JPS61120378A - Reproducing device - Google Patents

Abstract

PURPOSE:To perform excellent dropout compensation without generating any unnatural sound by adjusting the address of a memory when a dropout of the playback signal of a recording medium is detected and removing a signal corresponding to the dropout. CONSTITUTION:The playback signal of a magnetic head 31 is supplied to a dropout detecting circuit 56. This detecting circuit 56 generates a detection pulse with a threshold level for the playback signal. This detection pulse is supplied to a memory controller 55. The write address of an address counter 52 is counted down by, for example, ten at the start part of this detection pulse and writing is restarted with the address which is counted down by ten 10 address clocks after the end of the detection pulse. Therefore, this circuit removes a noise part in this period as shown by B when a dropout appears as shown by A, and an audio signal is outputted thereafter continuously as an output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to recording and reproducing audio signals using a still image recording and reproducing device such as a so-called electronic still camera device.

[Conventional technology]

An electronic still camera device that has an imaging device such as COD and records the signal of one arbitrary field or frame on a magnetic disk has been proposed (Utility Model Application Publication No. 1983-1999).
No. 197,021, etc.).

In other words, in such a device, one field or one frame of the video signal from the imaging device is gated and extracted at the time of arbitrary shutter operation, and one field of this signal becomes one annular track. recorded on a magnetic disk. Note that one frame of signal is recorded using two tracks. Therefore, in this device, a video signal of a still image can be formed by repeatedly reproducing one track or two tracks alternately.

It has been proposed to provide such devices with the additional possibility of recording audio signals. To do this, for example, there is a method that uses digital signal processing technology to compress the audio signal's time axis, converts the frequency band of the audio signal to the band of the video signal, and records it using the same recording system as the video signal. Conceivable.

In this case, for example, by compressing the time axis of an audio signal up to 5 kHz by a factor of 600, it is possible to create a signal with a video band of 3 MHz. And in this case, 1
During the field period (1/60 second), 600 times that amount, about 10
It can record audio signals for seconds.

That is, FIG. 5 shows a block diagram of an example of a recording device for this purpose. In this figure, a video signal is supplied to an input terminal 11, converted into a predetermined recording signal by a recording circuit (2), and sent to an FM modulation circuit (5) via a non-linear pre-emphasis circuit (3) and a changeover switch (4). supplied, F
The signal is recorded on the disk D by the magnetic head (6) as an M signal.

The audio signal is also supplied to the input terminal (11) and is supplied to the AD conversion circuit (13) through the encoder circuit II (12) of the noise reducer. This digitally converted signal is supplied to the memory device (14). Also 5 kHz
The sampling signal of the audio signal in the band z is sent to the oscillator (21
), and this signal drives an AD conversion circuit (13) and a memory device (14).
supplied to Furthermore, an oscillator (23) having an oscillation frequency 600 times that of the above-mentioned oscillator (21) is provided, and a signal from this oscillator (23) is supplied to the address counter (22). In addition, pulses related to the rotational phase of the disk from a magnetic piece provided at a predetermined portion of the disk D are
It is detected by the knob head (24) and this signal is provided to the memory controller (25). For example, as shown in FIG. 6, the signal written in the memory device (14) every 2.5 seconds, which is obtained by dividing 10 seconds into four, is read out 600 times faster, and the timing is As shown in FIG. 7, pulses related to the rotational phase from the head (24) are sequentially output at timings that are sequentially delayed in phase by 1/4 every 2.5 seconds.

This read signal is supplied to the DA conversion circuit (15). A signal from an oscillator (23) is supplied to this conversion circuit (15). This analog-converted signal is connected to a pre-emphasis circuit (16) with linear characteristics and a selector switch (4).
) is supplied to the FM modulation circuit (5), and recorded on the disk D by the magnetic head (6) as an FM signal.

In this way, the audio signal can be compressed on the time axis and recorded on the disc D using the video signal recording system.

However, when extracting the audio signal from the disk D recorded in this manner, in a recording/reproducing apparatus such as a disk where the relative speed between the recording medium and the head is high, failures due to so-called dropouts are likely to occur. For such dropouts, the conventional method is to detect dropouts and
For example, if there is a dropout as shown in Figure 8A, the audio output during this period can be muted or pre-held as shown in Figure 8B to prevent unpleasant noise from occurring due to the dropout. I was trying to do that. However, in such a method, a waveform different from the original audio signal will be mixed in during the muting or pre-hold period, and especially if the time axis is stretched as described above, this will correspond to dropouts. As the time became longer, 211 separate thunders were formed.

Furthermore, in conventional devices, since the compensation operation is performed after dropout is detected, there is always a period at the start end where compensation cannot be performed due to the delay time of the operation. Furthermore, if the sensitivity of dropout detection is increased in order to shorten this period, a compensation operation will be performed even for slight level fluctuations in the reproduced signal, and there is a risk that the sound quality will deteriorate on the contrary.

[Problem that the invention seeks to solve]

Conventional devices were constructed as described above. However, when such a conventional device is applied to a playback device that performs time axis expansion, there is a problem that a sufficient compensation effect cannot be obtained.

