JP3403924B2 - 1-bit signal transmission or recording / reproducing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus suitable for being implemented in a digital audio system and transmitting or recording / reproducing a 1-bit signal obtained by ΔΣ modulation.

[0002]

2. Description of the Related Art In the above digital audio, a multi-bit coding system has been widely used. In this multi-bit encoding method, for example, the sampling frequency is set to 44.1 kHz or 48 kHz and the number of quantization bits is set to 12, 14 or 16 bits, and the reproduction frequency bandwidth is determined by the sampling frequency. The dynamic range is determined by the number of digitized bits. For example, the reproduction frequency bandwidth is about 20 kHz, and the dynamic range is 90 kHz.
It is about 100 dB.

On the other hand, in order to suppress noise in a signal for transmission or recording / reproducing, conventionally, a signal to be transmitted or recorded is subjected to pre-emphasis processing, and a received or reproduced signal is subjected to de-emphasis processing. It is widely practiced. For example, by emphasizing the high frequency side by pre-emphasis processing and suppressing the high frequency side by de-emphasis processing, although the frequency characteristic of the signal output from the receiving or reproducing apparatus is flat, noise is suppressed, The dynamic range is substantially expanded.

In this respect, in the multi-bit encoding method which is a conventional encoding method, since the reproduction frequency bandwidth is defined in advance as described above, the turn which is the start frequency of pre-emphasis and de-emphasis. The over frequency and the roll-off frequency, which is the ending frequency of the pre-emphasis and the de-emphasis, are uniquely determined to have values adapted to the reproduction frequency bandwidth.

On the other hand, the 1-bit signal obtained by the ΔΣ modulation can be demodulated into an analog audio signal by using a simple low-order low-pass filter when the 1-bit signal is an audio signal, for example. However, there is an advantage that a complicated processing circuit is unnecessary for demodulation. Further, since the 1-bit signal is a finely subdivided data flow that does not require word synchronization, it has the advantage that it is less susceptible to the influence of the transmission line, etc., and thus is resistant to errors and does not require an error correction circuit. is doing. Therefore, in recent years, the 1-bit coding method, which has many advantages over the multi-bit coding method, has been receiving attention.

[0006]

In the 1-bit encoding method, it is relatively easy to change the sampling frequency, and it is possible to set the optimum reproduction frequency bandwidth for the system economically and performance-wise. It has the advantage that it can. By changing the algorithm of the 1-bit digital / analog converter, it is possible to change the reproduction frequency bandwidth and the dynamic range which are related to each other.

Therefore, as in the prior art, if the emphasis characteristics such as the turnover frequency and roll-off frequency remain constant, various characteristics cannot be changed and tracked, which is an excellent advantage of the 1-bit encoding method. There is a problem that you can't make the most of it.

It is an object of the present invention to provide a 1-bit signal transmission or recording / reproducing apparatus capable of optimally setting the emphasis characteristic.

[0009]

A 1-bit signal transmission or recording / reproducing apparatus according to the present invention is an apparatus for transmitting or recording / reproducing a 1-bit signal obtained by ΔΣ modulation. 1-bit analog /
A pre-emphasis circuit provided in the preceding stage of the digital converter, and a pre-emphasis control means capable of switching the characteristics of the pre-emphasis circuit and transmitting or recording an emphasis control signal corresponding to the switching state as subcode data on a recording medium. The receiving or reproducing apparatus includes a de-emphasis circuit provided after the digital / analog converter and an emphasis control signal obtained by reproducing the sub-code data from a receiving or recording medium. And a de-emphasis control means for switching the characteristics of the de-emphasis circuit.

According to the above arrangement, the transmission or recording device side has a turnover frequency or a turnover frequency so that the emphasis characteristic is optimum for the reproduction frequency bandwidth determined by the sampling frequency or the algorithm of the analog / digital converter. When a pre-emphasis characteristic such as a roll-off frequency is set, the emphasis control signal representing the pre-emphasis characteristic is transmitted, for example, in the lead-in information area of a compact disc or the TOC of a mini disc.
It is recorded in the (Table Of Contents) area or the like, and is provided as subcode data together with the 1-bit signal from the transmitting or recording device side to the receiving or reproducing device side.
On the receiving or reproducing device side, the characteristics of the de-emphasis circuit are automatically switched so that the de-emphasis characteristics are adapted to the set pre-emphasis characteristics.

Therefore, it is possible to automatically and always set the optimum emphasis characteristic by following the change of the reproduction frequency bandwidth, which is an advantage of the 1-bit encoding method.

