JPH01200797A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the picture quality of a picture by modulating two color difference signals, forming a low area conversion chroma signal for a recording, demodulating the chroma signal, forming two color difference signals, processing and improving the S/N of the color difference signal. CONSTITUTION:A luminance signal Y and two color difference signals R-Y and B-Y are outputted from the signal processing circuit 4 of a video camera, the signal Y turns to an FM luminance signal through an AGC 17, a superimposing circuit 18, circuits 19 and 20 by a circuit 21. The signals R-Y and B-Y are respectively inputted to clamp circuits 31 and 32, superimposing circuits 33 and 34, filters 37 and 38, clamp circuits 39 and 40, circuits 41 and 42, switches 65 and 66, LPF 67 and 68, clamp circuits 71 and 72, and multiplication circuits 73 and 74. A carrier from a circuit 80 is balance-modulated on the circuits 73 and 74 by the signals R-Y and B-Y. The output signal is added on a circuit 75 and the low frequency conversion chroma signal is formed. This signal is processed on a circuit 76, frequency-multiplexed 22 with the luminance signal from the FM modulation circuit 21 through an LPF 79 and supplied to video heads 25 and 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal recording and reproducing device such as a video tape recorder integrated with a video camera, and in particular,
The present invention relates to a video signal recording and reproducing apparatus that performs FM modulation on a luminance signal and performs low frequency conversion on a chroma signal for recording and reproduction.

[Conventional technology]

-ζ - Conventionally, in a video signal recording and reproducing apparatus (hereinafter referred to as a VTR) using magnetic tape as a recording medium, as disclosed in Japanese Patent Publication No. 55-19116, a luminance signal is FM modulated and a chroma signal is modulated. The signal is frequency-converted to a band lower than the band of the FM-modulated luminance signal (hereinafter referred to as FM luminance signal), and the chroma signal frequency-converted in this way is hereinafter referred to as low-frequency converted chroma signal)
Recorded by frequency multiplexing with MFM luminance signal area conversion chroma signal.

It's playing.

[Problem to be solved by the invention]

In video signal recording and reproducing devices of this type, the luminance signal is usually subjected to various types of signal processing to improve the S/N ratio, such as noise removal and drop compensation, thereby improving the image quality of the reproduced image. There used to be.

However, for color difference signals, the chroma signal obtained by quadrature two-phase modulation of the carrier is directly converted to a low frequency band by a frequency conversion means to form a low frequency converted chroma signal, and this is transferred to a magnetic recording medium. In addition to recording
At the time of reproduction, the reproduced low frequency converted chroma signal is directly converted to a high frequency frequency by the frequency conversion means to obtain a chroma signal of the original carrier frequency. In this way, in conventional video signal recording and reproducing devices, each color difference signal is processed in a modulated form, that is, as a chroma signal. It is difficult to carry out such processing, and dropout compensation is also very difficult because it requires maintaining the continuity of the carrier phase in the chroma signal, so it is not generally employed.

It is an object of the present invention to provide a video camera which solves such problems and improves the S/N ratio of the color difference signal when recording and reproducing the color difference signal as a low frequency converted chroma signal, thereby improving the image quality of the reproduced image. An object of the present invention is to provide a signal recording and reproducing device.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a means for modulating two color difference signals to generate a low frequency converted chroma signal for recording, and a means for demodulating the reproduced low frequency converted chroma signal to generate two color difference signals. Means for generating a signal, means for processing the color difference signal, and means for modulating the color difference signal processed by the means to generate a chroma signal of a video signal are provided.

[For production]

The color difference signal obtained by demodulating the reproduced low-frequency converted chroma signal is a baseband signal, and therefore, the color difference signal includes base clipping, noise canceling, etc. used for the baseband luminance signal. In addition, dropout compensation can be performed without considering carrier phase continuity.

In this way, signal processing equivalent to luminance signals is possible,
The S/N ratio of the color difference signal is significantly improved, and the quality of the reproduced image is significantly improved.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of a video signal recording and reproducing apparatus according to the present invention, in which 1 is a lens, 2 is a solid-state image sensor, 3 is an amplifier, 4 is a camera signal processing circuit, 5 is a switch, and 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
11 is a de-emphasis circuit, 11 is a noise processing circuit, and 12 is a de-emphasis circuit.
is a D・○ (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, and 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, 25.26 is a video head, 27
．． 28 is a preamplifier, 29 is a switch, 30.30' is a guide, 31 and 32 are clamp circuits, 33.34 is a superimpose circuit, 35.36 is a switch, 37.3
8 is a comb filter, 39.40 is a clamp circuit, 41
．． 42 is a base clip circuit, 43.44 is a burst level replacement circuit, 45 and 46 are switches, 47.48 is a clamp circuit, 49.50 is a multiplication circuit, 51 is an addition circuit,
52 is a BPF (pan q-dopass filter), 53 is a switch, 54 to 58 are input terminals, 59 is a superimpose circuit, 60 is a switch, 61 is an ACC (automatic chroma control) circuit, and 62 is an ACC
Detection circuit, 63.64 is a multiplication circuit, 65.66 is a switch, 67 and 68 are LPF (low pass filter), 6
9゜70 is a switch, 71.72 is a clamp circuit, 73
．． 74 is a multiplication circuit, 75 is an addition circuit, 76 is a burst emphasis circuit, 77 and 78 are switches, and 79 is an LPF.
, 80 is a four-phase rotation circuit, st 82 is a switch, 83 is a comparison amplifier, 84 is a loop filter, 85 is a switch, 86 is a 90° 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 adder circuit, 95 is an AFC
The VCO 197 is a frequency divider circuit, 96 is a frequency divider circuit, 98 is a frequency divider circuit, and 99 and 100 are input terminals.

