JPH0568022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an identification signal recording and reproducing method. The present invention relates to a method of mixing and recording an identification signal for automatically controlling the operation of a disc playback device, and separating and extracting only this identification signal when playing a disc.

(Prior art and its problems) Conventionally, on signal recording disks such as analog disks and digital disks, identification signals used for locating the beginning of information, the tracking status of pickups, whether or not signal processing is used, or determining the type of signal processing are used as main information ( For example, when the disc is played back, this identification signal is separated,
Identification signal recording for automatic control of a disc playback device, such as automatic cueing, automatic tracking control, or automatic selection of a signal restoration method that matches the signal processing method being used, by extracting and determining its contents. Various regeneration methods have been proposed.
Some of them are actually used.

These methods can be broadly classified into the following three types.

(1) Provide a dedicated track or channel for identification signals separate from the main information.

(2) An identification signal having a frequency outside the frequency band occupied by the main information is used in the recording track of the main information, and is reproduced together with the main information in a main information reproducing pickup and separated from the main information.

(3) By using a carrier signal having a higher frequency than the main information occupied frequency band and modulating the carrier signal with an identification signal, one channel is multiplexed with the main information as a signal outside the main information occupied band.

Of course, it is reproduced together with the main information by reproduction pickup, separated, and then demodulated to extract the identification signal.

Of the three methods mentioned above, method (1) is used for capacitance detection type video discs (dedicated tracks) and digital audio discs (channels dedicated to sub-coding), but it requires less recording space for main information. Since the amount of main information recorded is reduced, the amount of main information recorded is limited.

In method (2), below the audible frequency band (less than 20Hz)
In some cases, a signal with a frequency higher than the audible frequency band (>20 Hz) is used, but if the identification signal is below the audible frequency, there is a high risk of malfunction due to noise. This is because the modulation noise generated by disk warping exists in the frequency band of 0.5Hz to 10-odd Hz, and the resonance frequency of the tone arm is around 10Hz, so there is a risk that the modulation noise level will increase significantly. There is a risk that this modulation noise may be mistakenly determined as an identification signal on the playback device side.

Furthermore, when the frequency is set higher than the audible frequency band, reproduction of this band tends to become unstable with a normal pickup, and a special pickup capable of wide-band reproduction for 4-channel stereo is required. Moreover, when considering compatibility with discrete 4-channel stereo discs, it becomes impossible to set an identification signal in a frequency band of 50 KHz or less, making it impossible to obtain a reproducible pickup. In addition, the high frequencies that can be handled as analog signals on digital audio disks are
Since it is less than 20KHz, it is not possible to employ an identification signal of >20KHz. The method (3) has the same drawback as the case where the identification signal is set at a frequency higher than the audible frequency band, which was explained in the method (2).

(Object of the present invention) The present invention solves the above-mentioned conventional drawbacks, and eliminates the need to provide a dedicated space for recording identification signals, reduces the probability of malfunction due to external noise, and eliminates the need to use a special pickup. The purpose of the present invention is to provide a method for recording and reproducing an identification signal.

(Summary of the present invention) The present invention sets a frequency signal below the audible frequency band (20Hz to 20KHz) as an identification signal used to automatically control the operation of a disc playback device,
This identification signal modulates a carrier signal with a frequency below the audible frequency band to obtain a modulated signal, and when recording main information such as audio signals and data on a disk, this modulated signal is mixed into the main information. The signal is recorded on a disc, and when the disc is reproduced, only the modulated signal is separated from the reproduced signal, and then the identification signal is demodulated and extracted.

(Example) The present invention will be described in detail below based on the illustrated example.

Note that the identification signal recording and reproducing method of the present invention can be applied to various automatic controls in a disc reproducing device, but in this embodiment, in an analog music disc reproducing device, noise reduction used when recording on a disc is applied. A case will be described in which the present invention is applied to a device that automatically selects a noise reduction system that matches the system.

