JPS58117790A - Processing circuit for video signal - Google Patents

Abstract

PURPOSE:To attain a small-sized circuit device and low cost, by realizing a circuit for Y/C separation and step difference cancellation at recording, and a comb type filter and a dropout compensating circuit at reproduction by means of one 1H delay line only. CONSTITUTION:A recording color video signal given from an input terminal 4 is applied to a 1H delay line 2, a subtractor 14, and an adder 15 via a changeover switch 30 and separated into a recording chroma signal and a luminance signal. The output of the subtractor 14 is applied to a subtractor 22A via an LPF19, a limiter 20 and a level adjusting device 21 and the step difference cancellation of the luminance signal is done. The step difference cancellation of the signal not through the delay line 2 is done at a subtractor 22B. The signals applied with the Y/C separation and the step difference cancellation at recording are outputted to output terminals 7 and 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal processing circuit applied to a color VTR process circuit.

The Y and C process circuits in a conventional color VTR have the configuration shown in FIG. In the recording circuit, J, j
g A Y4 separation circuit 3 using a /H (/water section) delay line 1 with a center frequency of MHz is provided, a recording color video signal is supplied from an input terminal 4, and a recording chroma signal is connected to an output terminal 5. At the same time, a luminance signal is outputted to the output terminal 1 via the level difference canceling circuit 6. This step canceling circuit 6 is constructed using a /H delay line 2 having a center frequency of 70.7 MHz. Further, the reproduced a''v signal from the input terminal 8 is supplied to the C-shaped comb filter 9 consisting of /HfMm#1 to remove crosstalk components from the momentary contact track, and then sent to the adder 10.
The reproduced luminance signal from the input terminal 11 is supplied to the Y-shaped comb filter and dropout compensation circuit 12 consisting of the /H delay line 2, the output of which is supplied to the adder 10, and the reproduced luminance signal is supplied to the output terminal 13. A color video signal is obtained.

As mentioned above, in the conventional Y, C process circuit,
More than 0 /HH wire extensions are always required. At present, the power consumption of /HH line extension using COD is too large, so a glass delay line is used. When making VTR circuit devices ultra-miniaturized, the IC part is made into a mini package or chip carrier, and resistors, capacitors, etc. are made into modules, but the glass delay line mentioned above can be made ultra-miniaturized in principle. This has hindered the miniaturization of single-circuit devices.

In consideration of the above points, this invention can perform dropout compensation for reproduced chroma signals in addition to the same functions as conventional Y and C process circuits, by simply using seven /HH wires. The purpose of this invention is to realize a signal processing circuit.

In addition, the configuration of the recording side in the conventional Y and C process is as follows.
It is shown in FIG. By subtracting the output of the /HH extension line 1 from the input color video signal by the subtractor 14, the chroma signal is separated, and the output of the %/H delay line 1 is added to the input color video signal by the adder 15. By adding these signals, the luminance signals are separated. In this case, the output of the adder 15 increases due to the /H delay 11, so a bandpass filter 16 and a subtracter 11 are provided to compensate for this. 1+, camera output, etc., a step occurs in which the overall Ofi level fluctuates in units of horizontal sections.

To round off this, the difference between the input and output of the /HH wire extension 20 is detected by the subtracter 18, and this is supplied to the subtracter 22 via the low-pass filter 1g, the limiter 20, and the level adjuster 21, and the /HH wire extension A step canceling circuit 6 is provided for subtracting from the output of No. 2.

Pan pass filter 16 of the above-mentioned separation circuit 3
It is necessary that the delay line 1 and the passband characteristics match. However, the /H delay! ! ! If there is any variation in the characteristics of 1, it is difficult to completely correct it, and there are problems such as phosphorescence appearing in the output after correction.

The present invention enables the frequency characteristics of the luminance signal to be well corrected in the % separation circuit.

This invention basically consists of, for example, 7 as shown in FIG.
By means of a circuit arrangement 23 comprising seven /HH extensions 2 having a transmission characteristic centered at 0.7 MHz.

It is possible to perform Y4 separation two-step difference cancellation during recording, and the circuit device '24 including this /HH wire extension 2 realizes %C-shaped comb filter characteristics and Y-shaped comb filter characteristics, as well as chroma signal. Dropout compensation for the □ signal and dropout compensation for the luminance signal are performed.