In the same figure, the lens 1. Solid-state image sensor 2. Amplifier 3. The camera signal processing circuit 4 constitutes a video camera, and the luminance signal of the external color video signal is inputted from an input terminal 57, and the chroma signal is inputted from an input terminal 58. Here, the NTSC system and VH3 system will be explained, and for this purpose, the carrier frequency of the chroma signal is 3.58 MHz, and the carrier frequency of the low-frequency chroma signal is 40 fH' (where fH is the horizontal scanning frequency).

The operation of this embodiment will be described below, but first, the case where an output signal from a video camera is recorded will be described. In this case, in FIG. 1, switches 5.69.
70 is on the camera side, switches 13°45, 46.60.
77, 78, 81, 82, 90 are closed to the REC side, switches 35, 36, 65, 66, 85 are closed to the camera REC side, switch 53 is closed to the (camera RFC + PB) side, and switch 93 is open. ing.

The camera signal processing circuit 4 of the video camera separately outputs a luminance signal Y and two color difference signals RY and BY. These are all baseband signals, and
One of the two color difference signals R-Y and B-Y (here,
A pulse for forming a burst (hereinafter referred to as a burst pulse) is added to each horizontal blanking period of the color difference signal B-Y.

The luminance signal Y passes through the switch 5, and after level fluctuations are removed by the AGC circuit 17, it is supplied to the superimpose circuit 18. Here, when adding a date, title, etc. to the screen, the luminance component of the image signal representing these is
The luminance superimpose signal is supplied from the input terminal 56 to the superimpose circuit 18 and superimposed on the luminance signal Y. Superimpose circuit 1
The luminance signal Y output from 8 is sent to the emphasis circuit 19.
After the high-frequency components are emphasized in the clipping circuit 20 and the level components that cause overmodulation during FM modulation are clipped in the clipping circuit 20, the signal is supplied to the FM modulation circuit 21 to become an FM luminance signal.

Further, the color difference signals R-Y and B-Y are respectively output from the clamp circuit 9.
After the blanking period is clamped to a constant level at 31.32, it is supplied to the superinvoice circuit 33.34, and the color difference components of the image signal representing the date and title, respectively, are output from the input terminals 54.55. R-
Y, B-Y is the R-Y superimposed signal, B-,
When supplied as a Y superimposed signal, it is superimposed on the color difference signals R-Y and B-Y, respectively.

Superimposition on these color difference signals R-Y and B-Y is performed during the R-Y superimpose signal period.
By replacing the DC voltage with the color difference signal B-Y during the B-Y superimposed signal period, the hue and color displayed on the screen can be adjusted by appropriately setting the levels of these DC voltages. The degree of saturation can be set arbitrarily and easily.

It goes without saying that the clamp circuits 31 and 32 perform clamping in the blanking period except for the burst pulse period.

The color difference signals R-Y and B-Y output from the superimpose circuits 33 and 34 pass through switches 35 and 36, respectively, and then are supplied to comb filters 37 and 38 to avoid leakage of the luminance signal Y. Interfering components are removed = 12-. Here, the comb filters 37 and 38 have baseband comb filter characteristics, and have a high precision delay time (with an error of ±3n') like a comb filter for a chroma signal with a carrier frequency of 3.58 MHz. sec) is not necessary, and the accuracy can be significantly reduced compared to this. Color difference signal R output from comb filters 37 and 38
-Y and B-Y are each clamped by a clamp circuit 39.40 during a period excluding the burst pulse period of the blanking period, and base clipped by a base clip circuit 41.42 to remove noise near the pedestal level. .

Color difference signal R output from base clip 41.4'2
-Y.

B-Y are respectively switches 65. Through '66, LPF6
After the band is limited at 7°68, the switch 69.
70, the clamp circuits 31, 39, 32. ' As in 40, the signal is clamped and supplied to 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 converted chroma signal from the baseband color difference signals R-Y and B-Y. Further, a carrier generation circuit for this purpose is a four-phase rotation circuit 80. AFC circuit 95. VCO96,
A frequency divider circuit 97 and a frequency divider circuit 98 are constructed. V
The output signal of CO96 is input to input terminal 100 at AFC circuit 95.
The frequency is compared with the horizontal synchronizing signal from the VCO 96, and the VCO 96 is controlled by the error voltage. As a result, VCO9
The output frequency of 6 is set to 320f11. ■C○9
The output signal of No. 6 is also frequency-divided by a divide-by-2 circuit 97 and further divided by a divide-by-four circuit 98;
8 outputs four signals with a frequency of 4oro and whose phases are shifted by 90 degrees from each other. The four-phase rotation circuit 80 is controlled by a head switching signal from an input terminal 99 and a horizontal synchronization signal from an input terminal 100.
The four output signals of the frequency dividing circuit 98 are switched and selected every horizontal scanning period (hereinafter referred to as IH), and 90° carrier signals are sequentially output for each IH. Here, as shown in the figure, two video heads 25° 26 are provided on the cylinder 24, and the cylinder 24 is
The magnetic tape 2 is spirally spread over approximately 180° around the outer periphery of the
3, the head switching signal from the input terminal 99 corresponds to the rotation period of the cylinder 24 during which the video head 25 scans the magnetic tape 23 and the rotation period of the cylinder 24 during which the video head 26 scans the magnetic tape 23. By controlling this head switching signal, the two carriers output from the 4-phase rotation circuit 80 are output at different levels for each IH period when one of the video heads 25 and 26 scans the magnetic tape 23. Assuming that the phase advances by 90 degrees, the phase lags by 90 degrees every period IH during which the other side scans the magnetic tape.

