JPS5935555B2 - PAL-M color video signal recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention subjects the luminance signal of a PAL-M color video signal to angle modulation, for example frequency modulation, on the high frequency side, frequency converts this color subcarrier signal to the low frequency side, and generates a composite signal. Regarding the PAL-M color video signal recording device which is designed to record , especially when copying, so-called dubbing, is repeated multiple times using this PAL-M color video signal recording device, the recorded media will not be affected. This allows a good color reproduction image to be obtained.

Conventionally, the luminance signal of a color video signal is angularly modulated, for example, frequency modulated, this color subcarrier signal is frequency-converted to the lower frequency side, and the composite signal is recorded on a magnetic tape, and the composite signal is recorded on a magnetic tape. As a color video signal recording and reproducing apparatus for reproducing color video signals, a device as shown in FIG. 1 has been proposed.

Furthermore, the color video signal recording and reproducing apparatus shown in FIG. It is known that this component causes bright and dark dot interference on the playback screen, so in order to improve this, the frequency of the color subcarrier signal converted to the lower frequency side is set as fc, and the horizontal frequency is set as fH. The relationship is as follows: fc=(44-T)fH, that is, the blue line offset.

That is, in FIG. 1, first of all, in the case of recording, numeral 1 indicates a color video signal input terminal to which a PAL-M color video signal to be recorded is supplied. The supplied color video signal is supplied to a low-pass filter 2 to extract a luminance signal, which is supplied to a frequency modulator 3, and the resulting frequency-modulated luminance signal is synthesized via a high-pass filter 4. Supplied to circuit 5.

On the other hand, the color video signal supplied to the color video signal input terminal 1 is supplied to a band pass filter 6 to extract a color subcarrier signal having a color subcarrier frequency Fs, and this is supplied to a frequency conversion circuit 7. Also, the color video signal from the color video signal input terminal 1 is supplied to the synchronization signal separation circuit 9 through the recording side fixed contact R of the changeover switch 8, and the phase of the horizontal synchronization signal obtained at the output side of the synchronization signal separation circuit 9 is compared. circuit 1
For example, the output signal of a variable frequency oscillator 11 that oscillates a signal with a frequency of 351fH, which is 351 times the horizontal frequency FH, is supplied to one input side of the A signal having a horizontal frequency FH, which is heard on the output side of the frequency generator 12, is supplied to the other input side of the phase comparison circuit 10, and the phase of this horizontal frequency FH signal and the horizontal synchronization signal is compared, and this phase error is calculated. The signal is supplied to the variable frequency oscillator 11 through a low pass filter 13 to control its oscillation frequency.

Then, the output signal of this variable frequency oscillator 11 is supplied to a red frequency divider 14 with a frequency division ratio according to the offset, that is, a blue frequency division ratio, and a signal with a frequency is obtained on the output side of this responsible frequency divider 14. , this signal is supplied to the frequency conversion circuit 15, and the oscillation output signal of the crystal oscillator 16 whose oscillation frequency is the color subcarrier frequency Fs is supplied to this frequency conversion circuit 15, and the output signal is obtained on the output side of this frequency conversion circuit 15. The signal is supplied to the bandpass filter 17, and a signal with a frequency of Fs+FO is obtained at the output side of the bandpass filter 17, and this frequency is Fs+F.
The signal c is supplied to the frequency conversion circuit 7 through the recording side fixed contact R of the changeover switch 18, and the signal obtained at the output side of this frequency conversion circuit 7 is supplied to the low pass filter 19. The frequency is F on the output side of 19.

=(44-I) A color subcarrier signal whose frequency is converted to the low frequency side of FH (low frequency converted color subcarrier signal) is obtained, and a low frequency converted color subcarrier signal obtained at the output side of this low pass filter 19 is obtained. The signal is supplied to a combining circuit 5, and a combined signal obtained by combining the low-pass conversion color subcarrier signal with a frequency of Fc and a frequency-modulated luminance signal is obtained on the output side of the combining circuit 5, and this combined signal is switched. It is supplied to the recording/reproducing magnetic head 21 through the recording side fixed contact R of the switch 20 and recorded on the magnetic tape. During reproduction, the reproduced video signal from the magnetic head 21 is supplied to the high-pass filter 23 and the low-pass filter 24 through the reproduction side fixed contact P of the changeover switch 20 and further through the reproduction amplifier 22, respectively. The frequency-modulated luminance signal obtained at the output side of this high-pass filter 23 is sent to a limiter circuit. 25 to a frequency discrimination circuit 26, and the luminance signal obtained at the output side of this frequency discrimination circuit 26 is supplied to a synthesis circuit 27.

