JPH0452672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When recording and reproducing a color video signal, the present invention determines the recording method of a carrier color signal recorded in one of two different methods, and selects a reproduction method that matches the recording method. The present invention relates to a television signal recording and reproducing device that can reproduce television signals.

General home video tape recorder (hereinafter referred to as
One of the systems for VTR (VTR) is the VHS system. In addition, the television system also includes NTSC.
There are methods such as PAL method, SECAM method, etc.
In line with these methods, the color signal recording and playback methods for VHS VTRs also include NTSC, PAL, and
It stipulates a different method called the SECAM method.

To record color video signals on magnetic tape,
A method is used in which the luminance signal is FM modulated and the carrier color signal is converted to a lower frequency. During reproduction, the luminance signal is demodulated and the carrier color signal is returned to its original frequency.

In other words, as shown in Figure 1, the VHS system
In the SECAM color signal recording and reproducing process in a VTR, during recording, a color video signal is supplied from an input terminal 11 to a low-pass filter 12, and a luminance signal extracted by the low-pass filter 12 is sent to an FM modulator 13.
The signal is supplied to FM and modulated. And that FM
The modulated luminance signal is supplied to a combiner 15 through a high-pass filter 14 .

On the other hand, when the color video signal from the input terminal 11 is supplied to the bandpass filter 16, the carrier color signal Co is taken out at the output of the bandpass filter.
In the SECAM method, this carrier color signal Co is f _OR =
The spectrum is distributed around two color subcarrier frequencies consisting of 282f _H and f _OB = 272f _H , and the above two color subcarrier frequencies f _OR and f _OH are alternated for each scanning line of the television device. Switch to . In addition, this carrier color signal Co is a signal obtained by compressing frequency components near the color subcarrier of the original carrier color signal using an inverse bell filter with a center frequency of 4.28MHz to reduce dot interference between scanning lines. It is.

The recording bell filter 17 expands the frequency components near the color subcarrier of the carrier color signal Co, and returns it to the original carrier color signal. The frequency divider 18 converts this signal to 1/4 the frequency and outputs it as a low frequency converted color signal. The low-pass converted color signal is supplied to the synthesizer 15 through a low-pass filter 19. Then, the synthesizer 15 adds the FM modulated luminance signal and the low-frequency conversion signal to create a composite video signal,
The composite video signal is amplified by the recording amplifier 20,
The signal is supplied to the head 22 through the recording side contact R of the changeover switch 21 and recorded on the magnetic tape 23.

During reproduction, the composite video signal reproduced by the head 22 is input to the reproduction amplifier 24 through the reproduction side contact P of the switch 21, amplified by the reproduction amplifier 24, and supplied to the high-pass filter 25. The FM modulated luminance signal extracted by the high-pass filter 25 is
The signal is input to the FM demodulator 26, which demodulates the signal, and the demodulated luminance signal is supplied to the synthesizer 28 through the low-pass filter 27.

On the other hand, the composite video signal amplified by the reproduction amplifier 24 is supplied to a low-pass filter 29, which removes the FM modulated luminance signal and extracts a low-frequency converted color signal. And the quadrupling circuit 30
The low frequency converted color signal is multiplied by 4 to convert it to a high frequency, and a bandpass filter 31 suppresses the low frequency converted color signal and high frequency components and extracts a carrier color signal from the multiplied signal. Furthermore, a reproducing inverse bell filter 32 suppresses frequency components centered around 4.28 MHz of the carrier color signal, outputs a carrier color signal matching the SECAM television signal, and supplies the signal to the synthesizer 28. do. Then, the reproduced luminance signal and the carrier color signal are added by the synthesizer 28, and a color image is obtained at the output terminal 33.

However, the recording/playback method of the SECAM method is significantly different from the color conversion method of VHS VTRs such as the PAL method and the NTSC method. Therefore, problems occur when recording and reproducing signals of different television broadcasting systems. In particular, in Europe, the PAL system for television broadcasting and
Because it is adjacent to the SECAM method area,
A device that can record and play back both PAL and SECAM television signals is desired. VHS method
VTRs record and play back SECAM television signals using the same method as PAL recording and playback devices, recording and playing back both PAL and SECAM systems. Replicating this SECAM signal processing method
It is called the SECAM method.

FIG. 2 shows a block diagram of a video signal recording and reproducing system using the approximate SECAM system.

In the approximate SECAM method, as shown in Figure 2,
The luminance signal processing circuit for recording, which processes the luminance signal in the color video signal and is comprised of a low-pass filter 12, an FM modulator 13, a high-pass filter 14, etc., is exactly the same as the SECAM system shown in FIG.

On the other hand, in the color signal processing circuit for recording, a color video signal is inputted from the input terminal 11 to a bandpass filter 34, and a carrier color signal is extracted from the output of the bandpass filter 34. This carrier color signal is input to the average modulator 35, where it is balanced-modulated with a frequency carrier of _fA . And the low pass fillet 36,
A low frequency color change signal obtained by converting the carrier color signal to a lower frequency is extracted from the balanced modulation output signal.

