JPH07236156A - Signal processing circuit of magnetic recording / reproducing apparatus - Google Patents

Abstract

(57) [Summary] [Object] To perform signal processing of dropout compensation, reproduction of a wide band luminance signal, and recording / reproduction with a single delay circuit in a signal processing circuit of a magnetic recording / reproducing apparatus. [Structure] A delay circuit (22) is shared during recording and reproduction, and a circuit for separating a recorded video signal into a luminance signal and a chrominance signal during recording is configured, and a dropout of the reproduced video signal is dropped out during reproduction. A detection circuit (5) detects and performs dropout compensation, a line noise canceller circuit reduces noise, and forms a C comb for removing adjacent crosstalk. Further, the band limiting circuit (15) attenuates the component corresponding to the reproduction chrominance signal band of the reproduction luminance signal and also corresponds to the reproduction of the broadband luminance signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video signal processing of a recording / reproducing apparatus such as a VTR and a camera-integrated VTR.

[0002]

2. Description of the Related Art In VTR video signal processing, there are many configurations in which a video signal is delayed by 1H (where H is a horizontal synchronizing signal period), and it is necessary to reduce the number of delay circuits used. This is because the delay circuit is expensive and has a large mounting area. Therefore, it is preferable that the delay circuit is as small as possible, particularly for a signal circuit such as a camera-integrated VTR. As an example of reducing the delay circuit, as shown in Japanese Patent Publication No. 1-34435, a comb filter for a color signal at the time of reproduction (hereinafter referred to as C comb) and a line noise canceller circuit can be processed by one delay circuit. There is a configuration. This is realized by adding the reproduced luminance signal and chrominance signal, and calculating the added signal and a signal delayed by 1H by supplying it to a delay circuit.

[0003]

When reproduction is performed with a normal VTR, a dropout may occur due to a scratch on the tape or the like and the reproduction image quality may be deteriorated. In that case, a delay circuit is used to replace the signal before 1H to perform dropout compensation and prevent deterioration of image quality. As described above, the delay circuit is required to perform the dropout compensation, but the prior art described above does not consider this.

On the other hand, VT such as VHS standard and 8 mm standard
In R, there are a standard mode in which the luminance signal band is a signal band equal to or lower than the color subcarrier frequency and a wide band mode in which the luminance signal band is a signal band equal to or higher than the color subcarrier frequency. The above-mentioned conventional technique is effective for the reproduction process in the standard mode,
Since the reproduction luminance signal and the reproduction color signal are added at the input of the delay circuit, the high frequency component of the luminance signal is added to the color signal in the wideband mode, which disturbs the color signal. As described above, in the above-mentioned related art, no consideration is given to reproduction in the wide band mode.

Further, at the time of recording, particularly in the wide band mode, it is necessary to separate the recorded video signal input using a delay circuit into a luminance signal and a chrominance signal. This configuration is also taken into consideration in the above prior art. Not yet, so you need another delay circuit.

[0006]

To solve the above problems, first, as dropout compensation, a dropout detection circuit and a switch circuit that switches when the signal is detected are provided. In addition, a band limiting circuit for limiting the band of the FM demodulated luminance signal input to the delay circuit is provided so as to be compatible with reproduction in the wide band mode. Further, in order to process recording and reproduction with one delay circuit, a switch circuit for switching a recorded video signal and a reproduced video signal is provided, and the circuit operates so as to separate a luminance signal and a color signal during recording.

[0007]

According to the present invention, there is no deterioration in the image quality even when reproducing in the wide band mode, the dropout is compensated for, and it operates as a separation circuit for the luminance signal and the chrominance signal during recording. Therefore, the signal processing of the recorded video signal and the reproduced video signal can be processed by one delay circuit.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing signal processing of a recording / reproducing apparatus according to an embodiment of the present invention.