The multiplication circuit 73 receives the color difference signal R from the clamp circuit 71.
906 from the 4-phase rotation circuit 80 with -Y
Balanced modulation is performed on the carrier whose phase is delayed, and the multiplication circuit 74
Then, the other carrier from the four-phase rotation circuit 80 is balanced-modulated using the color difference signal B=Y from the clamp circuit 71. Then, the output signals of the multiplication circuits 73 and 74 are added by an addition circuit 75 to form a low frequency converted chroma signal. This low frequency conversion -15=Roma signal is processed by a color difference signal B-Y in the multiplication circuit 74.
A burst signal obtained by modulating the carrier with a burst pulse added during the horizontal blanking period is added.

The low-frequency converted chroma signal is processed by the burst emphasis circuit 76 to amplify the burst signal by 6 d'B, then passes through the switch 77 and is processed by the LPF 79 to amplify the burst signal by 6 d'B. The signal is band-limited to a low band, and further passes through a switch 78 and is frequency-multiplexed with the FM luminance signal from the FM modulation circuit 21 by an adder circuit 22. The output signal of the adder circuit 22 is appropriately amplified and then supplied to the video heads 25; 26 and 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 R-Y and B-Y output from the base clip circuits 41 and 42 are also used for monitoring and the like.

For this purpose, this luminance signal Y is passed through the switch 13,
The signal is supplied to the adder circuit 14.

Further, the color difference signals R-Y and B-Y output from the base clips 41 and 42 respectively pass through switches 45 and 46.
After being clamped by clamp circuits 47 and 48 in the same way as clamp circuits 31 and 32, the signals are supplied to 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 with a carrier frequency of 3.58 MHz.

In addition, the carrier generation circuit for this purpose is a 90° phase shift circuit 8.
69 phase detection circuit 87. Loop filter 8B, VC08
It consists of 9. The frequency of VCO89 is 3.58M
The Hz output signal is supplied to a phase detection circuit 87, and its phase is compared with a stable reference signal having a frequency of 3.58 MHz, which is supplied from an input terminal 92 via a switch 85.

The output error signal of the phase detection circuit 87 is sent to a loop filter 88.
is corrected by VC and sent as a control signal via switch 90.
Supplied to O89. Thereby, the output signal of the VCO 89 is stabilized in phase with the reference signal from the input terminal 92. The output signal of the VCO 89 is supplied as a carrier to a multiplication circuit 50, and after being phase-shifted by a 90° phase shift circuit 86, it is supplied as a carrier to a multiplication circuit 49.

From the multiplication circuit 49.50, color difference signals R-Y and B- are obtained by balanced modulation of carriers with a frequency of 3.58 MHz, respectively.
Y is output, and these are added by an adder circuit 51 to obtain a chroma signal. This chroma signal is band-limited by the BPF 52, passes through the switch 53, and is added to the luminance signal Y from the switch 13 in the adder circuit 14 to form a color video signal. This color video signal is supplied to a counter addition circuit 15, and the count value of the tape counter is superimposed on it as required, and the superimposed signal is outputted from an output terminal 16.

As described above, when recording the output signal of a video camera, the baseband luminance signal Y1 color difference signal R-Y, B
A recording signal consisting of an FM luminance signal and a low frequency converted chroma signal can be directly formed from -Y. Further, before modulation, processing for improving image quality can be performed on these luminance signal Y1 color difference signal RY, 113-Y.

Next, the recording operation of an external color video signal in this embodiment will be explained. In this case, switch 5.6
9.70 is on the outside side, switch 13.45° 46, 60
．． 77, 7B, and 8182.90 are on the REC side, and switches 35.36.65.66 and 85 are on the camera REC side.
The switches 53 are closed to the camera REC+PB sides, and the switch 93 is open.

The external color video signal is supplied separated into a luminance signal Y and a chroma signal C, and the luminance signal Y is supplied from the input terminal 57.
The chroma signals C are input from input terminals 58, respectively. The luminance signal Y passes through the switch 5 and is sent to the AGC circuit 17. Superimpose circuit 18. Emphasis circuit 19. The clip circuit 20 processes the brightness signal Y output from the video camera, and the FM modulation circuit 21 forms an FM brightness signal, which is then supplied to the adder circuit 22 . Further, the brightness signal output from the superimpose circuit 18 is transmitted to the switch 13.
Similarly to the luminance signal Y output from the video camera, the luminance signal Y is provided to a monitor or the like.

