JPH0514355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a player for playing digital audio disks (DAD).

Conventional configuration and its problems Figure 1 shows the configuration of a DAD player called a compact disk (CD) system. In FIG. 1, 1 is a DAD, and this DAD 1 is rotated by a spindle motor 2. Reference numeral 3 refers to an optical pickup, which is composed of a light source such as a semiconductor laser and an optical lens, and focuses the laser beam 4 on an uneven groove called a pit recorded in a nearly concentric spiral on the DAD 1. At the same time, a servo is applied so that the laser beam 4 always follows the pits recorded in a spiral shape (called a tracking servo). The output signal 3a from the optical pickup 3 is amplified by a preamplifier called a head amplifier 5, and is supplied to a focus servo circuit 6 or a tracking servo circuit 7 to perform the above-mentioned focus servo and tracking servo, and is used as a control signal for each servo. is formed. Furthermore, the output signal 5a from the head amplifier 5 is passed through a waveform shaping circuit called a data punching circuit 8, and is then passed through a waveform shaping circuit called a data punching circuit 8, and then passes through a waveform shaping circuit called a data punching circuit 8.
The result is a digital signal 8a expressed as . This digital signal 8a is input to a PLL circuit 9, and a clock 9a for reading the digital signal 8a is reproduced. Furthermore, the digital signal 8a is inputted to the synchronization circuit 10 together with this clock. As will be described later, the synchronization circuit 10 detects a synchronization signal, extracts a desired digital signal, and supplies it to the digital signal processing circuit 11 at the subsequent stage. The digital signal processing circuit 11 is controlled by a control circuit 12 driven by a crystal oscillator, and uses a random access memory (RAM) to handle data errors caused by data rearrangement or damage to the DAD 1. The correction is made and the correct data is sent to the DA conversion circuit 13.
supply to The DA-converted signal is divided into left and right channels and taken out to output terminals 13L and 13R through a low-pass filter. In addition to this,
In a CD-type DAD player, the signal from DAD1 is read at a constant linear velocity, so
The error signal from the PLL circuit 9 and the signal from the control circuit 12 are supplied to the spindle servo circuit 14 to control the rotation speed of the spindle motor 2. Furthermore, there is a system control circuit 15 comprised of a microprocessor or the like for controlling various servos and output signals of such a DAD player.

Also, if we focus on the tracking servo, the playback time that can be tracked by the optical pick-up 3 itself is at most several tens of seconds. Such a device is required.
In FIG. 2, 3 is the aforementioned optical pickup;
6 is a feed screw mechanism for mounting this optical pickup 3 and moving it in the radial direction of the DAD 1; 17;
is its drive motor, and like the optical pickup 3, the drive motor 17 is also controlled by a control signal from the tracking servo circuit 7. In this way, the optical DAD is regenerated.

By the way, in such a DAD, for example, in the case of the above-mentioned optical type, it is possible to search for the beginning of a desired song from among the plurality of songs recorded on one side of the disc, or to perform cue (fast forward playback) in a so-called tape recorder. There may be cases where it is possible to obtain a playback output equivalent to that of a review (rewind playback).

A conventional synchronous circuit used for this purpose will be described below.

FIG. 3 shows an example of the configuration of digital signals in the DAD. Since the digital signal is a time series of only logical values 1 and 0, synchronization signals 18 are periodically recorded at regular time intervals to indicate data divisions. It is assumed that time t advances from left to right on the drawing. Further, one section from one synchronization signal to the next synchronization signal is referred to as one frame. Reference numeral 19 is a data section containing information such as music signals.

FIG. 4 shows an example of a synchronization circuit for correctly detecting a synchronization signal from such a digital signal.
The digital signal 8a described in FIG. 1 and the clock 9a reproduced by the PLL circuit 9 are first input to the synchronization pattern detection circuit 20. Here, for example, a synchronization pattern determined by a combination of 1 and 0 is detected using a multi-stage shift register and a multi-input AND gate, and a pattern detection signal 20 is detected.
generate a. On the other hand, timing generating circuits 21 and 22 are similarly driven by the clock 9a and generate a mask signal 21a and a pseudo synchronization signal 22a, respectively. The mask signal 21a is generated by the synchronization pattern detection circuit 2 in order to ignore even if there is a pattern exactly the same as the synchronization signal in the data portion 19 of the digital signal 8a.
It has the role of essentially stopping the operation of 0. The pseudo synchronization signal 22a is a signal indicating the position of a synchronization signal, which is expected to be detected again one frame after the synchronization signal is detected once. Reference numeral 23 denotes a synchronization detection/determination circuit, which generates a synchronization detection signal 23a or a synchronization non-detection signal 23b in each frame, and drives counters 24 and 25 at the next stage, respectively. When the counters 24 and 25 reach respective preset values, the carry output 24a or 25 is output.
a and drives the set/reset flip-flop (RS/FF) 26. 27 is R gate,
28 is an AND gate. An example of these operations is shown in the timing chart of FIG. counter 2
Setting values of 4 and 25 are examples of 2 and 3, respectively.

What should be noted here is the output 2 of RS/FF26.
6a indicates the state of synchronization establishment.
That is, when 26a has a logical value of 0, it is in the established state;
When , it is in a non-established state (resynchronization in progress or out of synchronization). Furthermore, the output 27a of the R gate 27
If we pay attention to this, when 27a has a logical value of 1, it means that a synchronization signal is about to be detected. The above is a conventional example of a synchronous circuit.