The reproduced video signal input from the input terminal (1) is subjected to FM modulation luminance signal extraction by the high-pass filter circuit (2) and input to the FM demodulation circuit (3) for demodulation. After that, it is input to the de-emphasis circuit (4), suppressed by the amount by which the high frequency range is emphasized during recording, and input to the switch circuit (6). On the other hand, the output of the high-pass filter circuit (2) is also input to the dropout detection circuit (5) to detect the missing portion of the signal due to scratches on the tape, and the detected output is input to the switch circuit (6). And control the switching of the switch. The output of the switch circuit (6) is input to the band limiting circuit (15) to attenuate the band component corresponding to the color signal, and the addition circuit (19).
Is input to. This band limiting circuit (15) can eliminate interference with the color signal component. On the other hand, the reproduced video signal input from the input terminal (1) is input to the low pass filter circuit (16) to extract the low-pass conversion color signal. Thereafter, the main converter circuit (17) frequency-converts it into a carrier color signal, and the bandpass filter circuit (18) attenuates unnecessary band components, and the addition circuit (1
9) is input. The addition circuit (19) adds the output of the band limiting circuit (15), delays it by 1H through the delay circuit (22) and the equalizer circuit (44), and inputs it to the subtraction circuit (23). On the other hand, the signal before being delayed by 1H is also input to the subtraction circuit (23), and the signal delayed by 1H is subtracted to generate C comb. The subtraction circuit (23)
The bandpass filter circuit (24) attenuates the frequency component other than the part corresponding to the color signal band, and the output of is output from the output terminal (25) as a reproduced color signal.

On the other hand, the output of the delay circuit is input to the switch circuit (6) as a replacement signal when dropout occurs.

Further, the output signal of the switch circuit (6), the band limiting circuit (15), and the adding circuit (1)
9), the signal delayed by the delay circuit (22) is input to the line noise canceller circuit (37). In this embodiment, the line noise canceller circuit (37) is replaced by an equalizer circuit (7), a trap circuit (8), an adding circuit (9),
(11), subtraction circuits (10) and (13), and a limiter circuit (12). The output of the delay circuit (22) is input to the trap circuit (8) to attenuate the color signal component.
Then, the output is input to the adder circuit (9). On the other hand, the output of the switch circuit (6) is input to the equalizer circuit (7) and the group delay time of the trap circuit (8) is adjusted. Then, it is input to the adder circuit (9) and the subtractor circuit (10). The output from the trap circuit (8) is added by an adder circuit (9) to generate a luminance comb filter (hereinafter referred to as Y comb). The output of the adder circuit (9) is the subtractor circuit (10) and the adder circuit (11).
Is input to. The subtractor circuit (10) subtracts the output of the adder circuit (9) from the output of the equalizer circuit (7), and the result is input to the adder circuit (11) and the limiter circuit (12). This output takes out only the difference component around 1H, but 1H
Since the signals before and after are correlated, signals without them can be regarded as noise. The adder circuit (11) adds the output of the adder circuit (9) and sends it to the subtractor circuit (13). On the other hand, the limiter circuit (12) extracts only the true noise component and sends it to the subtraction circuit (13). In the subtraction circuit (13), from the output of the addition circuit (11) to the output of the limiter circuit (12),
That is, the noise component is subtracted. Then, the output of the subtraction circuit (13) is derived from the output terminal (14) as a reproduction luminance signal obtained by subtracting the noise component.

Next, a configuration in which the comb filter (38) for reproducing color signals shown in FIG. 1 is of a feedback type will be described with reference to FIG.

The signal input from the input terminal (60) is
One is supplied to the subtraction circuit (23) via the equalizer circuit (40) and the subtraction circuit (39). Subtraction circuit (23)
A C-comb is generated at the output of and is output from the output terminal (66).

On the other hand, the signal input from the input terminal (60) is delayed by 1H by the equalizer circuit (40), the subtraction circuit (39) and the delay circuit (22), and the addition circuit (4
1). In addition circuit (41) input terminal (6
By adding the input signal of (0) and the output of the delay circuit (22), the output of the adding circuit (41) becomes a Y comb, and the adjacent crosstalk component of the color signal is extracted. An unnecessary component of this adjacent crosstalk component is removed by a bandpass filter (42), and a feedback amount is set by a feedback coefficient setting circuit (43).
By supplying to the subtraction circuit (39) that forms a comb, C
The comb band can be narrowed, and the ratio of removing adjacent crosstalk components can be increased.

The dotted lines (61), (62), (6)
3), (64), and (65), the delay times of the routes are t1, t2, t3, t4, and t5, respectively.
By setting the delay times of the equalizer (40), the equalizer (44), the bandpass filter (42), and the delay circuit (22) so that −t1 = 1H, t4-t3 = 1H, and t5 = 1H, the comb is set. Optimization of shape filter characteristics can be realized.

Next, the delay circuit is commonly used for recording and reproduction,
Another embodiment of the present invention, in which a luminance signal / color signal separation circuit is used for recording, will be described with reference to FIG.

