KR950006455B1 - Image signal converting circuit - Google Patents

Abstract

a signal output means for synchronizing a bust signal which is a shifted bust signal of an image signal by 45 degrees with a horizontal synchronous signal of an original bust signal by a bust gate pulse during entering the bust signal, the image signal entered in an NTSC method; an amplifier for amplifying twice the sub-carrier frequency of a color signal entered in the NTSC method; and a signal processor receiving the output signals of the signal output means and the amplifier, detecting the difference of the two signals and generating the detected difference signal into an image signal in an M-PAL method.

Description

Image signal conversion circuit

1 is a block diagram showing a conversion circuit of a conventional video signal.

FIG. 2 is a timing diagram showing an output state of each part of FIG.

3 is a block diagram showing a conversion circuit of a video signal according to the present invention;

4 is a state diagram showing the output state of each part of FIG.

* Explanation of symbols for main parts of the drawings

10: signal output means 20: amplifier

30: signal processing circuit 40: mixer circuit

110: phase shifter 120: synchronous separation circuit

130: control signal generator 140,340: switch

310: balance modulator 320: band pass filter

330 flip-flops

The present invention relates to an image processing system for processing an input video signal and displaying on a screen. More particularly, the present invention relates to a conversion of a video signal for processing an image signal recorded in NTSC and displaying it on a screen in an M-PAL method. It is about a circuit.

Currently, the TV system used in various countries of the world includes NTSC method centering on Japan, USA, Canada and Korea, SECOAM method centering on Europe, and PAL system centering on communism. The methods are being broadcast in a mixed state.

Therefore, recently produced televisions or video tape recorders have tended to produce compatible systems capable of processing video signals input in accordance with broadcasting systems of respective countries.

However, for example, in a television capable of processing an M-PAL system in which the luminance signal of the video signal broadcasted in Brazil is close to the NTSC system, and the color signal is close to the PAL system, playback of a tape recorded in the NTSC system is difficult. impossible.

That is, as described above, in order to reproduce the video signal recorded in the NTSC system on a television produced in Brazil, a separate circuit for converting the NTSC system tape output signal to the M-PAL system is required.

In the conventional video signal conversion circuit in which the NTSC video signal is converted to the M-PAL system, as shown in FIG. 1, the burst signals input during one horizontal synchronization period are respectively +45 degrees and -45 degrees, respectively. Here, the converted video signal of -45 degrees among the converted signals is removed, so that the input NTSC video signal is converted into the M-PAL video signal and displayed on the screen.

In this case, there is a problem that the image quality is degraded due to the loss of the video signal input during the input of the one horizontal synchronization signal.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to detect a difference component between a signal shifted by +45 degrees of a burst signal input in the NTSC scheme and a signal amplified twice the frequency of a color signal subcarrier. Since the shifted phase of the detected difference signal +45 degrees is output in synchronization with one horizontal synchronizing signal, it is possible to obtain a clear image quality of the M-PAL system without loss of the input image signal. It is to provide a conversion circuit.

In order to achieve the above object, the present invention provides an image processing system in which an input NTSC video signal is converted into an M-PAL method and displayed on a screen. A signal output means which is output in synchronization with a horizontal synchronous signal to which a +45 degree shifted signal and an input original signal are input, an amplifier of which a sub-carrier frequency of the input NTSC color signal is doubled, and the signal; Signal processing means for detecting the signal passing through the signal output from the output means and the signal output from the amplifier is detected, the signal processing means for shaping the detected signal is output as a video signal of the M-PAL method; In a video signal conversion circuit.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a conventional video signal conversion circuit, which is briefly shown, and FIG. 2 shows the timing output from each part of FIG.

That is, as shown in FIG. 2A, the image signal A input in the NTSC method is applied to phase shifts (1) and (2), respectively, to shift the phase by +45 and -45 degrees. The shifted signal is applied to and output from the switch SW1 switched according to the control signal C1 output as a high signal only while the burst signal shifted in phase +45 degrees is input as shown in FIG. 2B.

On the other hand, the signal that the switch (SW1) and the originally input NTSC signal (A) is switched in accordance with the control signal (C2) output as a high signal during the input period of the burst signal, as shown in Figure 2c A signal applied to (SW2) and passed through, and the signal passed through the switch (SW2) is turned on / off in accordance with the control signal (C3) output by combining the control signal (C1), (C2) as shown in FIG. It is applied to the switch SW3 which is turned off and a signal as shown in Fig. 2e is output. That is, the M-PAL video signal of the burst signal shifted out of the -45 degree phase is removed, thereby degrading the image quality.

FIG. 3 is a block diagram showing a video signal conversion circuit according to the present invention, where 10 is an input NTSC scheme, in which the phase of the burst signal is shifted by +45 degrees and the input burst signal is high while the burst signal is input. A signal output means output by a burst gate pulse output as a signal, 20 is an amplifier amplified at twice the subcarrier frequency of an input NTSC color signal, and 30 is a signal output through the signal output means 10 And a difference signal of a signal doubled in the subcarrier frequency of the color signal, and the detected difference signal is shaped and outputted as an M-PAL video signal.

