JP2695167B2 - Recording and playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a recording / reproducing apparatus having a function of removing a time-axis fluctuation that occurs when an audible sound signal is reproduced from a recording medium. [Prior Art] This type of conventionally known jitter removal technology is used, for example, in a device that records and reproduces audio on a disk-shaped recording medium by time-axis compression. In such an apparatus, the disc-shaped recording medium is rotated based on the reference signal output from the reference signal generator. The signal reproduced by the pickup is demodulated, frequency-corrected by the de-emphasis circuit, and output as a time-axis-compressed audio signal. This time-axis-compressed audio signal is A / D converted by the second clock output from the above-mentioned reference signal generator, written in the memory, and output from the above-mentioned reference signal generator by the second clock. Is read from the memory with a third clock that has a constant ratio with, D / A converted, unnecessary frequency components such as the third clock are removed by an LPF (low-pass filter), and then power amplification is performed. It was configured to be input to the speaker. [Problems to be Solved by the Invention] However, the above-described conventional device has the following drawbacks because writing and reading of the memory are all performed by a self-running clock. (1) At the time of reproduction, the disk motor rotates based on the reference signal output from the signal generator of the free-running clock. Since the reference signal is one pulse per one rotation of the motor,
Although the rotation speed of the motor is controlled, the fluctuation of rotation cannot be controlled sufficiently. (2) Since different disk motors are used for different recording / playback decks, wah and flutter due to eccentricity occur due to the deviation of the center axes of these decks, and this is the time-axis fluctuation of the playback signal. (3) When the load of the disk motor fluctuates due to external vibration or the like and the time-axis fluctuation of the reproduction signal occurs, the control loop of the motor has a slow response, and therefore the time-axis fluctuation can hardly be absorbed. Therefore, in view of the above points, an object of the present invention is to provide a recording / reproducing apparatus capable of surely removing a time axis fluctuation that occurs when an audible sound signal is reproduced from a recording medium. [Means for Solving Problems] A recording / reproducing apparatus according to the present invention includes a memory for storing an audio signal, a compression means for time-axis-compressing an input audio signal using the memory, and a time axis for the compression means. Multiplexing means for multiplexing a reference signal having a frequency outside the band of the audio signal with respect to the compressed audio signal, and recording and reproducing the audio signal and the reference signal multiplexed by the multiplexing means with respect to a recording medium. A recording / reproducing means, a clock generating means for generating a clock phase-synchronized with a reference signal reproduced from the recording medium by the recording / reproducing means, and a reference clock having a frequency lower than that of the clock generated by the clock generating means. And a reference clock generating means for reproducing the recording medium from the recording medium according to the clock generated by the clock generating means. The audio signal is written in the memory, and the audio signal stored in the memory is read out in accordance with the reference clock to expand the audio signal on the time axis. [Operation] According to the present invention, it is possible to suppress the influence of the fluctuation of the time axis before and after the time axis expansion by performing the time axis correction not only on the signal but also on the time axis compressed signal. It will be possible. Further, in the present invention, not only the memory is shared between the time axis compression and the time axis expansion, but also the time axis expansion and the time axis correction can be performed using the same memory. More detailed description is as follows. As in the present invention, in an apparatus for recording / reproducing an audio signal by time-axis compression, the influence of time-axis fluctuations in the reproduced signal becomes very large with respect to the audio signal after time-axis expansion. The reason for this is that the 1
This is because the time-axis fluctuation for the clock corresponds to the time-axis fluctuation for several clocks in the signal after the time-axis expansion. From this point of view, the present invention is mainly characterized by performing the following four operations. 1. Compress and record the audio signal on the time axis. 2. Multiplex and record a time axis compressed audio signal with a reference signal (having a frequency outside the band of the audio signal) used for time axis correction processing during playback. 3. Share memory for time axis compression and time axis expansion. 4. Perform time axis extension and time axis correction at the same time. EXAMPLES Hereinafter, the present invention will be described in detail based on examples. FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, reference numeral 15 is a pulse generator which outputs a single cycle clock CLK 0, CLK 1, a disk motor clock DMC, CLK 2 with reference to a free-running oscillation clock. 41 is a microphone that collects the audio signal to be recorded, 42 is an amplifier that amplifies the sound that is collected by the microphone 41, SW61 is an A / D converter 12 described below during recording (REC) and playback (PB)
Switch for switching the input signal of, an A / D converter for converting the input analog signal into a digital signal of several bits, and a clock for the output digital signal of the A / D converter 12 selected by the switch SW62 described later. n × CLK 0 or C
The clock (CLK 1 or CLK 1) that is stored in synchronization with LK 1) and is output from the pulse generator 15 selected by SW64 described later.