A description will be given from the time of recording. The recording side of the recording video signal input from the input terminal (20) is selected by the switch circuit (21). The output is the delay circuit (2
2) The signal is delayed by 1H and input to the subtraction circuit (23) via the equalizer circuit (44). On the other hand, the output of the switch circuit (21), that is, the signal not delayed by 1H,
It is input to the subtraction circuit (23) and the signal delayed by 1H is subtracted to generate a C comb. The output C comb is attenuated by the band pass filter circuit (24) for frequency components other than the part corresponding to the color signal band, is low-pass converted by the low-pass conversion circuit (27), and is output from the output terminal (28). It is derived as a recording low frequency conversion color signal. On the other hand, the output of the band pass filter circuit (24) is the band limiting circuit (2
9), the band for forming the Y comb is set, and the band is input to the subtraction circuit (31). On the other hand, the switch circuit (2
The output of 1) is input to the equalizer circuit (30), and the equalizer circuit (30) outputs the bandpass filter circuit (2).
4) and the group delay time generated in the band limiting circuit (29) are corrected and input to the subtracting circuit (31). Subtraction circuit (31)
Then, from the equalizer circuit (30) to the band limiting circuit (2
The output of 9) is subtracted to generate the Y comb. afterwards,
The output of the subtraction circuit (31) is input to the equalizer circuit (32) to correct the group delay characteristic flat, and the pre-emphasis circuit (33) emphasizes high frequency components. And F
It is modulated by the M modulation circuit (34) and is derived from the output terminal (35) as a recording FM luminance signal.

At the time of reproduction, processing is performed by the method already described in the description of FIG. 1, except that the output of the adder circuit (19) is once input to the switch circuit (21) and the reproduction side is selected. It is about to be input to the delay circuit (22), and other than that is basically the same.

The feedback comb filter at the time of recording also performs the same operation as at the time of reproduction by the method already described.

[0021]

As described above, according to the present invention,
The dropout compensation, the reproduction of the wide band luminance signal, and the signal processing of the recording / reproduction can be performed by only one delay circuit, and the cost of the delay circuit having a large mounting area can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal processing circuit according to the present invention during reproduction.

FIG. 2 is a block diagram showing an embodiment of a feedback comb filter circuit.

FIG. 3 is a block diagram showing an embodiment of a video signal processing circuit according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input terminal (recording video signal), 2 ... High pass filter circuit, 3 ... FM demodulation circuit, 4 ... De-emphasis circuit, 5 ... Dropout detection circuit, 6, 21 ... Switch circuit, 7, 30, 32, 40, 44 ... Equalizer circuit, 8 ... Trap circuit, 9, 11, 19, 41 ... Addition circuit, 10, 13, 23, 31, 39 ... Subtraction circuit, 12 ... Limiter circuit, 14 ... Output terminal (reproduction luminance signal), 15 , 29 ... Band limiting circuit, 16 ... Low pass filter circuit, 17 ... Main converter circuit, 18, 24, 42 ... Band pass filter circuit, 20 ... Input terminal (recording video signal), 22 ... Delay circuit, 25 ... Output terminal ( Reproduction color signal), 27 ... low-frequency conversion circuit, 28 ... output terminal (recording low-frequency conversion color signal), 33 ... pre-emphasis circuit, 34 ... FM modulation circuit, 35 Output terminal (recording FM modulation luminance signal), 36 ... Dropout compensation circuit, 37 ... Line noise canceller circuit, 38 ... Feedback comb filter circuit, 43 ... Feedback coefficient setting circuit, 60 ... Input terminal (feedback comb filter circuit) Input signal), 61, 62, 63, 64, 65 ... Route, 66 ... Output terminal (feedback comb filter circuit output signal).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Asami Kuroyanagi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi Media & Video Media Research Laboratories

Claims (5)