Further, in the 1-bit signal transmission or recording / reproducing apparatus according to the present invention, the transmission or recording apparatus further comprises sampling frequency switching means capable of switching the sampling frequency of the 1-bit analog / digital converter. The pre-emphasis control means switches the characteristics of the pre-emphasis circuit so that the pre-emphasis characteristics are adapted to the switched sampling frequency, and the receiving or reproducing apparatus is configured to sample the digital / analog converter. Sampling frequency switching means capable of switching the frequency is further provided, and the de-emphasis control means switches the characteristic of the de-emphasis circuit so that the de-emphasis characteristic is adapted to the switched sampling frequency.

According to the above configuration, the pre-emphasis characteristic on the transmitting or recording apparatus side and the de-emphasis characteristic on the receiving or reproducing apparatus side are switched automatically by automatically following the change in the reproduction frequency bandwidth due to the switching of the sampling frequency. can do.

[0014] In the transmission or recording and reproducing apparatus of the 1-bit signal according to the present invention, the pre-emphasis control means also, in response to the sampling frequency, it is preferable to perform the switching of 1-bit analog / digital converter of the algorithm .

According to the above configuration, 1-bit analog /
The pre-emphasis characteristic on the transmission or recording device side and the de-emphasis characteristic on the reception or reproducing device side can be switched automatically by automatically following the change in the reproduction frequency bandwidth due to the switching of the algorithm of the digital converter.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding one embodiment of the present invention,
The following is a description based on FIGS. 1 to 5.

FIG. 1 is a block diagram showing an electrical configuration of a 1-bit signal recording / reproducing apparatus 1 according to an embodiment of the present invention. The 1-bit signal recording / reproducing apparatus 1 is used for recording / reproducing an audio signal. The analog audio signal input to the input terminal 2 is supplied to the pre-emphasis circuit 3
As will be described later, after the pre-emphasis processing is performed to emphasize the high frequency component, it is input to the analog / digital converter 4. The analog / digital converter 4 encodes the input analog audio signal into a 1-bit signal by ΔΣ modulation and outputs the 1-bit signal to the recording device 5. The recording device 5 is
The bit signal is recorded on the recording medium 6 such as a magneto-optical disk or a magnetic disk. The 1-bit signal reproduced from the recording medium 6 by the reproducing device 7 is demodulated into an analog audio signal by the digital / analog converter 8 and then subjected to a de-emphasis process for suppressing a high frequency component in a de-emphasis circuit 9. Then, it is output from the output terminal 10.

In the 1-bit signal recording / reproducing apparatus 1, the control circuit 11 can set the reproduction frequency bandwidth and the dynamic range.
Switches the sampling frequency of the analog / digital converter 4 via the sampling frequency control circuit 12 in accordance with the reproduction frequency bandwidth. Also, corresponding to the reproduction frequency bandwidth and dynamic range,
The algorithm of the analog / digital converter 4 is switched. Furthermore, the pre-emphasis control circuit 13 corresponds to the algorithm and the sampling frequency.
Switches the pre-emphasis characteristic of the pre-emphasis circuit 3 as described later.

The emphasis control signal EMP supplied from the pre-emphasis control circuit 13 to the pre-emphasis circuit 3 and the sampling frequency control signal fs supplied from the sampling frequency control circuit 12 to the analog / digital converter 4 are input to the recording device 5. The recording device 5 records the data in an empty area such as a lead-in area or a TOC area of the recording medium 6.

Correspondingly, the sampling frequency control signal fs reproduced by the reproducing device 7 is input to the sampling frequency control circuit 14, and the sampling frequency control circuit 14 causes the digital / analog converter 8 to operate.
Is adapted to the sampling frequency to perform digital / analog conversion. Further, the emphasis control signal EMP reproduced by the reproducing device 7 is inputted to the de-emphasis control circuit 15, and the de-emphasis control circuit 1 is supplied.
5, the de-emphasis characteristic of the de-emphasis circuit 9 is switched as described later.

FIG. 2 is an electric circuit diagram showing a configuration example of the pre-emphasis circuit 3. The pre-emphasis circuit 3 includes feedback bias resistors R1 and R1 of the operational amplifier 21.
2 is a circuit having frequency characteristics, and the bias resistor R is provided between the output terminal of the operational amplifier 21 and the ground potential.
A series circuit of 1 and R2 is connected, and this bias resistor R
The potential at the connection point of 1 and R2 is fed back to the input side of the operational amplifier 21. Capacitors C11, C12, C13; C21, C are connected in parallel to the bias resistors R1, R2, respectively.
22 and C23 are provided. These capacitors C
C11, C12, C13; C21, C22, C23 are selectively connected in parallel to the bias resistors R1, R2 by switches SW1, SW2 in response to an emphasis control signal EMP from the pre-emphasis control circuit 13. .