[Means for solving problems]

In the present invention, when extracting the audio signal from a recording medium in which the audio signal is recorded with time axis compression, the signal reproduced from the recording medium is written to the /mo IJ (43), and the clock frequency (51 ) (53) and expands the time axis, detects dropout of the playback signal from the recording medium (56), and when this dropout is detected, reads the address of the memory (43). 811 (55) This is a playback device characterized in that No. 111, which corresponds to the above-mentioned dropout, is removed.

[Effect]

According to the above-mentioned device, a waveform different from the audio signal is not mixed during dropout compensation, and extremely good dropout compensation can be performed.

〔Example〕

In FIG. 1, a signal reproduced from a disk D by a magnetic head (31) is supplied to an FMinotet11 circuit (32). When the demodulated signal is a video signal, this signal is sent to a de-emphasis circuit (33) with non-linear characteristics.
It is taken out to an output terminal (35) through a reproducing circuit (34).

Furthermore, when the demodulated signal is an audio signal, this signal is passed through the de-emphasis circuit ff1 (41) with linear characteristics to A
The signal is supplied to the D conversion circuit (42). This digitally converted signal is supplied to the memory device (43). Further, an oscillator (51) having the same frequency as the above-mentioned oscillator (23) is provided, and a signal from this oscillator (51) is supplied to an address counter (52) that drives an AD conversion circuit (42) and a memory device (43). be done. Furthermore, the above-mentioned oscillation! (2
An excavator (53) with a frequency equal to that of
2). Further, a signal from a pink amplifier head (54) equivalent to the above-mentioned head (24) is supplied to the memory controller (55). For example, the sixth
The operation reverse to the recording operation shown in FIG. 7 is performed, and the signal written in the memory device (43) is read out at a speed of 1/600.

This read signal is supplied to the DA conversion circuit (44). A signal from an oscillator (53) is supplied to this conversion circuit (44). This analog-converted signal passes through the noise reduction decoder circuit (45) to the output terminal (
46).

Furthermore, in this circuit, the reproduced signal from the magnetic head (31) is supplied to a dropout detection circuit (56). In this detection circuit (56), a detection pulse as shown in B is formed at a predetermined threshold level for a reproduced signal such as that shown in FIG. 3, for example.

This detection pulse is supplied to the memory controller (55). Then, at the beginning of this detection pulse, the write address of the address counter (52) is moved back by 10 addresses, and after 10 address clocks have elapsed from the end of the detection pulse, writing resumes from the address that was moved back by 10 addresses. be done.

Therefore, in this circuit, if there is a dropout as shown in Figure 4, the noise part in between is deleted as shown in Figure 4B, and the subsequent audio signal is continued as an output signal. taken out.

This is how -ζ dropout compensation is performed, but according to the circuit described above, the signal after the dropout is directly continued after the noise part due to the dropout is removed, and during this period, an abnormal signal is mixed in. Because it never happens,
As a result, unnatural sounds are not produced, and extremely good dropout compensation can be performed.

That is, in the above-mentioned circuit, the audio signal is expanded on the time axis, and therefore the reproduced signal is once written into the memory and then outputted to obtain the output signal, so that the above-mentioned dropout compensation can be performed.

In addition, in the above circuit, by moving the write address back by 10 addresses at the start of the dropout detection pulse, it is possible to eliminate the delay in detection at the start of the dropout/knobout, and for example, the dropout detection threshold level can be made deep enough to perform retroactive compensation only when a dropout is reliably detected. If such processing is not necessary, for example, as shown by the broken line in the figure,
A gate circuit (57) is provided on the output side of the oscillator (51),
The detection pulse from the detection circuit (56) causes the AD conversion circuit (
42) and the address counter (52) may be cut off to stop writing. In this case as well, there is an ItM at the starting end that cannot be compensated as in the conventional
The effects other than the generation of gaps are the same as those described above, and the circuit configuration becomes extremely simple.

Furthermore, FIG. 2 shows another example. In this example, the memory (43) is continuously written with a dropout, and when a dropout is detected by the detection circuit (56), the address counter (5) at the start and end of the dropout is detected.
The output address of 2) is the Doro knob out register (6
0). And when memory (43) continues to appear,
Reading is performed by jumping the address of this register (60).

Even in this case, the same dropout compensation as described above can be performed. Note that by adding or subtracting a constant to the start and end addresses of the dropout stored in the register (60),
It is also possible to equivalently expand the width of the detection pulse.

〔Effect of the invention〕

According to the present invention, when performing dropout compensation, a waveform different from that of the audio signal is not mixed, and extremely good dropout compensation can be performed.

[Brief Description of the Drawings] Fig. 1 is a block diagram of one example of the present invention, Fig. 2 is a block diagram of another example, Figs. 3 to 7 are diagrams for explaining the present invention, and Fig. 8 is a diagram for explaining a conventional circuit. (31) is a magnetic head, (42) is an AD conversion circuit, (4
3) is a memory device, (44) is a DA conversion circuit, (46)
is an output terminal, (51) is an oscillator, (52) is an address counter, (55) is a memory controller, and (56) is a dropout detection circuit. 3rlA Figure 4 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] When retrieving the audio signal from a recording medium in which the audio signal has been recorded with time axis compression, the signal reproduced from the recording medium is written to a memory, read out by changing the clock frequency, and expanded in the time axis. A playback device that detects a dropout of a playback signal from a recording medium, adjusts the address of the memory when the dropout is detected, and removes the signal corresponding to the dropout. .