JPH0634514B2 - Video signal converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an NTSC color composite video signal by superimposing (superimposing) a video image from a computer (personal computer) on a video image from a television broadcast, a VTR, a video disc, or the like. The RGB signal from the computer and external video equipment or its associated equipment in order to convert the color composite video signal to a video signal and display it on a television receiver or record it on a video cassette recorder (VTR). Of the selected video signal, converts the mixed signal into a color composite video signal, and outputs the color composite video signal to the external video device or its associated auxiliary device.

(Prior Art) In recent computers, a function of synchronously connecting (GENLOCK) to an input video signal and transmitting an RGB signal of the computer is becoming common, and by utilizing this function, a television receiver side is mixed. A system that has a circuit and is capable of superimposing display of an input video signal and a computer RGB signal is commercially available. In addition, V does not stop at the superimpose display.
A video signal conversion device that can record on TR and display on a monitor TV with a video input terminal has been developed and put on the market. N of this superimpose video
The TSC conversion is an extremely effective means as a new editing method of inserting a title or graphic created by a computer into a video when editing a VTR, and the current situation is that development in this direction is rapidly progressing.

Generally, a display clock (dot clock) frequency used in a computer is higher than that of an NTSC signal. Consider, for example, a type in which two modes of horizontal 40-character (320 dot) mode and 80-character (640) mode can be designated for display. Even in the case of 40-character mode, the display clock frequency is 7.16 MHz (color). 2 times the sub-carrier frequency), and from this, the minimum pulse width that can be taken by the RGB signal of the computer is the value obtained by dividing the horizontal period into 320 parts,
That is, 64 μsec × 0.8 × 1/320 = 0.16 μsec, which is equivalent to one cycle of the color subcarrier (1 / 3.58 = 0.28).
Since there are RGB signals that are only about half of the (.mu.sec), the following problems occur when NTSC conversion is performed.

Due to the above-mentioned pulse width, dot interference may occur such that the smallest dot is not sufficiently colored, and since the RGB signal of the computer has a spectrum component outside the band of the NTSC signal, a high-frequency component is generated. It is liable to mix in and easily cause cross-color interference, and due to these dot interference and cross-color interference, there was a drawback that a so-called flicker phenomenon that colors and characters flicker near the boundary of the superimposed image. .

Conventional devices of this type include a device that converts an RGB signal of a computer into a composite video signal and then mixes an input video signal and a composite video signal with a switch SW (referred to as a first conventional example) and an input video. Demodulate the signal,
It is known that the demodulated color difference signals (RY, BY) and the luminance signal Y are mixed with RGB signals of a computer (referred to as a second conventional example).

(i) First Conventional Example As shown in FIG. 4, a chroma oscillation circuit 102 that inputs an input video signal to a chroma oscillation circuit 102 through a bandpass filter (BPF) 101 is a crystal oscillation based on the input chroma signal. The child 103 outputs a signal of 3.58 MHz, and
This is phase-shifted by the phase shift circuit 104 to 0 ° and 90 ° to obtain two color synchronization signals. These two color synchronization signals are input to the encoder 105. On the other hand, the RGB signal from the computer is converted into a signal conversion circuit.
The color difference signals (RY, BY) and the luminance signal Y are input to 106 and the separated color difference signals (RY, BY).
Y) is input to the encoder 105, which is encoded here while performing color synchronization with a color synchronization signal to obtain a chroma signal, and the chroma signal and the luminance signal are superposed by the mixing circuit 107 and the RGB signal of the computer is obtained. The NTSC color composite video signal (video signal) is obtained, and the switch SW is switched by the switching signal from the signal conversion circuit 106 to superimpose both the video signal of the external video signal and the video signal of the computer. It is designed to output a video signal.

However, the above-mentioned one has an advantage that the circuit scale is small with one switch, but when the switch SW is switched, in the case of the RGB signal of the computer, the color sub-carrier frequency is determined from the relationship of the pulse width described above. Since the composite video signal must be switched at a higher speed than that, the color subcarrier near the boundary between the input video signal and the RGB signal of the computer is easily modulated and formed. The NTSC composite video signal has a drawback that the flicker phenomenon becomes noticeable.

