JP2642379B2 - Video signal recording and playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video signal recording / reproducing apparatus such as a video tape recorder integrated with a video camera, and in particular, modulates a luminance signal by FM and converts a chroma signal. The present invention relates to a video signal recording / reproducing apparatus which performs low-frequency conversion for recording and reproducing.

[Conventional technology]

2. Description of the Related Art Conventionally, in a video signal recording / reproducing apparatus (hereinafter, referred to as VTR) using a magnetic tape as a recording medium, as disclosed in Japanese Patent Publication No. 55-19116, for example,
In addition to the modulation, the chroma signal is frequency-converted into a band lower than the band of the FM-modulated luminance signal (hereinafter, referred to as FM luminance signal) (hereinafter, the frequency-converted chroma signal is referred to as a low-frequency converted chroma signal). ), FM luminance signal and low-frequency conversion chroma signal are frequency multiplexed and recorded and reproduced.

[Problems to be solved by the invention]

In a video signal recording / reproducing apparatus of such a system, a luminance signal is usually subjected to various signal processings such as noise removal and drop compensation for S / N improvement, thereby improving the image quality of a reproduced image. I have.

However, with regard to the color difference signal, the chroma signal obtained by quadrature two-phase modulation of the carrier is directly converted into a low band by a frequency converting means to form a low band converted chroma signal, which is magnetically recorded. At the time of recording on the medium and at the time of reproduction, the reproduced low-frequency-converted chroma signal is directly converted to the high-frequency band by the frequency conversion means to obtain the original carrier-frequency chroma signal. As described above, in the conventional video signal recording / reproducing apparatus, each color difference signal is processed in a modulated form, that is, as a chroma signal, so that noise such as a base clip or a noise canceller for a luminance signal is removed. Is difficult to perform, and dropout compensation is very difficult and is not generally employed because the continuity of the carrier phase in the chroma signal must be maintained.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem, and when recording and reproducing a color difference signal as a low-frequency conversion chroma signal, it is possible to improve the S / N of the color difference signal to realize an improvement in image quality of a reproduced image, An object of the present invention is to provide a recording and reproducing device.

[Means for solving the problem]

In order to achieve the above object, the present invention is a video signal recording / reproducing apparatus which is integrated with a video camera and frequency-multiplexes and records and reproduces a frequency-modulated luminance signal and a low-frequency conversion chroma signal. A first switch for selecting a chroma signal of the color video signal when recording an external color video signal, and selecting a reproduced low-frequency conversion chroma signal for reproduction during reproduction; Demodulated the macro signal or the low-frequency-converted chroma signal,
Demodulating means for outputting a second color difference signal; and third and third color difference signals to be recorded from the video camera or the first and second color difference signals.
A second switch for selecting a fourth color difference signal; processing means for performing signal processing on the color difference signal selected by the second switch; modulating the color difference signal output from the processing means; A first modulating means for forming a chroma signal and a second modulating means for modulating a color difference signal output from the processing means (or the demodulating means) during recording to form a low-frequency converted chroma signal are provided. .

(Operation)

The chroma signal of the external color video signal and the reproduced low-frequency converted chroma signal are demodulated into baseband color difference signals by the demodulation means and then subjected to predetermined processing by the processing means. Is converted into a chroma signal of a monitor color video signal, and at the time of recording, the color difference signal from the processing means (or the demodulation means) is modulated by the second modulation means to perform low-frequency conversion for recording. It becomes a chroma signal.

In this way, the reproduced low-frequency converted chroma signal is demodulated into a color difference signal as a baseband signal, and then modulated to be a chroma signal of a color video signal. For the chrominance signal, the signal processing used for the baseband luminance signal, for example, processing for removing noise such as base clipping and no-noise cancellation can be adopted. The drop-out compensation can be performed without considering the characteristics, and the above-described processing means can also perform such signal processing.

Therefore, the chroma signal obtained by the reproduction can be also subjected to the same signal processing as that of the luminance signal, and the S / N of the reproduced chroma signal is greatly improved, so that the image quality of the reproduced image is remarkably improved.

In addition, when the low-frequency conversion chroma signal is generated from the color-difference signal during recording, the color-difference signal is modulated by the second modulation means to obtain the low-frequency conversion chroma signal. Compared with the prior art in which a chroma signal is obtained by performing quadrature two-phase modulation, and the chroma signal is frequency-converted to obtain a low-band converted chroma signal, the quality of the obtained low-band converted chroma signal is less deteriorated.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking a VTR (camera integrated VTR) integrated with a video camera as an example.

