JPS6115492A - Video signal converting device - Google Patents

Abstract

PURPOSE:To record an SECAM video signal as a color video signal by a PAL videotape recorder by using an SECAM video signal as a color signal of line sequence base band, and AM-demodulating by modulation axes deviated by 90 deg. to each other. CONSTITUTION:SECAM video signals are supplied to an LPF21 and a BPF22 through an input terminal 10, and luminance signals Y is taken out from the LPF21, and FM modulated blue and red color difference signals are taken out from the BPF22 in line sequence. FM modulated color signals SE are supplied to an FM demodulating circuit 31 and a line discriminating circuit 32, and color signals of base band BB are obtained from the FM demodulating circuit 31 in the state that the level ratio of blue color difference signal and red color difference signal is matched to that of PAL video signals. The line sequence base band color signals BB are supplied to a balanced modulating circuit 51. Further, subcarrier Cb equal to subcarrier frequency of PAL video signal is supplied from a subcarrier generating circuit 60 and AM modulated. Thus, video signals that can be recorded in the PAL videotape recorder are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention enables a PAL video tape recorder to record a SECAM video signal on a magnetic tape as a color video signal, and a PAL television receiver to record a SECAM video signal as a color video signal on a magnetic tape. The present invention relates to a video signal conversion device that converts video signals so that they can be displayed as images.

Background Art and Problems The SECAM video signal is FM-modulated in a line-sequential manner on subcarriers with different frequencies for the blue and red color difference signals, so that the blue and red color difference signals are out of phase by 90 degrees from each other. Although the method is different from that of a PAL video signal in which the subcarrier is AM-modulated on each line, the line frequency, field frequency, etc. are the same as the PAL video signal. Therefore, SECA
A possible method is to record the SRCAM video signal as a color video signal on a magnetic tape with a PAL video tape recorder and display it as a color image on a PAL television receiver by converting the M video signal. It has been implemented.

By the way, in this case, conventionally, line-sequential FM-modulated color signals for the blue and red color difference signals of the SRCAM video signal are synchronized for the blue and red color difference signals in the same way as the carrier color signal of the PAL video signal. is converted into an AM-modulated color signal, and a burst signal, which is the same as the burst signal of the PAL video signal, is added to this. Therefore, for the above purpose, a PAL videotape recorder or PAL
Conventional video signal conversion devices that are connected to or added to television receivers require a delay circuit with a delay time of one line to synchronize blue and red color difference signals, and this delay circuit is expensive. Therefore, there is an inconvenience that the price of the device increases.

OBJECTS OF THE INVENTION In view of this, the present invention provides a color video signal on a magnetic tape in a PAL video tape recorder without synchronizing the SECAM video signal, that is, with the blue and red color difference signals remaining line sequential. We propose a new video signal conversion device that does not require a delay circuit for the line delay time, and converts it so that it can be recorded as a color image and displayed as a color image on a PAL television receiver. It is something to do.

Summary of the Invention The present invention demodulates line-sequential FM modulated color signals for blue and red color difference signals of a SECAM video signal,
Line-sequential baseband color signals are obtained for the blue and red color difference signals, and the line-sequential baseband color signals are converted into blue color difference signals in the PAL video signal in the line of the blue color difference signal without being synchronized. The first phase axis corresponds to the modulation axis of the signal, and the red color difference signal line has a second phase axis that is delayed by 90 degrees with respect to the first phase axis.
M modulating the blue and red color difference signals to obtain AM-modulated color signals with modulation axes shifted by 90° from each other in line sequence,
This AM-modulated color signal has a third phase axis that is 135° ahead of the first phase axis in the line of the blue color difference signal, and a third phase axis that is advanced by 135° with respect to the first phase axis in the line of the red color difference signal. A burst signal of a fourth phase axis advanced by 90° with respect to the axis is added.

As a result, the video signal obtained by the video signal conversion device of the present invention is a certain line in which the modulation axis of the red color difference signal of the PAL video signal is advanced by 90 degrees with respect to the modulation axis of the blue color difference signal. On the Tsuoki line, the blue color difference signal is PA
The L video signal is AM-modulated with the first phase axis corresponding to the modulation axis of the blue color difference signal, and the first phase axis that is 135° advanced with respect to the first phase axis that is the modulation axis of the blue color difference signal. A burst signal with a phase axis of 3 is added, and the modulation axis of the red color difference signal of the PAL video signal is 90 degrees with respect to the modulation axis of the blue color difference signal.
° In every other line corresponding to the delayed line, the red color difference signal is AM-modulated on the second phase axis corresponding to the modulation axis of the red color difference signal of the PAL video signal. 4 for the second phase axis, which is the modulation axis of the red color difference signal.
Since the burst signal of the fourth phase axis delayed by 5 degrees is added, the blue and red color difference signals are recorded as color video signals on the magnetic tape with a PAL video tape recorder, keeping the line sequential order. It can also be displayed as a color image on a PAL television receiver.

