JPS63247972A - Digital reproducing device - Google Patents

Abstract

PURPOSE:To obtain an audio signal by providing a changeover circuit capable of selecting either digital information at the time of a fixed speed reproducing or 1/N digital information at the time of a high speed reproducing and using a single D/A converter circuit. CONSTITUTION:At the time of the fixed speed reproducing, a circuit 11 is changed by a control circuit 7 to perform the fixed speed reproducing of the digital information of a signal processing circuit 5, and an audio output is obtained from the D/A circuit 9. At the time of the high speed reproducing N times as the speed of the fixed speed reproducing, a rotating drum and a capstan are controlled by a servo circuit 8 at N times higher speed than that of the fixed speed reproducing, and a digital signal is obtained from a rotary head 2 as N times as many as frequency as in the case of the fixed speed reproducing. This signal is amplified 4 and demodulated by the signal processing circuit 5 into the digital information of N times larger pitch. Then, it is reduced down to the same pitch as in the case of the fixed speed reproducing via a 1/N circuit 10, and hence the 1/N digital information is outputted via the changeover circuit 11 and the D/A converter circuit 9 as to be an audio output.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a digital playback device that plays back a recording medium in which analog input signals and digital input signals are recorded in the form of digital signals and outputs at least an analog output signal, and more specifically, a digital playback device that is capable of high-speed playback. Regarding.

[Conventional technology]

In recent years, with the development of digital technology, recording and reproducing devices that convert analog signals such as general audio signals and video signals into digital signals, record them on a recording medium, and play them back have been put into practical use. Audiochi recorder (DAT). A typical example is a digital audio disc player (DAC). In such a recording/reproducing apparatus, when reproducing a recording medium on which a digital signal is recorded, high-speed reproduction is performed in order to detect a desired signal. In this high-speed reproduction, the relative speed between the recording medium and the detection means (head) is configured to be high. FIG. 3 shows the basic configuration of a DAT as this type of digital playback device. In this Figure 3, the symbol 1
2 is a rotary head that reproduces the digital signals recorded on the magnetic tape 1; 3 is a rotary transformer that transmits the digital signals obtained from the rotary head 2 without contact; , 4 indicates an amplifier circuit that amplifies the digital signal, and 5 indicates a signal processing circuit that performs signal processing such as interleaving and demodulation on the amplified digital signal. Further, reference numeral 6 denotes an RA that stores digital data processed by the signal processing circuit 5.
7 is a control circuit that is composed of a microcomputer or the like and controls the signal processing circuit 5, etc.; 8 is a rotating drum (not shown) that determines the relative speed of the magnetic tape 1;
A servo circuit that controls the capstan and the like, and 9 a D/A conversion circuit that converts digital data output to the signal processing circuit 5 into analog signals. The servo circuit 8 controls the playback speed determined by the relative speed between the magnetic tape 1 and the rotary head 2.
A constant playback speed and a playback speed N times the constant playback speed (high-speed playback speed) can be selected. In normal constant speed playback, the digital signal obtained from the rotary head 2 is input to the amplifier circuit 4 via the rotary transformer 3 and amplified, and then the digital signal is processed by the signal processing circuit 5 and the storage circuit 6. is demodulated into digital data. In addition, ATF (
An auto track finding (auto track finding) signal is supplied to perform tracking control. The demodulated digital data is converted into an analog signal by the D/A conversion circuit 9 and output as an audio signal.

[Problems to be solved by the invention]

Since the conventional DAT digital playback device is configured as described above, when performing high-speed playback with this playback system configuration, the rotating drum and capstan, which determine the relative speed, are controlled by a servo circuit at N times the constant speed. Since it is controlled by rotation, the rotary head follows the same scanning locus as in the case of constant speed reproduction, and the obtained digital data has a pitch N times higher. Therefore, the D/A conversion circuit is
! It cannot be operated with the @ configuration, and it will not work unless you change the circuit or use a new D/A conversion circuit for high-speed playback.
There was a problem in that it was not possible to output audio for double-speed playback (high-speed playback).