FIG. 1 is a block diagram showing an embodiment of a video signal recording / reproducing apparatus according to the present invention, wherein 1 is a lens, 2 is a solid-state image pickup device, 3 is an amplifier, 4 is a camera signal processing circuit, 5 is a switch, 6 Is a peaking circuit, 7 is an AGC (automatic gain control) circuit, 8 is a waveform equalization circuit, 9 is an FM demodulation circuit, 10 is a de-emphasis circuit, 11 is a noise processing circuit, and 12 is a D / O.
(Dropout) Compensation circuit, 13 is a switch, 14 is an addition circuit, 15 is a counter addition circuit, 16 is an output terminal, 17 is an AGC
Circuit, 18 is a superimpose circuit, 19 is an emphasis circuit, 20 is a clip circuit, 21 is an FM modulation circuit, 22 is an addition circuit, 23 is a magnetic tape, 24 is a cylinder, 25 and 26 are video heads, 27 and 28 are Preamplifier, 29 is a switch, 30 and 30 'are guides, 31 and 32 are clamp circuits, 33 and 34 are superimpose circuits, 35 and 36 are switches, 37 and 38 are comb filters, 3
9,40 is a clamp circuit, 41,42 is a base clip circuit, 43,
44 is a burst level replacement circuit, 45 and 46 are switches, 47 and 48
Is a clamp circuit, 49 and 50 are multiplication circuits, 51 is an addition circuit, 52
Is BPF (Band Pass Filter), 53 is Switch, 54-58
Is an input terminal, 59 is a superimpose circuit, 60 is a switch, 61 is an ACC (automatic chroma control) circuit, 62 is an ACC detection circuit, 63 and 64 are multiplication circuits, 65 and 66 are switches, and 67 and 68 are LPFs.
(Low-pass filter), 69 and 70 are switches, 71 and 72 are clamp circuits, 73 and 74 are multiplication circuits, 75 is an addition circuit, 76 is a burst emphasis circuit, 77 and 78 are switches, 79 is a LPF, 80
Is a 4-phase rotation circuit, 81 and 82 are switches, 83 is a comparison amplifier, 84 is a loop filter, 85 is a switch, 86 is 90
相 Phase shift circuit, 87 is a phase detection circuit, 88 is a loop filter,
89 is a VCO (voltage controlled oscillator), 90 is a switch, 91 is a reference voltage source, 92 is an input terminal, 93 is a switch, 94 is an addition circuit,
95 is an AFC circuit, 96 is a VCO, 97 is a divide-by-2 circuit, 98 is a divide-by-4 circuit, and 99 and 100 are input terminals.

In the figure, a color video signal from a video camera and, for example, a received video signal (hereinafter referred to as an external color video signal) can be recorded and reproduced, and a lens 1, a solid-state imaging device 2, an amplifier 3. The camera signal processing circuit 4 forms a video camera, and the luminance signal of the external color video signal is supplied from the input terminal 57 and the chroma signal is supplied to the input terminal.
Input from 58 respectively. Here, the description will be made from the NTSC system to the VHS system. For this reason, the carrier frequency of the chroma signal is 3.58 MHz, and the carrier frequency of the low-band chroma signal is 4
0f _H (where, f _H is the horizontal scanning frequency) is.

Hereinafter, the operation of this embodiment will be described.
A case where the output signal of the video camera is recorded will be described. In this case, the switches 5,69,70 in FIG.
On the camera side, switches 13, 45, 46, 60, 77, 78, 81, 82, 90
On the REC side, the switches 35, 36, 65, 66, 85 are closed on the camera REC side, the switch 53 is closed on the (camera REC + PB) side, and the switch 93 is open.

From the camera signal processing circuit 4 of the video camera, a luminance signal Y and two color difference signals RY and BY are separately output. Each of these signals is a baseband signal, and a pulse (B) for forming a burst is generated every horizontal blanking period of one of the two color difference signals RY and BY (here, the color difference signal BY). Hereinafter, a burst pulse is added.

The luminance signal Y passes through the switch 5 and is supplied to the superimpose circuit 18 after the level fluctuation is removed by the AGC circuit 17. When a date, a title, and the like are added to the screen, the luminance component of the image signal representing these is supplied from the input terminal 56 to the superimpose circuit 18 as a luminance superimpose signal. Superimposed. The luminance signal Y output from the superimpose circuit 18 has its high-frequency component emphasized by an emphasis circuit 19, and a clipping circuit 20 clips a level component that causes overmodulation during FM modulation. The signal is supplied to become an FM luminance signal.

The color difference signals RY and BY are respectively supplied to the clamp circuit 3
After the blanking period is clamped at a fixed level at 1, 32, the blanking period is supplied to the superimpose circuits 33, 34, and supplied from the input terminals 54, 55 to the color difference component RY of the image signal representing the date and title, respectively. , BY are supplied as the RY superimpose signal and the BY superimpose signal, respectively, are superimposed on the color difference signals RY and BY, respectively. The superimposition on the color difference signals RY and BY is performed by replacing the DC voltage with the color difference signal RY during the RY superimpose signal period and by changing the color difference signal BY between the BY superimposed signal periods. The hue and the color saturation displayed on the screen can be arbitrarily and easily set by appropriately setting the levels of these DC voltages.

Needless to say, in the clamp circuits 31 and 32, the clamp is performed in a portion other than the burst pulse period in the blanking period.

The color difference signals RY and BY output from the superimpose circuits 33 and 34 are supplied to comb filters 37 and 38 after passing through switches 35 and 36, respectively. Interfering components are removed. Here, the comb filters 37 and 38 have base band comb filter characteristics, and have a highly accurate delay time (with an error of ± 3n) like a comb filter for a chroma signal having a carrier frequency of 3.58 MHz.
(approximately sec), and the accuracy can be greatly reduced. The color difference signals R-Y and B-Y output from the comb filters 37 and 38 are clamped by clamp circuits 39 and 40, respectively, during a period excluding the burst pulse period of the blanking period. Base clipping removes noise near the pedestal level. The color difference signals RY and BY output from the base clips 41 and 42 pass through switches 65 and 66, respectively, are band-limited by LPFs 67 and 68, and further pass through switches 69 and 70 to a clamp circuit 71. , 72
Then, similarly to the clamp circuits 31, 39, 32, and 40, they are clamped and supplied to the multiplication circuits 73 and 74.