(ii) Second Conventional Example As shown in FIG. 5, an input video signal is input to a demodulation circuit 203 via a bandpass filter 201 and a trap (TRAP) 202, respectively, and the color difference signal and luminance signal are output from the demodulation circuit 203. It is designed to output each. On the other hand, the RGB signals from the computer are input to the signal conversion circuit 204, and the color difference signals (RY, BY) and the luminance signal Y are separated and output. The chrominance signal and the luminance signal from the demodulation circuit 203 and the signal conversion circuit 204 respectively
To the switch circuit 205 including the third switches SW1, SW2, and SW3, and the demodulation circuit 203 and the signal conversion circuit 204 alternately and antithetically output respective color difference signals in response to the switching signal from the signal conversion circuit 204. Encoder
The luminance signal is alternately and antithetically output to the mix circuit 207 while being input to the 206. Further, a signal is taken out from the demodulation circuit 203, the color synchronization signal generated through the crystal oscillator 208 and the 0 ° and 90 ° phase shift circuit 209 is input to the encoder 206, and while synchronizing with this color synchronization signal. An NTSC composite video signal is obtained, the composite video signal and the luminance signal are mixed by a mixing circuit 207, and the superimposed composite video signal is output.

According to this example, since there is no color subcarrier, no problem occurs not only in mixing the color difference signals which are low frequency components but also in mixing the luminance signals.
Further, since the same color synchronization signal is used to encode the color difference signals, there is an advantage that the flicker phenomenon can be greatly reduced as compared with the case of the first conventional example by eliminating the unnaturalness near the boundary. .

However, in order to configure the switch circuit 205 for signal combination, three switches are required, which has a drawback that the circuit scale becomes large and the cost becomes high.

(Object of the Invention) The present invention has been made in view of such circumstances, and an object of the present invention is to provide a composite image signal that can be superimposed and output with less flicker phenomenon with a reduced number of switch circuits and at a low cost. And

(Structure of the Invention) In order to achieve such an object, the video signal conversion device of the present invention uses a color composite video signal from an external video device or an accessory device related thereto as a first luminance signal component and a first chroma signal. A first separating means for separating into a component, a second separating means for separating into a second luminance signal component and a color difference signal component on the basis of an RGB signal from a computer, and a second separating means from the color difference signal separated by the second separating means. The first output means for outputting two chroma signal components and both chroma signal components
First extracting means for selectively extracting by a switching signal based on the logical sum of B signals, second extracting means for selectively extracting both luminance signal components by the switching signal, and second
The first or second luminance signal component extracted by the extracting unit and the first or second chroma signal component extracted by the first extracting unit are respectively mixed to produce a color composite video signal in which different video signals are superimposed. And a second output means for outputting.

In other words, the first extracting means mixes and combines the chroma signal component separated from the color composite video signal from the external video device or an accessory device related thereto and the color difference signal component separated from the RGB signal from the computer, and The extraction means mixes and synthesizes the first luminance signal component separated from the color composite image signal from the external image device or the accessory device related thereto and the second luminance signal component separated from the RGB signal from the computer, and the combined chroma signal. The component and the luminance signal component are mixed to obtain a superimposed color composite video signal.

(Example) Hereinafter, the present invention will be described in detail based on examples shown in FIGS. 1, 2, and 3.

FIG. 1 is a block diagram showing the configuration of a video signal conversion device of the present invention in blocks, FIG. 2 is a concrete circuit diagram of the video signal conversion device of the present invention, and FIG. 3 is in FIG. 1 and FIG. 3 is a signal waveform diagram in each part of FIG.

First, (n1) ... (n17) after the line and each signal in FIGS. 1 and 2 correspond to each waveform shown in FIG.

In FIG. 1, reference numeral 1 is composed of a bandpass filter 2 and a trap 3, and a separating means for separating a chroma signal component (n2) and a luminance signal component (n3) from an input video signal (n1), 5 is the above The APC type chroma oscillating circuit for receiving the chroma signal component (n2) and outputting the locked chroma signal of 3.58 MHZ together with the crystal oscillator 8, and 9 indicates the chroma signal from the chroma oscillating circuit 5 as 0 °, respectively. 9
It is a phase shift circuit that outputs a color synchronization signal (n11), (n12) to the encoder 10 described later by performing a phase shift to 0 °.

Further, 7 is a signal conversion circuit, which has input terminals 6a, 6b,
R signal (n4), G from computer input from 6c
The signal (n5) and B signal (n6) are converted into color difference signal components RY (n7) and B-
Y (n8) and the luminance signal component Y (n9) are separated and output, and the switching signal (n1
Output 0).

Reference numeral 10 denotes an encoder, which uses the color difference signals RY (n7) and BY (n8) from the signal conversion circuit 7 and the color synchronization signals (n11) and (n12) from the chroma oscillation circuit 5 to generate a chroma signal component. (n2)
Synthesized chroma signal component (n
13) is encoded and output.

SW1 and SW2 are switching signals (n10) from the signal conversion circuit 7.
Are first and second extracting means for selecting and extracting two input signals respectively. The first extracting means SW1 selects the chroma signal component (n2) from the input video signal (n1) of the external video device and the composite chroma signal component (n13) on the computer side and extracts it as a mixed composite chroma signal (n14). . The second extracting means SW2 is an input video signal
The luminance signal component (n3) from (n1) and the luminance signal component Y (n9) on the computer side are selected and taken out as a mixed luminance signal component (n16).

