JPS6028072A - Digital audio disk reproducer - Google Patents

Abstract

PURPOSE:To attain the reproduction of a disk just by loading it by performing an automatic switch to a prescribed revolving speed of the disk after detecting a channel number display signal out of a control signal to judge a prescribed channel number. CONSTITUTION:The channels 2 and 4 are judged and displayed when the first bit of a control signal is ''0'' and ''1'', respectively. When a disk of the channel 2 is judged by the control signal, the outputs of terminals 12a and 12c are set at H levels and then set at L levels if a disk of the channel 4 is judged. When the 4- channel disk is loaded, the levels of terminals 12a and 12c are changed to L from H. Therefore switches S1-S3 are changed to the channel 4 from the channel 2. As a result, the disk undergoes the phase control at the linear speed of the channel 4 and the audio signal of the channel 4 is reproduced. Thus the reproduction is possible just by loading a disk without confirmation and switching performed by a user each time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital audio reproducing apparatus for reproducing analog audio signals from a disc on which digital audio signals are recorded, and more particularly to a digital audio reproducing apparatus for both 2-channel discs and 4-channel discs.

In a compact disc (CI) digital audio system, there are two channel discs and four channel discs. In the case of a 4-channel disc, the linear recording density is the same as that of a 2-channel disc, and the recording signal format is also the same.

Since the recording linear velocity of the disc is set to twice that of a 2-channel disc, by doubling the reproduction linear velocity and the transfer rate of recorded data, it is possible to process twice the amount of data as with υ22 channels. Then, the 4-channel disk is reproduced. The 2-channel disk and the 4-channel disk have the same shape, and as mentioned above, the recording signal format is the same, so the 4-channel disk can be installed even during 2-channel playback.

This can be rotationally controlled at a linear velocity for two channels. At that time, the sound will not be played. Therefore, the only way to determine whether it is a 2-channel or 4-channel disc is by looking at the label on the disc.The user must check the label on each disc to determine which channel the disc is for, and manually switch the playback device each time. It was necessary to perform playback, and the operation was complicated. Moreover, even if you insert a disc by mistake, the rotation system will continue to operate normally and only the sound will not be played.

There was a drawback that it was difficult for the user to notice if the device was attached incorrectly.

The invention was made to eliminate the above-mentioned drawbacks by detecting a channel number display signal in a control signal (subcode) that is pre-recorded on a disc together with a digital audio signal.

Determine if it is the predetermined number of channels of the playback device,
Otherwise, a digital audio disc playback device that automatically switches the disc rotation speed to the playback state that matches the loaded disc, without the user having to check the label and switch each time. It provides:

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, in which (I) is a disk, (2) is a motor for rotating this disk, (3) is a pickup that reads signals from the disk, and (4) is a front panel. (5) is a waveform shaping circuit;
(6) is a peak hold circuit that generates a running voltage according to the rotational speed of the disk (1), (7) is a differential amplifier that generates a false rare voltage for controlling the motor rotational speed, (8) is a motor drive control circuit, ( 9) is a phase-locked loop circuit that creates a reproduced clock pulse, and 01 is an EFM demodulation circuit.

aυ is a sequence circuit that controls each part of the playback device, (12a), (12b), and (12c) are output terminals of this sequence circuit, 03 is a clock generation circuit that generates various clock signals, a4 is a phase comparison circuit, and 01 is a sequence a channel display circuit whose display is switched by a control command signal from the output terminal (12c) of the circuit αυ;
81, 82, and 83 are 2-channel and 4-channel changeover switches that are switched by the control command signal from the output terminal (12a) of the sequence circuit +111.

S4 is switched to the control command signal from the output terminal (12b) of the sequence circuit aυ. Disk rotation servo OAFC (Automatic Frequency)
y Control) loop and A P C (Auto
atic Pha8e Control) loop changeover switch, gl is the reference voltage source for 2 channels,
E2 is a reference voltage source for 4 channels.

Next, the operation will be explained with reference to FIGS. 2 and 3. First, a case will be explained in which a 4-channel disk is installed in this digital audio playback device. When a disk is mounted, the output terminal (12a) of the sequence circuit α becomes high (atgh) regardless of the disk mounted, and the switches 81 and 82°S3 are all connected to the 2 channel side. At the same time, the output terminal (12b) also becomes high, and the switch 84 is connected to the A side. Then, according to the command of the sequence circuit aD, the motor (2) starts rotating. When the motor (2) starts rotating, the servos fire in the order of focus servo, tracking servo, and pickup (
3) signal reading from the disk (1) is started.

In the CD system, the digital signal is RF M (Eeight
Fourteen Modulation) is applied and recorded on the disc. What is EFM modulation?2As is well known, an 8-bit digital signal is converted to 1 in the conversion table.
Convert to 4 bits and add 3 more bits to make 11 bits.

