JPS5972608A - Reproducer - Google Patents

Abstract

PURPOSE:To prevent distortion of a sound output due to dropout with a simple constitution by muting a reproduced output signal if a prescribed amount or more of dropout of the reproducing signal occurs at a prescribed time. CONSTITUTION:When lots of dropouts occur continuously in a detecting circuit 55, a multivibrator 73 is inverted, switches 53L, 53R are turned off for a prescribed time and the sound reproducing output signal is muted. A demodulating sound signal is extracted in this way. If lots of dropouts take place continuously, a signal havng distorted waveform is not outputted because of holding of pre-stage circuits, because the output signal is muted. Thus, the distortion of sound output due to dropout is prevented with a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The first field of industrial application is that audio signals are frequency modulated (FM modulation 11.1).
), frequency-multiplexed with the video signal, and recorded the signal in 11. Hi1ora~-Fureni1-ta (V T
R) to IA river (lri + fishing naigyuso; iq related.

1? Tagijutsu and its problems Video A, 1゛Brightness in the bow <r<> 1111 on the power side
・゛M modulation J -j1, G, 2, ri 117h? Interlease the frequency between adjacent tracks 1 and 8.)C
, : Low frequency conversion, 11. 211 which becomes 11' of the asin angle. ! Recording without placing a guard band on the slanted trunk of the tape was carried out using the rotary hem F' of No. 11.

In such a VTR, audio signals have conventionally been recorded using a fixed head with continuous 1, 1, and
It was carried out on a rack in a similar manner to the so-called audio tape recorder.

In the VTR mentioned above, ``When increasing the areal density of C1 recording, the tape transport speed has been increased to extremely high speeds, and is currently up to, for example, 1.33 cm/sec. For this reason, when recording audio signals, the relative speed between the fixed head and the tape becomes slow, making it impossible to record good audio signals.

Therefore, if the audio signal is transmitted with FM-modulated luminance, it will be low-frequency converted or FM-modified in the band between l:17 signal.
, IL, it has been proposed that the video signal be multiplied by IFT and recorded on an inclined track.

4-Nawashi Figure 1 is 9 years old, (1) is -y-yuna, and the image from this tuner (1) (elephant C is ΔG
The C amplifier (2), the encoder circuit (3), and the clamp circuit are fed to the FM modulator (5) so that, for example, the frequency of the amplifier chip is 4.0 MHz and the white peak is 5.2 MHz. An FM luminance signal YFM which is FM modulated is formed.The video signal from the tuner (1) is passed through a band pass filter (6) and an ACC circuit (7).
) and is supplied to a low-pass filter (9) through a frequency converter (8) to form a low-pass converted chroma signal CD having a subcarrier frequency of 68811z.

Furthermore, the first audio signal (left signal for stereo, main signal for dual audio) AL and second audio signal (return signal for stereo, sub signal for dual audio) AR from the tuner (1) are each sent to an AGC amplifier. (IOL), (IOI+),
It is supplied to the FM converter (141), <142>, (143), (144) through the noise canceller (ILL), (IIR), pre-emphasis circuit (12L), (12R), and the carrier frequency is 1, respectively. .325
MHz, , 1.475 MH2-1,625 MHz,
],,150 with constant frequency deviation width at 775 MHz
kHz, and the respective levels are as shown in Figure 2, ALFI<8LF2<ARdo3<ARF4ALF2,
ARF3 and ARF4 are formed. Of these, the FM audio signals ALF 1 and A RF3 are supplied to the ζ mixing amplifier (16o) through bandpass filters (151) and (15"3"), respectively, and the FM audio signals ALF2
, ARP4 are each a bandpass filter (152),
(154) to the mixing amplifier (16e). Signals from the mixing amplifiers (16o) and (16e) are supplied to adder circuits (17o) and (17e), respectively. The above-mentioned FM luminance signal YFM and low frequency conversion chroma signal CD are commonly supplied to the adder circuits (17o) and (17e). Then, this added W signal is applied to each recording amplifier (1
8o) and (18e) to rotary heads (19o) and (19e) having mutually different azimuth angles.

In this apparatus, the spectrum of the recorded signal is as shown in FIG. And among these, F for belly button) = (19o)
The head (19e) has the M audio signal ALF2, the signal from which 8 FIF4 has been removed, and the FM audio signal ALFI, 8 RF3.
A signal from which the signal is removed is provided.