Embodiment FIG. 1 shows an example of a video signal conversion device of the present invention, in which a SECAM video signal to be converted is supplied to a low-pass filter 21 and a band-pass filter 22 through an input terminal 10, and a luminance signal Y is output from the low-pass filter 21. A line-sequential FM-modulated color signal SR is taken out from the bandpass filter 22 for the blue and red color difference signals, and an FM-modulated color signal SE is supplied to the FM demodulation circuit 31 and the line discrimination circuit 32. . Further, the luminance signal Y is supplied to the synchronization separation circuit 4I, a horizontal synchronization signal H is taken out from the synchronization separation circuit 41, and this horizontal synchronization signal H is supplied to the line discrimination circuit 32. Then, in the line discrimination circuit 32, the line of the blue color difference signal and the line of the red color difference signal are determined by unmodulated subcarriers having different frequencies between the line of the blue color difference signal and the line of the red color difference signal included in the FM modulated color signal SE. The line of the red color difference signal is discriminated, and as shown in FIG. In the line Lr of the color difference signal, a low level line discrimination signal LI is obtained. This line discrimination signal Ll is supplied to the FM demodulation circuit 31, and the demodulation characteristic in the FM demodulation circuit 31 is the line Lb of the blue color difference signal.
The FM demodulation circuit 31 demodulates the line-sequential FM-modulated color signal BE, and as shown in FIG. The blue color difference signal Eb is the baseband color signal B of the red color difference signal Er in the line Lr.
B is obtained when the level ratio of the blue color difference signal Eb and the red color difference signal Er is matched to that of the PAL video signal.

This line-sequential baseband color signal BB is supplied to a balanced modulation circuit 51 forming an AM modulation circuit 50.

Further, a subcarrier cb having a frequency equal to the subcarrier frequency of the PAL video signal is obtained from the subcarrier generation circuit 60,
This subcarrier cb is supplied to the input terminal of the switch 52 of the AM modulation circuit 50 with the same phase, and further, the subcarrier cb is supplied to the phase shift circuit 53 of the AM modulation circuit 50 so that the phase is delayed by 90°. , 9 for this subcarrier cb
The subcarrier Cr with a 0° phase delay is supplied to another input terminal r of the switch 52 . Then, the line discrimination signal Ll output from the line discrimination circuit 32 is supplied to the control terminal of the switch 52, and the switch 52 is connected to the input terminal side for the line Lb of the blue color difference signal. The red color difference signal line Lr is switched to the input terminal r side, and the output of the switch 52 is connected to the second input terminal R.
As shown in the figure, in the line Lb of the blue color difference signal, the subcarrier cb has a phase indicated by the U axis (BY axis) in FIG. ) for 9
A subcarrier Cc of the subcarrier Cr whose phase is delayed by 0° is obtained, and this subcarrier Cc is supplied to the balanced modulation circuit 51 and balanced modulated by the line sequential baseband color signal BB. Therefore, from the balanced modulation circuit 51, that is, A
From the M modulation circuit 50, as shown in FIG.
In line b, the blue color difference signal Db is AM-modulated on the U axis (B-Y axis) shown in Figure 4, and in line Lr it is delayed by 90° with respect to the U axis (13-Y axis) shown in Figure 5. A modulated color signal AC of the red color difference signal Dr subjected to AM modulation on the phase axis is obtained.