Hereinafter, this invention will be described as a color VTR as described above.

An example applied to a C process circuit will be described.

FIG. 9 shows the overall configuration of an embodiment of the present invention. In reality, this /HH extension 2 is, for example, an AM modulation circuit 25 with a carrier frequency of 7.5 MHz, as shown in FIG.
The signal passed through the VSB filter 26 is delayed! i! !
27, and its output is sent to the emperoso detection circuit 28.
and a low-pass filter 29.

In addition, in FIG. 9, 30 indicates a recording switch controlled by the output of the system control section of the VTR.
31 indicates a switch that is switched when a dropout is detected depending on the envelope level of the playback output;
2 indicates a switch that is switched depending on the presence or absence of line correlation, and 33 indicates a switch that is switched depending on color and monochrome.

During recording, when the recording power 2-video signal is supplied from the input terminal 4 via the re-switching switch 30, the /HH extension 2
The input and output of i12 are supplied to the subtracter 14 to separate the recorded chroma signal, and the input and output of /H slow [[i12 are supplied to the adder 15 to separate the luminance signal. The output of this adder 15 is supplied to an adder 35 via a bandpass filter 34A, and added to the output of a subtracter 36. This subtracter 36 can be supplied with the output of the /HH extension 2, and is also supplied with its own output via a pan-P pass filter 34B. The bandpass filters 34A and 34B have the same characteristics as each other, and also have /H:llAl7 as a line 20 passband and a bald 4-band (slightly wide band considering the variation). . Here, even if there is a difference in frequency characteristics between the band pass filters 34A and 34B and the /Hjl extension 1112, the band pass filters 34A and 34B
Since the frequency characteristics of the luminance signal are strong, the frequency characteristics of the luminance signal can be corrected satisfactorily.

Further, by supplying the output of the subtracter 14 to the subtracter 22A via a low-pass filter 19, a limiter 20, and a level adjuster 21, the level difference in the luminance signal is canceled.

/H Step cancellation for a signal that does not go through the delay line 2 is performed by subtraction @22B. In this way, noise separation and step cancellation during recording are performed using the /H delay line 2.

The recording luminance signal appearing at output terminal 1 is as follows.

Processing such as FM modulation is performed. Further, the recording chroma signal appearing at the output terminal 5 has a low frequency carrier frequency, for example ('I
'/-1fH = 6g g kHz, and at the same time, phase inversion or phase shift by 900 for each horizontal interval is performed at the time of low-frequency conversion, and the above-mentioned F
The M-modulated luminance signal and the low-frequency conversion color signal are added together, and then supplied to a rotary head via a recording amplifier, a rotary transformer, etc., and are sequentially recorded on the magnetic tape so that one field corresponds to one track.

Then, during playback when the recording/playback switch 30 is switched to the playback side, the input terminal 1 is separated from the playback signal by the Hyper 2 filter and obtained through processing such as FM demodulation.
The reproduced luminance signal from 1 is supplied to an adder 31. In addition, the reproduced low-frequency converted chroma signal separated from the reproduced signal by the low-pass filter is sent from the input terminal 8 to the frequency converter 38.
supplied to This frequency converter 38 is supplied with a carrier signal from their ApclB path, and by selecting the frequency of this carrier signal, the frequency converter 38
A converted color signal having a carrier frequency of mfH (m: an integer) and located on the higher side than the luminance signal band, for example 0-Hiro, = MHz, is extracted from the output of adder 31.
supplied to

- As an example, if the carrier frequency fl of the low-frequency converted chroma signal is (, = (dada1->tH>), then the frequency of the carrier signal supplied from the APC circuit to the frequency converter 38, 8, is selected as the following value. .

rs=(,27/+,)fH=4'-J MHz Therefore, the carrier frequency fc of the output (sum component) of the frequency converter 38 is fc=fL+fB=l+-7)fH+C27/+÷)
fIl [= J / 3 fH'= '1.9 b M
Hz. A1gA shows the frequency spectrum of the low frequency converted chroma signal, and B of the same figure shows the frequency spectrum of the frequency converter 3.
The frequency spectrum of the converted chroma signal obtained at the output of adder 31 is shown in FIG. In these frequency spectra, the diagonal lines indicate the p-stoke component from the adjacent track. Further, the carrier signal supplied to the frequency converter 38 is phase-inverted or phase-shifted as in recording, and the output of the frequency converter 38 contains crosstalk components with respect to the original color signal. is frequency interleaved.

