JPH09219873A - Luminance signal and chroma signal time adjustment circuit - Google Patents

Abstract

It is an object of the present invention to provide a luminance and chroma signal delay circuit corresponding to each color television system at a low price. SOLUTION: An IF signal is detected by an IF processing circuit 2, a luminance signal is detected by an LPF circuit 4, and a chroma signal is detected by a BPF circuit 14.
To separate. M / on each of the luminance signal side and the chroma signal side
A microcomputer provided with delay circuits (6, 7, 8, 16, 17, 18) corresponding to the NTSC system and the B / PAL, G / PAL system, and I / PAL, D / PAL, and K / PAL systems. In accordance with a system selection control signal from 24, each delay circuit is selectively switched by the first switch 9 and the second switch 19, and the brightness signal and the chroma signal are time-aligned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit compatible with a plurality of color television systems.

[0002]

2. Description of the Related Art Conventionally, NTSC (National Television) has been used for color television broadcasting, which has been adopted by Japan, the United States and the like.
There is a broadcasting system such as a levision system committee (PAL) system and a PAL (Phase Alternation by Line) system mainly used in European countries. Conventionally, these broadcasts are generally performed by terrestrial broadcasts. However, recently, many broadcasting satellites (BS), communication satellites (CS), etc. have been launched, and the diversification of broadcasting has progressed.
In Southeast Asia, terrestrial broadcasting is performed by the PAL system,
Satellite broadcasting is performed by the NTSC system, and the area where a plurality of broadcasting systems coexist is increasing. NTSC system, PAL
A color television system such as a system is combined with a black-and-white and color common broadcasting system, which is assigned a code from A to N, depending on a difference between a video signal and an audio signal standard and a transmission system thereof, for example, an M / NTSC system. It is prescribed as such. Therefore, in these areas, devices capable of receiving a plurality of broadcasting systems, for example, multi-system color television receivers and video tape recorders are in widespread use.

FIG. 5 shows two broadcasting systems (NTSC, PA).
FIG. 16 is a block diagram of a conventional video signal processing circuit of a video tape recorder used in a region where L) is mixed. In the figure, a received signal of the NTSC system or the PAL system input from the antenna 51a is converted into an IF (intermediate frequency) signal by the tuner circuit 51b, and the IF processing circuit 5
2a.

Broadcast waves of channels received by this video tape recorder are, for example, M / NTSC system and B / PAL, G / PAL, I / PAL, D / PAL, K.
There is a case of any one of the / PAL systems. Therefore, the microcomputer 52b identifies the color television system that the video tape recorder is currently receiving and sends a system selection control signal for selecting the corresponding color television system to the IF processing circuit 52a. The IF processing circuit 52a is provided with a plurality of SAW (Suface Acoustic Wave) filters corresponding to each color television system, and switches to the color television system SAW filter designated by the microcomputer 52b. As a result, the IF signal transmitted from the tuner circuit 51b passes through the SAW filter corresponding to each color television system, is detected, and is output. The signal detected at this time is divided into a video signal and an audio signal and output.

The relationship between the luminance signal and the chroma signal of each color television system is that the time difference between the luminance signal and the chroma signal of the M / NTSC system is zero nanosecond (0 nSE).
If C) is set to the reference value, B / PAL, G / P
Approximately 50 nSEC, I / PAL, D / PA in AL system
In the L / K / PAL system, the chroma signal is transmitted with a delay of about 170 nSEC with respect to the luminance signal.

For this reason, it becomes necessary to correct the time difference between the luminance signal and the chroma signal in correspondence with each color television system. Therefore, in the above conventional video signal processing circuit, three types of SAW filters are used as IF processing circuits. 52a.

Next, the video signal output from the IF processing circuit 52a is processed by an AGC (auto gain controller) circuit 5
The signal is output to the circuit 3, the amplitude is adjusted, and then the signal is supplied to the LPF (low-pass filter) circuit 54 and the BPF (band-pass filter) circuit 64.

A luminance signal is taken out from the LPF circuit 54, supplied to an AMP (amplification) circuit 55, and amplified.
The amplified use is pre-emphasized by the pre-emphasis circuit 60, and then the W / D (white / dark) clipping circuit 61 clips the white peak and dark side overshoot and preshoot, and then FM
The modulation circuit 62 performs FM modulation. Next, after a low frequency band component is removed by an HPF (high pass filter) circuit 63, it is supplied to a Y / C MIX (luminance / chroma / mixing) circuit 73.