Memory that outputs the memory signal in synchronization with 2), 14 is a D / A converter that converts the output digital signal of memory 13 to an analog signal, and 43 is only the audio signal included in the output signal of D / A converter 14. LPF (low-pass filter) that selectively outputs the signal, 44 is a pre-emphasis circuit that emphasizes the high-frequency signal of the output of LPF 43, 45 is an FM modulator that modulates the oscillation frequency according to the output of the pre-emphasis circuit 44, and 48 is a pulse generator BPF (bandpass filter) that selects and outputs only the fundamental wave of the output pulse CLK 0 of the device 15, 46 is an adder that adds the output of the FM modulator 45 and the output of the BPF 48 at a fixed ratio, 47 is the adder 46 A recording amplifier that amplifies the output signal with power, 11 is a magnetic head that records the output of the recording amplifier 47 on a recording medium (not shown) or picks up a signal recorded on the recording medium, and 21 is a pickup signal of the magnetic head 11. Amplifies Reproducing amplifier 22 selects and outputs only the modulated audio signal contained in the reproduction amplifier output an HPF (high-pass filter), the 23, HPF 2
FM demodulator that demodulates the modulated audio signal of 2 outputs, 24 is a de-emphasis circuit that suppresses the high frequency signal in the demodulated audio signal (the opposite of the pre-emphasis performed before modulation), and SW63 is an amplifier at the time of REC A switch that selectively outputs the output of 42 to the output of the D / A converter 14 during PB, 25 is an LPF that selectively outputs only the audio signal of the signal selected by SW63, and 26 is for driving a speaker 27 described later. Amplifier that amplifies the LPF25 output by power, 27 is a speaker that converts the output of the amplifier 26 into an audible signal, SW61 selects the output of the amplifier 42 during REC, and the output of the de-emphasis circuit 24 during PB, and the A / D conversion in the subsequent stage The switch that outputs the audio signal to the device 12, SW62 is the CLK 1 of the pulse generator 15 at the time of REC and the multiplier at the time of PB.
A switch that selects the output of 29 and outputs it as the writing clock of the memory 13 in the subsequent stage, SW63 selects the audio signal output of the amplifier 42 during REC, the audio signal output of the D / A converter 14 during PB, and The switch SW64 that outputs to the LPF 25 is a switch that selects the CLK 2 output of the pulse generator 15 at the time of REC and the CLK 1 output of the pulse generator 15 at the time of PB, and outputs it as the read clock of the memory 13 at the subsequent stage. First, the operation during recording (REC) will be described. The audio signal to be recorded is input from the microphone 41 and the amplifier 42
Amplified by The amplified audio signal passes through SW63 and LPF2
5, monitor output is performed via the amplifier 26 and the speaker 27. Also, the output of the amplifier 42 passes through SW61 and is output by the A / D converter 12.