The output of the adder 37 is supplied via the recording/reproducing switch 30 and the switch 31 to the Y-shaped comb filter constituted by the adder 15 and the /H slow arc line 2. As shown in Figure 6, the Y-shaped comb filter has a pass band at a position that is an integer multiple of fgo, so this Y-shaped comb filter removes crosstalk components related to both the luminance signal and the chroma signal. can do. In the sixth diagram, the frequency components of the luminance signal and the converted chroma signal are
A crosstalk component is shown by a dashed line and a dashed line, and a broken line shows a crosstalk component. During pinching and reproduction, the /H delay line 2' and adder 15 also constitute a comb filter for the chroma signal.

is converted to a carrier frequency of 9% mfH, so
The carrier signals at the input and output of the /H delay line 2 have the same phase. Therefore, by supplying the output of this /Ii delay Ij12 to the terminal that is selected as a source at the time of dropout of the switch 31, it is possible to compensate not only the brightness ffi signal but also the dod and dipout of the ripple signal.

The output of the adder 15 is K as shown in FIG. 6E.

A luminance signal and a converted chroma signal from which the p-Stoke component has been removed are obtained, and these are supplied to a low-pass filter 40 and a band-pass filter 41 for frequency separation. The converted chroma signal separated by the bandpass filter 41 is supplied to a 5-frequency converter 42. This frequency converter 42 is connected to a terminal 43, for example 2X
(Honda 1) A carrier signal with a frequency of fH is supplied,
Therefore, its output is s 3J g Ml (force t-
A chroma signal with t decarrier frequencies is obtained. Then, it is added to the luminance signal by the adder 44, and a reproduced composite color video signal can be obtained at the output terminal 13.

FIG. 7 shows another embodiment of the invention. This example a, *
In the case of configuring a relic comb filter, basically, a subtracter 45 is provided on the input side of /Hjihime[2, and the output of the subtracter 14 is fed back to this, and
The input of the H delay line 2 and the output of the subtracter 14 are supplied to a subtracter 46, and a reproduced signal from which crosstalk has been removed is obtained at the output of the subtracter 46C).

Further, to explain, the output of the subtracter 14 is supplied to a bypass filter 47 and a low-pass filter 48, and is separated into a converted chroma signal of carrier frequency fc and a luminance signal. A limiter 49 is connected to the low-pass filter 48 , and the output of the limiter 49 is multiplied by K1 by a 7-point attenuator 50 and supplied to an adder 51 .
The signal is multiplied by 2 and supplied to the adder 53. The output of the bypass filter 47 is multiplied by Ka') by an attenuator 54 and supplied to an adder 51.
5 by J) Kg and supplied to the adder 53. The feedback signal appearing at the output of adder 51 is supplied to subtracter 45, and the feedforward signal appearing at the output of adder 53 is supplied to subtracter 46. As mentioned above,
Since the limiter 49 is provided, the characteristics of the comb filter regarding the luminance signal are such that the valleys of the combs are shallow. The comb-shaped curves are set by the coefficients of each of the 7 tsutenators.

The configuration of the other embodiment of the invention described above during recording is similar to that of the one embodiment described above. The signal for level difference correction of the luminance signal is output from the 9t vine 49 and sent to the 7t tsunator 56.
I try to use 8 times as many friends as I like.

In addition, in the above embodiment, the low frequency converted chroma signal is
After converting to c, 3. ! ; t MHz K, so the APC circuit needs to generate a carrier signal for these two frequency conversions. One example and another example of the PC circuit are shown in FIGS. 3 and 9, respectively.

These 0APC circuits are (2-17+2)fHt
J/! crystal oscillators 51 and 58 having respective oscillation frequencies of f fH, a frequency converter 59 to which both outputs are supplied and forming a carrier signal for terminal 43, and an output of crystal oscillator 51 and an output of frequency converter 42 A phase comparison circuit 60 and a phase comparison circuit 6,1 to which the output of the crystal oscillator 58 and the converted Cooma signal output from the comb filter are supplied.