By the way, in a DAD player using such a synchronization circuit, when searching for the beginning of a song or playing a queue as described above, the device shown in Fig. 2 picks up the optical pick-up 3 at a feed speed several times that of normal playback. moves, so when looking at the reproduced digital signal, synchronization signals do not exist at regular intervals as shown at 8a in FIG. 5.

To explain the operation of the optical pickup 3 in more detail, for example, when playing at double speed, the tracking servo is applied for 0.5 seconds to perform normal playback, and immediately after that, the forwarding mechanism is activated for an amount equivalent to 0.5 seconds in real time. It is sufficient to repeat the process of instantly moving the optical pickup 3 and performing normal playback again. If the tracking servo is not turned off during this movement, it is conceivable that the movement in real time will not be constant (for example, 0.4 seconds or 0.6 seconds) due to the tracking ability of the optical pick-up 3 itself. The operation of the synchronization circuit when performing such reproduction is explained in the sixth section.
As shown in the figure. 29 is the reproduced digital signal, and the portion indicated by section A is where the optical pickup 3 has been forcibly moved. The time axis of the reproduced digital signal 29 is disturbed by the forced movement of the optical pickup 3. In this example, Chiyodo 1/2
Indicates that the frame is misaligned. Considering that synchronization is established immediately after the movement of the optical pickup 3 ends, the set value of the counter 25 is 3, so at time t= _t1 when the movement ends, it is not yet determined that synchronization has been lost, so the first synchronization signal B cannot be detected. . Time t=
It is determined that synchronization is lost for the first time at t ₂ . For this reason 1
This has the disadvantage that data playback is delayed by a frame amount. In this example, the set value of the counter 25 is 3, but if it is made larger than 3, more parts of the data will not be reproduced correctly. Conversely, if the setting value is smaller than 3, during normal playback,
If the probability of loss of synchronization is high and the same pattern as the synchronization signal is present in the data section, there is a drawback that an erroneous synchronization establishment state will occur, resulting in an increase in data errors.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a digital audio disc player that can quickly and accurately locate the beginning of a song. Another object of the present invention is to provide a digital audio disc player that can provide sufficient playback output during queue and review playback.

Structure of the Invention The present invention uses a tracking servo control signal that controls on/off the tracking servo circuit of a digital audio disc player to cause a synchronization circuit to perform a resynchronization operation when the tracking servo is turned off. By performing a resynchronization operation immediately after an intentional track jump occurs, it is possible to greatly improve the accuracy of quickly and accurately reading data after being tracked again.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 7 and 8. In this embodiment, the RS/FF 26 is controlled by the tracking servo control signal shown at 30 in FIG. 6 (logical value 1: servo N, 0: FF), and at the same time the tracking servo is turned FF, the synchronization is lost. This will cause the system to make a determination and immediately perform resynchronization.

FIG. 7 shows a main part of an embodiment of the present invention in which the RS/FF 26 and its surroundings in FIG. 4 are improved. i.e.
In order to set the RS/FF 26, the logical sum (R) of the carry output 25a and the inverted tracking servo control signal 30 is used as this input. A timing chart in this case is shown in FIG. As a result, the set input for RS/FF26 is 31.
Since resynchronization is started simultaneously with the movement of the optical pickup 3 as shown in a, the first synchronization signal B can be detected after the movement. Therefore, in queue and review playback, more playback output can be obtained as resynchronization is faster, and more address information necessary for locating the beginning of the song included in the data section of the digital signal 29 to be played back can be obtained. You can quickly find the beginning of a song.

Effects of the Invention As described above, according to the digital audio disk player of the present invention, an intentional track jump is performed in the beginning of a song, or during playback of a queue or review, and the synchronization signal in the data after tracking is applied again. By resynchronizing the synchronization circuit using a signal that controls the tracking servo, it is possible to read the information more quickly and accurately. This has the effect that more playback output can be obtained during review playback.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams for explaining the configuration of a conventional DAD player, Figure 3 is a diagram of an example of the configuration of a digital signal in a DAD, Figure 4 is a block diagram of a conventional synchronous circuit, and Figure 5 , FIG. 6 is a diagram for explaining the operation of the synchronous circuit, and FIGS. 7 and 8 are diagrams for explaining the operation of the synchronous circuit in one embodiment of the present invention. 20... Synchronization pattern detection circuit, 21, 22...
...Timing generation circuit, 23...Synchronization detection judgment circuit, 24, 25...Counter, 26...RS flip-flop, 30...Tracking servo control signal.

Claims (1)

[Claims] 1. A synchronization pattern detection circuit that detects the same pattern as a synchronization signal in a digital signal reproduced from a digital audio disk, a gate circuit that inputs the synchronization pattern detection signal from this detection circuit, and a gate circuit that reproduces the digital audio disk. A tracking servo circuit that controls the tracking of a pick-up, and a control circuit that generates a tracking servo control signal that controls on/off the tracking servo circuit, and while the tracking servo control signal outputs an off command. The digital audio disc player opens the gate circuit, and closes the gate circuit after a tracking control signal outputs an ON command and a synchronization signal is detected again.