The signal output means 10 is provided with a phase shifter 110, a synchronous separation circuit 120, a control signal generator 130, and a switch 140, and the phase of the burst signal of the NTSC system input by +45 degrees. The shifted signal and the original burst signal of the NTSC system are configured to be switched and output in accordance with the burst gate pulse output from the control signal generator 130.

In addition, the signal processing means 30 is composed of a balance modulator 310, a band pass filter 320, a flip-flop 330 and a switch 340, the amplifier 20 of the signal input from the signal output means 10 The difference signal of the signal output from the signal is detected, wherein the detected signal is shaped, and the brightness signal and the color signal through the switch 340 is switched according to the control signal output from the flip-flop 330 Is applied to the mixer circuit 40 to be mixed.

4 is a state diagram showing the output state of each part of FIG.

In this invention configured as described above, when the input NTSC burst signal is input as shown in FIG. 4A, the input signal is applied to the phase shifter 110 of the signal output means 10 so that the phase is changed. +45 degrees shifted, where the shifted signal is applied to switch 140.

Meanwhile, the burst signal of the original video signal input as shown in FIG. 4A is also applied to the switch 140.

In addition, the signal processed NTSC luminance signal is applied to the synchronous separation circuit 120 to separate the horizontal synchronous signal, wherein the burst gate pulse output in synchronization with the separated horizontal synchronous signal control signal generator 130 Is output from

The burst gate signal is output with the same period as the waveform shown in FIG. 2B.

At this time, the switch 140 is switched in synchronization with the burst gate pulse output from the control signal generator 130, and thus, the signal output from the phase shifter 110 and the video signal of the original NTSC system are input. Are alternately output.

Here, the switch 140 is output as a vector amount as shown in Figure 4c.

Meanwhile, the subcarrier frequency of the input NTSC color signal is applied to the amplifier 20 and amplified twice.

The signal output from the switch 140 is applied to the balance modulator 310 of the signal detecting means 30, and at the same time, the difference between the two signals inputted by applying the double carrier frequency increased by the output of the amplifier 20 is applied. The signal is detected, where the output difference signal is applied to the band pass filter 320 and shaped.

The waveform having the same phase as that of FIG. 4d output from the band pass filter 320 and the signal output through the switch 140 of the signal output means 10 are applied to the switch 340.

On the other hand, the horizontal synchronous signal separated from the synchronous separation circuit 120 of the signal output means 10 is applied to the flip-flop 330 is delayed, the switch 340 is switched according to the output signal.

That is, by switching the switch 340, a waveform having a phase as shown in FIG. 4E is output, and the signal passing through the switch 340 is applied to the mixer circuit 40 to be mixed with the luminance signal. Then output.

In this invention as seen above, in the input NTSC video signal, the phase shifted signal of the burst signal +45 degrees by the phase shifter 110 and the color signal of the original signal by the amplifier 20. The difference signal is detected from the signal of which the subcarrier frequency of the signal is amplified twice, and the signal obtained by shifting the phase of the detected signal and the burst signal by +45 degrees by the balance modulator 310 is output in synchronization with the horizontal synchronization signal. M-PAL type video signal is output.

As described above, in the present invention, a difference signal obtained by amplifying a phase shifted signal of an NTSC burst signal and a subcarrier frequency of a color signal of an input signal is doubled, wherein the detected signal and the phase shifted signal are detected. Is alternately outputted in synchronization with the horizontal synchronization signal, thereby improving image quality due to the loss of the image signal shifted by a conventional -45 degree phase.

Claims (3)

In an image processing system in which an input NTSC video signal is converted into an M-PAL method and displayed on a screen, a signal having a +45 degree shifted phase of a burst signal of an video signal input in an NTSC method and an original signal input The signal output means is output in synchronization with the horizontal synchronization signal is input, the amplifier of which the subcarrier frequency of the input NTSC color signal is amplified twice, and the signal and amplifier through which the signal output from the signal output means has passed; And a signal processing means for receiving the output signal, the difference signal of the input signal is detected, and the detected signal is shaped and outputted as an image signal in an M-PAL manner. 2. The signal output means (10) according to claim 1, wherein the signal output means (10) separates a horizontal synchronizing signal from a phase shifter (110) in which a phase of an input NTSC burst signal is shifted by +45 and an input luminance signal (Y). A control signal generator 130 and a control signal generator 130 in which a burst gate pulse is output in synchronization with a burst signal received by a signal output from the sync separator circuit 120 and the input signal from the sync separator circuit 120; And a switch (140) connected to the output side of the phase shifter (110) for outputting the signal output from the phase shifter (110) and the original video signal in synchronization with a burst gate pulse. According to claim 1, wherein the signal detecting means 30, the balance modulator 310 and the balance modulator for outputting the difference signal of the two signals input through the switch 140 of the signal output from the amplifier 20, and the balance modulator A band pass filter 320 connected to an output side of the 310 to shape an input difference signal, a flip-flop 330 for delaying an input horizontal synchronization signal to output a control signal, and the band pass filter 320. And a switch (340) cut out so that the signal output from the signal is passed in synchronization with the signal output from the flip-flop (330).