The multiplication circuits 73 and 74, together with the addition circuit 75, constitute a quadrature two-phase modulation circuit for directly forming a low-frequency conversion chroma signal from the baseband color difference signals RY and BY. The carrier generation circuit for this purpose includes a four-phase rotation circuit 80, an AFC circuit 95, a VCO 96, a divide-by-2 circuit 97, and a divide-by-4 circuit 98. The output signal of the VCO 96 is compared in frequency with the horizontal synchronizing signal from the input terminal 100 by the AFC circuit 95, and the VCO 96 is controlled by the error voltage. Accordingly, the output frequency of the VCO96 is set to 320f _H. The output signal of VCO96 is
Also, is divided by two circuit 97, but further divided by divide-by-four circuit 98, four signals frequency from the divide-by-4 circuit 98 is 40f _H a and phases shifted by 90 ° Is output. The four-phase rotation circuit 80 is controlled by a head switching signal from an input terminal 99 and a horizontal synchronizing signal from an input terminal 100, and outputs the four output signals of the four-frequency dividing circuit 98 for one horizontal scanning period (hereinafter, referred to as "the horizontal scanning period"). The switching is selected every 1H, and two carrier signals whose phases are sequentially switched by 90 ° every 1H and whose phases are different from each other by 90 ° are output. As shown, two video heads 25 and 26 are provided on the cylinder 24, and the magnetic tape 23 is spirally wound around the outer periphery of the cylinder 24 by guides 30 and 30 'over substantially 180 degrees. When the vehicle runs in contact with the head, the head switching signal from the input terminal 99 indicates the rotation period of the cylinder 24 in which the video head 25 scans the magnetic tape 23 and the rotation period of the cylinder 24 in which the video head 26 scans the magnetic tape 23. The levels of the four-phase rotation circuit 80 are controlled by controlling the head switching signal.
The two carriers output from Video Heads 25 and 26
Assuming that the phase advances by 90 ° every 1H during the period in which one scans the magnetic tape 23, the phase delays by 90 ° every 1H during the period in which the other scans the magnetic tape.

In the multiplication circuit 73, the color difference signal R−
The carrier whose phase is delayed by 90 ° from the four-phase rotation circuit 80 from Y is balanced-modulated, and the multiplication circuit 74 uses the color difference signal BY from the clamp circuit 71 to carry out the balance modulation. Balance modulation of the other carrier.
Then, the output signals of the multiplying circuits 73 and 74 are added by an adding circuit 75 to form a low-frequency conversion chroma signal. A multiplying circuit 74 adds the color difference signal BY to the low-frequency conversion chroma signal.
The burst signal obtained by modulating the carrier with the burst pulse added during the horizontal blanking period is added.

The low-frequency converted chroma signal is processed by the burst emphasis circuit 76 so as to amplify the burst signal by 6 dB, passes through the switch 77, and has a band lower than the FM luminance signal output from the FM modulation circuit 21 by the LPF 79. The frequency is multiplexed with the FM luminance signal from the FM modulation circuit 21 by the addition circuit 22 through the switch 78. Adder circuit 22
Output signals of the video heads 25 and 26
And is recorded on the magnetic tape 23.

On the other hand, the luminance signal Y output from the superimpose circuit 18 and the color difference signals RY and BY output from the base clip circuits 41 and 42 are also used for monitoring and the like.

For this purpose, the luminance signal Y is transmitted via the switch 13 to
The signal is supplied to the adding circuit 14.

The color difference signals RY and BY output from the base clips 41 and 42 pass through the switches 45 and 46, respectively, and are clamped by the clamp circuits 47 and 48 in the same manner as the clamp circuits 31 and 32. The signals are supplied to the multiplication circuits 49 and 50. The multiplication circuits 49 and 50 together with the addition circuit 51 constitute a quadrature two-phase modulation circuit for forming a chroma signal having a carrier frequency of 3.58 MHz.
The carrier generation circuit for this is a 90 ° phase shift circuit 86,
It comprises a phase detection circuit 87, a loop filter 88, and a VCO 89. The output signal of the VCO 89 having a frequency of 3.58 MHz is supplied to the phase detection circuit 87, and the phase of the output signal is compared with a stable reference signal having a frequency of 3.58 MHz supplied from the input terminal 92 via the switch 85. The output error signal of the phase detection circuit 87 is corrected by a loop filter 88, and is passed through a switch 90 as a control signal.
Supplied to VCO89. Accordingly, the output signal of the VCO 89 is stabilized in phase with the reference signal from the input terminal 92. VC
The output signal of O89 is supplied as a carrier to the multiplication circuit 50, and after being phase-shifted by the 90 ° phase shift circuit 86, is supplied to the multiplication circuit 49 as a carrier.

The multiplying circuits 49 and 50 output color difference signals RY and BY in which a carrier having a frequency of 3.58 MHz is balanced-modulated, respectively, and these are added by an adding circuit 51 to obtain a chroma signal.
This chroma signal is band-limited by the BPF 52 and the switch 53
And the addition circuit 14 adds the luminance signal Y from the switch 13 to form a color video signal. This color video signal is supplied to a counter addition circuit 15, where the count value of the tape counter is superimposed as necessary and output from an output terminal 16.