The chroma signal C input from the input terminal 58 is supplied to the superimpose circuit 59, and the chroma signal C input from the input terminal 58 is supplied to the superimpose circuit 59.
The brightness is superimposed so that the period of the brightness superimpose signal from No. 6 is at the pedestal level.

The chroma signal C output from the superimpose circuit 59 is supplied to the ACC circuit 61 via the switch 60.
The level of the burst signal is controlled by the detection output from the ACC detection circuit 62 so that the level of the burst signal is constant. A.C.
The chroma signal C output from the C detection circuit 61 is supplied to multiplication circuits 63 and 64.

Multiplication circuits 63 and 64 constitute a synchronous demodulation circuit.

In this case, the 3.58 MHz carrier generation circuit also has a 90° phase shift circuit 861 and a phase detection circuit 87. Loop filter 88
゜It is composed of VCO 89, and ACC circuit 61
By supplying the chroma signal outputted from the chroma signal to the phase detection circuit 87 via the switch 85, a 3.58 MHz carrier whose phase is synchronized with the burst signal of this chroma signal is obtained from the VCO 89, as explained earlier. . Note that the phase detection circuit 87 compares the phases of the burst signal of the chroma signal and the output signal of the VCO 89. For this purpose, although not shown, a burst-91=gate is provided within the phase detection circuit 87 or immediately before the switch 85.

The output signal of the VCO 89 is supplied as a carrier to the multiplication circuit 64 via the switch 82, whereby the baseband color difference signal B-Y is demodulated from the chroma signal C. Further, the output signal of the VCO 89 is phase-shifted by a 906 phase shift circuit 86, and is supplied as a carrier to the multiplication circuit 63 via the switch 81. As a result, the color difference signal RY is demodulated from the chroma signal C.

These color difference signals R-Y and B-Y are transmitted through the switches 65 and 65, respectively.
The color difference signal R-Y passes through the comb filter 37.66, is band-limited by the LPFs 67 and 68, and passes through the switch 35.36, similar to the color difference signals R-Y and B-Y output from the video camera. Clamp circuit 39. The color difference signal B-Y is processed by the base clipping circuit 41, and the color difference signal B-Y is processed by the comb filter 38. Clamp circuit 40. Processed by the base clip circuit 42. The color difference signals R-Y and B-Y output from the base clip circuits 41 and 42 are connected to switches 69 and 70, respectively.
After passing through and being clamped by clamp circuits 71 and 72,
It is supplied to 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, and is carried out from the switch 78 to the adding circuit 22.
A low frequency converted chroma signal is supplied to the FM luminance signal and recorded on the magnetic tape 23 together with the FM luminance signal.

A chroma signal for monitoring etc. is obtained from the ACC circuit 61 and is supplied to the adder circuit 14 via the switch 53.

Burst replacement circuits 43 and 44 are base clip circuits 41
, 42, the burst pulses of the color difference signals R-Y, B-Y are replaced with burst pulses of the correct level. When recording an external color video signal,
The chroma signal C is synchronously demodulated by multiplication circuits 63 and 64, and at this time, it is synchronously demodulated with the pulse 1- signal to form a burst pulse. Therefore, the base clip circuit 4L 42
A burst pulse is added to the horizontal blanking period of the color difference signals R-Y and +3-Y output from the chrominance signals R-Y and +3-Y. 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 clipping circuit 41 does not include a burst pulse.

By the way, the chroma signal C output from the ACC circuit 61
When there is a level change in the burst signal, the level of the burst signal also changes, and the color difference signal B- output from the base clip circuit 42 changes.
The level of the Y burst pulse also changes. The burst pulse of this color difference signal B-Y is compared in level with a reference level signal representing the correct level of the burst pulse set in the burst replacement circuit 44 in the ACC detection circuit 62, and these difference signals are used as the ACC control voltage in the ACC circuit 61. is supplied to As a result, the ACC circuit 61 adjusts the chroma signal C so that the Hurst level of the chroma signal C becomes equal to the reference level set in the burst level replacement circuit 44.
level is controlled.

As described above, even when recording an external color video signal, it is possible to perform processing to improve the image quality of the chroma signal, and the processing means includes processing of the color difference signal output from the video camera. You can use both methods.

Next, the reproduction operation of this embodiment will be explained.

In this case, switch 13.45.46.60.77
, 78°81, 82.90 are on the PB side, switch 35.
36, 65, and 66° 85 are closed to the camera REC side, the switch 53 is closed to the (camera RF C+ PB) side, and the switch 93 is closed.

The playback signals of video heads 25 and 26 are preamplified by 2 respectively.
7.28, and are alternately selected by the switch 29 controlled by the head switching signal from the input terminal 99, resulting in a continuous reproduction signal.

On the one hand, this reproduced signal is supplied to a peaking circuit 6, where an FM luminance signal is extracted and its frequency characteristics are corrected. The extracted FM luminance signal is processed by an AGC circuit 7 to remove level fluctuations for each video head 25, 26, processed by a waveform equalization circuit 8, and then demodulated into a baseband luminance signal by an FM demodulation circuit 9. This luminance signal is de-emphasized in a de-emphasis circuit 10, subjected to noise removal processing such as noise clipping and noise cancellation in a noise processing circuit 11, and subjected to dropout compensation processing in a D/0 compensation circuit 12, and then The signal is supplied to the adder circuit 14 via 13.