Reference numeral 18 denotes an output means, which is a chroma signal component (n14) and a luminance signal component (n16) selected by SW1 and SW2, respectively.
And outputs a color composite video signal (n17) in which different video signals are superimposed.

The operation of this video signal converter will be described below.

The video signal from the video (see FIG. 3 (n1)) is the separating means 1.
When the input video signal is input to, the separating means 1 separates the input video signal (n1) into a chroma signal component (n2) and a luminance signal component (n3), and outputs them. It becomes a chroma signal component and a luminance signal component, as schematically shown as n2 and n3 in FIG.

The chroma signal component (n2) is further sent to the chroma oscillation circuit 5. The chroma oscillating circuit 5 receives the chroma signal component (n2), and outputs the chroma signal of 3.58MHZ locked to the subcarrier of the input video signal (n1) together with the crystal oscillator 8. The 3.58 MHZ chroma signal is input to the phase shift circuit 9, where the color synchronizing signals phase-shifted to 0 ° and 90 ° are produced. In FIG. 3, these color synchronization signals are shown as (n11) and (n12).

On the other hand, the R signal (n
4), G signal (n5) and B signal (n6) are input terminals 6a, 6b, 6
When input to the signal converting means 7 via c, the signal converting means 7 extracts the color difference signal components RY and BY from these signals.
And the luminance signal component Y are separated and output. (Fig. 3,
See (n7), (n8), and (n9). ) Color difference signal components RY (n7) and BY (n8) are encoded by encoder 1
At 0, the color synchronization signal (n
By 11) and (n12), the combined chroma signal component (n13) on the computer side is synchronized with the chroma signal component (n2). Referring to FIG. 3, the color difference signal RY on the personal computer side
It can be seen that the chroma signal component (n13) is output corresponding to the period in which (n7) and BY (n8) exist.

From the signal converting means 7, R from the computer at the same time,
A switching signal such as n10 in FIG. 3 produced by taking the negative logical sum of the G and B signals is generated. This switching signal (n10) identifies the period in which the signal from the computer exists, as is apparent from FIG. Therefore, by controlling the switch circuits SW1 and SW2 using this switching signal, the signal from the computer can be inserted into the video signal only during the period when the signal from the computer exists.

For example, when a switching signal based on the logical sum of the color difference signals RY and BY is used as the switching signal, an external video signal is selected in a personal computer signal portion that is not white or black color. In contrast to this, since the present invention uses the negative OR signal of R, G, and B as the switching signal in the present invention, such inconvenience does not occur.

This switching signal is used as a control signal for the first and second extracting means. Thereby, the first take-out means SW1
From the chroma signal component (n2) from the input video signal (n1)
And the combined chroma signal component (n13) on the computer side is inserted into the hollowed-out portion of the input chroma signal component (n2) to synthesize the combined chroma component signal (Fig. 3, (n
14)) can be taken out.

At the same time, in the second take-out means SW2, the input of the luminance signal component (n3) from the input video signal (n1) is cut off in accordance with the switching signal (n10) based on the chroma signal RGB on the computer side. A luminance signal component Y on the computer side (see (n9) in FIG. 3) is inserted into and the synthesized luminance component mixed synthetic signal is taken out.

The chroma signal (n14) from the first take-out means SW1 and the luminance signal (n16) from the second take-out means SW2 are combined by the output means 18, and the video signal on the video side is combined with the video signal on the computer side. A color composite video signal (see (n17) in FIG. 3) is obtained as the output of the transistor Q6. As shown in FIG. 3, the color composite video signal (n17) is a video input signal, that is, a signal from a source, and a signal from a personal computer is inserted and synthesized.

FIG. 2 is a specific circuit diagram of the block diagram shown in FIG. In FIG. 2, the same parts as those in FIG. 1 are given the same numbers.

As is clear from the comparison with FIG. 1, the bandpass filter 2 is composed of a coil L1 and a capacitor C1,
The trap 3 is composed of a coil L2 and a capacitor C5. The separated chroma signal component (n2) is amplified by a resistor R2, R3, R4, R5, a chroma signal gain capacitor C2, and an amplifier circuit 4 including a transistor Q1 as necessary, and capacitors C3 and C4 are provided.
Are supplied to the chroma oscillating circuit 5 and the first take-out means SW1 via.

The luminance signal component (n3) separated by the trap 3 is the resistance R
7, R8, R9, an amplification circuit 11 composed of a peaking capacitor C6 for correcting the frequency characteristic of the luminance signal and a transistor Q2, and an amplification circuit 12 composed of resistors R10, R11 and a transistor Q3. It has become so. Further, the luminance signal component (n9) from the computer separated by the signal conversion circuit 7 is mixed in the chroma signal mixed by the removing means 13 composed of the coil L3 and the capacitor C7 in order to eliminate cross color interference. After the component is removed, it is output via the transistor Q4.

