JPH06101856B2 - PAL video signal separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial field of use B Outline of the invention C Conventional technology D Problems to be solved by the invention E Means for solving problems F Action G Example G-1 Structure and operation (Figs. 1 and 2) (Fig.) G-2 Modification H Effect of the invention A Industrial field of application The present invention is provided in a recording system of a video tape recorder for recording and reproducing a PAL video signal, and separates a luminance signal and a carrier color signal from the PAL video signal. The present invention relates to a PAL video signal separation device.

B. Summary of the Invention The present invention provides a PAL video signal separating device for separating a luminance signal and a carrier color signal from a PAL video signal, which is provided in a recording system of a video tape recorder for recording and reproducing a PAL video signal. A delay circuit for delaying the supplied input video signal by two horizontal cycles over the carrier color signal band and the entire low-frequency band, and the delay circuit is provided between the video signal input terminal and the first output terminal. A subtraction type comb filter including a circuit, and a signal separation unit that forms the addition type comb filter including the delay circuit between the video signal input terminal and the second output terminal; If there is a predetermined band on the low frequency side of the carrier color signal band of the video signal before and after the portion of the delay time for one horizontal period of a part of the circuit, or a part of this predetermined band and its high frequency side Is a signal extraction unit that subtracts the signal components of all bands, at least the predetermined value on the low frequency side of the carrier color signal band of the signal obtained at the first output terminal and the signal obtained from the signal extraction unit. A special delay circuit other than the delay circuit for signal separation is provided by providing a signal adding section for adding the signal components of the band and the entire band on the low frequency side to the signal obtained at the second output terminal. With a simple circuit configuration that does not require, it is possible to obtain a separated luminance signal in which a signal component of a frequency between a frequency that is an integral multiple of 1/2 of the horizontal frequency within a predetermined band is enhanced. Is.

C Conventional technology In a recording system of a video tape recorder that records and reproduces PAL video signals, a luminance signal and a carrier color signal are separated from a video signal obtained by reception of television broadcasting, and the luminance signal is frequency-modulated and carried. The color signal is low-frequency converted, and the frequency-modulated luminance signal and the low-frequency converted carrier color signal are combined and recorded on the magnetic tape by the rotary magnetic head. In this case, the luminance signal and the carrier color signal are combined. A comb filter is used for the separation.

That is, including a delay circuit that delays the input video signal by two horizontal cycles, the gain is minimum in the band lower than the carrier color signal band of the input video signal, and the gain is minimum in the carrier color signal band of the input video signal. Form a valley with minimum gain at a frequency that is an integral multiple of 1/2 the horizontal frequency, and
A filter circuit with a frequency characteristic that is a comb-shaped characteristic that forms a peak with a gain of 0 dB at a frequency that is an odd multiple of the frequency is obtained, and a carrier color signal is obtained from this filter circuit. In the band lower than the carrier color signal band of the signal, the gain has a flat characteristic of 0 dB, and in the carrier color signal band of the input video signal, 1 / horizontal frequency
A filter circuit with a frequency characteristic that is a comb-shaped characteristic is formed in which a peak with a gain of 0 dB is formed at a frequency that is an integral multiple of 2 and a valley with a minimum gain is formed at a frequency that is an odd multiple of 1/4 of the horizontal frequency. Then, a luminance signal is obtained from this.

D Problem to be Solved by the Invention By the way, in a reproducing system of a video tape recorder for recording and reproducing a PAL video signal, a frequency-modulated luminance signal reproduced from a magnetic tape by a rotary magnetic head and low-frequency converted. From the composite signal of the carrier color signal, the luminance signal frequency-modulated by the high-pass filter and the low-pass filter and the carrier color signal low-pass converted are separated, and the luminance signal is demodulated from the frequency-modulated luminance signal. The low-frequency-converted carrier color signal is converted to the original frequency, and the demodulated luminance signal and the carrier color signal having the original frequency are combined and output to the reproduction video signal output terminal. And
This reproduced video signal is supplied to the television receiver to obtain a reproduced image, and even in the television receiver, the comb signal filters separate the luminance signal and the carrier color signal from the reproduced video signal.