The reproduced signal output from the switch 29 is also supplied to the LPF 79 via the switch 77, and a low frequency converted chroma signal is extracted. This low-frequency conversion chroma signal is supplied to the ACC circuit 61 via the switch 78.60, and after being level-controlled so that the level of the burst signal is constant, it is supplied to the multiplication circuit 63.64 to determine the baseband color difference. It is demodulated into signals RY and 13-Y. These color difference signals R
-Y and B-Y pass through switches 65 and 66 respectively, and L
The band is limited to 500 KHz by P F67 and 68, and is further passed through a comb filter 37 through switches 35 and 36.
．． 38 and when the magnetic tape 23 is reproduced, unnecessary components such as crosstalk components from adjacent tracks are removed, and as will be described later, dropout compensation is also performed. The color difference signals R-Y and B-Y output from the comb filters 37 and 38 are clamped by a clamp circuit 39 for a period other than the burst pulse period of the blanking period, and are base clipped by base clip circuits 41 and 42 to eliminate noise. removed.

Here, the ACC detection circuit 62 detects the reference level signal from the burst level replacement circuit 44 and the color difference signal B-Y output from the base clip circuit 42, as in the case of recording the external color video signal described above. It compares the level with the burst pulse and outputs the ACC control voltage of the ACC circuit 61. However, since this burst pulse is emphasized by 6 dB by the burst emphasis circuit 76 etc. during recording, the burst level replacement circuit 44 outputs the ACC control voltage of the ACC circuit 61. The level of the reference level signal supplied to is also 6 dB higher than the normal burst level.

Further, the carrier generation circuit of the multiplication circuits 63 and 64 is a four-phase rotation circuit 80. Comparison amplifier 83. Loop filter 84. Addition circuit 94. AFC circuit 95. VC096
, 2 frequency divider circuit 97, and 4 frequency divider circuit 98. As explained earlier, the VCO 96 outputs a signal with a frequency of 32OfH based on the output signal of the AFC circuit 95, which is divided by the divide-by-2 circuit 97 and the divide-by-4 circuit 98 to have a frequency of 40f4 at 90° to each other. Four signals with different phases are formed, and the four-phase rotation circuit 80 sequentially selects the output signal of the four-frequency divider circuit 98 to generate two signals whose phases are switched by 90 degrees for each IH. Although carriers are formed, the direction in which the phase of the two carriers changes is the same as that during recording. In other words, the four-phase rotation circuit 80 supplies the carrier to the multiplication circuit 63 so that the phase matches the carrier of the balanced modulated color difference signal RY in the low frequency converted chroma signal output from the ACC circuit 61. The four-phase rotation circuit 80 changes the phase by 90 degrees for each IH, and the four-phase rotation circuit 80 changes the phase by 90 degrees for each IH so that the phase matches that of the carrier of the color difference signal B-Y, which is also balanced-modulated.
4. The phase of the carrier supplied to 4 is changed by 90° for each IH. As described above, the head switching signal is used in the four-phase rotation circuit 80 as a reference for defining the phase of each carrier.

The reproduced low-frequency converted chroma signal has a phase fluctuation, and when this is synchronously demodulated with a carrier created from the output of the VCO 96 with a constant phase, the hue and color saturation change. To prevent this, the comparison amplifier 83 and the loop filter 84
A phase control system for a VCO 96 is provided. Now, there is a phase fluctuation in the reproduced low frequency converted chroma signal,
Balanced modulated color difference signal R− supplied to the multiplication circuit 63
When a phase error occurs between Y and the carrier, an unnecessary pulse (hereinafter referred to as a pseudo burst pulse) due to a burst signal is generated during the horizontal blanking period of the demodulated color difference signal R-Y.

The comparison amplifier 83 is supplied with the output color difference signal R-Y of the clamp circuit 39 to which the demodulated color difference signal R-Y is supplied, and a reference level signal representing the blanking level at which this color difference signal R-Y is clamped. , this reference level signal and the pseudo burst pulse period of the blanking period in the color difference signal RY are compared in level. 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 multiplication circuit 63 and the carrier from the carrier generation circuit. The output signal of the comparison amplifier 83 representing this level difference is sent to the loop filter 84.
After being corrected, the signal passes through a switch 93 and is added to the output signal of the AFC circuit 95 in an adder circuit 94 to obtain V.
Supplied to CO96. As a result, even if there is a phase fluctuation in the reproduced low-frequency converted chroma signal, the multiplication circuit 6
The phase of the VCO 96 is controlled so that there is no phase difference with the carrier supplied to the multiplication circuit 63.64. Therefore, the multiplication circuit 63.65 outputs color difference signals R-Y and B-Y that are not affected by this phase variation. can get.

