JPS6126875B2 - - Google Patents

Description

[Detailed Description of the Invention] The world's color television signal systems include:
There are three formats: NTSC, PAL, SECAM, and
The PAL system includes systems such as PAL-M and PAL-N. VTR for recording signals of these methods
Recording and reproducing devices (hereinafter referred to as VTR) such as
A recording method is used that matches the characteristics of the signal. However, there are regions such as Europe and some parts of the Middle East where multiple formats can be received, and with the recent spread of soft tapes, it is now possible to play back each format in various parts of the world. In order to meet such demands, VTRs that can record and play back multiple systems are required, but even if the recording system for luminance signals is the same, VTRs that use different recording systems for color signals have different color signal recording systems. A part or most of the signal system is required in multiple pieces, making it a large-scale operation.
In addition, a VTR that can record and play back only color television signals and black-and-white television signals of the first method.
When recording and reproducing color television signals of other formats, the brightness signal may be affected by beat prevention, etc. due to the influence of the color signal, which may not only result in no color but also make black and white screens look very unsightly. .

In view of these points, the present invention provides an apparatus capable of reproducing good black and white images without beat interference in the luminance signal for color television signals of different systems.

The most effective type of device is the PAL method.
It is a SECAM method. Both types have exactly the same brightness signal and synchronization signal system, and the signal band is approximately 4MHz to 5MHz. There are various methods for recording and reproducing these color television signals.
The recording method of the VHS method, which is a method for home VTRs, will be explained as an example.

FIG. 1 shows the SECAM signal recording and reproducing method in this VHS system, and FIG. 2 shows the PAL color signal recording and reproducing method.

The luminance signal systems are exactly the same for both, and in the case of black-and-white television signals, a band switching configuration is used to widen the luminance signal band and obtain high resolution.

In FIG. 1, if the signal to be recorded and reproduced is a black and white television signal, switches 4, 7, 1
0 and 14 are switched to the B/W side by the switching signal 22 that operates manually or automatically, and the color killer circuits 18 and 2
1 blocks the signal. At this time, the black-and-white television signal input to the input terminal 1 is filtered by a low-pass filter 2 to remove only high-frequency unnecessary components, passed through a switch 4, and is modulated by an angle modulator (for example, a frequency modulator) 5. It is recorded on tape through head 8. The signal reproduced through the head 8 passes through a switch 10, is demodulated by a frequency demodulator 11 and a low-pass filter 12, and is obtained at an output terminal 15 via a switch 14. When the input signal is a SECAM color television signal, the switches 4, 7, 10, and 14 are set to the C side by the signal 22, and the killer circuits 18 and 21 allow the signal to pass. At this time, the SECAM signal input to the input terminal 1 is passed through a low-pass filter 3, which has a narrower band than the low-pass filter 2, to remove the chrominance signal component and convert it into only a luminance signal, which is then frequency modulated, and further passed through a high-pass filter 6. The low range is removed and the signal is directed to switch 7. On the other hand, the frequency of the carrier wave is reduced to 1/4 by the bandpass filter 16, passed through the killer circuit 18, and superimposed on the frequency modulated signal of the luminance signal from which the low frequency has been removed, and recorded on the tape through the head 8. During playback, the high-pass filter 9 and low-pass filter 19 separate the frequency-modulated luminance signal and the low-pass chrominance signal, and the luminance signal passes through the switch 10 and is demodulated by the demodulator 11 and the low-pass filter 13. and is guided to the switch 14.

On the other hand, the color signal is returned to its original frequency by a frequency quadrupler 20, and a demodulated luminance signal is added to it via a killer circuit 21, so that a reproduced SECAM signal is obtained at an output terminal 15.