As described above, when recording the output signal of the video camera, the baseband luminance signal Y, the color difference signals R-Y, B-
Since a recording signal consisting of an FM luminance signal and a low-frequency conversion chroma signal can be formed directly from Y, a chroma signal obtained by performing quadrature two-phase conversion of a conventional baseband color difference signal is frequency-converted to a low frequency. Compared to obtaining a low-frequency conversion chroma signal for recording, the quality of the low-frequency conversion chroma signal for recording obtained is less degraded. It becomes possible. Before the modulation, the luminance signal Y and the color difference signal R-
Processing for improving image quality can be performed on Y and BY.

Next, the recording operation of the external color video signal of this embodiment will be described. In this case, switches 5, 6
9,70 on the outside, switch 13,45,46,60,77,78,81,82,90
On the REC side, switches 35, 36, 65, 66, 85 On the side, switch 53 Each side is closed, and the switch 93 is open.

The external color video signal is supplied after being separated into a luminance signal Y and a chroma signal C, and the luminance signal Y is input from an input terminal 57.
The chroma signals C are input from the input terminals 58, respectively. The luminance signal Y passes through the switch 5 and is processed by the AGC circuit 17, the superimpose circuit 18, the emphasis circuit 19, and the clip circuit 20 in the same manner as the luminance signal Y output from the video camera.
The modulation circuit 21 forms an FM luminance signal and supplies it to the addition circuit 22. The luminance signal output from the superimpose circuit 18 is supplied to a monitor or the like via the switch 13 like the luminance signal Y output from the video camera.

The chroma signal C input from the input terminal 58 is supplied to a superimpose circuit 59, where the chroma signal C is superimposed so that the luminance signal is at a pedestal level during the period of the luminance superimpose signal from the input terminal 56 as necessary. The chroma signal C output from the superimpose circuit 59 is supplied to an ACC circuit 61 via a switch 60, and is supplied to an ACC detection circuit 62.
The level is controlled so that the level of the burst signal becomes constant by the detection output from. The chroma signal C output from the ACC detection circuit 61 is supplied to multiplication circuits 63 and 64.

The multiplication circuits 63 and 64 constitute a synchronous demodulation circuit. The 3.58 MHz carrier generation circuit in this case also includes a 90 ° phase shift circuit 86, a phase detection circuit 87, a loop filter 88, and a VCO 89, and the chroma signal output from the ACC circuit 61 is phase-shifted via a switch 85. By being supplied to the detection circuit 87, as described above, a 3.58 MHz carrier synchronized with the burst signal of the chroma signal is obtained from the VCO 89. The phase detection circuit 87 compares the phase of the burst signal of the chroma signal with the output signal of the VCO 89. For this purpose, although not shown, the phase detection circuit 87 or a switch
A burst gate is provided immediately before 85.

The output signal of the VCO 89 is supplied as a carrier to the multiplication circuit 64 via the switch 82, whereby the chroma signal C
, The baseband color difference signal BY is demodulated. The output signal of the VCO 89 is phase-shifted by a 90 ° phase shift circuit 86 and supplied to the multiplication circuit 63 via the switch 81 as a carrier. Thus, the color difference signal RY is demodulated from the chroma signal C.

These color difference signals RY and BY pass through switches 65 and 66, are band-limited by LPFs 67 and 68, pass switches 35 and 36, and the color difference signals RY and BY output from the video camera.
Similarly, the color difference signal RY is processed by the comb filter 37, the clamp circuit 39, and the base clip circuit 41, and the color difference signal BY is processed by the comb filter 38, the clamp circuit 40, and the base clip circuit 42. The color difference signals RY and BY output from the base clip circuits 41 and 42 are respectively connected to switches 69 and
After passing through 70 and being clamped by the clamp circuits 71 and 72, it is supplied to the multiplication circuits 73 and 74. The subsequent processing is the same as the processing for the color difference signals R-Y and B-Y output from the video camera. The low-frequency conversion chroma signal is supplied from the switch 78 to the addition circuit 22, and the magnetic tape 23 is supplied together with the FM luminance signal.
Will be recorded.

Chroma signal for monitor etc. is obtained from ACC circuit 61,
The signal is supplied to the adding circuit 14 via the switch 53.

The burst replacement circuits 43 and 44 replace the burst pulses of the color difference signals RY and BY output from the base clip circuits 41 and 42 with burst pulses of a correct level.
When recording an external color video signal, the chroma signal C is synchronously demodulated by the multiplying circuits 63 and 64, and at this time, synchronously demodulated with the burst signal to become a burst pulse. Accordingly, a burst pulse is added to the color difference signals RY and BY output from the base clip circuits 41 and 42 during the horizontal blanking period. However, in the case of the NTSC system, since the output signal of the VCO 89 is phase-synchronized with the burst signal of the chroma signal C, the color difference signal RY output from the base clip circuit 41 does not include a burst pulse.

By the way, if the level of the chroma signal C output from the ACC circuit 61 fluctuates, the level of the burst signal also fluctuates.
The level of the burst pulse of the color difference signal BY output from the base clip circuit 42 also varies. This color difference signal B-
The Y burst pulse is compared in level with the reference level signal indicating the correct level of the burst pulse set in the burst replacement circuit 44 by the ACC detection circuit 62, and the difference signal between these signals is A
It is supplied to the ACC circuit 61 as a CC control voltage. As a result, the level of the chroma signal C is controlled in the ACC circuit 61 so that the burst level of the chroma signal C becomes equal to the reference level set in the burst level replacement circuit 44.

As described above, even when an external color video signal is recorded, the processing for improving the image quality of the chroma signal can be performed, and the processing means includes processing of the color difference signal output from the video camera. Means can also be used.