Color difference output from base clip circuit 4.1.42 (
No. i R-Y and B-Y are respectively replaced with burst pulses of the correct level by burst level replacement circuits 43/44, and then passed through switches 45 and 46 to clamp circuit 4.
7 is clamped as previously described and multiplier circuit 49.
50. The carrier generation circuit of these multiplication circuits 49.50 is a 90° phase shift circuit 86. The VCO 89 consists of a reference voltage source 91, and the VCO 89 generates a stable carrier of 3.58 MHz using the reference voltage from the reference voltage source 91. This carrier is supplied to the multiplication circuit 50, and is also phase-shifted by a 90° phase shift circuit 86 and supplied to the multiplication circuit 49. Therefore, the multiplication circuit 49.5
A chroma signal with a carrier frequency of 3.58 MHz is formed by a quadrature two-phase modulation circuit consisting of 0 and an adder circuit 51.

This chroma signal is band-limited by the BPF 52, passes through the switch 53, and is passed through the adder circuit 14 to the D/0 compensation circuit 12.
NTS for monitors etc.
A C color video signal is formed.

In this way, even during playback, the chroma signal is processed to improve image quality, and the processing means for this also serves as the processing means during recording.

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

In the figure, a baseband color difference signal (RY or 113-Y) is input from an input terminal 104.

The switch 103 is closed to the D-0 side during recording, but is closed to the D-0 side during the dropout period during playback. IH
The delay circuit 101 includes a CCD delay circuit and an L for clock removal.
It is composed of PF.

The baseband color difference signal inputted from the input terminal 104 passes through the switch 103 and is directly supplied to the addition circuit 102 , and also delayed by the IH delay circuit 101 and supplied to the addition circuit 102 . The IH delay circuit 101 and the addition circuit 102 provide a comb-shaped filter characteristic that matches the frequency spectrum of the baseband color difference signal. noise) is removed.

Also, during the dropout period, the switch 103 is
The color difference signal output from the adder circuit 102 is supplied to the IH delay circuit 101 and the adder circuit 102 via the switch 103. This compensates for dropout of color difference signals.

In this way, the color difference signal is subjected to quadrature two-phase modulation with dropout being compensated for as explained in 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.
is an amplifier, and parts corresponding to those in FIG. 2 are given the same reference numerals.

In the figure, during recording, the switch 108 is closed to the REC side, and the IH delay circuit 101 and addition circuit 102 provide a comb filter characteristic.

During reproduction, the switch 108 is closed to the PB side, and the subtraction circuit 106, 107 and one of the amplifiers 110, 111 are added to form a feedback comb filter. I
The output color difference signal from the H delay circuit 101 is the subtraction circuit 107.
The signal at the valley of the frequency spectrum of this color difference signal is extracted and multiplied by 1.2 or 0.3 times by the amplifier 110 or 111, and then supplied to the subtraction circuit 106 to input the color difference signal. Subtract. As a result, the valleys of the frequency spectrum of the color difference signal are more sufficiently attenuated, and the effect of suppressing interleaved noise and the like is further increased.

Note that the switch 109 has a correlation of -32 for the signals around 18.
= Switching is controlled depending on the presence or absence of vertical correlation (that is, vertical correlation), and when there is correlation, switch 109 switches to amplifier 1.
10 output signals are selected, but the difference between the signals around 18 is 5.
When it is greater than or equal to IRE, it is assumed that there is no correlation and the switch 109 selects the output signal of the amplifier 111. Also,
During the burst pulse period, the switch 109 is connected to the amplifier 11.
Select output signal 1.

During the dropout period, the switch 103 is closed to the D/0 side, as in the specific example of FIG. 2.

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

In this specific example, switch 103 for dropout compensation
is provided after the switch 108, and the other parts are shown in FIG.
Its operation is also similar to 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, in which 112 to 114 are input terminals, 115 is a reference voltage source, 116 to 119 are switches, and 120 to 122 are buffer amplifiers. , 123°12
4 is the resistor, 125.126 is the output terminal, 127.128
is a current source.

In the figure, a color difference signal B-Y is inputted from an input terminal 112, a blanking pulse is inputted from an input terminal 113, and a burst pulse is inputted from an input terminal 114. Outside the blanking period, the switch 11G is closed to the A side, and the color difference signal B-Y input from the input terminal 112 is transmitted to the switch 116. Buffer amplifier 120, resistor 123. The signal passes through the buffer amplifier 121 and is supplied from the output terminal 125 to the switch 46 (FIG. 1).

When a blanking pulse is input to the input terminal 113 during the blanking period of the color difference signal B-Y, the switch 116 is closed to the B side and the reference voltage source 115 is switched to the buffer amplifier 120.
The DC voltage at the correct vedestal level determined by the output voltage level of this reference voltage source 115 is connected to the output terminal 1.
Obtained on 25th. During this blanking period, input terminal 11
When a burst pulse is input from 4, switch [7,
118 closes, current source 127 causes reference voltage source 115
A current with a value of 2 flows from the resistor 123 through the resistor 123, and a current with a value of 21 similarly flows through the resistor 124 from the current source 128.

The resistance values of resistors 123 and 124 are equally set to R. The value of the current flowing through the resistor 123 is the buffer amplifier 1.
Since the output voltage of the buffer amplifier 121 is set to be at the normal burst level, and the resistance value of the resistor 124 is equal to the resistance value of the resistor 123, the output voltage of the buffer amplifier 122 is set to a level twice the normal burst level. That is, the burst signal at a normal level is transmitted to the burst emphasis circuit 76.
It is equal to the level when 6 dB emphasis is applied, such as in (Fig. 1).