The switching signal (n10) is input to the base of the transistor Q3 as a switching signal (n15) via the buffer 14 of the open collector type. If there is a video signal on the personal computer side, the switching signal (n10) becomes low level as shown by (n10) in FIG. When the switching signal (n10) is low level, the output of the buffer 14 also becomes low level, the base of the transistor Q3 is set to low level, and the transistor Q3 is turned off. Therefore, the video side luminance signal component is not output to the collector of the transistor Q3.

On the other hand, the brightness signal component (n9) from the personal computer side is supplied to the level adjusting / setting circuit 15 to be described later, which is taken out from the emitter of the transistor Q4, and therefore is cut off when the switching signal (n10) is at a low level. Further, the luminance signal in a form in which the luminance signal component on the personal computer side is inserted instead of the luminance signal component on the video side is taken out and supplied to the output means 18.

Reference numeral 15 denotes a level adjusting / setting circuit composed of a buffer 16 similar to the buffer 14, variable resistors VR1 and VR2, and a capacitor C12, which is used for inputting a luminance signal component from the signal converting circuit 7 to a "black" level. The level is adjusted and set to the pedestal level for hollowing out. Here, the capacitor C12 is
The output of the buffer 16 is delayed in advance so that the signal input to the base and collector of the transistor Q3 via the buffers 14 and 16 does not have a time lag inside the transistor Q3, and the image is displayed at the edge of the hollow signal. It is to prevent the white edge of the.

The circuit including the transistors Q2 and Q3, the buffer 14, and the level adjusting / setting circuit 15 described above constitute the second extracting means SW2 shown in FIG.

The composite chroma signal component (n1 from the first extracting means SW1)
4) is amplified by an amplifier circuit 17 composed of resistors R14 and R15, a transistor Q5, a synthetic chroma signal gain capacitor C8 and a resistor R16, and then input to an output means 18, where the above-mentioned luminance is outputted. Color composite video signal (n17) that is mixed and combined with the signal that superimposes the signal components (n3) and (n9) to fit different video signals.
Is output from the transistor Q6.

(Effects of the Invention) As described above, according to the video signal conversion device of the present invention, it is separated from the color composite video signal from the external video device or an accessory device related thereto, and the separated chroma signal component is obtained. Since the RGB signals of the computer are mixed and combined with the separated color difference signal components, and the separated luminance signal components are mixed and combined, there is no chrominance subcarrier there, and like the second conventional example described above. The flicker phenomenon can be reduced. In addition, since the color composite video signal is not demodulated, a circuit for demodulation is unnecessary, and moreover, a switch circuit may be provided at two places of the first and second extracting means. Less, and overall,
It has become possible to provide a composite image signal that is superimposed with little flicker phenomenon, with a small circuit scale and at a low cost.

Further, since the first and second extracting means are adapted to select the chroma signal component and the luminance signal component respectively by the switching signal based on the logical sum of the RGB signals, for example, the color difference signals RY and BY are selected. When the switching signal based on the logical sum is used, there is a problem that the personal computer signal portion that is not white or black color becomes an external video signal, whereas the present invention does not have such a problem.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of a video signal converter of the present invention, FIG. 2 is a concrete circuit diagram, FIGS. 3 (a) and 3 (b) are waveform diagrams of output signals, respectively. Is a schematic block diagram showing a first conventional example, and FIG. 5 is a schematic block diagram showing a second conventional example. 1 ... 1st separation means, 7 ... 2nd separation means, 18 ... Output means, SW1 ... 1st extraction means, SW2 ... 2nd extraction means.

Claims (1)

[Claims] Claim: What is claimed is: 1. An RGB image signal from a computer is mixed with an image signal selected from an external image device or an accessory device related thereto, and the mixed signal is converted into a color composite image signal to obtain the external image device. Or a video signal conversion device for outputting to an accessory device related to the same, wherein a first composite chroma signal component that does not demodulate the color composite video signal from the external video device or the accessory device related thereto with the first luminance signal component Separating means for separating the RGB signals from the computer into a second luminance signal component and a color difference signal component, and a signal converting means connected to the signal converting means,
An encoder that synchronizes with a chroma signal and modulates and synthesizes into a similar shape to output a second chroma signal component, and selectively outputs the first and second chroma signal components by a switching signal based on a logical sum of the RGB signals. First to take out
Extracting means, second extracting means for selectively extracting the first and second luminance signal components by the switching signal, first or second luminance signal components extracted by the second extracting means, and the first A video signal conversion device having output means for respectively mixing the first or second chroma signal component extracted by the extraction means and outputting a color composite video signal in which different video signals are superimposed.