JPS5947517B2 - PAL-NTSC signal converter - Google Patents

Description

[Detailed Description of the Invention] The carrier color signal of a PAL color television signal is
The red color difference signal and the blue color difference signal have carrier waves with the same frequency but a phase difference of 900 degrees, which are amplitude-modulated for each horizontal section, and the phase of the carrier wave modulated by the red color difference signal is reversed every horizontal section. are doing.

That is, the state of this carrier color signal is as shown in FIG. 1, where every other horizontal section is represented by U+jV, and every other horizontal section of the remaining D is represented by U-jV. Then, in the section of the signal U+jV, there is a difference of 1 with respect to the U axis (BY axis).
A burst signal B+ whose phase is advanced by 350 is inserted, and a burst signal B- whose phase is delayed by 1350 with respect to the U axis is inserted in the section of the signal U-jV. Among the color video signals of the PAL system in which the phase relationship is defined in this way, there is one called the M system in which the frequency of the horizontal synchronizing signal, the frequency of the vertical synchronizing signal, and the frequency of the color subcarrier are special.

This means that the frequency FHP of the horizontal synchronization signal and the frequency Fvp of the vertical synchronization signal are those of the NTSC system, FHN and FVN.
The carrier frequency Fcp of the carrier color signal is that of the NTSC system F.

N (=3.579545MHz), and is selected as .

The present invention is directed to the M method (hereinafter referred to as PAL) of such PAL method.
-M system) color video signal to an NTSC system color video signal, and conversely, this converted NT
It is possible to convert an SC system color video signal into a PAL-M system color video signal using the same device, simply by switching a switch.

Hereinafter, an example of the conversion device according to the present invention will be described.
Let us explain by taking as an example the case of recording and reproducing an M system color video signal.

In FIG. 2, 10 is a conversion device according to the present invention, 40 is a recording/playback device, and the conversion device 10 has switches 1 and 2 for switching the input color video signal between the NTSC system and the PAL-M system. However, the recording/playback device 40 has a recording/playback switching switch 3.

Further, in this example, switches 4 and 5 are provided on the input side and the output side of the conversion device 10 to switch between recording and reproduction. In order to record a PAL-M color video signal on the recording/reproducing device 40, switches 1 and 2 are switched to the contact M side, and switches 3 to 5 are switched to the contact R side.

At this time, the PAL-M color video signal Svp through the terminal 50 is supplied to the input end 11 of the converter 10 through the contact R side of the switch 4.

The PAL-M color video signal Svp through the input terminal 11 is supplied to a low-pass filter 12 to extract a luminance signal, which is supplied to a synthesizer 13. Input end 1
The signal Svp from 1 is also outputted from bandpass filter 1, which is supplied to frequency converter 15.
The carrier color signal Scp from 4 is also supplied to the APC circuit 16, from which the frequency is the color subcarrier frequency Fcp of the PAL-M system and the phase is, for example, an intermediate phase between the burst signal B+ and the burst signal B-, Therefore, a continuous wave signal with a phase of one (B-Y) axis is obtained, and this is supplied to the frequency converter 17.

On the other hand, the oscillation signal of the NTSC color subcarrier frequency FCN from the oscillator 18 is supplied to the frequency converter 17 through the contact M of the switch 1.
A signal with a frequency of cp+FcN is obtained, and this is supplied to the frequency converter 15, from which the bandpass filter 14
The color subcarrier frequency of the carrier color signal Scp (FOp+
A signal FN converted into FON)-FOp=FCN is obtained. Then, this signal FN is directly transmitted to the switch circuit 2.
The signal is supplied to one input terminal A of the switch circuit 21 and the other input terminal D of the switch circuit 21, and also to a so-called modifier 22. To explain this modifier, it means that in this case,
A carrier color signal FN whose angular frequency of the carrier wave is =2πFCN is supplied to a balanced modulator 221, and a signal with a frequency FCN from the oscillator 18 is supplied to a multiplier 222, from which the frequency is doubled, and therefore the angular frequency is A signal S2fN with 2(i)N is supplied to the balanced modulator 221, where the signal S2fN is amplitude-modulated by the carrier color signal FN, and the modulated signal is sent to the low-pass filter 22.
3, and only those components having a higher angular frequency are extracted. That is, if the carrier color signal FN is the signal S2fN, the modulated signal 2FNX obtained from the modulator 221 is
S2fN (represented with a coefficient of 2 for convenience of subsequent calculations)
Ha,,V! becomes.

Therefore, if the filter 223 removes the component with the angular frequency 30)N and extracts only the component with the angular frequency ωN, the output FNO will be the same as the input carrier color signal FN of the modifier 22, as shown in FIG. On the other hand, the U axis, that is, B
- It becomes symmetrical about the Y axis.

The signal FNO from the modifier 22 obtained in this way
is supplied to the other input terminal B of the switch circuit 20 and also supplied to one input terminal C of the switch circuit 21.

