip-flop D-FF ₃ is connected to one end of the resistor R ₃ , and the output terminal Q of the D flip-flop D-FF ₄ is connected. One end of the resistor R ₄ is connected to.

The other ends of these resistors R ₁ , R ₂ , R ₃ , R ₄ are connected to form an output terminal 33 from the connection point, and a capacitor C inserted between the connection point and the ground.
Is used to smooth the analog output.

Since the analog FIR filter 23 smoothes the output to obtain an analog signal, the copy protect signal can be removed in the digital-analog conversion process.

The analog signal from the analog FIR filter 23 is converted into an analog audio signal by passing through the analog LPF 24 and is derived from the output terminal 25.

On the other hand, the analog BPF 26, which constitutes the copy protection extraction section together with the level detector 27, passes a narrow band centered on the frequency of the 16 _fs sine wave superposed as the copy protection signal from the 1-bit digital data. It is a bandpass filter that allows.

In the level detector 27, the level of the filter output of the BPF 26 is compared with a predetermined reference level and the above B
When it is detected that the filter output level of the PF 26 is equal to or higher than the predetermined reference level, the controller 28 turns off the switch 29 to prohibit the output of the 1-bit digital data from the output terminal 30.

When the level detector 27 judges that the filter output of the BPF 26 is below the predetermined reference level and the copy protection signal cannot be extracted, the controller 28 turns on the changeover switch 29 so as to release the prohibition of the copy work. The output of the 1-bit digital data from the output terminal 30 is permitted.

If the user attempts to illegally copy, the 1-bit digital data from the reproduction processing circuit 22 is passed through a digital notch filter having a frequency characteristic having a valley at 16f _S as shown in FIG. When data is to be taken out, the copy protect signal can be removed. However, since the output data becomes a multi-bit signal by this processing, it is possible to take out the original 1-bit digital audio data while canceling the copy protect function. Can not.

[0039] That is be removed copy protection signals in the digital notch filter having 16f _S in the valley, is transformed into a multi-bit form, which is also removed to band around around the 16f _S, an output terminal 30 Will output a multi-bit digital signal instead of a 1-bit digital signal.

When performing digital copying, it is desirable to record the 1-bit digital signal itself from the recording medium on which the 1-bit digital signal is recorded. However, when the copy protection is removed as described above, Since it is converted to multi-bit by the digital notch filter, it becomes impossible to record the 1-bit digital signal itself on the recording medium, and it is prohibited to use the high-quality sound and the high bandwidth which are the original characteristics of the 1-bit digital signal. To be done.

Therefore, the digital data reproducing apparatus 20 makes the 1-bit digital audio data itself, which is the main data, into multi-bit data in response to an attempt to illegally cancel the copy protection function. Can protect
The copy protection function can be used most effectively.

Next, as a third embodiment, FIG. 9 shows an audio data recording device 40 for converting an analog audio signal into 1-bit digital audio data by ΣΔ modulation processing and recording it on the magnetic tape 8.

The audio data recording device 40 is different from the audio data recording device 1 according to the first embodiment in that the audio data recording device 1 adds a copy protect signal to an analog audio signal and then adds the copy protect signal. While the output is 1-bit ΣΔ converted, a digital sine wave copy protection signal is added to the 1-bit ΣΔ-converted 1-bit digital audio data, and the added output is further 1-bit ΣΔ-modulated. It is a point.

That is, the audio data recording device 40 converts the analog audio signal from the sound source 41 into 1-bit digital audio data.
A Δ converter 42, a 1-bit data recorder 43 for temporarily recording the 1-bit digital audio data from the 1-bit Δ converter 42, and a digital oscillator 45 for oscillating a 16 f _S digital sine wave used as a copy protect signal. A digital adder 44 for adding the digital copy protect signal to the 1-bit digital audio data from the 1-bit data recorder 43, and a 1-bit ΣΔ modulation for modulating the addition output from the digital adder 44 into 1-bit digital data again. And a recording processing circuit 47 for recording the 1-bit digital data from the 1-bit ΣΔ modulator 46.
It comprises.

The analog audio signal from the sound source 41 is ΣΔ converted by the 1-bit ΣΔ converter 42 at a sampling frequency 64f _S that is 64 times the sampling frequency f _S (= 44.1 KHz) of the CD. The 1-bit digital audio data from the 1-bit Δ-converter 42 is once recorded in a 1-bit data recorder 43,
It is supplied to a digital adder 44.

The digital adder 44 adds the 1-bit digital audio data from the 1-bit data recorder 43 and the multi-bit digital copy protect signal from the digital oscillator 45. The addition output (64f _S / multi-bit) from the digital adder 44 is modulated into 1-bit digital data by the 1-bit ΣΔ modulator 46 and supplied to the recording processing circuit 47. The 1-bit digital data recorded by the recording processing circuit 47 is recorded on the magnetic tape 8 by the recording head 48.
Recorded in.

This audio data recording device 40 also has 1
It is possible to record by superimposing a copy protect signal on a band sufficiently separated from the band of bit digital audio data.

Therefore, also in the audio data recording device 40, the copy protect signal can be superimposed on the main data, and the illegal operation of canceling the copy protect function on the reproducing side can be prevented. Further, since the frequency band that does not affect the audio band is used as the band on which the copy protect signal is superimposed, it is possible to prevent the sound quality deterioration of the main audio data.