FIG. 1A shows a device for mixing an identification signal into a music signal to be recorded on a disc, 1a, 1b,
1c is an identification signal oscillator, and in this embodiment, each is set to output an extremely low frequency signal below the audible frequency band of 0.8 Hz, 1.0 Hz, and 1.5 Hz.

Here, the reason for setting three types of identification signals is as follows.
In this example, two types of noise reduction systems (hereinafter referred to as NR) are installed in the disk recording system (not shown).
This is to enable the user to freely select and set NR1, NR2 and NR system OFF (not shown), with the 0.8Hz signal being NR1 and the 1.0Hz signal being NR1.
2. 1.5Hz signal represents NR/OFF. Reference numeral 2 denotes a switch that selects an output signal from one of the identification signal oscillators 1a, 1b, and 1c in conjunction with a switching operation of an NR system selection mechanism (not shown).

Reference numeral 3 denotes an amplitude modulator, which uses the identification signal A (FIG. 2A, in the embodiment, the 1.0 Hz identification signal of the identification signal transmitter 1b) supplied from the switching device 2 to convert the carrier signal supplied from the carrier signal transmitter 4. Amplitude modulation is performed on signal B (Figure 2 B), and amplitude modulated signal C (Figure 2 C) is generated.
Output.

Note that the carrier signal frequency in this example is
Set to 9.0Hz. 5 is a low frequency amplifier, which amplifies the amplitude modulation signal C from the amplitude modulator 3. 6 is an inverter, which receives the amplitude modulation signal C through the amplifier 5.
This is to obtain a negative phase signal. This reverse phase signal is used to cancel ultra-low frequency noise mixed in when music information is recorded on the disc playback side, and its function will be explained in detail later.

The amplitude modulated signal C that has passed through the amplifier 5 is added to the L channel recording signal (music signal) compressed by the NR system in the mixing circuit 7a on the one hand to obtain a (L+C) signal, and on the other hand is added to the inverter 6 as described above. After becoming a reverse phase signal, the mixing circuit 7b adds it to the R channel recording signal compressed by the NR system to obtain an (R-C) signal.

The obtained (L+C) signal and (R-C) signal are supplied to a disk cutting device (not shown) and are mechanically recorded in the sound groove of the disk as an L channel signal and an R channel signal, respectively.

With the above configuration, for example, as shown in FIG. 1A,
When NR system/NR2 is selected, the 1.0Hz signal from oscillator 1b is selected as the identification signal,
The signal is supplied to an amplitude modulator 3 to obtain an amplitude modulation identification signal C.

This amplitude modulation identification signal C is, on the one hand, L
On the other hand, the reverse phase signal -C is added to the R channel recording signal.

That is, new L channel signals (L+C) and R channel signals (R-
C) is formed.

In addition, as in this embodiment, the NR on the disc playback side
In the case of a system automatic selection device, the amplitude modulation signal C
and its reverse phase signal should be recorded in all sound grooves including the inter-track no-recording groove. This is because even if playback is started from the middle of the disc, it is necessary to immediately determine and select the type of NR system from the starting point.

Next, FIG. 1B shows a device for reproducing and identifying identification signals in a disc reproducing device, and a pickup (not shown) of the disc reproducing device.
The regenerated L channel signal (L+C) and R channel signal (R-C) are supplied to respective regenerative amplifiers (not shown) and also to the differential amplifier 11, which generates a difference signal between the L and R channels. (LR+2C) is obtained. At this time,
Infra-low noise below the audio frequency included in each channel signal can be canceled out.

In other words, the music signal recorded on the disc contains flicker noise (1/noise,...frequency) and 0.5Hz to 10Hz caused by the warping of the disc.
There is ultra-low-frequency noise that is in phase with the L channel and the R channel, such as noise of several Hz and noise mixed into the recording signal due to power supply voltage fluctuations occurring in equipment on the music signal recording side.

In the present invention, the identification signal is transmitted as a modulated signal, so unlike the conventional technology (2) in which the identification signal itself is recorded on a disk, the S/N of the identification signal deteriorates due to noise, making it impossible to distinguish. The possibility of that happening is almost inconceivable.