Further, the low-pass converted color subcarrier signal obtained at the output side of the low-pass filter 24 is supplied to the frequency conversion circuit 28 . In addition, the luminance signal obtained on the output side of the frequency discrimination circuit 26 is transferred to the synchronization signal separation circuit 9 through the reproduction side fixed contact P of the changeover switch 8.
The horizontal synchronizing signal obtained at the output side of the synchronizing signal separation circuit 9 is supplied to one input side of the phase comparator circuit 10 in the same way as during recording. The output signal of the variable frequency oscillator 11 that oscillates the signal is supplied to the one frequency divider 12 that makes this signal equal, and the frequency obtained at the output side of this one frequency divider 12 is phase-compared with the horizontal frequency FH signal. circuit 10
This signal of horizontal frequency FH is phase-compared with the horizontal synchronizing signal of the reproduced video signal, and this phase error signal is supplied to the variable frequency oscillator 11 through the low-pass filter 13. , to control its oscillation frequency.

Then, the output signal of this variable frequency oscillator 11 is supplied to a high frequency divider 14 with a frequency division ratio according to the offset, that is, a red frequency division ratio, and a signal with a frequency is obtained on the output side of this high frequency divider 14. , this signal is supplied to the frequency conversion circuit 15, and the oscillation output signal of the crystal oscillator 16 whose oscillation frequency is the color subcarrier frequency F8 is supplied to this frequency conversion circuit 15, and the output signal is obtained on the output side of this frequency conversion circuit 15. The signal is supplied to the bandpass filter 17, and a signal with a frequency of F8+Fc is obtained at the output side of the bandpass filter 17, and this frequency is Fs+F.
The signal of c is supplied to the frequency conversion circuit 28 through the playback side fixed contact P of the changeover switch 18, and the frequency conversion circuit 2
The signal obtained at the output side of 8 is passed through a bandpass filter 29 to obtain an original color subcarrier signal with a frequency of Fs, and this is supplied to a synthesis circuit 27, where it is combined with a color subcarrier signal. The original color video signal obtained at the output terminal 30 of the combining circuit 27 is supplied to a monitor to obtain a color reproduced image.

In such a conventional color video signal recording/reproducing device, there is a relationship between the frequency Fc of the low-pass converted color subcarrier signal and the frequency FH of the horizontal synchronization signal, so that jitter in the low-pass converted color subcarrier signal is can be completely corrected by the horizontal synchronization signal.

However, when dubbing is performed using a color video signal recording and reproducing apparatus as shown in FIG. 1, the frequency relationship is as follows.

Here, the crystal oscillator 16 of the recording device for the first duping
The oscillation frequency is FSlR, the frequency of the low-pass conversion color subcarrier signal at this time is FCl, the oscillation frequency of the crystal oscillator 16 of the reproducing device for the first duping is FSlP, the jitter of the horizontal synchronization signal at this time is α1, The jitter of the low-pass conversion color subcarrier signal at this time is β1, and the oscillation frequency of the crystal oscillator 16 of the recording device for the second duping is FS2R,
At this time, the frequency of the low-pass conversion color subcarrier signal is set to FC2.
The oscillation frequency of the crystal oscillator 16 of the reproducing device for the second duping is FS2P, the jitter of the horizontal synchronization signal at this time is α2, and the jitter of the low-pass conversion color subcarrier signal at this time is β
2, and the following are the 3rd, 4th, kth...
・There are 3 saphics that change each corresponding to the nth time.
, 4, k...n. Here, the relationship between αk and βk is as follows.

Now, if the frequency of the color subcarrier signal of the input signal during the first recording is Fs, and the frequency of the horizontal synchronizing signal at this time is FH, then in the first recording, fc1=FslR+(44-1)FH- Fs゜゛゜゜゜゜゜゜゜゜゜ (2) The frequency FSl of the color subcarrier signal in the first reproduction is calculated by substituting equation (2) into equation (3): fs1 = Fslp - FslR + (44-s)
Yu - β1 + FS Here, from the relational expression (1), β1 = (4
4-Y) Since α1.

Similarly, in the second recording, the frequency FS2 of the color subcarrier signal in the second reproduction is
Now, when calculating by substituting equation (5) into equation (6), from equation (1), β2=(44 Ikkaku)α2, and so on, when dubbing is performed n times in the same manner, it becomes.