On the other hand, a chroma signal is extracted from the video signal supplied to the BPF circuit 64, amplified by an AMP (amplification) circuit 65, and adjusted by an ACC (automatic chroma level control) circuit 70 to adjust the chroma level.
Then, the low-frequency conversion circuit 71 performs low-frequency conversion, the LPF (low-pass filter) circuit 72 removes high-frequency components other than the low-frequency conversion chroma signal component, and then Y / C MIX (luminance / luminance /
(Chroma / mixing) circuit 73, which is mixed with a luminance signal and recorded as a color composite signal by a recording amplifier circuit (not shown).
Supplied to

In the conventional technique described above, the SAW filter and its switching circuit are expensive. Therefore, in order to reduce the cost, one type of SAW filter processes all the luminance signals and chroma signals of the color television system, and the signals having a time difference of about 170 nsec at the maximum are used as they are, or A method is adopted in which a signal having a time difference of 170 ns is time-adjusted by a simple method in a subsequent processing circuit.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art. The delay circuit for the luminance signal and the chroma signal is composed of a simple circuit using inexpensive parts, It is an object of the present invention to provide a time matching circuit for a luminance signal and a chroma signal corresponding to each color television system at a price.

[0012]

In order to solve the above problems, the present invention comprises a Y / C separation circuit for separating a luminance signal and a chroma signal of a video signal and separates the luminance signal and the chroma signal. In a video signal processing circuit for performing video signal processing, receiving the luminance signal output of the Y / C separation circuit,
A plurality of luminance signal delaying means for delaying the luminance signal for a time suitable for a predetermined color television system and one of the plurality of luminance signal delaying means are selected to output the luminance signal of the Y / C separation circuit. Receiving a chroma signal output from the Y / C separation circuit and a first switching means connected to the selected luminance signal delay means, and delaying the chroma signal for a time suitable for the predetermined color television system. A plurality of chroma signal delay means and a second switch for selecting one from the plurality of chroma signal delay means and connecting the chroma signal output of the Y / C separation circuit to the selected chroma signal delay means. Means and a color television system selected from the predetermined color television systems, and a luminance signal delaying means and a chroma signal delaying means adapted to this color television system. To select, there is provided a circuit combined time of the luminance signal and chroma signal, characterized by a control means for outputting a control signal to the first switching means and second switching means.

Further, the above-mentioned luminance signal and chroma signal time adjusting circuit is characterized in that one of the luminance signal delay means and the chroma signal delay means is a pair of delay means adapted to the M / NTSC system. provide.

Further, one set of the luminance signal delay means and the chroma signal delay means is a B / PAL system or a G / PA system.
There is provided a time matching circuit for the luminance signal and the chroma signal, which is a set of delay means adapted to the L system.

Further, one of the luminance signal delay means and the chroma signal delay means is an I / PAL system or a D / PA system.
There is provided a time matching circuit for the above luminance signal and chroma signal, which is a set of delay means adapted to the L system or the K / PAL system.

The time adjustment circuit for the luminance signal and the chroma signal separates the video signal after detecting the IF signal into the luminance signal and the chroma signal, and corresponds to each color television system on the luminance signal side and the chroma signal side, respectively. With the delay circuit, the system selection control signal from the microcomputer
By switching each delay circuit with a switch and outputting the same, time adjustment of the luminance signal and the chroma signal is performed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a video signal processing circuit to which a time adjustment circuit for a luminance signal and a chroma signal of the present invention is applied, FIG. 2 is a chroma delay circuit diagram of a time adjustment circuit for a luminance signal and a chroma signal of the present invention, and FIG. FIG. 4 is a frequency characteristic diagram of the chroma delay circuit, and FIG. 4 is a block diagram of a time alignment circuit for the luminance signal and the chroma signal according to another embodiment of the present invention.

FIG. 1 is a block diagram of a recording system video signal processing circuit of a VTR (video tape recorder) to which a time alignment circuit for a luminance signal and a chroma signal of the present invention is applied. The reception signal received by the antenna 1a is converted into an IF (intermediate frequency) signal by the tuner circuit 1b and then supplied to the IF processing circuit 2. The signal supplied to the IF processing circuit 2 passes through one type of SAW filter and is detected,
It is supplied to the AGC circuit 3. Then, the amplitude is adjusted by the AGC (auto gain controller) circuit 3, and the LPF is adjusted.
It is supplied to a (low-pass filter) circuit 4 and a BPF (band-pass filter) circuit 14, respectively. A luminance signal is extracted from the LPF circuit 4, and a chroma signal is extracted from the BPF circuit 14. And the brightness signal is AMP
The chroma signal supplied to the (amplification) circuit 5 is supplied to the AMP circuit 1.
5 and are amplified respectively.