Here, when the color subcarrier frequency is f _S and the horizontal scanning frequency is f _H , f _A is a frequency expressed by f _A = f _S + (40+1/8) f _H. As a result, the output signal of the low-pass filter 36 is output as a low-pass converted color signal in which the color subcarrier frequency is low-pass converted to a low frequency of f _S −f _A =(40+1/8) f _H. This low frequency converted color signal is then supplied to the synthesizer 15, where it is combined with the FM modulated luminance signal output from the recording luminance system signal processing circuit. The composite signal is amplified by a recording amplifier 20 and recorded on a magnetic tape 23 via a head 22.

In the color signal processing circuit during reproduction, the composite video signal amplified by the reproduction amplifier 24 is passed through the low-pass filter 37.
The low-pass filter 37 suppresses the FM modulated luminance component in the reproduced composite signal and extracts the low-pass converted color signal in the reproduced composite signal.

This low-pass converted color signal is input to the balanced modulator 38, and is balanced-modulated with the frequency carrier _fA . This balanced modulation output signal includes, in addition to the carrier color signal centered on the color subcarrier frequency, extra frequency components such as a low-pass conversion color signal, a luminance signal, and harmonics. A chroma comb filter 39 suppresses extra frequency components and outputs only the carrier color signal via a bandpass filter 40 connected to the output of the comb filter 39.

On the other hand, high pass filter 25, FM demodulator 2
6. The brightness signal processing circuit for reproduction, which is composed of a low-pass filter 27 and the like, is processed in the same way as the SECAM method shown in FIG. 1, and demodulates the FM modulated brightness signal extracted by the high-pass filter 25 and returns it to a brightness signal The luminance signal is input to the synthesizer 28. Then, the synthesizer 28 adds the carrier color signal and the luminance signal output from the bandpass filter 40 and outputs the result from the output terminal 33 as a color video signal. In addition, in FIG. 2, the same parts as in FIG. 1 are given the same numbers.

Using this system, it is possible to record television signals in the RAL system and reproduce television signals in the PAL system, and it is also possible to record and reproduce television signals in the same system for the SECAM system. However, it is not possible to record and play back compatible PAL and SECAM formats.

In addition, in the NTSC system, the modulation frequency f _A is f _A
=f _S +40f _H , and since the modulation frequency is only slightly different, it is easy to change the circuit. In other words, as a VHS system VTR, it is possible to use a device that uses a combination of PAL/simulated SECAM, or a device that uses a combination of PAL/simulation SECAM/NTSC.

However, the carrier color signal of the SECAM television signal is counted down to 1/4 the frequency.
There is no recording/playback compatibility between SECAM system VTRs and imitation SECAM system VTRs. In other words,
When playing magnetic tape recorded using other methods,
Even if the recorded signal is in color, it is reproduced as a black and white reproduced signal.

The present invention solves the above-mentioned problems by reproducing video signals recorded on a magnetic tape using a color signal processing circuit suitable for the recording method, and combining the output of the reproducing process with a predetermined luminance signal. It is an object of the present invention to provide a television signal recording and reproducing apparatus capable of obtaining an original color video signal.

FIG. 3 shows an embodiment of the reproducing circuit configuration of the television signal recording and reproducing apparatus of the present invention, in which the same numbers are given to the same parts as in FIGS. 1 and 2, and the luminance signal processing The configuration is shown in Figures 1 and 2.
It is similar to the figure.

The first color signal processing circuit for reproduction includes a system from a low-pass filter 29 to a quadrupling circuit 30, a band-pass filter 31, and an inverse bell filter 32 for reproduction at the same time as the SECAM color signal processing circuit shown in FIG. It is. In this system, during reproduction, a signal that has passed through the bandpass filter 31 is input to an inverse bell filter 32 for reproduction, and is also input to a signal discrimination circuit 43 for black and white signals/color signals. If the input signal level of the signal discrimination circuit 43 is low, it is assumed that the carrier color signal is not input, and the switch 42 is made non-conductive by the control signal from the signal discrimination circuit 43, and the output signal of the inverse bell filter 32 is It is not transmitted to the synthesizer 44. Conversely, if the input signal of the signal discrimination circuit 43 is at the normal level, it is assumed that the carrier color signal is being input, and the switch 42 is made conductive by the control signal from the signal discrimination circuit 43, so that the output signal of the inverse bell filter 32 is The information is transmitted to the synthesizer 44.

Next, the second color signal processing circuit for reproduction includes a low-pass filter 37, a balanced modulator 38, a chroma comb filter 39, and a band-pass filter 40.
The system up to this point is the same as the color signal processing circuit of the approximate SECAM system shown in FIG. During reproduction, in this system, the output signal of the bandpass filter 40 is switched to the switch 45.
At the same time, the signal is input to a signal discrimination circuit 46 for black and white signals/color signals. If the input signal level of the signal discrimination circuit 46 is low, it is assumed that the carrier signal is not input, the switch 45 is made non-conductive by the control signal from the signal discrimination circuit 46, and the output signal of the bandpass filter 40 is passed to the synthesizer 44. I can't tell you. Conversely, if the input signal to the signal discrimination circuit 46 is at the normal level, it is assumed that the carrier color signal is being input, and the switch 4 is activated by the control signal from the signal discrimination circuit.
5 is made conductive, and the output signal of the bandpass filter 40 is transmitted to the combiner 44.