Even in the PAL system shown in Figure 2, the luminance signal is the first signal.
Since it is exactly the same as the case shown in the figure, the luminance signal system is omitted. In FIG. 2, blocks designated by the same numbers as in FIG. 1 represent the same elements and perform the same operations. PAL entering input terminal 1
The color signal (carrier frequency cp) separated from the color television signal by the band filter 16 is converted to a lower frequency signal by the frequency converter 23 using the continuous signal a. Signal a is a continuous signal 24 having a frequency cp+(40+1/8)H, which is the sum of a continuous signal with a frequency of 40H created from a horizontal synchronizing signal (frequency H) separated from the input signal and a continuous signal with a frequency cp+1/8H. Of the A and B tracks that are adjacent to each other, the phase of the A track remains unchanged, while the phase of the B track is delayed by 90 degrees for each line. The color signal thus converted into a low frequency signal passes through the killer circuit 18 and is recorded while being superimposed on the frequency-modulated luminance signal. During reproduction, the color signal separated from the luminance signal by the low-pass filter 19 is returned to the original frequency cp by the frequency converter 26 using the continuous signal a. The reproduction continuous signal a has a frequency controlled by a horizontal synchronization signal separated from the reproduction signal and a phase comparison error signal between the reference signal and the reproduction burst signal.
The continuous signal 24 created from the continuous signal of cp+1/8H is created by passing it through the phase shifter 25, and this continuous signal a
By performing frequency conversion in , time axis fluctuations that occur in color signals during recording and reproduction are removed. The output of 26 is summed with the signal passed through the 2-line delay line 27, and after interference signals from adjacent tracks are removed, it is added to the demodulated luminance signal via the killer circuit 21 and sent to the output terminal 15. A playback PAL signal can be obtained.

Consider the case where a PAL signal is recorded with a SECAM-VTR as shown in FIG. When the signal 22 is set to the monochrome side, the color signal is also modulated and demodulated without being separated from the luminance signal. At this time, the time axis fluctuations of the color signal are not removed, and since the color signal has a high frequency and large energy, it is easy to cause inversion phenomena and beats with the FM carrier during modulation, and this signal is
Or, even if you put it into a SECAM TV receiver, no color will appear, and beat interference of color signals and beat interference of other unnecessary components that occur during modulation will appear in the luminance signal.
It becomes very unsightly. Also, when the signal 22 is set to the color side, the color signal is recorded with its frequency divided to 1/4, but jitter is not removed during playback, and the frequency division and
During the multiplication process, amplitude components are lost, and noise in areas where there is no color signal increases, causing interference with the luminance signal. When such a signal is input to a television receiver, the normal colors are not displayed, color stripes appear, and even beat disturbance and inversion phenomena occur in the luminance signal. This phenomenon also occurs when the signal 22 is set to the black and white side during recording and set to the color side during playback, and vice versa.

The above-mentioned phenomenon also occurs when SECAM signals are recorded on a PAL-VTR as shown in FIG. At this time, when the signal 22 is set to the color side, the color signal is converted to a low frequency band and recorded, but interference from adjacent tracks cannot be removed, and in the case of the SECAM signal, the color signal carried between two lines cannot be removed. Since the phases are not always the same, the color signal is distorted by the circuit using the two-line delay line, and a normal color signal cannot be obtained.
This color signal becomes a beat for PAL television receivers, and also interferes with SECAM television receivers by not displaying the proper colors.

The same thing can be said about the mutual exchange of tapes recorded on VTRs as shown in FIGS. 1 and 2.

The present invention provides an apparatus that eliminates beat interference and the like for these luminance signals and obtains good black and white reproduced signals for color television signals of different formats. Figure 3 shows a SECAM system VTR.
An embodiment of the present invention for recording and reproducing PAL signals and automatically switching between the black and white side and the color side will be shown and explained. In FIG. 3, the same numbers as in FIG. 1 represent the same things and have the same functions. input signal
In the case of a SECAM color television signal, the output color signal of the bandpass filter 16 has amplitude characteristics in accordance with the bell filter characteristics of the SECAM system. The amplitude of this signal is flattened by an inverse bell filter 28 and then guided to a limiter 29 and an ACC circuit 30. The output of the limiter 29 is the frequency divider 17
The carrier wave frequency is reduced to 1/4, and the signal is led to the killer circuit 18 through a circuit 31 that also serves as a low-pass filter to remove harmonics and an equalization circuit to give the same amplitude characteristics as the original signal. On the other hand, ACC circuit 3
The unmodulated carrier (ID signal) contained in the back pouch of the horizontal synchronizing signal of each line is separated from the ID signal from the output color signal of 0. ACC circuit 30
is controlled by the level of this ID signal. 32
The output ID signal is guided to a SECAM signal discriminator 33 and a level detector 34. 33 is the level at which the output signal of 28 is present (e.g. -26dB of normal level)
When the above SECAM color signals are used, for example, a high level output is output, and at other times, a low level output is output. This means that the ID signal of the SECAM color signal is 4.406MHz on the RY line and 4.25MHz on the B-Y line.
Hz, this is possible by detecting this frequency difference and the level of the ID signal. On the other hand 3
4 outputs an output that is, for example, a high level when the ID signal is above a certain level, and a low level at other times. The color killer circuit 18 is controlled by the output of 33, and operates to conduct when the level is high and cut off when the level is low. In addition, the black and white/color imperial area changeover switches 4 and 7 are controlled by the OR signal 35 of each output of 33 and 34, and when the level is high, the color side is C, and when the level is low, it is the black and white side (B/W). . In this way, if the color signal of the input signal is a regular SECAM signal with a certain level or higher, the outputs 33 and 34 and the signal 35 will all be at a high level, and the configuration in FIG. 3 will be the SECAM signal in FIG. It operates in the same way as when recording a signal. When the input signal is a monochrome signal, the outputs 33, 34, and signal 35 are both at a low level, and the same operation as for the monochrome signal in FIG. 1 is performed, resulting in a high-resolution reproduced image. PAL with input signal color signal above a certain level
In the case of a signal, a burst signal is separated by an ID signal separator 32 and guided to a SECAM signal discriminator 33 and a level detector 34. At this time, PAL
Since the burst signal in the signal has a frequency of 4.43MHz on all lines, the output of 33 will be at a low level. On the other hand, the output of the level detector 34 becomes high level due to the burst signal. Therefore, the killer circuit 18 is cut off by the output of the SECAM signal discriminator 33 and the output of the level detector 34, and unnecessary color signals are not recorded.Also, since the signal 35 is at a high level, the switch 4, 7 is on the color side, and since the color signal component is removed from the luminance signal, no interference due to the color signal occurs.

Here, the signal 35 may be the output of the level detector 34 as it is, but the SECAM signal discriminator 33
By taking the OR of the output of the level detector 34 and the output of the level detector 34, when the signal is a small level, even if there is a slight difference between the thresholds of 33 and 34, when the signal is a SECAM signal, the killer circuit 18 and the switch are reliably detected. 4 and 7 can be on the color side. Also, switch 4,
7 were both controlled by the signal 35, but one of them was controlled by the signal 35, and the other was controlled by the SECAM signal discriminator 33.
The PAL color signal that enters the luminance signal can be removed even if controlled by the output of .

During reproduction, the chrominance signal separated from the luminance signal by the low-pass filter 19 has its amplitude leveled again by the reproduction equalization circuit 36, and is guided to the limiter 37 and the ACC circuit 38. The output color signal of the limiter 37 is returned to its original frequency by a quadruple multiplier 20 and a band filter 39, given an amplitude characteristic by a bell filter 40, and guided to a killer circuit 21. An ID signal is separated from the output signal of the band filter 39 by an ID signal separator 41 and guided to a SECAM signal discriminator 42.
On the other hand, an ID signal is separated from the output signal of the ACC circuit 38 by an ID signal separator 43 and guided to a level detector 44. The ACC circuit 38 is controlled by the level of the output ID signal of the ID signal separator 43.
SECAM signal discriminator 42 and level detector 44 are recording system SECAM signal discriminator 33 and level detector 3.
4, the killer circuit 21 is the output of the SECAM signal discriminator 42, and the monochrome/color band switching switches 10 and 14 are the OR signal 45 of the output of the SECAM signal discriminator 42 and the output of the level detector 44. It operates exactly the same way as when recording for SECAM signals, black and white signals, and PAL signals.