That is, in a television receiver that reproduces a PAL video signal, a delay circuit that delays the reproduced video signal by two horizontal periods is included to form a valley with a minimum gain at a frequency that is an integral multiple of 1/2 of the horizontal frequency. A subtractive comb filter having a frequency characteristic that forms a peak with a maximum gain at a frequency that is an odd multiple of 1/4 of the horizontal frequency is formed, and a carrier color signal is obtained from this, and the delay circuit is included. The peak is formed at a frequency that is an integral multiple of 1/2 of the horizontal frequency, and
A summing comb filter having a frequency characteristic that forms a valley having a minimum gain at a frequency that is an odd multiple of 1/4 is constructed, and a luminance signal is obtained from this.

Therefore, the filter circuit for separating the luminance signal, which is provided in the recording system of the video tape recorder that records and reproduces the PAL video signal, has a constant gain in the band lower than the carrier color signal band of the input video signal as described above. When the luminance signal obtained from this filter circuit has a constant gain in the band lower than the carrier chrominance signal band of the input video signal, the above-mentioned addition comb type is used in the television receiver. The filter attenuates the signal component of the frequency between the integral frequency of 1/2 of the horizontal frequency in the luminance signal, especially the signal component of the odd multiple of 1/4 of the horizontal frequency, and improves the quality of the reproduced image. to degrade.

Therefore, in consideration of the attenuation in this television receiver, in the recording system of the video tape recorder, the signal component of the frequency between the integral frequency of 1/2 of the horizontal frequency in the predetermined band is enhanced as the luminance signal. It is desirable to ensure that what is obtained is obtained.

However, for this reason, when a delay circuit is provided separately from the signal separation delay circuit, there is a disadvantage that the cost of the device is significantly increased.

In view of such a point, the present invention has a simple circuit configuration that does not require a special delay circuit other than a delay circuit for signal separation, and is an integral multiple of 1/2 of a horizontal frequency in a predetermined band as a separated luminance signal. It is intended that a signal component having a frequency between those frequencies is obtained.

E Means for Solving the Problems The present invention has a delay circuit for delaying the input video signal supplied to the video signal input terminal by two horizontal periods over the carrier chrominance signal band and the entire low-frequency band. Then
The subtraction type comb filter is configured by including the delay circuit between the video signal input terminal and the first output terminal, and the delay circuit is provided between the video signal input terminal and the second output terminal. A signal separation unit that includes an addition-type comb filter, and a predetermined band on the low frequency side of the carrier color signal band of the video signal before and after the delay time portion for one horizontal period of a part of the delay circuit. , Or a signal extraction unit for subtracting the signal components of the predetermined band and a part or all of the band on the high frequency side, a signal obtained at the first output terminal and a signal obtained from the signal extraction unit, respectively. The signal component of at least the predetermined band in the low-frequency side of the carrier color signal band and the entire band of the low-frequency side is set to the second band.
And a signal adding section for adding to the signal obtained at the output terminal.

F operation In the PAL video signal separation device according to the present invention configured as described above, the first of the video signal input terminal and the signal separation unit is provided.
The frequency characteristics with the output terminal of the input video signal form a valley with a minimum gain at a frequency that is an integral multiple of 1/2 of the horizontal frequency in the carrier chrominance signal band of the input video signal and the entire low-frequency band thereof, The frequency characteristic between the video signal input terminal and the second output terminal of the signal separation unit is the comb-shaped characteristic that forms a peak with a gain of 0 dB at a frequency that is an odd multiple of 1/4 of the horizontal frequency. The gain is 0 dB at a frequency that is an integral multiple of 1/2 of the horizontal frequency in the carrier color signal band of the signal and all bands on the low frequency side.
It has a comb-shaped characteristic that forms a peak and has a valley with minimum gain at a frequency that is an odd multiple of 1/4 of the horizontal frequency. The frequency characteristic between the video signal input terminal and the output terminal of the signal extraction unit is , In a predetermined band lower than the carrier chrominance signal band of the input video signal, a valley having a minimum gain is formed at a frequency that is an integral multiple of the horizontal frequency, and is a minimum at a frequency that is an odd multiple of 1/2 of the horizontal frequency. The frequency characteristics between the video signal input terminal and the output terminal of the signal addition section are comb-shaped characteristics that form a gain peak that is sufficiently larger than the gain. In, the waveform characteristics are such that a valley with a gain of 0 dB is formed at a frequency that is an integral multiple of the horizontal frequency, and a peak is formed that has a gain of greater than 0 dB at a frequency that is an odd multiple of 1/2 of the horizontal frequency. An integer multiple of the horizontal frequency within the specified band at the output terminal Luminance signal signal components in frequency between the wave number is enhanced is obtained.