[Means to solve the problem]

Therefore, during high-speed playback, this invention lowers the digital data played back at N times the speed to a pitch of 1/N.
The purpose is to obtain an audio signal with a simple configuration without changing the A/A conversion circuit or adding a D/A conversion circuit. A servo circuit that controls the speed, an amplifier circuit that amplifies the digital signal obtained from the recording medium, a signal processing circuit that demodulates the digital signal output from the amplifier circuit, and a tB signal processing circuit. A 1/N circuit that changes the pitch of the output digital data to 1/N, the digital data output from the signal processing circuit, and the 1/N digital data output from the 1/N@ path. The present invention is characterized in that it has one configuration including a switching circuit that can convert the digital data or the 1/N digital data selected by the switching circuit into an analog signal.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 and FIG. 2. First of all, FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.
．． This is similar to the one shown in FIG. 3 described above. In FIG. 1, reference numeral 10 is a 1/N circuit which changes the pitch of the digital data output from the signal processing circuit 2 to 1, /H, and 11 is a 1/N circuit which is controlled by the control circuit 7 to change the pitch of the digital data output from the signal processing circuit 5 to 1/H. /N times! ? The switching circuits for selectively switching 8io 1/N digital data between constant-speed playback and high-speed playback (N times the constant-speed playback) are shown. In the digital playback device configured as described above, in the case of constant speed playback, the switching circuit 1 is controlled by the control circuit 7.
1 switches the digital data of the signal processing circuit 5 to constant speed reproduction, and the D/A conversion circuit 9 converts the input digital data into an analog signal and outputs it. On the other hand, in the case of high-speed playback that is N times faster than constant-speed playback, the rotating drum and capstan are controlled by the servo circuit 8 at a speed that is N times faster than the constant-speed playback, and the rotating head 2 A digital signal multiplied by N is obtained as a frequency. This digital signal is amplified by the amplifier circuit 4 and demodulated by the signal processing circuit 5 to become digital data, which has a pitch N times larger. The N-times pitch digital data is then reduced to 1/N by a 1/N circuit 10, changed to the same pitch as constant speed reproduction, and output. 1/N digital data is transferred to D/A via switching circuit 11.
The signal is input to the conversion circuit 9, converted into an analog signal, and output as an audio output. The specific configuration of the 1/N circuit is shown in FIG. 2 as a 1/2 circuit. The flip-flop circuits 10A to 10F are provided with a clock signal that is switched by a constant speed playback/double speed playback switching signal as a clock input to the flip-flop circuits 10A to 10F. Then, during double-speed playback, the clock signal is halved, and parallel digital data Q^~Ql (with a pitch of 1/2) is output as the output of the flip-flop circuits 10A~IOF. This is a timing chart illustrating digital data Q. In the above explanation, high-speed playback speed is defined as N of constant-speed playback speed.
However, the high-speed playback speed is twice as high. The variable pitch control can be 4 times, 8 times, 16 times, etc., and in this case, the 1/N circuit is configured to be variably controlled by a control circuit controlled according to the variable pitch control signal. be able to. Effects of the Invention] As is clear from the above description, the digital playback device of the present invention includes a switching circuit that can select between digital data during constant speed playback and 1/N digital data during high speed playback. Since the audio signal is obtained using a single D/A conversion circuit, the circuit configuration becomes extremely simple.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a digital playback device according to the present invention, and FIG. 2 is a diagram showing the configuration of a 1/N circuit used in the present invention.
FIG. 3 is a timing chart showing parallel digital data Q^, and FIG. 4 is a diagram showing the structure of a conventional digital playback device. DESCRIPTION OF SYMBOLS 1... Magnetic tape, 2... Rotating head, 3... Rotary transformer, 4... Amplifying circuit, 5... Signal processing circuit, 6... Memory circuit, 1... Control circuit, 8...
Servo circuit, 9...D/A conversion circuit, 10...1/
N circuit, 11... switching circuit.

Claims (1)

[Claims] A servo circuit that controls a constant playback speed and a playback speed that is N times the constant playback speed, an amplifier circuit that amplifies a digital signal obtained from a recording medium, and a demodulates the digital signal output from this amplifier circuit. a 1/N circuit that changes the pitch of the digital data output from the signal processing circuit to 1/N; and a 1/N circuit that changes the pitch of the digital data output from the signal processing circuit and output from the 1/N circuit. A switching circuit that can select the 1/N digital data selected by the switching circuit, and a D/A conversion circuit that converts the digital data selected by the switching circuit or the 1/N digital data into an analog signal. A digital playback device characterized by: