JPH1168571A - Transmission or recoder reproducer for 1-bit signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set appropriate emphasis characteristics corresponding to a change in a reproduction frequency band at the time of recording and reproducing a sound signal as a 1-bit signal. SOLUTION: On a side of recording, a sampling frequency control signal fs, which corresponds to a sampling frequency of an analog-to-digital converter 4 by a ΔΣ modulation, and an emphasis control signal EMP, which expresses the optimal emphasis characteristics corresponding to an algorithm and the sampling frequency of this analog-to-digital converter 4, are stored in a table of contents area (TOC) of a recording medium 6 apart from a 1-bit signal. On a side of reproduction, demodulation is performed to an analog signal by the signal fs reproduced from this TOC area, an appropriate sampling frequency by corresponding to the EMP and de-emphasis characteristics. Thus, it is possible to automatically set the optimal emphasis characteristics by making use of the advantage of the 1-bit signal that can change a reproduction frequency band, a dynamic range, and so on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for transmitting or recording / reproducing a 1-bit signal obtained by ΔΣ modulation, which is preferably implemented in a digital audio system.

[0002]

2. Description of the Related Art In the digital audio, a multi-bit encoding 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, 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 coded 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 of a signal for transmission or recording / reproduction, conventionally, a signal to be transmitted or recorded is subjected to a pre-emphasis process, and a received or reproduced signal is subjected to a de-emphasis process. Widely used. For example, although the high-frequency side is emphasized by the pre-emphasis processing and the high-frequency side is suppressed by the de-emphasis processing, the frequency characteristic of the signal output from the receiving or reproducing apparatus is flat, but the noise is suppressed, The dynamic range is substantially expanded.

[0004] In this respect, the multi-bit encoding method, which is a conventional encoding method, has a reproduction frequency bandwidth defined in advance as described above, so that the turn frequency which is the start frequency of pre-emphasis and de-emphasis is used. The over-frequency and the roll-off frequency, which is the end frequency of the pre-emphasis and de-emphasis, are uniquely determined to have a value adapted to the reproduction frequency bandwidth.

On the other hand, a 1-bit signal obtained by the ΔΣ modulation can be demodulated into an analog audio signal only by using a simple low-order low-pass filter when the 1-bit signal is an audio signal. However, there is an advantage that a complicated processing circuit is not required for demodulation. Also, since the 1-bit signal is a finely divided data flow that does not require word synchronization, it is less susceptible to transmission paths and the like, and therefore has the advantage of being resistant to errors and not requiring an error correction circuit. doing. For this reason, in recent years, attention has been paid to a 1-bit encoding scheme having many advantages as compared with the multi-bit encoding scheme.

[0006]

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

Therefore, if the emphasis characteristics such as the turnover frequency and the roll-off frequency are kept constant as in the prior art, it is impossible to follow changes in various characteristics, and the superior advantage of the 1-bit encoding method is obtained. There is a problem that cannot be fully utilized.

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

[0009]

According to the first aspect of the present invention, there is provided:
A bit signal transmission or recording / reproducing device is a device for transmitting or recording / reproducing a 1-bit signal obtained by ΔΣ modulation, and a transmitting or recording device is provided with a pre-emphasis provided before a 1-bit analog / digital converter. And a pre-emphasis control unit that can switch the characteristics of the pre-emphasis circuit and transmit or record an emphasis control signal corresponding to the switching state as subcode data on a recording medium. A de-emphasis circuit provided at a subsequent stage of the digital / analog converter; Means. .

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

Therefore, the optimum emphasis characteristic can be automatically and always set according to the change of the reproduction frequency bandwidth, which is an advantage of the 1-bit encoding method.

Further, in the one-bit signal transmission or recording / reproducing apparatus according to the second aspect of the present invention, the transmitting or recording apparatus is capable of switching a sampling frequency of the one-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 reception or reproduction device includes:
The digital / analog converter further includes a sampling frequency switching unit capable of switching a sampling frequency, and the de-emphasis control unit includes a de-emphasis circuit having a de-emphasis characteristic adapted to the switched sampling frequency. The characteristic is switched.

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 by automatically following the change in the reproduction frequency bandwidth due to the switching of the sampling frequency. can do.

Further, in the one-bit signal transmission or recording / reproducing apparatus according to the third aspect of the present invention, the pre-emphasis control means also responds to the sampling frequency by using an algorithm of a one-bit analog / digital converter. Switching is performed.