It is converted into a digital signal of about a bit. The output CLK 1 of the pulse generator 15 is used as a write clock through the SW 62, and the digital signal is written in the memory 13. The data written in the memory 13 is read by the output CLK 2 of the pulse generator 15 and converted into an analog signal by the D / A converter 14. Here, CLK 2 is set to 320 times (or 640,1280) that of CLK 1, and the audio signal at the input of A / D converter 12 and the output of D / A converter 14 is 320 (or 640,1280). This means that it has been compressed to 1/1280). The LPF 43 removes unnecessary components such as clocks from the time-compressed audio signal, emphasizes high-frequency components in the emphasis circuit 44 to improve S / N during playback, and uses the modulator 45 to adjust the center frequency.
It is FM-modulated to about 6 MHz and input to the adder 46. On the other hand, from the pulse generator 15, a constant frequency outside the band of the FM-modulated audio signal, especially the memory reading clock CL
A signal having a frequency of 1 / n (for example, 1/8) of K 2 is output as CLK 0. This CLK 0 passes through the BPF 48 and becomes only the fundamental wave and is added to the second input of the adder 46. Then, the FM sound signal and the fundamental wave CLK 0 are added at a constant ratio, the power is amplified by the recording amplifier 47, and recorded on the recording medium (not shown) by the magnetic head 11. Next, the operation during reproduction (PB) will be described. The reproduction signal detected by the magnetic head 11 from the already recorded recording medium is amplified by the reproduction amplifier 21 to a sufficiently large level. Among the amplified signals, the modulated audio signal is demodulated into a compressed audio signal via the HPF 22 and the demodulator 23, and the high frequency component emphasized by the pre-emphasis circuit 44 is 24 de-emphasis circuits. It is suppressed by 24 and output. The output of the de-emphasis circuit 24 is selected by SW61, input to the A / D converter, and converted to a digital signal.
Input to the memory 13. On the other hand, the clock CLK 0 of the output of the reproduction amplifier 21 is BPF.
Selectively output by 28, multiplied by n by multiplier 29, SW6
Entered in 2. This clock has the same frequency as the clock for reading the audio digital signal from the memory 13 during recording. SW62 is output from the multiplier 29 (n times CLK 0)
Is selected, and this is written in the memory 13 using this as a clock. The audio digital signal written in the memory 13 is
Read by CLK 1 selected by D / A converter 14
Is converted into an analog signal by the LPF 25, unnecessary components such as a clock are removed by the LPF 25 through the SW 63, and output through the amplifier 26 and the speaker 27. As described above, since the memory write clock during reproduction is based on the single frequency written in the recording medium together with the audio signal, first, there is wow and flutter in the angular velocity of the disk-shaped recording medium during recording. , The recording pattern fluctuates along the time axis; there is wow and flutter in the angular velocity of the disk-shaped recording medium during playback, and the time axis fluctuates in the playback signal; The rotation axis of the disk-shaped recording medium during recording and during playback The write clock (n × CLK 0 ′) of the memory 13 follows in accordance with the time axis fluctuation such as deviation, so-called eccentricity, and so on. Therefore, a signal without time axis fluctuation is stored in the memory 13. Will be. Therefore, by reading the stored signal of the memory 13 with the clock (CLK 1) having a constant cycle, a good audio signal without harshness can be obtained. Next, other embodiments will be described. FIG. 2 is a block diagram showing a second embodiment. This drawing shows only a changed portion with respect to FIG. 1, and corresponds to the multiplication circuit 29 in FIG. Here, 51 is a phase comparator that performs phase comparison between the output signal of the BPF 28 and the output signal of the 1 / n frequency divider 54, which will be described later, and 52 is the low frequency band that passes only the low and medium frequency signals of the output signal of the phase comparator 51. The pass-through circuit (LPF) 53 is a voltage-controlled oscillator (VC) that changes the oscillation frequency according to the voltage of the output signal of the LPF 52.