However, in the case of amplitude modulation, it is relatively susceptible to the influence of noise, and it cannot be said that there is no risk of S/N deterioration.

Therefore, as in this embodiment, by mixing the modulation identification signal C into the L channel and its opposite phase signal -C into the R channel, and supplying both channel signals to the differential amplifier during reproduction, the above-mentioned L and R channels can be combined. By canceling only in-phase noise, deterioration of the S/N of the identification signal is avoided.

Note that the identification signal extraction and discrimination device of this embodiment, the restoration circuit (expansion processing circuit) of the NR system NR1, NR2 is not only a disc playback device, but also a regeneration amplifier (for example, The advantage in this case is that in current analog disks, according to the R1AA recording characteristics, the output of the lower frequency signal is attenuated before being recorded on the disk, and when the disk is played back. As a device pick-up
When using a speed proportional pickup such as an MM type or MC type, a recording characteristic compensation circuit is provided in the reproducing amplifier to obtain flat frequency characteristics. Therefore, it is easier to separate and extract the identification signal after the compensation circuit because the signal level is much higher than the signal level in the circuit before that.

Next, the difference signal (L
-R+2C) is added to the carrier tuning circuit 12,
Only the amplitude modulation identification signal C (FIG. 2C) is extracted.

This carrier tuning circuit 12 has a narrow band characteristic of 9.0 Hz±several Hz and a steep attenuation characteristic.
This amplitude identification signal is detected by an envelope detector 13, and an envelope D of the amplitude modulated identification signal C is obtained as shown in FIG. 2D. This envelope D
Since the low frequency component of is the identification signal A itself, this envelope D is passed through the bandpass filter 1.
4 to remove the carrier signal component and extract only the identification signal A (Figure 2 E) There are various methods for determining which NR system the extracted identification signal A corresponds to. However, in this embodiment, the Schmitt trigger circuit 15 is used to perform waveform shaping using a predetermined level h as a trigger level (FIG. 2 E), and the resulting shaped pulse E (second
The type of NR system is determined by detecting the period (in other words, the period of the identification signal A) in Fig. F).

That is, as shown in FIG. 2 E and F, the identification signal A
is added to the Schmitt trigger circuit 15 for waveform shaping to obtain a shaped pulse E, which is sent to the period detection circuit 1.
6a, 16b, 16c. Period detector 1
6a to 16c are identification signals of 0.8Hz each
(NR1), 1.0Hz (NR2), and 1.5Hz (OFF) periods, and the rising edge interval time t1 or falling edge interval time of the shaped pulse E.
Detect t2.

In this case, by measuring the period of not only one wave but continuously for a certain period (for example, detecting periods t1, t2, and t3 as shown in Figure 2) and detecting the period value, it is possible to measure the period of a single wave. The risk of erroneously detecting noise and the like is greatly reduced, and detection accuracy can be improved.

The detection output from each detector 16a to 16c is NR
The signal is supplied to the system selection control circuit 17, and controls switching to an appropriate NR system (or OFF) depending on which detector outputs the detection output.

Next, the block diagram shown in FIG. 3 shows another embodiment of the present invention, in which, instead of the amplitude modulation method in the above embodiment, a phase shift modulation method is used in which the phase of the carrier signal is shifted by 180 degrees for each period of the identification signal. was adopted.

In the identification signal mixing device shown in FIG.
is a carrier signal oscillator that outputs a 9.0 Hz carrier signal (pulse), and the carrier signal is supplied to the carrier input terminal of the 180° phase shift modulator 22. Reference numerals 23a, 23b, and 23c are identification signal oscillators that output identification signal pulses of 0.8 Hz and 1.5 Hz, respectively, and are phase-shifted via a switch 24 that is linked to a switching device of an NR system selection mechanism (not shown). A control input terminal of modulator 22 is provided.

Here, the operation of the phase shift modulator 22 will be explained using the waveform diagram shown in FIG. 4.