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

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
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 input to the pre-emphasis circuit 3
After a high frequency component is emphasized by performing pre-emphasis processing as described later, the signal 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 signal to the recording device 5. The recording apparatus 5
The bit signal is recorded on a 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 a digital / analog converter 8 and then subjected to de-emphasis processing for suppressing high-frequency components in a de-emphasis circuit 9. After that, it is output from the output terminal 10.

In the 1-bit signal recording / reproducing apparatus 1, the control circuit 11 can set a reproduction frequency bandwidth and a dynamic range.
Performs switching of the sampling frequency of the analog / digital converter 4 via the sampling frequency control circuit 12 in accordance with the reproduction frequency bandwidth. Further, corresponding to the reproduction frequency bandwidth and the 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 given from the pre-emphasis control circuit 13 to the pre-emphasis circuit 3 and the sampling frequency control signal fs given 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 the lead-in area or the TOC area of the recording medium 6.

In response to this, the sampling frequency control signal fs reproduced by the reproducing device 7 is input to a sampling frequency control circuit 14, and the digital / analog converter 8
Is adapted to the sampling frequency to perform digital / analog conversion. The emphasis control signal EMP reproduced by the reproducing device 7 is input to a de-emphasis control circuit 15, and the de-emphasis control circuit 1
5, the de-emphasis characteristic of the de-emphasis circuit 9 is switched as described later.

FIG. 2 is an electric circuit diagram showing one configuration example of the pre-emphasis circuit 3. As shown in FIG. The pre-emphasis circuit 3 includes feedback bias resistors R1, R
2 has a frequency characteristic, and the bias resistor R is provided between the output terminal of the operational amplifier 21 and the ground potential.
1 and R2 are connected, and the bias resistor R
The potential at the connection point between 1 and R2 is fed back to the input side of the operational amplifier 21. Capacitors C11, C12, C13; C21, C
22, C23 are provided. These capacitors C
11, 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 changed to C
1 and the capacitor C2 selected by the switch SW2
When the capacitance of C1, C22 or C23 is represented by C2, a boost circuit for boosting from the turnover frequency f1 determined by R1 / C1 is constituted by the bias resistor R1, the capacitors C11, C12, C13 and the switch SW1. , Bias resistor R2, capacitor C21,
R22 / C23 is determined by C22 and C23 and the switch SW2.
A roll-off circuit that performs a roll-off operation from the roll-off frequency f2 determined by C2 is configured.

The roll-off circuit can be omitted if a high-frequency limiting filter is interposed on the downstream side of the pre-emphasis circuit 3.

When the capacitors C11 and C21 are selected, for example, by the pre-emphasis circuit 3 configured as described above, as shown by reference numeral α1 in FIG.
For example, it is possible to realize a pre-emphasis characteristic in which the enhancement is performed at about 6 (dB / oct).
By selecting capacitors C12, C22;... Having smaller capacitances than C11, C21, respectively, the turnover frequency is set to f1a and the roll-off frequency is set to f2a.
, A pre-emphasis characteristic as shown by the reference numeral α1a can be obtained.

In response, the de-emphasis circuit 9
Is configured, for example, as shown in FIG. 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 terminal of the resistor R3 and a ground potential.
33, and in response to the emphasis control signal EMP,
And a switch SW3 for selectively switching the capacitors C31, C32, and C33. The capacitor C3
When “1” is selected, the de-emphasis characteristic is determined by selecting the capacitors C32,... While the attenuation starts from the turnover frequency f1, as indicated by the reference numeral α2 in FIG. Sign α2
As shown by a, attenuation starts at the turnover frequency f1a.

As a result, a 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, when recording and reproducing the audio signal, it is possible to suppress high-frequency component noise.

In the de-emphasis circuit 9,
Since the higher frequency side than the roll-off frequency f2 is outside the reproduction frequency band or equal to or higher than the upper limit of the reproducible frequency band of the analog device and does not often affect the reproduction frequency characteristics, it is omitted. Therefore, when considering the higher frequency side than the roll-off frequency f2, the de-emphasis circuit 9 may be configured by an active circuit, like the pre-emphasis circuit 3.