As shown in FIG. 4, these heads (19o) and (19e) alternately form inclined tracks to- and te with different recording azimuths on the tape T-I, respectively, and the respective signals (YFff1+G o +ALF1+
ΔRF3) Also signal [Y + CD + A LF 2
+ARF4) is recorded. In addition, a control signal CT from a servo thread (not shown) is applied to the continuous track tc.
L is recorded.

In this way, video signals and audio signals are recorded.

To reproduce the signal recorded in this manner, for example, the following procedure is performed.

In Figure 5, the rotating head (19o), (1
The reproduction signal of 9e) is output to the amplifier (40o) and (40o), respectively.
e). The signal from this amplifier (40o) has a center frequency of 1.325 MHz and 1
．． 625M H2 bandpass filters (4h) and (413), and the signals from the amplifier (40e) have center frequencies of 1.475M HZ and 1.77M HZ.
5 Mllz pan 1' pass filter (412), (4
14). These bandpass filters (4
The signals from 1, s) to (414) are sent to the FM demodulator (43t) through limiter circuits (421) to (424), respectively.
) to (43→) are supplied with the respective audio signals AL.
.

AR is demodulated. These audio signals AL and AR are supplied to low-pass filters (441) to (444), respectively. Signals from the low-pass filters (44z) and (442) are supplied to the switch circuit (451,), and signals from the low-pass filters (443) and (444) are supplied to the switch circuit (45R).

These switch circuits (45L) and (45R) are connected, for example, to a terminal (
'C is controlled by the head switching signal supplied to 46). The signals from these switch circuits (45L) and (45R) are transmitted through low-pass filters (47L) and (47R), respectively.
R), noise canceller (48L), (48R), de-emphasis circuit (49L), (49R), output amplifier (51,L), (51R) to audio output terminal (52).
L), (52R).

Further, the voltage from the amplifiers (40o) and (40e) is supplied to the switch circuit (60), and this switch circuit (
60) is controlled by a signal from terminal (46).

The signal from this switch circuit (60) is supplied to a bypass filter (61) to extract an FM luminance signal Yptt, which is then sent to a limiter (62), FMffitJI
The brightness signal Y is demodulated by being supplied to the illumination unit (63) and the emphasis circuit (64). In addition, the switch circuit (60
) is supplied to a low-pass filter (65) to extract a low-frequency converted chroma signal C, and this signal is supplied to a high-frequency conversion circuit (66) and a band-pass filter (67) to obtain a chroma signal C. taken out. This luminance signal Y
and chroma signal C are mixed in a mixing circuit (68) to form a video signal, which is supplied to a video output terminal (69).

The video signal and audio signal are reproduced as follows.

In this case, since the audio signal is FM-modulated and recorded and reproduced together with the video signal by the rotary head, the audio signal will not deteriorate even if the tape transport speed is reduced.

In addition, the recorded FM audio signal has reduced crosstalk from adjacent tracks due to azimuth loss, and
The carrier frequencies are set to differ by 150 kHz between adjacent tracks. Therefore, the frequency of the beat signal is outside the audible band, allowing good reproduction without interference.

However, in this apparatus, the tracks To and Te recorded by the rotary head have extremely narrow track widths, and the signals are of high frequency, so that so-called dropouts are likely to occur. In this case, if a dropout occurs in the FM audio signal, the FMfJj tone signal in between becomes random noise, which significantly distorts the audio output.

For example, as shown in Fig. 6, the de-emphasis circuit (49L), (49R) and the output amplifier (51L),
(51R'), switch (53L), (53
R) and capacitor (54L), (541'l)
In addition to providing a front bold circuit consisting of
40o) and (40e) are supplied to the dropout detection circuit (55), and this detection signal is sent to the switch (55).
It has been proposed to pre-hold the demodulated audio signal by supplying the signal to the control terminals of the switches (53L) and (53R') to turn off the switches (53L) and (53R) during the mud/knob-out period.

However, in this case, if a dropout as shown in Figure 7B is detected for the original signal as shown in Figure 7A, for example, when the dropout frequency is low as shown on the left side of the figure, the output signal is approximately equal to the original signal as shown in Figure 7C, but if a large number of dropouts occur in succession as shown on the right, the waveform of the output signal will be distorted, and such distortion will be audibly negligible. It disappears.

OBJECTS OF THE INVENTION The present invention takes into consideration these points and provides a playback device that can prevent distortion of audio signals due to dropouts and the like.

SUMMARY OF THE INVENTION The present invention detects a dropout of the reproduced signal when reproducing a recorded signal in which an audio signal is frequency-modulated and frequency-multiplexed with a video signal, and this dropout is detected at a predetermined time. This is a playback device that mutes a playback output signal when a predetermined number of noises occur, and is capable of preventing distortion of audio output due to dropouts and the like with a simple configuration.