Modulation is performed so that the inversion interval (the number of bits from when the content of a bit becomes 1 to when the next 1 appears) is always a minimum of 3 bits and a maximum of 11 bits. The digital signal thus modulated (FIG. 2a) is recorded on the disk (1) in the form of bits aaO with the point at which the bit becomes 1 as the inversion position, as shown in FIG. 2bK. Pick this up (
3), the read preamplifier (4) amplifies the waveform, the waveform shaping circuit (5) shapes the EFM signal α shown in FIG. 2C, and the EFM pulse signal corresponding to the inversion of this signal aη is obtained. The α cylinder 2 (d) is output from the waveform shaping circuit (5). The EFM pulse signal is applied to the peak hold circuit (6) and the pulse interval of the gFM pulse signal (IIs (EFM
The sawtooth wave voltage DI corresponding to the inversion interval of the signal Q7)
(Fig. 2e) ft is created, whereby a peak hold signal - which holds its maximum value, that is, a voltage value corresponding to the maximum interval of the pulses a and Enoki, is obtained at the output of the peak hold circuit (6). EFM signal a? Since the maximum inversion interval of l is determined as IIT (T is time per 1 bit) as mentioned above, the voltage value of the peak hold signal - is
) is always constant if the rotational linear velocity of ) is constant. Since both the 2-channel disk and the 4-channel disk are recorded in the same signal format and at the same density, if the rotational speed is the same, the voltage value of the peak hold signal - will also be the same. Therefore, the voltage value of this signal wire is proportional to the rotational linear speed of the disk, regardless of the disk mounted, and when the linear speed is slower than a predetermined value, the peak hold signal becomes large.

If it is faster than a predetermined value, it will be smaller. This peak hold signal (to) is applied to a differential amplifier (7), where it is compared with the two-channel motor rotation reference voltage E1.

The error voltage is applied to the motor drive control circuit @f8) through the contact Ai of the changeover switch S, and the speed of the motor (υ) is controlled, and an AFC loop operation is performed.The operation of this AFC loop causes the JEFM signal Q? Maximum reversal interval of 11
The rotation speed of the disk (1) is controlled so that T becomes a predetermined time, and the linear velocity becomes constant. Here, 4 channel disk +11 is installed.

Since switch 81 is connected to the 2nd channel side,
The linear velocity is controlled to a predetermined linear velocity for two channels determined by voltage E1. When the AFC loop operates in this manner, the wave number of the EFM pulse signal α layer output from the waveform shaping circuit (5) via the pickup (3) and preamplifier (4) becomes the same as the frequency of the second channel. The EFM pulse signal a1 is also input to the phase-locked loop circuit (9). The phase-locked loop circuit (9) is a switch 82
Since it is connected to the 2nd channel side, the 4.321 for 2nd channel is phase synchronized with the EFM pulse signal.
A recovered clock signal Cη (see FIG. 2) of 8 MHz is obtained. The reproduced clock signal Qυ and the EFM pulse signal are applied to the EFM demodulation circuit al and demodulated, but as mentioned above, the signal from the 4-channel disk is regenerated with its frequency reduced to 1/2. , and the EiFM pulse signal for two channels is added thereto. The EFM demodulation circuit Ql) demodulates the EFM signal into a digital audio signal, and at the same time decodes a control signal (subcode) recorded in each frame period together with the digital audio signal and detects a frame synchronization signal. This control signal is applied to the sequence circuit I.

In the CD system, the control signal or subcode is recorded in 8 bits for each frame period, and each bit has P and Q.

. . , W are allocated, and each 98-bit channel extracted every 98 frames is used for control display. Among them, FIG. 3 shows a Q channel signal including a channel number display signal for distinguishing between 2 channels and 4 channels.

If the first bit of the Q channel control signal is 0, it means 2 channels, and if it is 1, it means 4 channels, thereby indicating the number of channels. Q
In addition to this channel distinction, channels have synchronization signals and emphasis.

The song number, index for subdividing a song, performance time of each song, etc. are recorded. In sequence circuit I,
This Q channel control signal determines how many channels the disc has, and if it is 2 channels, the outputs of the output terminals (12a) (12c) are high (Ht
gh), and if there are 4 channels, these output terminals (
The outputs of 12a) and 12c are low. Since a 4-channel disk is currently installed, the sequence circuit I detects the 4-channel display bit 1 of the subcode Q channel, determines that it is a 4-channel disk, and outputs the level of its output terminal (12a) (1'2c). changes from high to low.

Therefore, the switches 81 and 82, 83 controlled by the output of the output terminal (12a) are switched from the 2 channel side to the 4 channel side, and the display of the channel display circuit (I! By switching the switch S1 to the 4 channel side, the AFC loose reference voltage source is 4 channels, which is 1/2 of the 2 channel reference voltage.Therefore, the disk has a linear velocity twice that of 2 channels. 8FC is applied to the signal read from the disk (1), and the frequency of the signal read from the disk (1) is doubled compared to when there are two channels, and the frequency of the EFM pulse signal a8, which is the output of the rR shaping circuit (5), is also doubled. .The phase-locked loop circuit (9) is in the 4-channel mode because the switch S2 is switched to the 4-channel side.