Note that when PAL signals are recorded using the recording method shown in Figure 3, color signals are not recorded, so when playing back
The outputs of the SECAM signal discriminator 42 and level detector 44 are on the black and white side, but since the color signals are already blocked on the recording side, they do not affect the reproduced signal in any way. Furthermore, when the color of the PAL signal is cut off in the recording system as shown in FIG. It is also possible to simply control the color killer circuit 21 and the switches 10 and 14 using the output. On the other hand, when the color killer circuit 18 and switches 4 and 7 are controlled only by the output of the SECAM signal discriminator 33 without providing the level detector 34 and the signal 35 in the recording system, and when recording is performed using the method shown in FIG. When reproducing a PAL signal, by adding a circuit consisting of an ACC circuit 38, an ID signal separator 43, and a level detector 44 to the reproduction system, the same effect as when the color of the PAL signal is cut off in the recording system can be obtained. is obtained.

In Fig. 3, the method of automatically obtaining the black-and-white/color switching signal has been explained, but even in the case of manual operation, the signals controlling the killer circuits 18 and 21 and the signals controlling the band switching switches 4, 7, 10, and 14 can be used. of
It is sufficient to give SECAM signals, PAL signals, and black and white signals separately.

In the above explanation, VHS system SECAM/VTR is used.
The present invention has been described with respect to recording and reproducing PAL signals as black and white signals, but conversely, PAL/VTR
The present invention is also effective when recording and reproducing SECAM signals. At this time, the PAL signal can be determined by comparing the phases of the 4.43 MHz continuous signal and the burst signal.

By using the present invention in a VTR other than the VHS system, it is possible to obtain a luminance signal without beat interference due to color signals when recording and reproducing different signals in PAL and SECAM-VTR.

The present invention can also be applied to color television signals of systems other than PAL and SECAM. for example,
The PAL-M system and the NTSC system have the same brightness signal and synchronization signal, and only the color signal differs; however, the frequency of the color subcarrier is approximately 3.58MHz, and the VTR color signal recording method is also different, so in the case of PAL/SECAM The present invention can be applied in the same manner.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a recording/reproducing method conventionally used in a VHS system SECAM color VTR, and Fig. 2 is a block diagram showing an example of a recording/reproducing system conventionally used in a VHS system PAL color VTR. FIG. 3 is a block diagram of essential parts showing one embodiment of the present invention. 1...Input terminal, 2, 3, 12, 13, 19...
...Low pass filter, 4,7,10,14...Switch, 5...Frequency modulator, 6,9...High pass filter, 8...Head, 11...Frequency demodulator, 15
...Output terminal, 16,39...Band filter, 1
7... Frequency divider, 18, 21... Killer circuit, 20... Multiplier, 28... Inverse bell filter, 29, 37... Limiter, 30, 38...
ACC circuit, 31... Equalize circuit, 32, 4
1,43...ID signal separator, 33,42...
SECAM signal discriminator, 34, 44...level detector, 36...reproduction equalization circuit, 40...bell filter.

Claims (1)

[Claims] 1 Separate a predetermined standard color television signal to be recorded into a luminance signal and a modulated color signal, the luminance signal is angularly modulated, the modulated chrominance signal is frequency-converted to a low frequency band, and then the angularly modulated angularly modulated When recording and reproducing a standard color television signal of a method different from the predetermined standard color television signal by superimposing it on the low frequency side of the luminance signal on a magnetic recording medium, modulation is performed in either the recording system or the reproducing system. A magnetic recording and reproducing device configured to block color signals and reproduce only luminance signals.