Generally, the deviation in the oscillation frequency of the crystal oscillator 16 is approximately 50Hz.
Since the frequency is within the range of 200Hz, if the duping operation is performed multiple times, or in the worst case twice, the frequency will be similar to 200Hz, and the center frequency of Fsn will deviate from 200Hz compared to Fs.

Incidentally, the pull-in range of a normal color monitor is 200Hz.
As a result, the monitor loses its color lock, resulting in an image with no color. In view of this, the present invention is designed so that a good color image can be obtained even when dubbing is repeated a plurality of times.

An embodiment of the PAL-M color video signal recording apparatus of the present invention will be described below with reference to FIG.

In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted. In this example, during recording, a burst signal gate circuit 31 extracts a burst signal from a color subcarrier signal having a frequency of Fs of an input color video signal obtained at the output side of the bandpass filter 6 from this color subcarrier signal. The burst signal obtained at the output side of this burst signal gate circuit 31 is supplied to a ringing oscillator 32 for converting this burst signal into a continuous signal, and the burst signal obtained at the output side of this ringing oscillator 32 is A continuous signal of the burst signal is supplied to the crystal oscillator 16 as a synchronizing signal, and the oscillation phase of the crystal oscillator 16 is controlled by this continuous signal of the burst signal. The rest of the structure is the same as in FIG. In this example, reproduction is performed in the same manner as in FIG. Since the present invention is configured as described above, when recording a color video signal, the color subcarrier signal obtained at the output side of the bandpass filter 6 is passed through the burst signal gate circuit 31 to obtain a burst signal, and this burst signal is The signal is supplied to the ringing oscillator 32 to obtain a continuous burst signal, and the oscillation frequency of the crystal oscillator 16 is synchronized with this continuous burst signal.

That is, when recording an input color video signal, the oscillation frequency of the crystal oscillator 16 matches the burst signal of the input color video signal. Other operations are similar to those in FIG. 1. Therefore, when dubbing is performed using the color video signal recording apparatus of the present invention, Fs and FSlR in equation (2) are the same.

FCl2 (44-1/8) FH・・・・・・・・・・・・
・(9) Here, by substituting equation (9) into equation (3) and calculating, Fsl - Fslp + (44-1/8) α "β1 Here, from the relational expression of equation (1), P1 = (44-1/ 8) Since α1, FSl=FSlP.

Similarly, in the second recording, Fc2 = (44-1/8)FH...
・00), and the frequency FS2 of the color subcarrier signal in the second reproduction is Fs2=Fs2p+(
44-1/8)FH+(44-1/8)α2-(FC2
+β2), and by substituting the formula AO) into this formula (6) and calculating, it becomes FS2::FS2P, and when dubbing is done n times, similarly FSO-FSnP...
... a1), which is the same as the frequency of the crystal oscillator 16 when it was last reproduced, that is, the nth time, and is generally within 50 Hz of Fs, so it will not go out of the lock range of the color monitor.

Therefore, there is an advantage that a good color reproduction image can be obtained even when dubbing is performed multiple times. It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations can be taken without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional color video signal recording/reproducing apparatus, and FIG. 2 is a block diagram showing an embodiment of the PAL-M type color video signal recording apparatus of the present invention. 9 is a synchronization signal separation circuit, 10 is a phase comparison circuit, 11 is a variable frequency oscillator, 15 and 28 are respective frequency conversion circuits,
16 is a crystal oscillator, 21 is a magnetic head, 23 is a high-pass filter, 24 is a low-pass filter, 30 is an output terminal,
31 is a burst signal gate circuit.

Claims (1)

[Claims] 1. A first frequency converter that takes as an input signal a PAL-M color video signal reproduced by a magnetic recording and reproducing device and converts the color subcarrier signal of this input signal into a low frequency range;
an AFC circuit that forms a signal in the low frequency range from the horizontal synchronization signal of the input color video signal; and a second frequency converter for forming a frequency-converted carrier wave from the output signal of the crystal oscillator having fluctuations, wherein the color subcarrier signal and the output signal of the second frequency converter are at the first frequency. It is supplied to a converter to form a low frequency chroma signal for dubbing, and the oscillation frequency of the crystal oscillator is converted to the PAL-M.
1. A PAL-M color video signal recording apparatus, characterized in that frequency control is performed by a continuous signal whose frequency is locked to a burst signal having playback jitter of a PAL-M color video signal.