The AP appearing at the outputs of these phase comparison circuits 60 and 61
and an adder 62 to which the C error is supplied. This adder 62 also includes an oscillator absolute error detection circuit 63.
and the AFC error from the AFC circuit. The error voltage generated from this adder 62 is the VCO
(Voltage controlled keepsake) 640 control voltage.

The APC circuit in Figure 3 uses the center frequency of this VCO 64! , 9MH1, and a carrier signal having a distortion component ΔfH of the following frequency is generated at its output.

(-koku + number) fH- (!Hiro-7) (fH + ΔfH) The output of this VCO 64, together with the output of the crystal oscillator 57,
jI skill converter 65, and the output of this frequency converter 65 is supplied to a detection circuit 63. At the same time, the output of vco@4 is supplied to the frequency converter 6, and 8 carrier signals are formed at the following frequencies using the 1 frequency converter 5-psfJ (D output).

fs=(=77+÷)fH7(14-7)ΔfH The jitter component is canceled by frequency conversion using the carrier signal.

Further, the APC circuit shown in FIG. 9 sets the center frequency of the VCO 64 to 1.27 MHz, and generates a carrier signal including a jitter component ΔfH of the following frequency at its output.

tB = (2 near + ÷) fH + (cup - ÷) (fH + Δ
fH) The jitter component is canceled by frequency conversion using this carrier signal. Along with this.

The output of the VCO 64 and the output of the crystal oscillator 58 are supplied to a frequency converter 67, whose output is supplied to a detection circuit 63.

Since the APC loop is constituted by the two APC errors from the above-mentioned APC circuit expansion and phase comparator circuits 60 and 61, responsiveness and stability are good.

As understood from the above explanation, according to the present invention,
To realize Y bee separation and vertical filter cancellation during recording, and a comb filter and dropout compensation circuit during playback, similar to the conventional Y, C7'o process circuit, by using only seven /H delay lines. I can do it.

It is possible to reduce the size and cost of the circuit device.

However, according to the present invention, dropout compensation for chroma signals is also possible, and even better dropout compensation is possible. Further, according to the present invention, even if the frequency characteristics of the /H delay line vary, it is possible to satisfactorily correct the frequency characteristics of the luminance signal after noise separation.

[Brief explanation of drawings]

1 and 2 are block diagrams used to explain the conventional Y and C process circuits of vTR, FIG. 3 is a block diagram used to explain the present invention, and FIGS. 9 and S are block diagrams used to explain the conventional Y and C process circuits of the vTR. A block diagram of the entire embodiment and a part thereof, FIG. 6 is a frequency spectrum used to explain the operation of one embodiment of the present invention, and FIG. 7 is a block diagram showing the configuration of another embodiment of the present invention.
FIG. 3 and FIG. 9 are block diagrams of one example and other examples of the APC circuit. 1.2.../H delay line, 4... Input terminal for recording color video signal, 5... Output terminal for recording p-ma signal. 1... Output terminal for recording luminance signal, 8... Input terminal for reproduced low frequency conversion chroma signal, 11... Input terminal for reproduced luminance signal, 30... Bell re-switching switch % 31... Drop Out compensation switch, 38.43-...Frequency converter. Agent Masatomo Sugiura

Claims (2)

[Claims] (1) Convert the frequency of the low-frequency converted p-ma signal into a signal with a carrier frequency on the high-frequency side of the luminance signal band at mfH (wl is an integer), and convert the frequency-converted p-ma signal into a luminance signal. The added output is supplied to a Y-shaped comb filter to remove crosstalk components included in the luminance signal and chroma signal, and then the luminance signal and o''v signal are separated, and the above four signals are separated. A video signal processing circuit that converts the frequency of the main signal to a low frequency so that it has a predetermined carrier frequency and adds it again to the luminance signal. (2) Y-shaped comb filter has l horizontal period Oj! A delay means having a delay amount and a means for substantially adding an input signal and an output signal to the delay means]. The output signal is fed back to the input of the delay means through a switch means, and the switch means is operated in accordance with the dropout detection output of the human-powered video signal. A video signal processing circuit according to scope 1.