Next, the reproducing operation of this embodiment will be described. In this case, switches 13,45,46,60,77,78,81,82,90 are on the PB side, switches 35,36,65,66,85 are on the camera ▲ ▼ side,
The switches 53 close to the (camera REC + PB) side, respectively, and the switch 93 closes.

The playback signals of video heads 25 and 26 are preamplifiers 27 and 28, respectively.
, And are alternately selected by a switch 29 controlled by a head switching signal from an input terminal 99 to become a continuous reproduced signal.

On the other hand, the reproduced signal is supplied to a peaking circuit 6, where an FM luminance signal is extracted and its frequency characteristic is corrected. The extracted FM luminance signal is subjected to the AGC circuit 7 to remove the level fluctuation of each of the video heads 25 and 26, processed by the waveform equalization circuit 8, and then demodulated to the baseband luminance signal by the FM demodulation circuit 9. This luminance circuit is a day-emphasis circuit
After de-emphasis at 10, noise removal processing such as noise clipping and noise cancellation is performed at the noise processing circuit 11, drop-out compensation processing is performed at the D / O compensation circuit 12, and then supplied to the addition circuit 14 via the switch 13. You.

The reproduction signal output from the switch 29 is supplied to the LPF 79 via the switch 77, and a low-frequency conversion chroma signal is extracted. This low-frequency conversion chroma signal is
Is supplied to the ACC circuit 61 through the ACC circuit 61, and the level of the burst signal is controlled so as to be constant.
4 and demodulated into baseband color difference signals RY and BY. These color difference signals RY and BY pass through switches 65 and 66, respectively, are band-limited to 500 KHz by LPFs 67 and 68, are further supplied to comb filters 37 and 38 through switches 35 and 36, and are supplied to the magnetic filters 37 and 38. Unnecessary components such as crosstalk components from adjacent tracks when reproduced from the tape 23 are removed, and drop-out compensation is also performed as described later. The color difference signal R output from the comb filters 37 and 38
-Y and BY are clamped by the clamp circuit 39 during periods other than the burst pulse period of the blanking period, and the base clip circuits 41 and 42 remove noise by the base clip.

Here, the ACC detection circuit 62 converts the reference level signal from the burst level replacement circuit 44 and the color difference signal BY output from the base clip circuit 42, as in the case of recording the external color video signal described above. The level is compared with the burst pulse, and an ACC control voltage of the ACC circuit 61 is output.
Since the 6 dB emphasis is performed by the above, the level of the reference level signal supplied from the burst level replacement circuit 44 to the ACC detection circuit 62 is 6 dB lower than the normal burst level.
It has become something that has been raised only.

The carrier generation circuits of the multiplication circuits 63 and 64 include a four-phase rotation circuit 80, a comparison amplifier 83, a loop filter 84,
Adder circuit 94, AFC circuit 95, VCO 96, 2 divider circuit 97, 4 divider circuit 98
From As explained earlier, VCO96 is an AFC circuit
I go-between frequency to 95 the output signal of the outputs a signal of 320f _H,
This is divided by a divide-by-2 circuit 97 and a divide-by-4 circuit 98 to reduce the frequency.
40f to each other 90 DEG one phase four different signal _H is formed, the four-phase Roteshiyon circuit 80 for each sequentially selects the output signal of the divide-by-4 circuit 98 IH 90 DEG one phase is switched with each other
Two carriers having phases different from each other by 90 ° are formed, and the direction of change in the phase of these two carriers is the same as that during recording. That is, the four-phase rotation circuit 80 controls the carrier supplied to the multiplying circuit 63 so that the phase of the carrier of the color difference signal RY subjected to the balanced modulation in the low-frequency conversion chroma signal output from the ACC circuit 61 matches the phase. The phase is changed by 90 ° every 1H, and the four-phase rotation circuit 80 changes the phase of the carrier supplied to the multiplication circuit 64 so that the phase of the carrier of the color difference signal BY that is similarly modulated is in phase. 90 per 1H
Change the phase by ゜. In this manner, the four-phase rotation circuit 80 is used as a reference for defining the phase of each carrier.
The head switching signal is used.

The reproduced low-frequency converted chroma signal has phase fluctuations,
When this is synchronously demodulated by a carrier created from the output of the VCO 96 having a fixed phase, the hue and the color saturation change. In order to prevent this, a phase control system of the VCO 96 including the comparison amplifier 83 and the loop filter 84 is provided. Now, the reproduced low-frequency converted chroma signal has a phase variation, and the multiplication circuit 63
When a phase error occurs between the balanced modulated chrominance signal RY supplied to and the carrier, the demodulated chrominance signal R-Y
Unwanted pulses (hereinafter, referred to as pseudo-burst pulses) due to the burst signal are generated during the Y horizontal blanking period.

The comparison amplifier 83 is supplied with an output color difference signal RY of the clamp circuit 39 to which the demodulated color difference signal RY is supplied and a reference level signal representing a blanking level at which the color difference signal RY is clamped. The level of the reference level signal is compared with the pseudo burst pulse period of the blanking period in the color difference signal RY. These level differences represent the phase difference between the balanced-modulated color difference signal RY in the low-frequency converted chroma signal supplied to the multiplying circuit 63 and the carrier from the carrier generating circuit. The output signal of the comparison amplifier 83 representing this level difference is corrected by the loop filter 84, passes through the switch 93, is added to the output signal of the AFC circuit 95 by the addition circuit 94, and is supplied to the VCO 96. As a result, even if there is a phase change in the reproduced low-frequency converted chroma signal, the VCO 96 is phase-controlled so that the phase difference between the reproduced low-frequency converted chroma signal and the carrier supplied to the multiplying circuits 63 and 64 is eliminated. Thus, the color difference signals RY and BY which are not affected by the phase fluctuation are obtained from the multiplying circuits 63 and 65.