The analog / digital converter 4
Is a ΔΣ modulation type analog / digital converter configured to include a 7th-order integrator as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-162743, and an algorithm control signal ALG from the control circuit 11 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, etc., the sampling frequency remains constant, and the reproduction frequency bandwidth and the dynamic It is configured to be able to change the range.

Therefore, for example, FIG.
(B), 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, thereby combining the control of the reproduction frequency bandwidth and the dynamic range with the control of the pre-emphasis characteristics. hand,
Advanced 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 In response to the signals fs and EMP, the optimal time constant is automatically set and the reproduction is performed, so that the reproduction frequency band is more than the reproduction frequency bandwidth specified by the digital audio of the multi-bit encoding system. Taking advantage of the advantage of the 1-bit encoding method that can increase the width several times, the optimal pre-emphasis characteristics and de-emphasis characteristics suitable for 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 one or more bits, etc., and a circuit for encoding / decoding a music title, performance time, and the like can be realized by a greatly simplified circuit. Such a circuit may be provided in the recording device 5 and the reproducing device 7.
In the above-described embodiment, the present invention is applied to the recording and reproduction of a 1-bit signal. However, when the present invention is applied to the transmission of a 1-bit signal, a transmitting device is used instead of the recording device 5. A transmission medium is used instead of the recording medium 6, and a receiving apparatus is used instead of the reproducing apparatus 7. Further, 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 to perform the pre-emphasis processing with the digital signal processor. do it.

[0032]

As described above, the 1-bit signal transmission or recording / reproducing apparatus according to the first aspect of the present invention has the optimum reproduction frequency bandwidth determined by the sampling frequency and the algorithm of the analog / digital converter. When pre-emphasis characteristics such as turnover frequency and roll-off frequency are set on the transmission or recording device side so that the emphasis characteristics are obtained, the reception or reproduction device side automatically adapts to the set pre-emphasis characteristics. The characteristics of the de-emphasis circuit are switched so as to obtain the de-emphasis characteristics.

Therefore, the optimum emphasis characteristic can be automatically and always set according to 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 second aspect of the present invention, as described above, the transmitting or recording apparatus is provided with a 1-bit analog / digital converter switched by the sampling frequency switching means. The characteristics of the pre-emphasis circuit are switched so that the pre-emphasis characteristics are adapted to the sampling frequency. The characteristics of the de-emphasis circuit are switched so that

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 by automatically following the change in the reproduction frequency bandwidth due to the switching of the sampling frequency. .

Further, according to the third aspect of the present invention, a 1-bit signal transmission or recording / reproducing apparatus responds to the sampling frequency as described above.
The algorithm of the digital converter is switched.

Therefore, the pre-emphasis characteristic on the transmitting or recording device side and the de-emphasis characteristic on the receiving or reproducing device side are automatically followed by a change in 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 the drawings]

FIG. 1 is a block diagram illustrating 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 apparatus shown in FIG.

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

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

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 1-bit signal recording / reproducing device 3 pre-emphasis circuit 4 analog / digital converter 5 recording device 6 recording medium 7 reproducing 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 (3)

[Claims] An apparatus for transmitting or recording / reproducing a 1-bit signal obtained by ΔΣ modulation, comprising: a pre-emphasis circuit provided before a 1-bit analog / digital converter; A pre-emphasis control means for 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; A de-emphasis circuit provided at a subsequent stage, and de-emphasis control means for switching characteristics of the de-emphasis circuit in response to an emphasis control signal obtained by receiving or reproducing the subcode data from a recording medium. 1-bit signal transmission or Recording and reproducing apparatus. 2. The transmission or recording apparatus further comprises sampling frequency switching means for switching a sampling frequency of the 1-bit analog / digital converter, and wherein the pre-emphasis control means comprises a switching sampling frequency. Switching the characteristics of the pre-emphasis circuit so as to obtain an emphasis characteristic adapted to the above, the receiving or reproducing apparatus further includes a sampling frequency switching means capable of switching a sampling frequency of the digital / analog converter, 2. A 1-bit signal transmission or recording / reproducing apparatus according to claim 1, wherein said de-emphasis control means switches the characteristics of the de-emphasis circuit so that the de-emphasis characteristics are adapted to the switched sampling frequency. . 3. The pre-emphasis control means further comprises a one-bit analog / digital converter responsive to the sampling frequency.
3. The 1-bit signal transmission or recording / reproducing apparatus according to claim 2, wherein an algorithm of the digital converter is switched.