Embodiment In FIG. 8, a signal from a detection circuit (55) is supplied to a non-retriggerable monostable multi-by break (71) having a predetermined inversion period, and an output signal of this multi-by break (71) is sent to a counter (72). ) is supplied to the glue cent terminal. Also, signals from the detection circuit (55) are supplied to the count terminal of the counter (72). When this counter (72) counts a predetermined number, the output signal has a predetermined inversion period or is turned into a triggerable monostable multi-bi break (73). 53L), (
53R') -A<controlled.

In this circuit, for an original signal as shown in FIG.
If the dropout detection circuit as shown in FIG. 9B is output, the multi-bye break (71) is inverted as shown in FIG. 9C. Furthermore, during this reversal period, the counter (
72), the number of dropouts is counted. When this count value exceeds a predetermined number, the multi-bye break (73) is inverted by the output of the counter (72). During this inversion period, switch (53L), (53
R) is turned off.

That is, in this circuit, when a large number of dropouts occur in succession, the multi-bye break (73) is inverted, the switches (53L) and (53R) are turned off for a predetermined period, and the audio playback output signal becomes as shown in FIG. 9F. It is muted as shown.

In this way, the 'ζ repeat voice signal is extracted.

In this case, when many dropouts occur in succession, the output signal is muted, so
A signal with a distorted waveform due to pre-holding or the like is not output, and an audio signal with extremely good audibility can be obtained.

Therefore, for example, even when a tape with many tracking errors or scratches is played back, the playback can be performed with good audibility.

FIG. 10 shows another example, in which muting is performed even for long dropouts.

In the figure ζ, the signal from the detection circuit (55) has a predetermined inversion time or a triggerable monostable multi-bibreak (
74), and the output of this multi-by-break (74) is inverted by an inverter (75) and sent to an AND circuit (74).
6). Further, a signal from the detection circuit (55) is supplied to an AND circuit (76). This AND circuit (7
The output of 6) is supplied to a retriggerable monostable multivibrator (77) having a predetermined inversion time.

The output of this multi-by break (77), the output of the above-mentioned multi-by break (73), and the signal from the detection circuit (55) are supplied to an OR circuit (78), and each OR circuit (
Sui Nochi (53L), (53) with the output signal of 78)
R) is controlled.

In this circuit, when the °C, 1st and 1st note detection signals are output for the original signal as shown in Figure 11A, the multi-bye break (
71), counter (72), multivibrator (7
The output of step 3) is as shown in FIG. 11 C, D, and E. On the other hand, the output of the inharter (75) is as shown in FIG. 11F, and a signal as shown in FIG. 11G is taken out from the AND circuit (76). The multi-by-break (77) is inverted by this signal, and an output as shown in FIG. 11H is obtained. Then, the signals B and EH in FIG. 11 are combined in an OR circuit (78), and the switches (531,) and (53R) are controlled by the signals shown in FIG. 11.

Therefore, in this circuit, when the dropout is longer than the inversion time of the multi-by break (74), the multi-by break (77) is inverted and the switch (
53L) and (531?) are turned off, and the audio reproduction output signal is muted as shown in FIG. 11J.

In this way, when a dropout that may impair the auditory sense occurs, the audio reproduction output can be muted to prevent the auditory sense from deteriorating.

Effects of the Invention According to the present invention, distortion of audio output due to dropouts and the like can be prevented with a simple configuration.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams for explaining the recording device, and Figures 5 to 4 are diagrams for explaining the recording device.
FIG. 7 is a diagram for explaining a conventional device, FIG. 8 is a system diagram of an example of the present invention, FIG. 9 is a waveform diagram for explaining the same, and FIGS. 10 and 11 are diagrams of other examples. It is a figure for explanation. (431,), <43R) is the FM demodulator, (53L)
, (53R) are switches, (54L) and (54R) are capacitors for front bold, (55) are dropout detection circuits, (71) and (73) are monostable multi-byte 6th
Figure 55 Figure 7 Figure 8 Figure 10, 53L l11.3 Figure 11

Claims (1)

[Claims] The audio signal is frequency modulated, and the video signal and frequency multiplier L1 (
+lr, when reproducing a signal recorded as
I believe it! Nido Knobu out, this do 1-!
A playback device configured to mute a J signal when a sound occurs more than a predetermined time in a predetermined time.