Therefore, the capacitance of the capacitor C11, C12 or C13 selected by the switch SW1 is C
1 and the capacitor C2 selected by the switch SW2
When the electrostatic capacitance of 1, C22 or C23 is represented by C2, the bias resistor R1, the capacitors C11, C12, C13 and the switch SW1 constitute a boost circuit for boosting from the turnover frequency f1 determined by R1 / C1. , A bias resistor R2, a capacitor C21,
C22, C23 and switch SW2 allow R2 /
A roll-off circuit that performs a roll-off operation is configured from the roll-off frequency f2 determined by C2.

The roll-off circuit can be omitted when a high-frequency limiting filter is provided at a stage subsequent to the pre-emphasis circuit 3.

When the capacitors C11 and C21, for example, are selected by the pre-emphasis circuit 3 thus constructed, as shown by reference numeral α1 in FIG. 3, from the turnover frequency f1 to the roll-off frequency f2,
For example, it is possible to realize a pre-emphasis characteristic in which the enhancement is performed at about 6 (dB / oct).
By selecting the capacitors C12, C22; having smaller electrostatic capacitances than 11, C21 respectively, the turnover frequency is set to f1a and the roll-off frequency is set to f2a.
It is possible to obtain a pre-emphasis characteristic as indicated by reference numeral α1a.

Correspondingly, the de-emphasis circuit 9
Is configured as shown in FIG. 4, for example. The de-emphasis circuit 9 includes a resistor R3 interposed in series in a signal path and capacitors C31, C32, C selectively interposed between an output end of the resistor R3 and a ground potential.
33, and in response to the emphasis control signal EMP,
A passive high-order primary high-cut filter including a switch SW3 for selectively switching the capacitors C31, C32, and C33. The capacitor C3
When 1 is selected, the de-emphasis characteristic starts to attenuate from the turnover frequency f1 as indicated by reference numeral α2 in FIG. 3, while the de-emphasis characteristic is referred to by selecting the capacitors C32 ,. Mark α2
As indicated by a, the attenuation starts from the turnover frequency f1a.

As a result, the de-emphasis characteristic opposite to the pre-emphasis characteristic is realized, and the output terminal 1
The frequency characteristic of the analog audio signal output to 0 is a flat characteristic as indicated by reference numeral α3. In this way, it is possible to suppress noise of high frequency components when recording and reproducing the audio signal.

In the de-emphasis circuit 9,
The high frequency side of the roll-off frequency f2 is outside the reproduction frequency band or higher than the upper limit of the reproducible frequency band of the analog device, and there is often no influence on the reproduction frequency characteristic, and therefore it is omitted. Therefore, when considering the high frequency side of the roll-off frequency f2, the de-emphasis circuit 9 may be configured by an active circuit like the pre-emphasis circuit 3.

Also, the analog / digital converter 4
Is a ΔΣ modulation type analog / digital converter configured by including a 7th order integrator, as disclosed in Japanese Patent Application Laid-Open No. 9-162743, and the algorithm control signal ALG from the control circuit 11 is In response, for example, by changing the time constant of the time constant element of the integrator, changing the gain of the integrator, and controlling the zero point, the sampling frequency remains constant and the reproduction frequency bandwidth and the dynamic frequency that are related to each other are changed. It is configured to change the range and.

Therefore, for example, FIG. 5A and FIG.
As shown in (b) and, the reproduction frequency bandwidth can be changed. Therefore, the pre-emphasis control circuit 13 also switches the pre-emphasis characteristics in response to the algorithm control signal ALG to combine the control of the reproduction frequency bandwidth and the dynamic range with the control of the pre-emphasis characteristics. hand,
A high degree of noise floor control can be performed.

As described above, in the 1-bit signal recording / reproducing apparatus 1 according to the present invention, the sampling frequency control signal fs representing the sampling frequency and the emphasis control signal EMP representing the emphasis characteristic are recorded on the recording medium 6 and reproduced. In response to the signals fs and EMP, the optimum time constant is automatically set and reproduction is performed, so that the reproduction frequency band is larger than the reproduction frequency band defined by the digital audio of the multi-bit encoding system. By utilizing the advantage of the 1-bit encoding method capable of expanding the width several times, the optimum pre-emphasis characteristic and de-emphasis characteristic adapted to the reproduction frequency bandwidth can be automatically set.

The sampling frequency control signal f
s and the emphasis control signal EMP can be realized by a simple flag of 1 or more bits, and the circuit for encoding / decoding the song title, playing time, etc. can be realized by a circuit greatly simplified. Such a circuit may be provided in the recording device 5 and the reproducing device 7.
Although the present invention is applied to the recording and reproducing of the 1-bit signal in the above-described embodiment, when the invention is applied to the transmission of the 1-bit signal, the transmitting device is used instead of the recording device 5. A transmission medium is used instead of the recording medium 6, and a receiving device is used instead of the reproducing device 7. Furthermore, when the signal input to the input terminal 2 is a multi-bit digital signal, a digital signal processor is used instead of the pre-emphasis circuit 3, and the pre-emphasis processing is performed by the digital signal processor. do it.