The color difference signal R output from the base clip circuits 41 and 42
-Y and BY are replaced with burst pulses of the correct level by burst level replacement circuits 43 and 44, respectively, and then the switch 4
5 and 46, the signal is clamped by the clamp circuit 47 as described above, and supplied to the multiplication circuits 49 and 50. The carrier generation circuit of these multiplication circuits 49 and 50 comprises a 90 ° phase shift circuit 86, VCO 89, and a reference voltage source 91. With the reference voltage from the reference voltage source 91, the VCO 89 generates a stable 3.58 MHz carrier. . This carrier is supplied to the multiplication circuit 50,
The phase is shifted by a 90 ° phase shift circuit 86 and supplied to a multiplication circuit 49.
Accordingly, a quadrature two-phase modulation circuit including the multiplication circuits 49 and 50 and the addition circuit 51 forms a chroma signal having a carrier frequency of 3.58 MHz.

The chroma signal is band-limited by the BPF 52, passes through the switch 53, and is added to the luminance signal from the D / O compensation circuit 12 by the adding circuit 14 to form an NTSC color video signal for a monitor or the like. .

In this way, even during reproduction, the chroma signal is processed for improving the image quality, and the processing means for recording is also used as the processing means for this purpose.

FIG. 2 is a block diagram showing one specific example of the comb filters 37 and 38 in FIG. 1. 101 is a 1H delay circuit, 102 is an adder circuit, 103 is a switch, 104 is an input terminal, and 105 is an output terminal. It is.

In the figure, a baseband color difference signal (RY or BY) is input from an input terminal 104. Switch 10
3 when recording Side, but during playback, the drop-out period D
・ Close to O side. The 1H delay circuit 101 includes a CCD delay circuit and an LPF for removing a clock.

The baseband color difference signal input from the input terminal 104 passes through the switch 103, directly to the addition circuit 102, and to the 1H
The signal is delayed by the delay circuit 101 and supplied to the addition circuit 102. 1H
The delay circuit 101 and the adder circuit 102 provide comb filter characteristics that match the frequency spectrum of the baseband color difference signal, thereby providing frequency-interleaved noise (interleave noise) for color difference signals such as crosstalk from adjacent tracks. ) Is removed.

Also, during the dropout period, switch 103
Closed to the O side, the color difference signal output from the addition circuit 102 is supplied to the 1H delay circuit 101 and the addition circuit 102 via the switch 103. Thereby, the dropout of the color difference signal is compensated.

As described above, the color difference signal is compensated for the dropout and is subjected to quadrature quadrature modulation as described with reference to FIG. 1, so that the carrier phase of the chroma signal obtained thereby maintains continuity.

FIG. 3 is a block diagram showing another specific example of the comb filters 37 and 38 in FIG. 1, wherein 106 and 107 are subtraction circuits, 108 and 109 are switches, 110 and 111 are amplifiers,
Parts corresponding to those in the figures are given the same reference numerals.

In the figure, at the time of recording, the switch 108 is closed to the REC side, and a comb filter characteristic is obtained by the 1H delay circuit 101 and the addition circuit 102.

At the time of reproduction, the switch 108 closes to the PB side and the subtraction circuit 10
6,107 and one of the amplifiers 110,111 are added to form a feedback comb filter. The input and output chrominance signals of the 1H delay circuit 101 are subtracted by a subtraction circuit 107, and a valley signal of the frequency spectrum of the chrominance signal is extracted, and is amplified to 1.2 times or 0.3 times by an amplifier 110 or 111. The color difference signal supplied to and input to 106 is subtracted. As a result, the valleys of the frequency spectrum of the color difference signal are more sufficiently attenuated, and the effect of suppressing interleave noise and the like is further increased.

The switch 109 is controlled to be switched depending on the presence or absence of the correlation (that is, vertical correlation) of the signals around 1H, and when there is the correlation, the switch 109 selects the output signal of the amplifier 110. When the difference between the signals is 5 IRE or more, the switch 109 selects the output signal of the amplifier 111 because there is no correlation. In the burst pulse period, the switch 109 selects the output signal of the amplifier 111. During the dropout period, the switch 103 closes to the DO side as in the specific example of FIG.

FIG. 4 is a block diagram showing still another specific example of the comb filters 37 and 38 in FIG. 1, and portions corresponding to FIG. 3 are denoted by the same reference numerals.

This example shows a switch 103 for dropout compensation.
Are provided at the subsequent stage of the switch 108, and the other parts are the same as those of the comb filter shown in FIG. 3, and the operation is the same as that of the comb filter shown in FIG.

FIG. 5 is a block diagram showing a specific example of the burst level replacement circuit 44 in FIG. 1, wherein 112 to 114 are input terminals, 115 is a reference voltage source, 116 to 119 are switches, and 120 to 122.
Is a buffer amplifier, 123 and 124 are resistors, 125 and 126 are output terminals, and 127 and 128 are current sources.