The synthesizer 44 then switches 42 or 4.
One of the carrier color signals selected by the conduction of 5 and the luminance signal supplied from the low-pass filter 27 are combined, and a color video signal is outputted to the output terminal 47.

Next, the signal discrimination means will be explained in detail.

When reproducing a recorded signal using the approximate SECAM method,
When reproduced by the SECAM type first color signal processing circuit from the low-pass filter 29 to the inverse bell filter 32 for reproduction, the low-pass converted color signal of 630KHz, which is the frequency of (40 + 1/8) f _H , is multiplied by 4.
The frequency is 2.52 MHz, but since the center frequency of the bandpass filter 31 connected to the output of the quadrupling circuit is 4.2 MHz, the quadrupled signal is attenuated. Then, when the signal level becomes low, the signal discrimination circuit 43 assumes that there is no input of the carrier color signal, and switches the switch 42 by the control signal of the signal discrimination circuit 43.
becomes non-conducting and the processed signal is not transmitted to combiner 44. At this time, the second
The carrier signal processed by the color signal processing circuit (37 to 40) is transmitted to the combiner 4 by the conduction of the switch 45.
4 can be conveyed.

Next, when reproducing the SECAMB method recording signal, when reproducing it in the second color signal processing circuit (37 to 40) of the analogous SECAM method, the low-pass converted color signal is input from the reproducing amplifier 34 to the low-pass filter 37. Although the frequency is 1.1MHz, the signal is attenuated by the 630KHz low-pass filter 37, resulting in a low signal level. Then, the input signal level of the signal discrimination circuit 46 decreases, it is assumed that there is no carrier color signal at the input of the signal discrimination circuit 46, the switch 45 is made non-conductive by the control signal of the signal discrimination circuit 46, and the processed signal is sent to the synthesizer. I can't tell 44. At this time,
SECAM type first color signal processing circuits 29 to 32
The processed carrier color signal is transmitted to the combiner 44 by turning on the switch 42.

In other words, according to the configuration example shown in FIG. 3, even if a recorded signal whose color video signal format is unknown is reproduced,
Color signal processing that matches the recording signal format can be performed without being reproduced by another color signal processing circuit with a different format.

FIG. 4 shows another embodiment of the invention. In the example shown in Figure 3, the signal discrimination circuit 46 for the imitation SECAM system and the signal discrimination circuit 43 for the SECAM system are integrated to form a signal discrimination circuit 48, and the switch 42 and switch 45 are integrated to form a switch. In this example, it is set to 49.

Note that the signal discrimination circuit 48 for black and white signals/color signals
Even if the discriminator always has a signal discrimination function for both the SECAM method and the imitation SECAM method, or even if it is a discriminator that discriminates the signal of the other when there is no color signal in one. good.

As described above, according to the present invention, a dedicated signal discrimination circuit is provided in each of the output circuits of the first and second color signal processing circuits, so that color video signals recorded on the same magnetic tape are Regardless of the signal format, a highly reliable determination can be made by simply detecting the level of the carrier color signal, and reproduction processing can be performed in accordance with the recording signal format.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional SECAM system recording and reproducing device, FIG. 2 is a configuration diagram of a conventional simulated SECAM system recording and reproducing device, and FIGS. 3 and 4 are a television signal recording and reproducing device according to the present invention. FIG. 2 is a configuration diagram of a reproduction system. 22...head, 23...magnetic tape, 24...
...Reproduction amplifier, 25...High pass filter, 26
...FM demodulator, 27,29,37...Low pass filter, 30...4 multiplier circuit, 31,40...
Bandpass filter, 32... Reverse bell filter for reproduction, 38... Balanced modulator, 39... Comb filter for chroma, 42, 49... Switch, 4
3, 46, 48...Signal discrimination circuit, 44...Synthesizer, 47...Output end.

Claims (1)

[Scope of Claims] 1. A quadrupling circuit that quadruples a first low-frequency converted color signal extracted from a reproduced composite video signal, and a first carrier color signal is extracted from the output signal of the quadrupling circuit. a first color signal processing circuit having a bandpass filter;
a first switch that controls non-conduction; a first signal discrimination circuit that makes the first switch non-conductive when the first carrier color signal is input and the level of the first carrier color signal is low; a low-pass filter for extracting a second low-pass converted color signal having a lower frequency than the first low-pass converted color signal from the composite video signal; and a balanced modulation for converting the second low-pass converted color signal to a higher frequency. and a comb filter for extracting a second carrier color signal from the output signal of the balanced modulation circuit;
a second switch that controls non-conduction; a second signal discrimination circuit that makes the second switch non-conductive when the second carrier color signal is input and the level of the second carrier color signal is low; A television signal recording and reproducing apparatus, characterized in that the first and second switches select and output one of the output signals of the first and second color signal processing circuits.