Therefore, during both recording and playback, the output terminal 1
A color difference signal B-Y in which the Bedestal level and the Hurst level are set normally is output to the switch 46 (
(Fig. 1) is supplied to the PB side.

Also, during recording, the switch 119 is closed to the REC side,
Color difference signal B-Y output from Han-Hwa amplifier 121
is supplied from the output terminal 126 to the ACC detection circuit 62 (FIG. 1). During playback, the switch 119 is closed to the PB side, and the color difference signal B-Y whose burst level is twice the normal output from the buffer amplifier 122 is supplied from the output terminal 126 to the ACC detection circuit 62.

In FIG. 5, the burst level replacement circuit 43 in FIG. 1 has an input terminal 114, switches 117 to 119 . Buffer amplifier 122° current source 1
27.128. The 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 parts corresponding to those in FIG. 1 are given the same reference numerals.

In the embodiment shown in FIG. 1, base clip circuit 41.
Baseband color difference signals R-Y, B output from 42
-Y are directly supplied to the burst level replacement circuits 43 and 44, respectively, but in the embodiment of FIG. The output signal is also supplied to the burst level replacement circuit 43.44, and the problem during playback is that the color difference signals R-Y, B-Y-36= output from the base clip circuit 41.42 are clamped, respectively. After being clamped in circuit 71.72,
Burst level replacement circuit 43. '44. Other configurations and operations are similar to those of the embodiment shown in FIG.

According to this embodiment, during reproduction, the color difference signal RY.

After 13-Y is clamped and the reference level becomes constant, the vedestal level and burst level become ICE m.

Since these levels are set, the accuracy of setting these levels is improved.

FIG. 7 is a block diagram showing still another embodiment of the video signal recording and reproducing apparatus according to the present invention, in which 44' is a burst level replacement circuit, 129 is a burst de-emphasis circuit, and parts corresponding to those in FIG. are given the same symbol.

In this embodiment, an ACC circuit 61 and a multiplication circuit 63
．． The burst de-emphasis circuit 129 is provided between the LPFs 67 and 64, and the switches 69 and 70 in FIG. The difference from the embodiment shown in FIG. 1 is that the chroma signal is supplied to the chroma signal, and is also subjected to quadrature two-phase transformation via clamp circuits 71 and 72 to form a low frequency converted chroma signal.

The burst de-emphasis circuit 129 de-emphasizes the burst signal only during reproduction, and simply passes the chroma signal C during recording.

During playback, this burst de-emphasis circuit 129
The burst pulse of the color difference signal 42 output from the base clip circuit 42 is returned to its original level by the action of What is necessary is to compare the burst level with the normal burst level set by the burst level replacement circuit 44'. For this purpose, the burst level replacement circuit 44' includes switches 118, 119° buffer amplifiers 122, . resistance 1
24. The output terminal 126° current source 128 is no longer necessary, and the color difference signal B-Y output from the output terminal 125 can be supplied to the ACC detection circuit 62. Further, as shown in FIG. 7, the switch 4 at the subsequent stage of the burst level replacement circuit 44'
The color difference signal B-Y output from the ACC detection circuit 62
It may also be supplied to In this case, when recording an external color video signal, the two input color difference signals B-Y of the ACC detection circuit 62 are equal, so the ACC circuit 61 is set to a constant gain.

Furthermore, in this embodiment, when recording an external color video signal, each color difference signal RY to be recorded.

Although B-Y is not processed by the comb filter and base clip circuit, it is processed by these for monitoring, making it possible to monitor with high image quality.

FIG. 8 is a block diagram showing still another embodiment of the video signal recording and reproducing apparatus according to the present invention, in which 130 is a phase comparison circuit, 13L and 132 are switches, and parts corresponding to those in FIG. 7 are denoted by the same reference numerals. I'm wearing it.

In the embodiment shown in FIG. 7, during reproduction, the clamp circuit 39
The burst pulse period level and Bediskle level of the baseband color difference signal R-Y output from
In the H carrier generation circuit, comparison amplifier 83 compares the signal, and the output signal is passed through loop filter 84 to
96, 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 in accordance with the phase fluctuation contained in this low frequency converted chroma signal.

On the other hand, in FIG. 8, the switch 131°13
2 is provided, and during reproduction, by supplying the carrier from the VCO 89 in the 3.58 MHz carrier generation circuit and the carrier from the 90'' phase shift circuit 86 to the multiplication circuit 74.73, the 3.58 MHz frequency is output from the addition circuit 75. A phase comparison circuit 130 generates a chroma signal of the carrier, and compares the burst signal of this chroma signal with the output signal of the VCO 89.
By detecting the phase fluctuation component of the low-pass converted chroma signal reproduced by comparing the phases at This controls the output phase.

The configuration and operation of other parts are similar to the embodiment shown in FIG.

Note that although the above embodiments have been described with respect to NTSC video signals, video signals of other formats may also be used.
It goes without saying that the present invention is applicable.