Therefore, one input terminal A of the switch circuit 20 and the other input terminal D of the switch circuit 21 are supplied with a signal FN (self) 4A) whose carrier wave phase is inverted every horizontal section, and the switch circuit The other input terminal B of the switch circuit 20 and one input terminal C of the switch circuit 21 are supplied with a signal FNO- (FIG. 4B) which is symmetrical about the U axis with respect to the signal FN.

- On the other hand, the luminance signal from the low-pass filter 12 is supplied to the horizontal synchronization signal separation circuit 23 to extract the horizontal synchronization signal, which is passed through the OR circuit 24 to the flip-flop circuit 23.
5, from which a signal SH whose state is inverted every horizontal interval is obtained, which causes the switch circuits 20 and 21 to alternately switch between one input end and the other input side every horizontal interval. Can be switched.

Therefore, the switch circuit 20 provides a carrier color signal in which the phase of the color subcarrier is defined to be one phase.

In this case, the carrier color signal obtained from the switch circuit 20 is the burst signal B. as shown in FIG. 4C. It is defined that f is continuous. For this purpose, the carrier color signals obtained from switch circuits 20 and 21 are supplied to burst gate circuits 26 and 27, respectively, and a burst signal is taken out, and the burst signal from burst gate circuit 26 is supplied to a phase shifter 28 and rotated by 90°. The phase is advanced, and this 90° phase advanced signal is detected by the burst signal from the burst gate circuit 21 in the phase detector 29 .

When the burst signal Bf is continuously obtained from the burst gate circuit 26 as shown in FIG. 4C, the burst signal B- is continuously obtained from the switch circuit 21. 28, a signal having the same phase as the burst signal B- is obtained as shown by the solid line in FIG. 4D, so the output from the phase detector 29 is zero.

Further, when the burst signal B- is continuously obtained from the burst gate circuit 26 as shown in FIG. 4E, the burst signal Bf is continuously obtained from the burst gate circuit 2T as shown in FIG. 4C. On the other hand, at this time, the phase shifter 28
Therefore, as shown by the solid line in FIG. 4F, the burst signal B- is phase-advanced by 90 degrees.
An output of "1" is obtained, which is supplied to the flip-flop circuit 25 through the OR circuit 24 through the contact M of the switch 2, and the flip-flop circuit 25 is inverted one more time in the middle of one horizontal section, and the switch is turned on. The burst signal Bf is continuously obtained from the circuit 20 and the burst gate circuit 26. That is, a carrier color signal in the form of continuous burst signals Bf is obtained from the switch circuit 20, which is supplied to the combiner 13 and combined with the luminance signal from the loss filter 12. Therefore, at the output end 30, a color video signal SVN converted to the NTSC system is obtained.

The color video signal SVN converted to the NTSC system is supplied to the input end 41 of the recording/reproducing device 40 through the contact R of the switch 5, and the color video signal SVN through the human power end 41 is transmitted through the recording circuit 42 to the switch 3. The signal is supplied to the circuit magnetic heads 44 and 45 through the contact point R, and is recorded on the tape 46.

The color video signal SVN recorded in this manner is reproduced as follows and returned to the PAL-M color video signal Svp.

That is, switches 1 and 2 are switched to the contact N side, and switches 3 to 5 are switched to the contact P side.

The color video signals taken out by the heads 44 and 45 are supplied to the reproducing circuit 47 through the contact P of the switch 3 to reproduce the NTSC color video signal SVN, which is output to the output terminal 48.

The color video signal S led out to this output terminal 48
VN is supplied to the input terminal 11 of the converter 10 through the terminal P of the switch 4.

The color video signal SVN from the input terminal 11 is supplied to a low-pass filter 12 to extract a luminance signal, which is then supplied to a synthesizer 13. The color video signal SVN is also supplied to a bandpass filter 14 to provide a carrier color signal. SCN is extracted and supplied to the frequency converter 15, and the carrier color signal SCN is supplied to the APC circuit 16, from which the frequency is the NTSC color subcarrier frequency FCN and the phase is the same as that of the bust signal B+. A wave signal is obtained and supplied to the frequency converter 17, while an oscillation signal of the color subcarrier frequency Fcp of the PAL-M system from the oscillator 19 is supplied to the frequency converter 17 through the contact N of the switch 1, and this frequency F from converter 17. A signal with a frequency of P+FON is obtained, which is supplied to the frequency converter 15, from which the carrier color signal SCN from the bandpass filter 14 is converted into a signal whose color subcarrier frequency is (Fcp+FcN)-
A signal Fp converted to FcNOfcp is obtained. This signal Fp is supplied as it is to one input terminal A of the switch circuit 20, and this signal Fp is also supplied to the other input terminal B of the switch circuit 20 through the modifier 22.