Phase synchronized to EFM pulse signal line. A reproduced clock signal clυ (FIG. 2g) of 8.6436 MHz necessary for signal processing at the time of 4 channels is created. The reproduced clock signal QIl and the HMF pulse signal QIl are connected to the EFM demodulation circuit 0.
1, RFM demodulation, subcode decoding, and frame synchronization signal detection are performed. A frame synchronization signal whose frequency is twice that of the two-channel signal is applied to the phase comparison circuit I. On the other hand, since the switch 83 of the clock generation circuit 6 is switched to the 4 channel side, the rate of all the generated clock signals is doubled, and the 1st phase comparator circuit I receives a stable reference signal for the APC loose. Provides a reference frame synchronization signal of 14.7 kHz (twice that for 2 channels). This reference frame synchronization signal and the reproduced frame synchronization signal from the KFM demodulation circuit a value are compared in phase by a phase comparison circuit (+2, and a phase error voltage of 1 is output. Switch S4 is a disc controlled by AFC loose). When the rotational speed reaches a predetermined linear speed, the switch is switched to the B side by a command from the sequence circuit αη, that is, its output terminal (12b) becomes low.Therefore, the phase error voltage is transferred to the B side of the switch S4. is applied to the motor drive control circuit (8), and the disc (
1) rotational phase control is performed. When the phase of a 4-channel disk is controlled at the linear velocity of 4 channels in this way, the data post-modulated by the EFM demodulation circuit is further decoded, error corrected, and then digital-to-analog converted. Four channels of audio signals are played.

Next, when installing a 2 channel disc.

Initially, the operation is exactly the same as in the case of the 4-channel disk described above, but since the first bit of the Q-channel control signal of the subcode that is decoded by the gFM demodulation circuit and added to the sequence circuit αυ is 0, , it is determined that it is a 2-channel disk, and the output terminals (12a) (12c) of the sequence circuit aυ are still high.
It is. As a result, the switches 81, 82, and 83 are not switched, and the reproduction operation continues as a 2-channel disk.

In the above embodiment, the playback device i is always set for 2 channels, and when a 4 channel disk is installed, it automatically plays 4 channels.
The reason for switching for channels is that switching from a low disk rotation speed for 2 channels to a high disk rotation speed for 4 channels takes less time to reach the specified speed than switching from a high rotation speed to a low rotation speed. This is because it is short. However, the present invention is not necessarily limited to this embodiment, and may be set for 4 channels at all times.
Of course, even if the system is automatically switched to 2-channel mode when a 2-channel disk is installed, this does not depart from the technical scope of the present invention.

Note that in the above two embodiments, a CD-based digital audio disc reproducing apparatus has been described.

Even if the number of channels of the digital audio signal is different, the linear recording density of the disc and the recording signal format are the same,
If the system has a channel number display signal recorded in the disk control signal.

It goes without saying that the same effect can be achieved with other types of digital audio disc playback devices.

Since this invention is configured as above, the user does not need to check the label of each disc channel to be played or manually switch channels, and can perform playback calculations just by loading all the discs. It has the advantage of being very easy to use.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a signal waveform diagram of each part thereof. FIG. 3 is a diagram showing the Q channel signal of the subcode recorded on the disc. In the figure, fi+ is a disk, (2) is a motor, (3) is a pickup, (5) is a waveform shaping circuit, (6) is a peak hold circuit, (7) is a differential amplifier, and (8) is a motor drive control circuit. . (9) is a phase-locked loop circuit, (II is KFM
demodulation circuit, all is a sequence circuit, 0th floor is a clock generation circuit, a4) is a phase comparison circuit, 09 is a channel display circuit. 81, $2.84 is a channel changeover switch. S4 is an AFC/APC loop changeover switch, El is a reference voltage source for 2 channels, and IC2 is a reference voltage source for 4 channels.

Claims (1)

[Claims] By playing back multi-channel audio signals from a disc that has recorded multi-channel digital audio signals and control signals including an indication of the number of channels, and by switching the rotation speed of the disc, it is possible to play discs with different numbers of channels. In the digital audio disc playback device, a pickup for reading digital signals recorded from the disc, a rotation drive control device for the disc, and a voltage according to the rotational speed of the disc from the signal read from the pickup are provided. The extracting means compares the voltage corresponding to the rotational speed with a reference voltage having a predetermined magnitude corresponding to the number of channels of the digital audio signal recorded on the disc to be reproduced, and uses the difference between the voltages according to the rotational speed and the rotational drive device. means for rotating the disk at a predetermined speed according to the reference voltage, means for demodulating the signal read from the pickup, and detecting a channel number display signal recorded on the disk from the demodulated signal. , comprising a means for determining whether the number of channels corresponds to the reference voltage, and if not, switching the reference voltage to a magnitude corresponding to the number of detected channels, and recording the rotational speed of the disk on all disks. A digital audio disc playback device characterized in that the number of channels of a digital audio signal is automatically changed according to the number of channels of a digital audio signal.