JPS6032389B2 - Dubbing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an RF dubbing method for video signals, and more specifically, chroma signal low frequency conversion, Y signal FM video recording/
This invention relates to an improved method for performing Rr dubbing in a reproduction method.

The present invention also relates to an intensifier with non-linear characteristics that can be preferably used when dubbing a reproduced RF signal from a video recorder. In the chroma signal low frequency conversion and Y signal FM video recording/playback systems, the chrominance and luminance components of the video signal are separated, the chrominance component is converted to low frequency, and the luminance component is FM modulated and then combined. The signal is then recorded on a recording medium, and during playback, the chrominance signal is reconverted to the original frequency, and the luminance signal is demodulated and then mixed together to be played back as the original video signal.

RF dubbing refers to dubbing without separating the chrominance and luminance components of a video signal. Problems when performing RF dubbing with a video tape recorder (VTR) are overmoji and resolution deterioration. These two are contradictory elements, and if you suppress over-moji, the resolution will deteriorate. One of the factors that causes overmoji is the HPF (B
It is known that the purpose is to pass the video signal through the PF. Therefore, if the signal processing is performed as an RF signal with the Y component and the C component mixed together, it is possible to prevent the resolution from deteriorating and the over-moji from occurring. Further, since the Y component and the C component are never filtered, there should be no phase distortion and no filter delay amount in principle.
However, if the Y+C RF signal from the VTR is passed through a normal limiter circuit for RF dubbing, the public
Spurious signals having frequency components such as low frequency fc, high frequency low frequency c, high frequency low frequency component, etc. are generated, and the S/N of the Y component is rapidly deteriorated.

Also, since chroma information exists as an AM component, the limiter circuit suppresses the AM component, and the chroma component S/
The deterioration of N also becomes large. The object of the present invention is to provide an RF dubbing system that solves the above-mentioned problems, and FIG. 1 shows a principle diagram of the configuration of the present invention. 10 is the V that should be dubbed
An input terminal for the TR reproduction RF signal, and 12 indicate an output terminal to the recording intensifier.

The RF signal at terminal 10 is passed through an equalizing amplifier 14, a limiter 16 having non-linearity, and a low pass filter (LPF) 18.

The frequency characteristics of the equalization multiplier 14, limiter 16, and LPF 18 are shown in FIGS. 2, 3, and 4, respectively. The frequency characteristics shown in FIG. 2 and the frequency characteristics shown in FIG. 4 have a substantially complementary relationship. Signals passing through these circuits receive an overall flat frequency response.
In the figure, c is the chroma band, and fy is the FM modulated Y band.

FIG. 5 shows an example of a specific circuit of the limiter circuit 16.

The circuit has an intensifier section 20 receiving an input at terminal 21, first and second nonlinear elements 22, 24, and an output terminal 25. Each nonlinear element is connected between signal paths,
Element 22 includes a single diode connected in an anti-parallel relationship,
Element 24 also includes a pair of series diodes connected in an anti-parallel relationship. The input/output characteristics of this circuit are expressed by a hyperbrick tangent function, and the input is f(t
), and the output is J(t), it can be approximated as follows.

t)= is nh(f(t))=A{f(t)-tei(f
(t))3 Toyake5(f(t))51...}...{1} The output characteristics of a conventional limiter with linearity that is commonly used is expressed by the following equation, and Me'(t )=A′{f(t)
+Tei (f(t)) 30 words (f(t)) 50...}.・・■ Here, if we compare the formula '1} and the formula ■, we will consider the third-order and fifth-order terms and input fy + kfc (the value of k is 1'2 to 1' in the reproduced RF signal of an ordinary VTR). When the signal of 3) is input, the spurious response of the '1) formula is smaller.

(This is because the coefficient of the 5th order term is small and the polarity of the 3rd and 5th order terms are opposite, so there is a cancellation amount.) In the case of this application, the equivalent multiplier 14 adds a signal to the chroma signal. Since the input fy+k has been decreased, k of the input fy+k has a steepness of 0.2. Using this value of k, the output when passed through the non-linear limiter 16 of the present application is calculated using the formula '1', and the input is cos x 10. If MB is the y value of cos, which is the Ct of XoS and is the luminance component appearing on the output side, the input chroma signal was -14 dB, but the output becomes -17 dB, resulting in a slight decrease in level. However, the spurious 2y soil has -33 old, fy± is -4
Considering the S/N ratio of MB and Y, this level of spurious can be said to be practically acceptable. Of course, as can be seen from the equation, the amount of spurious will decrease in proportion to k as k becomes smaller, so if the characteristics of the equivalent multiplier 14 are changed, the spurious can be further reduced. Next, since the chroma component is raised in the circuit 18, the overall frequency characteristic is flat according to the combinational circuit configuration of this application, and the I
J-mitter was applied, and spurious noise was suppressed to a level that poses no problem for practical use. VT for general dubbing
The Y RF signal output from R is in the form of a single sideband, and if it is dubbed as is, it will have an AM component, so it is normally converted into a double sideband signal by passing it through a limiter circuit.

For example, the single-side wave RF signal e of Y, which is the output of a VTR, is expressed by the following equation. e=C. Swyt-ology. S(Wy-p
)tIf this signal is passed through a conventional limiter circuit having linearity, the output lel will be as shown in the following third equation.

lel=A″COS [10 other npt] ...'3, m
f: modulation index p: angular frequency of modulation signal Wy: angular frequency of carrier When dubbing this (single sideband type VTR) and reproducing it, a limiter with conventional linearity is used for the reproduction thread of the VTR. Since the circuit is provided, it is once again subjected to the limiter action.

In other words, the reproduced signal is further limited, and the output signal is: lel=A′′′COS [wyt Jugyo Sinpt] -
--[4] In other words, if a limiter with conventional linearity is inserted in the middle of RF dubbing, the modulation index becomes 1/4 of the original.

In other words, this results in a lower resolution. In the present invention, such a transmitter is not applied, so experiments have shown that the modulation index of equation 4 can be larger than 1/4, for example 1/2. It was possible to suppress the erectile dysfunction, and the deterioration in resolution was lower than with conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one implementation circuit of the present invention;
3 and 4 are diagrams showing preferable characteristics of each block element in FIG. 1, and FIG. 5 is a configuration diagram showing an example of a specific circuit of one element of the circuit in FIG. 1. In the figure, 14 is an equal-b amplifier, 16 is a limiter, and 18 is a low-pass filter. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In a method of RF dubbing a mixed color television reproduction signal of a low-frequency converted chroma signal and an FM-modulated luminance signal without separating the low-frequency converted chroma signal, the low-frequency converted chroma signal a first means for attenuating the band components relative to the FM-modulated luminance signal band components; a limiter receiving the output from the first means and having non-linearity at least in a low level region of the input level usage range; an amplifier, and a second means for receiving the output of the amplifier, boosting the chroma signal band components relative to the luminance band components, and compensating so that the overall frequency characteristic becomes flat. Dubbing method. 2. The dubbing system according to claim 1, wherein the input/output characteristics of the limiter amplifier are given by a hyperbrick tangent function.