This line-sequential modulated color signal AC is supplied to the input terminal C of a switch 71 constituting the burst signal addition circuit 70. Furthermore, the PA obtained from the subcarrier generation circuit 60
A subcarrier cb having a frequency equal to the subcarrier frequency of the LBII image signal and having a phase on the U axis (BY axis) in FIG. and 135 for this subcarrier cb.
°The subcarrier Cp whose phase is advanced is the burst signal addition circuit 7
The subcarrier Cp is supplied to the input terminal p of the switch 73 with the same phase, and the subcarrier Cp is further supplied to the phase shift circuit 74 of the burst signal addition circuit 70 to advance the phase by 90°. A subcarrier Cm that is 90° in phase and therefore 45° behind the subcarrier Cr output from the phase shift circuit 53 of the AM modulation circuit 50 is supplied to another input terminal m of the switch 73. Ru. Then, the line discrimination signal Ll output from the line discrimination circuit 32 is supplied to the control terminal of the switch 73, and based on the line discrimination signal Ll, the switch 73 selects the line r− of the blue color difference signal.
In line Lr of the red color difference signal, the input terminal is switched to the p side, and as shown in FIG. 135 for the glue axis (B-Y axis) in Figure 3
With the subcarrier Cp whose phase is advanced by 100 degrees, the subcarrier Cs of the subcarrier Cm whose phase is delayed by 135 degrees with respect to the U axis (B-Y axis) is obtained in the line Lr of the red color difference signal, and this subcarrier Cs is obtained. C5 is supplied to another input terminal S of the switch 71 mentioned above.

Further, the horizontal synchronization signal H obtained from the synchronization separation circuit 41 described above is supplied to the monostable multi-high break 42, and the trailing edge of the horizontal synchronization signal H causes the monostable multi-by break 4
2 is triggered, a pulse signal Hd is obtained from the monostable multi-high break 42, which is at a high level during a short period of time from the trailing edge of the horizontal synchronizing signal H and is at a low level during other periods. The pulse signal Hd is supplied to the monostable multi-high break 43, and the monostable multi-high break 43 is triggered by the trailing edge of the pulse signal Hd.
As shown in FIG. 2, a switching signal BF is obtained which is at a high level during a period corresponding to a burst signal period of a PAL video signal and is at a low level during other periods.

This switching signal BF is then applied to the burst signal addition circuit 70.
Based on the switching signal BF, the switch 71 is switched to the input terminal C side during periods other than the period corresponding to the burst signal period of the PAL video signal, and During the period corresponding to the burst signal period, the input terminal is switched to the S side, and the modulation axis of the red color difference signal of the PAL video signal is switched to the output of the switch 71, that is, the output of the burst signal addition circuit 70. At every other line Lb, which corresponds to a line advanced by 90° with respect to the modulation axis, as shown in Figs. 135 for the U axis (B-Y axis) for the color difference signal Db
A burst signal Bp with a phase advanced by 1° is added, and corresponds to a line in which the modulation axis of the red color difference signal of the PAL video signal is delayed by 90° with respect to the modulation axis of the blue color difference signal.
In the other every other line Lr, as shown in FIGS. 2 and 5, the red color difference signal Dr is AM-modulated with a phase axis delayed by 90 degrees with respect to the U axis (BY axis). On the other hand, the U axis (
A carrier color signal QP is obtained to which a burst signal Bm having a phase delayed by 135° with respect to the B-Y axis is added.

Then, the luminance signal Y obtained from the aforementioned low-pass filter 21 and the carrier color signal QP obtained from the burst signal addition circuit 70 are supplied to a synthesis circuit 80 and synthesized, and a converted video signal is obtained at an output terminal 90. It will be done.

The video signal obtained from the video signal conversion device of the present invention can be displayed as a color image on a PAL television receiver. That is, the above-mentioned carrier color signal QP is
When supplied to the color demodulation circuit of an L-television receiver, the carrier color signal QP has 135
° On every other line Lb where a burst signal Bp with an advanced phase exists, the AM-modulated blue color difference signal Db on that line and the l line delayed by the delay circuit with the delay time of one line. The added value of the previous AM-modulated red color difference signal Dr is supplied to the blue color difference signal demodulation circuit, and the blue color difference signal is generated by the subcarrier of the phase of the U axis (BY axis). At the same time as being synchronously detected, the AM modulated red color difference signal Dr of one line before is subtracted from the AM modulated blue color difference signal Db on that line, and the result is sent to the red color difference signal demodulation circuit. is supplied to the U axis (B
The red color difference signal is synchronously detected by the subcarrier whose phase is advanced by 90° with respect to the carrier color signal QP (B-Y axis).
- Burst signal B with phase delayed by 135° with respect to Y axis)
In every other line Lr where m exists, the sum of the AM-modulated red color difference signal Dr in that line and the AM-modulated blue color difference signal Db of the previous line is , the blue color difference signal is supplied to the demodulation circuit, and the U-axis (B
The blue color difference signal is synchronously detected by the subcarrier with the phase of -Y axis), and from the AM modulated red color difference signal Dr on that line, the AM modulated blue color difference signal Db of the previous line is detected. , and the subtracted signals are supplied to a red color difference signal demodulation circuit, and the red color difference signal is synchronously detected using a subcarrier whose phase is delayed by 90 degrees with respect to the U axis (BY axis). Therefore, a color image is displayed although the degree of color saturation is lowered.