Incidentally, instead of the recording apparatus according to the present invention, 1
A transmission device for transmitting bit digital data may be considered. In this case, the circuit configuration up to the preceding stage of the recording processing circuit is the same. In this transmission device, the copy protection signal can be transmitted as a 1-bit digital signal after being superimposed on the main audio data, and an unauthorized copy protection function canceling operation on the receiving side can be prevented. In addition, since the frequency band that does not affect the audio band is used as the band on which the copy protection signal is superimposed, the main audio data is not adversely affected at all.

In addition, the recording device according to the present invention can
The copy protection signal having a predetermined frequency included in the second band sufficiently separated from the first band is superimposed on the main signal having the band, and is subjected to ΣΔ modulation processing and recorded as a 1-bit digital signal. The recording medium
This makes it difficult to illegally cancel the copy protection signal. Further, at the time of correct reproduction, it is possible to suppress the influence of the copy protect signal on the main signal.

[0051]

As described above, the recording apparatus according to the present invention can superimpose the copy protect signal on the main audio data, and can prevent the illegal operation of canceling the copy protect function on the reproducing side. In addition, since the frequency band that does not affect the audio band is used as the band on which the copy protection signal is superimposed, the main audio data is not adversely affected at all.

The reproducing apparatus according to the present invention can make the copy protection function work most effectively against an attempt to illegally cancel the copy protection function.

The transmission apparatus according to the present invention can superimpose the copy protect signal on the main audio data and then transmit it as a 1-bit digital signal, thereby preventing an illegal operation of canceling the copy protect function on the receiving side. You can In addition, since the frequency band that does not affect the audio band is used as the band on which the copy protection signal is superimposed, the main audio data is not adversely affected at all.

The recording medium according to the present invention makes it difficult to illegally cancel the copy protection signal. Further, at the time of correct reproduction, it is possible to suppress the influence of the copy protect signal on the main signal.

[Brief description of drawings]

FIG. 1 is a block diagram of an audio data recording device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a 1-bit ΣΔ converter used in the audio data recording device.

FIG. 3 is a spectrum diagram of 1-bit audio data and a noise floor.

FIG. 4 is a spectrum diagram of a copy protection signal.

FIG. 5 is a spectrum diagram of 1-bit digital audio data on which a copy protect signal is superimposed.

FIG. 6 is a block diagram of an audio data reproducing device according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of an analog FIR filter used in the audio data reproducing device.

FIG. 8 is a diagram for explaining a case where an attempt is made illegally by using a digital notch filter having a frequency characteristic having a valley at 16f _S.

FIG. 9 is a block diagram of an audio data recording device according to a third embodiment of the present invention.

[Explanation of symbols]

1 audio data recording device, 2 sound sources, 3 adder, 5 1-bit ΣΔ converter, 6 recording processing circuit, 7
Recording head, 8 magnetic tape, 20 audio data reproducing device, 21 reproducing head, 22 reproducing processing circuit, 2
3 analog FIR filter, 24 analog low pass filter, 26 band pass filter, 27 level detector, 28 controller

Claims (10)

[Claims] 1. A 1-bit digital signal obtained by sigma-delta modulating a main signal having a first band and a copy protect signal having a predetermined frequency contained in a second band sufficiently separated from the first band. A recording device for recording as a signal on a recording medium, the adding means for adding the main signal and the copy protect signal, the sigma delta modulating means for converting the addition result from the adding means into a 1-bit digital signal, A recording device comprising: recording means for recording a 1-bit digital signal from the sigma-delta modulation means on a recording medium. 2. A second sigma-delta modulation means for converting the main signal into a 1-bit digital signal, and a source for generating the copy protection signal, which is included in a second band sufficiently separated from the first band. The recording apparatus according to claim 1, further comprising a digital oscillation source that oscillates a predetermined frequency. 3. The recording apparatus according to claim 1, wherein the main signal is audio information. 4. A 1-bit digital signal obtained by sigma-delta modulating a main signal having a first band and a copy protect signal having a predetermined frequency contained in a second band sufficiently separated from the first band. A reproducing device for reproducing a recording medium recorded as a signal, comprising reproducing means for reproducing a 1-bit digital signal from the recording medium, output means for outputting the 1-bit digital signal reproduced by the reproducing means, First extracting means for extracting a main signal having the first band from the 1-bit digital signal reproduced by the reproducing means, and included in the second band from the 1-bit digital signal reproduced by the reproducing means. Second copy means for extracting a copy protect signal, and the above-mentioned based on the copy protect signal extracted by the second extractor. Reproducing apparatus characterized by comprising a control means for prohibiting the output of the 1-bit digital signal from the force means. 5. The second extracting means includes a filter means for passing a predetermined frequency included in the second band,
The copy protection signal comprises a comparison means for comparing the level of the signal passed by the filter means with a reference level, and when the comparison means determines that the level of the signal from the filter means is higher than the reference level. 5. The reproducing apparatus according to claim 4, wherein 6. The reproducing apparatus according to claim 4, wherein the main signal is audio information. 7. An adding means for adding a main signal having a first band and a copy protect signal having a predetermined frequency included in a second band sufficiently separated from the first band, and the adding means. A transmission apparatus comprising: a sigma-delta modulation means for converting the addition output into a 1-bit digital signal, and a transmission means for transmitting the 1-bit digital signal from the sigma-delta modulation means. 8. The transmission device according to claim 7, wherein the main signal is audio information. 9. A sigma-delta modulation process is performed after superimposing a copy protect signal having a predetermined frequency included in a second band sufficiently separated from the first band on a main signal having the first band. A recording medium characterized by recording the 1-bit digital signal obtained as described above. 10. The recording medium according to claim 9, wherein the main signal is audio information.