G. Embodiment G-1 Structure and operation (FIGS. 1 and 2) FIG. 1 shows an example of a PAL video signal separation device according to the present invention.

The input video signal Vi, which is a PAL video signal and is supplied to the video signal input terminal 10, is supplied to the signal separation unit 20 having the delay circuit 21. The delay circuit 21 delays the input video signal vi by 2 horizontal periods over the carrier color signal band and the entire low-frequency side band. The delay circuit 21 has a delay time of 1 horizontal period in the front stage 21F and the rear stage 21R, respectively. Composed. The signal separation unit 20 includes a delay circuit 21 to form a subtractive comb filter between the video signal input terminal 10 and the output terminal 20c, and also includes the delay circuit 21 to connect the video signal input terminal 10 and the output terminal 20y. An addition type comb filter is formed between them.

That is, the input video signal Vi is supplied to the delay circuit 21 and delayed by two horizontal cycles as described above, the output signal of the delay circuit 21 is subtracted from the input video signal Vi in the subtraction circuit 22, and the output signal of the subtraction circuit 22 becomes The signal is supplied to the attenuator circuit 23 and attenuated to 1/2, the output signal of the attenuator circuit 23 is led to the output terminal 20c, and the subtractor circuit 24 attenuates the input video signal Vi from the attenuator circuit 23.
Is subtracted, and the output signal of the subtraction circuit 24 is led to the output terminal 20y.

Therefore, if the horizontal frequency of the input video signal Vi is f _H and the subcarrier frequency is f _SC , the video signal input terminal 10 and the output terminal
As shown in the uppermost part of FIG. 2, the frequency characteristic between 20c is a frequency that is an integral multiple of 1/2 of the horizontal frequency in the carrier chrominance signal band of the input video signal Vi and the entire low-side band thereof. It forms a valley with a minimum gain, and forms a crest with a gain of 0 dB at a frequency that is an odd multiple of 1/4 of the horizontal frequency. It has a comb-shaped characteristic, and the frequency characteristic between the video signal input terminal 10 and the output terminal 20y is As shown in the second row of FIG. 2, in the carrier chrominance signal band of the input video signal Vi and in all the bands on the low side thereof, a peak with a gain of 0 dB is obtained at a frequency that is an integral multiple of 1/2 of the horizontal frequency. It has a comb-shaped characteristic that forms a valley with a minimum gain at a frequency that is an odd multiple of 1/4 of the horizontal frequency. Therefore, the output terminal 20
The signal Cy obtained at c is a signal that includes the luminance signal component with respect to the carrier color signal, and the signal Y obtained at the output terminal 20y
c is the luminance signal including the carrier color signal component. However, the luminance signal obtained at the output terminal 20y is
A signal component having a frequency between frequencies that are integral multiples of 1/2 of the horizontal frequency, particularly a signal component having a frequency that is an odd multiple of 1/4 of the horizontal frequency is attenuated.

In this example, the band on the lower side of the carrier color signal band of the input video signal Vi is a low range of 0 to 1 MHz, a mid range of 1 to 2 MHz, and 2 MHz.
To a high frequency band up to the lower limit frequency f _L of the carrier chrominance signal band, and finally a luminance signal in which the signal component of the frequency between the integral multiples of the horizontal frequency in the mid range of 1 to 2 MHz is enhanced. Where nf _H is a frequency that is an integral multiple of the horizontal frequency in the center of the midrange.

For the video signal input terminal 10, the front stage part 21 of the delay circuit 21
A signal extraction unit 30 is provided which constitutes a subtractive comb filter for the middle band of 1 to 2 MHz including F. That is, in the subtraction circuit 31, from the input video signal Vi to the front stage part of the delay circuit 21.
The signal obtained at the connection point between 21F and the post-stage portion 21R is subtracted, and the output signal of the subtraction circuit 31 is supplied to a band pass filter 33 having a mid band of 1 to 2 MHz through an output terminal 32 and a band pass filter 33. The output signal of the
After being attenuated to 1 / A, the output signal of the attenuation circuit 34 is led to the output terminal 35. A is made a number greater than 2 and not too large.