Further, the video signal obtained from the video signal converting device of the present invention can be recorded as a color video signal on a magnetic tape using a PAL video tape recorder. FIG. 6 shows an example of a system in which a SECAM video signal is recorded on a magnetic tape by a PAL video tape recorder using the video signal conversion device of the present invention. The PALI! is supplied to the recording circuit 3 through the terminal 2 and subjected to recording processing, and the processed PALI! ItL image signal is recorded and played back switch 4
The PAL video signal is supplied to the magnetic head 5 through the recording side contact R and recorded on the magnetic tape, and the PAL video signal reproduced from the magnetic tape by the magnetic head 5 is sent to the reproduction circuit 6 through the reproduction side contact P of the recording/reproduction switch 4. The PAL video signal is supplied and subjected to playback processing, and the processed PAL video signal is output to the output terminal 7. And S E
The video signal conversion device 9 of the present invention described above is connected between the input terminal 8 to which the C, A M video signal is applied and the input terminal 2 to which the PAL video signal is applied, and the video signal converted as described above is generated. Signals are recorded on a magnetic tape by a PAL video tape recorder 1 and reproduced from the magnetic tape.

Effects of the Invention The video signal conversion device of the present invention demodulates line-sequential FM modulated color signals for the blue and red color difference signals of the SECAM video signal, and converts the blue and red color difference signals to a line-sequential basis. Obtain the color signal of the band, and without synchronizing the line-sequential baseband color signal, in the line of the blue color difference signal, the first phase is made to correspond to the modulation axis of the blue color difference signal in the PAL video signal. axis, and the red color difference signal line is 90" relative to the first phase axis.
AM is modulated with a delayed second phase axis, and AM is performed with modulation axes shifted by 90 degrees from each other in line sequential fashion for blue and red color difference signals.
Obtain a modulated color signal, and add to this AM modulated color signal,
In the line of the blue color difference signal, the third phase axis is advanced by 135 degrees with respect to the first phase axis, and in the line of the red color difference signal, the third phase axis is advanced by 90 degrees with respect to the third phase axis. 4
Since we added a burst signal on the phase axis of S
The ECAM video signal can be recorded as a color video signal on a magnetic tape with a PAL video tape recorder while keeping the blue and red color difference signals line sequential, and the color image can be recorded with a PΔL television receiver. Therefore, a delay circuit with a delay time of one line is not required.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram of an example of the video signal conversion device of the present invention, FIGS. 2 to 5 are diagrams for explaining its operation, and FIG. 6 is a connection diagram of an example of the video signal conversion device of the present invention. FIG. 2 is a connection diagram of an example of a system for recording an AMM video signal on a magnetic tape in a PAI-video tape recorder. In the figure, 31 is an FM demodulation circuit, 50 is an AM modulation circuit, and 60
7 is a subcarrier generation circuit, and 70 is a burst signal addition circuit.

Claims (1)

[Claims] Every other line of a SECAM video signal is a blue color difference signal that is FM modulated using one subcarrier frequency, and every other line is a blue color difference signal that is FM modulated using another subcarrier frequency. Demodulating the modulated color signal of the red color difference signal to obtain baseband color signals of the blue color difference signal for every other line and the red color difference signal for the other every other line. , FM demodulation circuit, and the frequency of the first phase in every other line and the second phase delayed by 90 degrees with respect to the first phase in the other every other line is PAL. A subcarrier equal to the subcarrier frequency of the video signal is AM-modulated with the baseband color signal obtained from the FM demodulation circuit, and every other line has the AM-modulated blue color difference signal. In the other every other line, an AM modulation circuit which obtains a modulated color signal of the AM modulated red color difference signal, and in the above-mentioned every other line, an AM modulation circuit which obtains a modulated color signal of the AM-modulated red color difference signal; 3, and in every other line, the subcarrier of the fourth phase, which is 90 degrees ahead of the third phase, and whose frequency is equal to the subcarrier frequency of the PAL video signal, is transmitted to the PAL video signal. and a burst signal addition circuit which extracts the modulated color signal in a period corresponding to a burst signal period and adds it as a burst signal to the modulated color signal obtained from the AM modulation circuit.