O) and 54 are 1 / n frequency dividers that divide the output signal of the VCO 53 into 1 / n. In this way, the phase comparator 51, LPF 52, VCO 53, 1 / n divider 54
C extracted by BPF 28 using a PLL circuit consisting of
It is possible to form the write clock n × CLK 0 ′ of the memory 13 that follows the frequency variation of the LK 0 ′ signal. FIG. 3 is a circuit diagram showing a third embodiment. In this embodiment, an input tuning oscillator circuit 70 is inserted between the BPF 28 and the multiplication circuit 29 shown in FIG. By this, it is reproduced
Even if CLK 0 ′ becomes a tooth drop signal due to dropout or the like, the input tuning oscillation circuit 70 self-runs in the tooth drop portion, and a signal similar to CLK 0 ′ is output to the tooth drop portion of CLK 0 ′. Can be played. In FIG. 3, R ₁ and R ₂ are base bias resistors of the transistor Tr1. L ₁ and L ₂ form a transformer, and BPF 2
Input CLK 0'output from 8 to this oscillator. R ₃ is Tr
It is the emitter resistance of 1. L ₃ and L ₄ form a transformer and transmit the output of this oscillator to the multiplier circuit 29 of the next stage. Transistor Tr1 configuring the oscillator with _{L 2, C 3, C 4} . C ₁ and C ₂ are DC component blocking capacitors, and R ₄ is an oscillation stabilizing resistor. To performs the free-running oscillation with a constant of Tr1, L _2, C _3, C ₄ in the present embodiment, the output of the BPF 28 is excited from L ₁ to L _2, from the oscillator output CLK of the BPF 28 The signal synchronized with 0'is L ₃ ,
It is output to the multiplication circuit 29 through the L ₄ transformer. Even if the input signal stops due to dropout, etc., since the free-running oscillation frequency of this oscillator is CLK 0, CLK 0'in the dropout section is supplemented and a continuous signal is generated by the multiplier circuit 29.
Is input to [Effects of the Invention] As described above, according to the present invention, not only a signal but also a time-axis-compressed signal is subjected to time-axis correction, so that the influence of time-axis fluctuations before and after time-axis expansion is affected. Can be suppressed. Further, in the present invention, not only the memory is shared between the time axis compression and the time axis expansion, but also the time axis expansion and the time axis correction can be performed using the same memory.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention (an example using a PLL circuit), and FIG. FIG. 6 is a circuit diagram showing a third embodiment (an example using a tuning oscillator and a multiplication circuit) of the present invention. 11 …… Recording / playback head, 12 …… A / D converter, 13 …… Memory, 14 …… D / A converter, 15 …… Pulse generator, 21 …… Playback amplifier, 22 …… HPF, 23 …… Demodulator, 24 …… de-emphasis circuit, 25 …… LPF, 26 …… Amplifier, 27 …… Speaker, 28 …… BPF, 29 …… Multiplying oscillator, 41 …… Microphone, 42 …… Amplifier, 43 …… LPF , 44 …… Emphasis circuit, 45 …… Modulator, 46 …… Adder, 47 …… Recording amplifier, 48 …… BPF, 51 …… Phase comparator, 52 …… LPF, 53 …… VCO, 54 …… 1 / n frequency divider, 70 ... Tuning oscillator.

Claims (1)

(57) [Claims] A memory for storing an audio signal, a compression means for time-axis-compressing an input audio signal using the memory, and a frequency of a frequency outside the band of the audio signal with respect to the audio signal time-axis compressed by the compression means. Multiplexing means for multiplexing the reference signal, recording / reproducing means for recording / reproducing the audio signal and the reference signal multiplexed by the multiplexing means on the recording medium, and the reference signal reproduced from the recording medium by the recording / reproducing means. Clock generating means for generating a clock phase-synchronized with the clock, reference clock generating means for generating a reference clock having a frequency lower than that of the clock generated by the clock generating means, and the recording according to the clock generated by the clock generating means. The audio signal reproduced from the recording medium by the reproducing means is written into the memory, and the reference clock is used. Recording and reproducing apparatus characterized by comprising a decompression means for expanding the time axis of the audio signal by I read the audio signal stored in the memory.