Therefore, the frequency characteristic between the video signal input terminal 10 and the output terminal 32 is as shown in the third stage of FIG. 2 by the broken line in the carrier color signal band of the input video signal Vi and all the bands on the low frequency side thereof. , Forms a valley with minimum gain at a frequency that is an integral multiple of the horizontal frequency, and has 0 dB at a frequency that is an odd multiple of 1/2 the horizontal frequency.
The output terminal has a comb-shaped characteristic that forms a larger mountain.
A non-vertical correlation component of the luminance signal is obtained at 32, and the frequency characteristic between the video signal input terminal 10 and the output terminal 35 has a low frequency of 0 to 1 MHz as shown by the solid line in the third stage of FIG. Range and 2MHz to f
_The gain is minimum in the high frequency band of _L and the carrier color signal band, and in the mid frequency band of 1 to 2 MHz, the valley having the minimum gain is formed at a frequency that is an integral multiple of the horizontal frequency, and the gain is 1/2 of the horizontal frequency. It has a comb-shaped characteristic that forms a peak of gain that is smaller than 0 dB but is sufficiently larger than the minimum gain at odd multiples.The output terminal 35 has a frequency that is an integral multiple of the horizontal frequency in the midrange of 1 to 2 MHz. Luminance signal components of frequencies between are obtained.

Then, in the signal addition unit 40, the signal Cy obtained at the output terminal 20c of the signal separation unit 20 and the output terminal 35 of the signal extraction unit 30.
Of the signal Yn obtained in the low range of 0 to 1MHz and 1 to 2M, respectively.
The signal component in the mid range of Hz is the output terminal of the signal separation unit 20.
The signal Yc obtained in 20y is added to the signal adding unit 40.
The output signal of is output to the luminance signal output terminal 50. That is, the signal Cy obtained at the output terminal 20c in the adder circuit 41 is
And the signal Yn obtained at the output terminal 35 are added, and the addition circuit 41
The output signal of the carrier color signal band and 2MHz through the output terminal 42
Is supplied to the band attenuating filter 43 that traps a high frequency band of up to f _L , the output signal of the band attenuating filter 43 is derived to the output terminal 44, and the signal Yc obtained at the output terminal 20y and the output terminal 44 in the adder circuit 45 are obtained. The added signal Ye is added, and the output signal of the adding circuit 45 is led to the luminance signal output terminal 50.

Therefore, the frequency characteristic between the video signal input terminal 10 and the output terminal 44 is, as shown in the fourth stage of FIG. 2, in the low range of 0 to 1 MHz, a frequency that is an integral multiple of 1/2 of the horizontal frequency. Shows a comb-shaped characteristic that forms a valley with a minimum gain and forms a peak with a gain of 0 dB at a frequency that is an odd multiple of 1/4 of the horizontal frequency.
In the mid range of ~ 2MHz, it forms a valley with minimum gain at a frequency that is an integral multiple of the horizontal frequency, and is a gain that is smaller than 0dB but sufficiently larger than the minimum gain at a frequency that is an odd multiple of 1/2 of the horizontal frequency. Is formed, and a peak having a gain larger than 0 dB is formed at a frequency that is an odd multiple of 1/4 of the horizontal frequency. It has a comb-shaped characteristic, and the gain is high in the high frequency band of 2 MHz to f _L and the carrier color signal band. It becomes the minimum, and the output terminal 44 is reinforced in the mid range of 1 to 2 MHz, which is a frequency between the low range of 0 to 1 MHz and the integral frequency of 1/2 of the horizontal frequency in the mid range of 1 to 2 MHz. A luminance signal component is obtained, and the frequency characteristic between the video signal input terminal 10 and the luminance signal output terminal 50 shows that the gain is 0d in the low range of 0 to 1 MHz, as shown in the bottom of FIG.
It becomes a flat characteristic of B, and in the mid range of 1 to 2 MHz, a valley with a gain of 0 dB is formed at a frequency that is an integral multiple of the horizontal frequency,
Becomes a characteristic of the waveform gain half an odd multiple of the frequency of the horizontal frequency to form a 0dB greater mountains, in the carrier chrominance signal band and the high band of 2MHz～f _L, an integer times 1/2 of the horizontal frequency It forms a peak with 0 dB gain at the frequency of, and forms a valley with minimum gain at a frequency that is an odd multiple of 1/4 of the horizontal frequency. It has a comb-shaped characteristic, and the luminance signal output terminal 50 has 1 to 2 MHz It is possible to obtain the luminance signal Yo in which the signal component of the frequency between the integral multiples of the horizontal frequency in the mid range is enhanced.