In the figure, a color difference signal BY is input from an input terminal 112.
However, a blanking pulse is output from the input terminal 113 to the input terminal 1
From 14, burst pulses are input respectively. During a period other than the blanking period, the switch 116 is closed to the A side, and the color difference signal BY input from the input terminal 112 is switched to the switch 116,
The signal passes through a buffer amplifier 120, a resistor 123, and a buffer amplifier 121, and is supplied from an output terminal 125 to a switch 46 (FIG. 1).

When a blanking pulse is input to the input terminal 113 during the blanking period of the color difference signal BY, the switch 116 switches to B
The reference voltage source 115 is closed and connected to the buffer amplifier 120, and a DC voltage having a correct pedestal level determined by the output voltage level of the reference voltage source 115 is obtained at the output terminal 125. When a burst pulse is input from the input terminal 114 during this blanking period, the switches 117 and 118 are closed, and the current of the value I flows from the reference voltage source 115 via the resistor 123 by the current source 127, and the current source 128 By the same resistance 1
A current of 2I flows through 24. The resistance values of the resistors 123 and 124 are set equal to R. The value I of the current flowing through the resistor 123
Is set so that the output voltage of the buffer amplifier 121 is at a normal burst level, and the resistance value of the resistor 124 is equal to the resistance value of the resistor 123. Therefore, the output voltage of the buffer amplifier 122 is twice as high as the normal burst level. That is, it is equal to the level when the burst signal of the normal level is subjected to 6 dB emphasis by the burst emphasis circuit 76 (FIG. 1) or the like.

Therefore, in both recording and playback, the output terminal
A color difference signal BY having a pedestal level and a burst level set normally is output to 125 and supplied to the PB side of the switch 46 (FIG. 1). At the time of recording, the switch 119 is closed to the PEC side, and the color difference signal BY output from the buffer amplifier 121 is supplied from the output terminal 126 to the ACC detection circuit 62 (FIG. 1). At the time of reproduction, the switch 119 is closed to the PB side, and the color difference signal BY having the burst level output from the buffer amplifier 122 being twice the normal level is supplied from the output terminal 126 to the ACC detection circuit 62.

In FIG. 5, the burst level replacement circuit 43 includes an input terminal 114 and a switch 117 in the case of the NTSC system.
~ 119, buffer amplifier 122, current source 127, 128, output terminal 126
Becomes unnecessary.

FIG. 6 is a block diagram showing another embodiment of the video signal recording / reproducing apparatus according to the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals.

In the embodiment shown in FIG. 1, the base clip circuits 41, 4
The baseband color difference signals RY and BY output from 2 are directly supplied to the burst level replacement circuits 43 and 44, respectively.
In the embodiment shown in FIG. 6, the switches 69 and 70 respectively select the base clip circuits 41 and 42 even during reproduction, and
The output signals of 1,72 are also supplied to the replacement circuits 43,44 at the burst level, and at the time of reproduction, the base clip circuit 4
After the color difference signals RY and BY output from 1, 42 are clamped by the clamp circuits 71 and 72, respectively, they are supplied to the burst level replacement circuits 43 and 44. Other configurations and operations are the same as those of the embodiment shown in FIG.

According to this embodiment, at the time of reproduction, the color difference signals RY, BY
After the is clamped and the reference level becomes constant, the pedestal level and burst level are replaced and set.
The setting accuracy of these levels is improved.

FIG. 7 is a block diagram showing still another embodiment of the video signal recording / reproducing apparatus according to the present invention, wherein 44 'is a burst level replacement circuit, 129 is a burst de-emphasis circuit, and corresponds to FIG. The same reference numerals are given to the portions to be performed.

In this embodiment, a burst de-emphasis circuit 129 is provided between the ACC circuit 61 and the multiplication circuits 63 and 64.
And the switches 69 and 70 in FIG.
The color-difference signals RY and BY output from 8 are switched to switches 35 and 36.
And a quadrature two-phase modulation through the clamp circuits 71 and 72 to form a low-frequency conversion chroma signal.
It differs from the embodiment of the figure.

The burst de-emphasis circuit 129 performs de-emphasis of the burst signal only at the time of reproduction, and simply passes the chroma signal C at the time of recording. At the time of reproduction, the burst pulse of the color difference signal 42 output from the base clip circuit 42 is returned to the original level by the operation of the burst de-emphasis circuit 129, and the base clip circuit is provided to the ACC detection circuit 62. Color difference signal output from 42
The burst pulse of 42 may be compared with the normal burst level set by the burst level replacement circuit 44 '.
For this reason, in FIG. 5, the switches 118 and 119, the buffer amplifier 122, the resistor 124, the output terminal 126, and the current source 128 are not required for the burst level replacement circuit 44 '.
The chrominance signal BY output from 25 may be supplied to the ACC detection circuit 62. Further, as shown in FIG. 7, the chrominance signal BY output from the switch 46 at the subsequent stage of the burst level replacement circuit 44 'may be supplied to the ACC detection circuit 62. In this case, when recording an external color video signal,
Since the two input color difference signals BY of the ACC detection circuit 62 are equal, the ACC circuit 61 is set to a constant gain.

In this embodiment, when recording an external color video signal, the color difference signals RY and BY to be recorded are not processed by the comb filter and the base clipping circuit. Therefore, a monitor with high image quality can be realized.

FIG. 8 is a block diagram showing still another embodiment of the video signal recording / reproducing apparatus according to the present invention, wherein 130 is a phase comparison circuit, 131 and 132 are switches, and parts corresponding to FIG. I'm wearing it.