[0032]

As described above , the 1-bit signal transmission or recording / reproducing apparatus according to the present invention has the optimum emphasis characteristic for the reproduction frequency bandwidth determined by the sampling frequency or the algorithm of the analog / digital converter. Therefore, when the pre-emphasis characteristics such as turnover frequency and roll-off frequency are set on the transmitting or recording device side, the de-emphasis characteristics adapted to the set pre-emphasis characteristic are automatically set on the receiving or reproducing device side. The characteristics of the de-emphasis circuit are switched so that

Therefore, it is possible to automatically and always set the optimum emphasis characteristic by following the change of the reproduction frequency bandwidth, which is an advantage of the 1-bit encoding method.

In the 1-bit signal transmission or recording / reproducing apparatus according to the present invention, the transmission or recording apparatus has a pre-emphasis characteristic adapted to the sampling frequency of the 1-bit analog / digital converter switched by the sampling frequency switching means. The characteristic of the pre-emphasis circuit is switched so that the de-emphasis circuit has a de-emphasis characteristic adapted to the sampling frequency of the digital / analog converter switched by the sampling frequency switching means. Switch the characteristics.

Therefore, the pre-emphasis characteristic on the transmitting or recording apparatus side and the de-emphasis characteristic on the receiving or reproducing apparatus side can be switched automatically by automatically following the change in the reproduction frequency bandwidth due to the switching of the sampling frequency. .

As described above , the 1-bit signal transmission or recording / reproducing apparatus according to the present invention preferably switches the algorithm of the 1-bit analog / digital converter in response to the sampling frequency.

Therefore, the pre-emphasis characteristic on the transmitting or recording device side and the de-emphasis on the receiving or reproducing device side are automatically tracked according to the change of the reproduction frequency bandwidth due to the switching of the algorithm of the 1-bit analog / digital converter. The characteristics can be switched.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a 1-bit signal recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a configuration example of a pre-emphasis circuit in the 1-bit signal recording / reproducing device shown in FIG.

3 is a graph for explaining switching between pre-emphasis characteristics in the pre-emphasis circuit shown in FIG. 2 and de-emphasis characteristics in the de-emphasis circuit shown in FIG.

4 is an electric circuit diagram showing a configuration example of a de-emphasis circuit in the 1-bit signal recording / reproducing device shown in FIG.

FIG. 5 is a graph for explaining a change in a quantization noise level with respect to a change in an algorithm in an analog / digital converter.

[Explanation of symbols]

1 1-bit signal recording / reproducing device 3 Pre-emphasis circuit 4 analog / digital converter 5 recording device 6 recording media 7 playback device 8 Digital / Analog converter 9 De-emphasis circuit 11 Control circuit 12 Sampling frequency control circuit 13 Pre-emphasis control circuit 14 Sampling frequency control circuit 15 De-emphasis control circuit

Claims (2)

(57) [Claims] 1. A device for transmitting or recording / reproducing a 1-bit signal obtained by ΔΣ modulation, wherein the transmitting / recording device comprises a pre-emphasis circuit provided in a preceding stage of a 1-bit analog / digital converter, and the pre-emphasis circuit. The pre-emphasis control means capable of switching the characteristics of the emphasis circuit and transmitting or recording an emphasis control signal corresponding to the switching state as subcode data on a recording medium, and the 1-bit analog / digital
To change the sampling frequency of the digital converter
And a sampling frequency switching means for the pre
The emphasis control means uses the sampling frequency
Pre-enhanced so that the emphasis characteristics are adapted to the wave number.
The characteristics of the phase circuit are switched, and the receiving or reproducing apparatus uses the de-emphasis circuit provided in the subsequent stage of the digital / analog converter and the emphasis control signal obtained by reproducing the subcode data from the receiving or recording medium. Responsive to de-emphasis control means for switching the characteristics of the de-emphasis circuit ,
Turn off the sampling frequency of the digital / analog converter.
Sampling frequency switching means capable of switching the de-emphasis control means.
De-emphasis characteristics adapted to different sampling frequencies
The characteristics of the de-emphasis circuit are switched so that
Cormorant that the transmission or recording and reproducing apparatus of the 1-bit signal, wherein. 2. The pre-emphasis control means also comprises
In response to the sampling frequency, 1-bit analog /
The 1-bit signal transmission or recording / reproducing apparatus according to claim 1 , wherein the algorithm of the digital converter is switched .