The signal Cy obtained at the output terminal 20c of the signal separation unit 20 is supplied to the bandpass filter 60 having the carrier color signal band as the passband, and the output signal of the bandpass filter 60 is derived to the carrier color signal output terminal 70. It

Therefore, although the frequency characteristic between the video signal input terminal 10 and the carrier color signal frequency 70 is not shown, the gain is minimum in the band lower than the carrier color signal band and horizontal in the carrier color signal band. A valley with minimum gain is formed at a frequency that is an integral multiple of 1/2 of the frequency, and a peak is formed with a gain of 0 dB at a frequency that is an odd multiple of 1/4 of the horizontal frequency. The carrier color signal Co is obtained at the terminal 70.

G-2 Modified Example In the case of the above example, the band attenuation filter 43 of the signal addition unit 40 traps the carrier color signal band and the high band of 2 MHz to f _L. Instead of the band-pass filter 33 having a pass band as a band, a band-pass filter or a high-pass filter having a pass band of a part or all of the mid band of 1 to 2 MHz and its high band may be provided. Good. In addition, in the signal adding section 40, instead of the band attenuation filter 43 that traps the carrier color signal band and the high band of 2 MHz to f _L , a low band of 0 to 1 MHz and a low band of 1 to 2 MHz in the pass band are used. A pass filter may be provided.

Further, for example, the low-pass filter provided in the signal adding unit 40 is the low band of 0 to 1 MHz, the mid band of 1 to 2 MHz, and 2M.
Is the high frequency of Hz～f _L Those in the pass band, the frequency characteristic between the video signal input terminal 10 and output terminal 44, 2MHz～
Even in the high frequency range of f _L , as in the low frequency range of 0 to 1 MHz, a valley with minimum gain is formed at a frequency that is an integral multiple of 1/2 of the horizontal frequency, and a frequency that is an odd multiple of 1/4 of the horizontal frequency. The gain has a comb shape with a gain of 0 dB, and the frequency characteristic between the video signal input terminal 10 and the luminance signal output terminal 50 has a low range of 0 to 1 MHz even in the high range of 2 MHz to f _L. Similarly, the gain is 0 dB
May have flat characteristics.

EFFECTS OF THE INVENTION According to the present invention, in a PAL video signal separating device for separating a luminance signal and a carrier color signal from a PAL video signal, which is provided in a recording system of a video tape recorder for recording and reproducing the PAL video signal, With a simple circuit configuration that does not require a special delay circuit other than the delay circuit of, the signal component of the frequency between the integer multiples of 1/2 of the horizontal frequency within the predetermined band is enhanced as the separated luminance signal. You can get what you want.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an example of a PAL video signal separation device according to the present invention, and FIG. 2 is a diagram showing frequency characteristics of each part thereof. In the figure, 10 is a video signal input terminal, 20 is a signal separation unit, 21 is a delay circuit, 20c is a first output terminal, 20y is a second output terminal,
Reference numeral 30 is a signal extraction unit, and 40 is a signal addition unit.

Claims (1)

[Claims] 1. A delay circuit for delaying an input video signal supplied to a video signal input terminal by two horizontal cycles over the carrier color signal band and the entire band on the lower side thereof, the video signal input terminal and And a delay circuit between the video signal input terminal and the second output terminal, and an addition comb filter between the video signal input terminal and the second output terminal. And a predetermined band on the low frequency side of the carrier color signal band of the video signal before and after the delay time of one horizontal period of a part of the delay circuit, or this predetermined band and its A signal extraction unit for subtracting a signal component of a part or all of the band on the high frequency side, and a signal obtained at the first output terminal and a signal obtained from the signal extraction unit, respectively, in the low carrier color signal band. At least the predetermined band and full-band signal component of the low frequency side of the side, PAL video signal separating apparatus and a signal adder for adding to the signal obtained to the second output terminal.