Furthermore, in each of the above embodiments, as shown in FIGS. 2 to 4, the comb filters 37 and 38 include a D.0 compensation circuit, but the D.・0
It goes without saying that a compensation circuit may be provided.

〔Effect of the invention〕

As explained above, according to the present invention, when recording and reproducing a color video signal by FM modulating the luminance signal and converting the chroma signal to low frequency, the S/N of the color difference signal forming the chroma signal is improved. Therefore, the excellent effect of significantly improving the image quality of the reproduced image can be obtained.

[Brief explanation of the drawing]

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 are block diagrams showing a specific example of the comb filter in FIG. FIG. 5 is a block diagram showing an example of the burst level replacement circuit in FIG. 1, and FIGS. 6, 7, and 8 are block diagrams showing other embodiments of the video signal recording and reproducing apparatus according to the present invention. be. 4... Camera processing circuit, 9... FM demodulation circuit, 14
... Addition circuit, 16 ... Color video signal output terminal, 21 ... FM modulation circuit, 22 ... Addition circuit, 2
3... 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...Brightness signal input terminal for external color video signal, 58...Chroma signal input terminal for external color video signal, 61...ACC circuit, 62...A
CC detection circuit, 63.64... Multiplication circuit, 73.74
. . . Multiplication circuit, 75 . . . Addition circuit, 76 . . . Burst emphasis circuit. Agent: Patent Attorney Junji Takeshi Department (1 other person) Fukaihei 1-
200797 (14) Figure 4 Figure 5

Claims (1)

[Claims] 1. In a video signal recording and reproducing device that frequency-multiplexes and records and reproduces a frequency-modulated luminance signal and a low-frequency converted chroma signal, a first subcarrier having the same frequency as the color subcarrier of a color video signal a first carrier generating means for generating a carrier of a frequency lower than that of the first carrier; a second carrier generating means for generating a second carrier having a lower frequency than the first carrier; a first modulating means that modulates the second carrier with a color difference signal to generate a low frequency converted chroma signal for recording; and a third carrier that generates a third carrier synchronized with a burst signal of the reproduced low frequency converted chroma signal. a third carrier generating means for demodulating the reproduced low-frequency converted chroma signal by the third carrier and generating a baseband third carrier;
demodulating means for outputting a fourth color difference signal; processing means for processing the third and fourth color difference signals; 1. A video signal recording and reproducing apparatus comprising: second modulation means for modulating and generating a chroma signal of a color video signal. 2. In a video signal recording and reproducing device that is integrated with a video camera and records and reproduces a frequency-modulated luminance signal and a low frequency converted chroma signal by frequency multiplexing, when recording a color video signal from an external source, the color video is a first switch that selects a chroma signal of the signal and selects a low-frequency converted chroma signal reproduced during reproduction; and a first switch that demodulates the chroma signal or the low-frequency converted chroma signal selected by the first switch. , a demodulating means for outputting a second color difference signal, and a second switch for selecting the first and second color difference signals or the third and fourth color difference signals to be recorded from the video camera;
a processing means for processing the color difference signal selected by the second switch; a first modulation means for modulating the color difference signal output from the processing means to form a chroma signal of a color video signal; 1. A video signal recording and reproducing apparatus comprising: second modulation means for modulating the color difference signal output from the processing means to form a low frequency converted chroma signal. 3. In a video signal recording and reproducing device that is integrated with a video camera and records and reproduces a frequency-modulated luminance signal and a low frequency converted chroma signal by frequency multiplexing, when recording a color video signal from an external source, the color video is a first switch that selects a chroma signal of the signal and selects a low-frequency converted chroma signal reproduced during reproduction; and a first switch that demodulates the chroma signal or the low-frequency converted chroma signal selected by the first switch. 1. demodulation means for outputting a second color difference signal;
a second switch for selecting a second color difference signal or third and fourth color difference signals to be recorded from the video camera; and processing means for signal processing the color difference signal selected by the second switch; a first modulating means that modulates the color difference signal output from the processing means to form a chroma signal of a color video signal; 1. A video signal recording and reproducing apparatus, comprising: second modulation means for forming a signal. 4. In claim 1, 2 or 3, the processing means:
A video signal recording and reproducing device characterized in that it includes at least means for compensating for dropout of a color difference signal. 5. In claim 1, 2 or 3, the processing means:
A video signal recording and reproducing apparatus comprising at least first and second comb filters for removing interleaved noise from color difference signals. 6. In claim 5, the first and second comb filters include a switch that selects an input color difference signal and an output color difference signal, and a delay circuit that delays the color difference signal selected by the switch by one horizontal scanning period. and an addition circuit that adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to produce the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to produce the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to produce the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to obtain the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to produce the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to produce the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to obtain the output color difference signal, and the switch circuit adds the color difference signal delayed by the delay circuit to the color difference signal selected by the switch to produce the output color difference signal, A video signal recording and reproducing device characterized in that dropout compensation is possible by selecting a color difference signal. 7. In claim 1, 2 or 3, the processing means:
A video signal recording and reproducing apparatus characterized by comprising burst level replacement means for setting at least the level of a burst pulse in the color difference signal to a specified level. 8. In claim 1, 2 or 3, the processing means:
A video signal recording and reproducing device comprising at least a base clip circuit.