Now, the identification signal F [1.0Hz] is sent via the switch 24.
(Fig. 4 A) is supplied to the phase shift modulator 22 from the identification signal oscillator 23b, the carrier signal G (Fig. 4 (b) Phase shift the pulse by 180°. In other words, 9 of carrier signal G
The trailing edge of the pulse is phase shifted by 180 degrees for each pulse to obtain a phase shift modulation signal H (FIG. 4C). In this way, the phase shift modulation signal obtained by 180° phase shift modulation of the pulse of the carrier signal corresponding to one period of the identification pulse is supplied to the low pass filter 25 to generate a sinusoidal phase shift modulation signal I ( (D) in FIG. 4, this modulation identification signal is mixed in the mixing circuit 27a with the L channel audio signal compressed by the NR system (not shown) (L+C);
b, the reverse phase signal of the modulation identification signal (inverter 26) and the R compressed by the NR system.
The channel audio signal is mixed (R-
C) is obtained.

On the other hand, the identification signal reproducing path of the disc reproducing device is almost the same as that shown in FIG. By using a bandpass filter having ) can be obtained.

Therefore, hereinafter, the identification signal extraction and detection control operations are exactly the same as in the previous embodiment.

In each of the above-mentioned embodiments, cases have been described in which the carrier signal is amplitude-modulated and phase-shift modulated with the identification signal, but the present invention is not limited to these modulation methods, and other modulation methods can also be used. For example, when using a modulated signal obtained by frequency modulating a carrier signal with an identification signal, an FM detector is installed after the carrier tuning circuit to extract only the identification signal.
Added to the identification signal detection means. That is, it is sufficient to simply change the modulation circuit of the identification signal recording system and the demodulation circuit (detection circuit) of the identification signal detection system according to the modulation method used, and this does not depart from the gist of the present invention.

Furthermore, the identification signal recording and reproducing method of the present invention can be applied to other automatic controls.

For example, automatic control can be used to identify 4-channel stereo disks, 2-channel stereo disks, and monaural disks and configure a transmission path suitable for each disk, or a regular matrix for 4-channel stereo may require signal processing. There are various methods depending on the difference, and it can also be applied to cases where a demodulation circuit of the same method as that used during disk recording is automatically selected on the disk playback side.

(Effects of the Invention) According to the present invention, the identification signal used for automatically controlling the operation of the disc playback device is set to a frequency band below the audio frequency band, and the identification signal is used to control the carrier signal below the audio frequency band. Since the identification signal is modulated and recorded on the disk along with the main information in the form of a modulated signal, there is no need to provide a dedicated recording space for the identification signal on the disk.
The main information recording amount can be increased, and deterioration of the S/N ratio of the identification signal due to noise can be improved.

[Brief explanation of the drawing]

FIG. 1A is a block diagram of an identification signal mixing device showing an embodiment of the present invention, FIG. 1B is a block diagram of an identification signal reproducing/discriminating device showing an embodiment of the present invention,
Fig. 2 is a waveform diagram for explaining the operation of the embodiment shown in Fig. 1, Fig. 3 is a block diagram showing another embodiment of this waveform diagram, and Fig. 4 explains the operation of the embodiment of Fig. 3. FIG. Explanation of symbols, 1a, 1b, 1c...Identification signal oscillator, 2...Switcher, 3...Amplitude modulator, 4...Carrier signal oscillator, 5...Amplifier, 6...Inverter, 7a, 7b...Mixing circuit, 11 ... Differential amplifier, 12 ... Carrier tuning circuit, 13 ... Detector, 14 ... Bandpass filter, 15 ... Schmitt trigger circuit, 16a, 16b, 16c ...
Period detector, 17...NR system selection control circuit.

Claims (1)

[Claims] 1 Main information such as audio signals and digital information, and identification information related to this main information, which is obtained by modulating a sub-audible carrier signal with an identification signal set in a sub-audible frequency band. A modulated signal is recorded on a disk together with the modulated signal, and when the disk is played back, the main information and the modulated signal are separated, and then the modulated signal is demodulated to extract the identification signal. A method for recording and reproducing identification signals.