[Claims] 1. An FM-modulated luminance signal obtained by frequency-modulating a luminance signal and a low-frequency conversion color signal obtained by frequency-converting a carrier color signal into a low frequency band are frequency-multiplexed, and a magnetic tape is produced by a rotary head. In a helical scan magnetic recording / reproducing apparatus for recording in a direction oblique to the traveling direction of a circuit, a circuit for separating an FM-modulated luminance signal from a reproduced reproduced video signal, and a dropout for detecting a loss of the FM-modulated luminance signal. A detection circuit, an FM demodulation circuit for demodulating the FM-modulated luminance signal, a band limiting circuit for attenuating a portion corresponding to the chrominance signal band of the demodulated reproduction luminance signal, and a reproduction band-limited by the band limiting circuit. An adder circuit for adding the luminance signal and the high-frequency converted color signal, a delay circuit for delaying the output of the adder circuit for a predetermined horizontal synchronizing signal period, and a signal output from the delay circuit. A switch circuit that switches the demodulated reproduced luminance signal with a detection signal obtained by the dropout detection circuit, and a noise component included in the reproduced luminance signal from the output signal of the switch circuit and the output signal of the delay circuit Means, a means for subtracting the noise component from the output signal of the switch circuit, and a crosstalk component by forming a comb filter of the reproduced color signal using the output signal of the adder circuit and the output signal of the delay circuit. And a means for removing the noise component from the reproduction luminance signal while compensating for the loss of the signal due to a scratch on the tape while maintaining the reproduction luminance signal band. A signal processing circuit of a magnetic recording / reproducing apparatus, which is configured to remove crosstalk. 2. A signal processing circuit for a magnetic recording / reproducing apparatus according to claim 1, wherein the comb filter for the reproduced color signal is of a feedback type. 3. An FM-modulated luminance signal obtained by frequency-modulating a luminance signal and a low-frequency conversion color signal obtained by frequency-converting a carrier color signal into a low frequency band are frequency-multiplexed, and a magnetic tape is produced by a rotary head. In a helical scan magnetic recording / reproducing device that records in a direction oblique to the traveling direction of the device, select a recording signal and a reproduction signal at the input of the delay circuit so that one delay circuit can be used for both recording and reproduction. A switch circuit for switching a recording signal and a reproduction signal at the time of recording, a delay circuit delaying the output of the switch circuit for a predetermined horizontal synchronizing signal period, an output of the delay circuit and an output of the switch circuit. Means for separating the luminance signal and the color signal by configuring a comb filter for the luminance signal and a comb filter for the color signal, and a recording luminance signal separated from the recording video signal. Is subjected to FM recording and FM-modulated to obtain an FM-modulated luminance signal, and the recording color signal separated from the recording video signal is subjected to recording processing and frequency-converted to a low frequency to obtain a low-frequency conversion color signal. With such a configuration, at the time of reproduction, a circuit for separating the FM modulated luminance signal from the reproduced reproduced video signal, a dropout detection circuit for detecting a loss of the FM modulated luminance signal, and demodulating the FM modulated luminance signal. An FM demodulation circuit and a band limiting circuit for attenuating a portion corresponding to the chrominance signal band of the demodulated luminance signal,
An adding circuit for adding the luminance signal band-limited by the band limiting circuit and the high frequency conversion color signal, a delay circuit for delaying the output of the adding circuit for a predetermined horizontal synchronizing signal period, and a signal output from the delay circuit. And a switch circuit that switches the demodulated reproduced luminance signal with a detection signal obtained by the dropout detection circuit, and a noise component included in the reproduced luminance signal from the output signal of the switch circuit and the output signal of the delay circuit. A means for extracting, a means for subtracting the noise component from the output signal of the switch circuit, a signal for adding the output of the adder circuit and an output signal of the delay circuit are used to form a comb filter for the reproduced color signal, thereby forming a cross filter. Means for removing a talk component, the delay circuit is configured to separate a recorded video signal into a luminance signal and a chrominance signal at the time of recording, and at the time of reproduction, a reproduction signal is reproduced. While removing the noise component from the reproduced luminance signal and the crosstalk from the high-frequency conversion color signal while compensating for the loss of the signal due to the scratches on the tape, etc. A signal processing circuit of a characteristic magnetic recording / reproducing apparatus. 4. A delay circuit and an equalizer circuit for delaying an input recording video signal for a predetermined horizontal synchronizing signal period, the means for separating the luminance signal and the chrominance signal, and the output of the equalizer circuit according to claim 3. A subtraction circuit that subtracts from the recorded video signal to generate a comb filter of the recorded color signal, a bandpass filter circuit that attenuates components other than the color signal component of the output of the subtraction circuit, and a band limitation of the output of the bandpass filter. A band limiting circuit, an equalizer circuit that corrects a group delay time of the recorded video signal by adding a group delay time of the band pass filter circuit and a group delay time of the band limiting circuit, and an output of the equalizer circuit. An addition circuit for generating a comb filter of a recording luminance signal by subtracting the output of the band limiting circuit, and a flat group delay characteristic of the output of the addition circuit. The equalizer circuit, the signal processing circuit of a magnetic recording and reproducing apparatus characterized by being configured. 5. A signal processing circuit for a magnetic recording / reproducing apparatus according to claim 3, wherein the comb filter for the reproduced color signal is of a feedback type.