In the embodiment shown in FIG.
The level and the pedestal level of the burst pulse duration of the color difference signals R-Y base band outputted from the carrier generating circuit 40f _H, compared with comparison amplifier 83, its output signal via the loop filter 84 VCO 96 In this case, the output phase of the VCO 96 is controlled, and the phase of the carrier for synchronous demodulation of the reproduced low-frequency-converted chroma signal is changed according to the phase fluctuation included in the low-frequency-converted chroma signal.

On the other hand, in FIG. 8, switches 131 and 132 are provided so that the Vs in the 3.58 MHz carrier generation circuit can be
By supplying the carrier from the CO 89 and the carrier from the 90 ° phase shift circuit 86 to the multiplication circuits 74 and 73, respectively, the addition circuit 75 is provided.
A 3.58 MHz carrier chroma signal is generated, and the phase variation of the reproduced low-frequency conversion chroma signal is detected by comparing the phase of the burst signal of the chroma signal with the output signal of the VCO 89 by the phase comparison circuit 130, This, in carrier generating circuit 40f _H, by supplying to the VCO 96 via the loop filter 84, thereby controlling the output phase of the VCO 96.

The configuration and operation of the other parts are the same as those of the embodiment shown in FIG.

In the above embodiments, the description has been given of the video signal of the NTSC system. However, it goes without saying that the present invention is applicable to video signals of other systems.

Further, in each of the above embodiments, as shown in FIGS. 2 to 4, the D / O compensation circuit is included in the comb filters 37 and 38, but the D / O compensation circuit is provided separately from the comb filters 37 and 38. -Needless to say, an O compensation circuit may be provided.

〔The invention's effect〕

As described above, according to the present invention, a color video signal, a luminance signal is FM-modulated, and a chroma signal is subjected to low-frequency conversion for recording and reproduction. Since the low-band conversion chroma signal is obtained directly from the baseband color-difference signal, it is possible to record the low-band conversion chroma signal with little quality deterioration, and it is also possible to record the S / S of the color-difference signal forming the chroma signal. Processing can be performed to improve N, and an excellent effect of greatly improving the image quality of a reproduced image can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a video signal recording / reproducing apparatus according to the present invention, and FIGS. 2, 3 and 4 each show an embodiment of a comb filter in FIG. FIG. 5 is a block diagram showing an example of a burst level replacement circuit in FIG. 1, and FIGS. 6, 7, and 8 are block diagrams showing another example of a video signal recording / reproducing apparatus according to the present invention. FIG. 14 is a block diagram showing an embodiment of the present invention. 4 camera processing circuit, 9 FM demodulation circuit, 14 addition circuit, 16 output terminal of color video signal, 21 FM modulation circuit, 22 addition circuit, 23 magnetic tape, 25 , 26…
… Video head, 37,38 …… Comb filter, 41,42 ……
Base clip circuit, 43, 44, 44 '... burst level replacement circuit, 49, 50 ... multiplication circuit, 51 ... addition circuit, 57 ...
Luminance signal input terminal for external color video signal, 58 Chroma signal input terminal for external color video signal, 61 ACC circuit, 62 ACC detection circuit, 63, 64 Multiplication circuit, 73, 74
... Multiplication circuit, 75 ... Addition circuit, 76 ... Burst emphasis circuit.

Continuation of front page (56) References JP-A-62-264792 (JP, A) JP-A-62-200892 (JP, A) JP-A-59-158690 (JP, A)

Claims (4)

(57) [Claims] 1. A video signal recording / reproducing apparatus which is integrated with a video camera, frequency-multiplexes a frequency-modulated luminance signal and a low-frequency conversion chroma signal, and records / reproduces the signal. A first switch for selecting a chroma signal of the color video signal and selecting a reproduced low-frequency conversion chroma signal during reproduction, and a macro signal or the low-frequency conversion chroma signal selected by the first switch. Demodulating means for demodulating a signal and outputting first and second color difference signals; and a third means for selecting the first and second color difference signals or the third and fourth color difference signals to be recorded from the video camera. 2 switch; processing means for processing the color difference signal selected by the second switch; and first modulation for modulating the color difference signal output from the processing means to form a chroma signal of a color video signal. hand When, during recording, a color difference signal outputted from said processing means to modulate,
And a second modulating means for forming a low-frequency conversion chroma signal. 2. A video signal recording / reproducing apparatus which is integrated with a video camera, frequency-multiplexes a frequency-modulated luminance signal and a low-frequency conversion chroma signal, and records / reproduces the color signal. A first switch for selecting a chroma signal of the color video signal and selecting a reproduced low-frequency conversion chroma signal during reproduction; and the chroma signal or the low-frequency conversion chroma selected by the first switch. Demodulating means for demodulating a signal and outputting first and second color difference signals; and a third means for selecting the first and second color difference signals or the third and fourth color difference signals to be recorded from the video camera. 2 switch; processing means for processing the color difference signal selected by the second switch; and first modulation for modulating the color difference signal output from the processing means to form a chroma signal of a color video signal. hand When, during recording, the second for modulating the color difference signal output from the processing means or the demodulation means to form the low-band converted chroma signal
A video signal recording / reproducing apparatus, comprising: 3. A video signal recording / reproducing apparatus according to claim 1, wherein said processing means has a burst level replacement means for setting at least a burst pulse level in said color difference signal to a specified level. 4. The video signal recording / reproducing apparatus according to claim 1, wherein said processing means includes at least a base clip circuit.