In this case, the signal Fp supplied to one input terminal of the switch circuit 20 is followed by the burst signal B+ as shown in FIG.
The resulting signal becomes a signal FpO followed by a burst signal B- as shown in FIG. 4E, which is symmetrical about the signal Fp<5U axis. Since the switch 20 is alternately switched between the input end A side and the input end B side every horizontal section by the output signal of the flip-flop circuit 25, the switch circuit 20 can be operated as shown in FIG. 4G. A carrier color signal in which a burst signal B+ and a burst signal B- appear alternately in each horizontal section, and a carrier color signal in which the phase of the carrier wave modulated by the red color difference signal is inverted in each horizontal section is obtained. The signal is supplied to a combiner 13 and combined with the luminance signal. Therefore, the original PAL-M color video signal Svp is obtained at the output terminal 30, and is led out to the output terminal 60 through the contact P of the switch 5. Furthermore, this NT
When converting from the SC color video signal SVN back to the PAL-M color video signal Svp, it is sufficient to simply invert the switch circuit 20 alternately every horizontal section. Burst gate circuit 2
6, 27, a phase shifter 28, and a phase detector 29 are not necessary, and the switch 2 is switched to the contact N side which is set as a free end as described above. In this way, according to the converting device according to the invention, using the same converting device, the P.A.
It is possible to convert an LM color video signal to an NTSC color video signal, and then convert the converted NTSC color video signal to the original PAL-M color video signal.

Therefore, if the device of the present invention is connected to a recording/playback device as an adapter as shown in the example in the figure, the recording/playback device, which can only record and playback NTSC system color video signals, can output PAL-M
It is possible to record and play back the color video signals of this system. Note that the converted NTSC color video signal is
When the phase of the color subcarrier is defined so that the burst signal B- is continuous as shown in FIG.
The phase of the continuous wave signal is 90 degrees ahead of the burst signal B- as shown by the solid line in FIG. A signal that is symmetrical about the V axis with respect to the color signal is obtained, and therefore, the switch circuit 20 generates a burst signal B- and a burst signal whose phase is advanced by 90 degrees as shown in FIG. 5D. Then, the original PAL
-The phase will be different from that of the M system color video signal, but as mentioned above, in the example shown in the figure, the phase of the color subcarrier is defined so that the burst signal B+ is continuous, so the modifier 22 Since a signal is obtained that is symmetrical about the U axis with respect to the carrier color signal supplied to it, the switch circuit 20 generates a correct PAL-M in which the burst signal B+ and the burst signal B- alternately continue every horizontal interval.
A carrier color signal of the system is obtained.

Note that the conversion device according to the present invention converts an NTSC color video signal to a PAL-M color video signal,
This converted PAL-M color video signal is
Needless to say, the present invention can also be applied to the case of converting to an SC color video signal.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining a PAL signal, Fig. 2 is a system diagram of an example in which the conversion device according to the present invention is connected to a recording/playback device like an adapter, and Figs. 3 to 5 are for explaining the same. This is a diagram for 10 is a conversion device according to the present invention, 12 is a low-pass filter, 14 is a band-pass filter, 15 and IT are frequency converters, 16 is an APC circuit, and 18 is a converter whose oscillation frequency is NTS.
An oscillator 19 has an oscillation frequency of a color subcarrier frequency of the PAL-M system, and 22 represents a modifier.

Claims (1)

[Claims] 1. A PAL color video signal in which the luminance signal has the same horizontal synchronization signal frequency and vertical synchronization signal frequency as the NTSC color video signal, and the carrier color signal has a phase inversion every horizontal interval is converted into an NTSC color video signal. A device for converting into a color video signal or vice versa, comprising: a luminance signal extraction circuit that obtains a luminance signal from an input color video signal; a carrier color signal extraction circuit that obtains a carrier color signal from the input color video signal; and the PAL system. a first oscillator with a color subcarrier frequency f_C_P of the NTSC system, a second oscillator with a color subcarrier frequency f_C_N of the NTSC system,
a first switch that is switched to obtain the output of either the first oscillator or the second oscillator when converting the signal to the signal converter and vice versa; and the output of the first switch and the carrier color. A first frequency conversion circuit obtains a frequency signal of f_C_P+f_C_N from the color subcarrier obtained from the carrier color signal from the signal extraction circuit, and converts the carrier color signal into a desired signal by the output signal of the first frequency conversion circuit. a second frequency conversion circuit that converts the frequency-converted carrier color signal from the second frequency conversion circuit into a color subcarrier frequency of the system; and a phase converter that obtains a signal whose phase is inverted with respect to a reference axis from the frequency-converted carrier color signal from the second frequency conversion circuit. and a switch circuit that alternately takes out the output of the phase converter and the output of the second frequency conversion circuit every horizontal interval, and a switch circuit that outputs the output of the phase converter and the output of the second frequency conversion circuit alternately for each horizontal interval, and a switch circuit that outputs the output of the phase converter and the output of the second frequency conversion circuit, and a switch circuit that outputs the output of the phase converter and the output of the second frequency conversion circuit. a switching signal forming circuit that supplies a switching signal; a phase detection circuit that detects the phase of the burst signal in the output signal of the switch circuit; a second switch for supplying the output of the phase detection circuit to the switching signal forming circuit only when converting the signal so that the output carrier color signal from the switching circuit always has a predetermined phase; , a synthesis circuit for synthesizing the carrier color signal from the switch circuit and the luminance signal from the luminance signal extraction circuit, and a color video signal converted from the synthesis circuit is obtained from the synthesis circuit.
TSC signal converter.