Next, a delay (DELAY) circuit for the luminance signal and the chroma signal will be described. The M system Y (luminance signal) delay circuit 6 is a circuit for delaying the M / NTSC system luminance signal, and the B and G system Y delay circuits 7 are B / P.
This is a circuit for delaying an AL or G / PAL type luminance signal, and the I, D, K type Y delay circuit 8 is an I / PAL, D
This is a circuit for delaying the luminance signal of the / PAL and K / PAL systems (I / PAL, D / PAL, and K / PAL have a small time difference, so that a Y delay circuit is integrated).
The input terminals of these three Y delay circuits 6, 7 and 8 are
It is connected to the output terminal of the AMP circuit 5.

The first switch (SW) 9 is, for example, a three-contact changeover switch. The first contact 9a is for the M type Y delay circuit 6, the second contact 9b is for the B and G type Y delay circuit 7, and the third switch.
The contact 9c is connected to each of the I, D and K type Y delay circuits 8. The common contact 9d of the first switch 9 is connected to the pre-emphasis circuit 10, and the switching control terminal 9e of the first switch 9 is connected to the microcomputer 24.

The M system chroma (chroma signal) delay circuit 16 is a circuit for delaying an M / NTSC system chroma signal. The B and G system chroma delay circuit 17 is a B / PA
The I / D / K system chroma delay circuit 18 is a circuit for delaying an L / G / PAL system chroma signal.
This is a circuit for delaying chroma signals of the L, D / PAL and K / PAL systems (the chroma delay circuits are combined into one because the time difference between the I / PAL, D / PAL and K / PAL systems is small). These three chroma delay circuits 16, 17,
Both 18 input terminals are connected to the output terminal of the AMP circuit 15.

On the other hand, the second switch (SW) 19 is, for example, a three-contact changeover switch, the first contact 19a is for the M system chroma delay circuit 16 and the second contact 19b is for the B and G system chroma delay circuit 17. The third contact 19c is connected to each of the I, D, and K system chroma delay circuits 18. The common contact 19d of the second switch 19 is connected to the input terminal of the ACC circuit 20, and the switching control terminal 19e of the second switch 19 is connected to the microcomputer 24.

Next, the relative relationship between the delay times of the three types of chroma delay circuits and the three types of Y delay circuits will be described. When the time difference between the luminance signal and the chroma signal of the M / NTSC system is set to zero nanoseconds (0nSEC) and set to the reference value, about 50nSEC, I / PAL, D / PAL, K for the B / PAL and G / PAL systems. In the / PAL system, the chroma signal is transmitted with a delay of about 170 nSEC with respect to the luminance signal.

Different for each color television system,
To correct the delay time difference between the luminance signal and the chroma signal,
The delay circuit shown below is used. First, the three Y delay circuits 6, 7 and 8 use delay circuits having uniform delay characteristics over the entire frequency band (group delay characteristics are linear). On the other hand, the above three chroma delay circuits 16, 17, 18
In order to utilize the group delay characteristic of the chroma frequency band, for example, the circuit shown in FIG. 2 is used.

In determining the delay amount of each delay circuit, first, I / PAL and D / where the chroma signal is the most delayed.
The delay amount of the I, D, K system chroma delay circuit 18 corresponding to the PAL, K / PAL system is set to a small value, and the delay amount of the I, D, K system Y delay circuit 8 is set corresponding to this delay amount. Decide

Next, the delay amount of the B and G system chroma delay circuit 17 is set to a delay amount of about 120 nSEC so that the delay amount is 170 nSEC-50 nSEC = 120 nSEC. The delay amount of the B and G system Y delay circuit 7 is determined according to this delay amount.

Further, the delay amount of the M-system chroma delay circuit 16 is set to a delay amount of about 170 nSEC so that a delay of about 170 nSEC-0nSEC = 170 nSEC is obtained. The delay amount of the M-system Y delay circuit 6 is determined according to this delay amount.

Next, the chroma delay circuit will be described with reference to FIG. The resistors R1 and R2 are connected in series, one end is connected to the input end, the other end is grounded, and the connection point of the resistors R1 and R2 is connected to the output end. The capacitor C and the coil L are connected in parallel (a parallel resonance circuit is configured), one end is an output end, and the other end is grounded via a resistor R3.

FIG. 3 shows the frequency characteristics of the chroma delay circuit, where the horizontal axis is the frequency (f) and the vertical axis is the voltage for curves a and c and the phase for curve b. Curve a
Indicates the frequency band of the chroma signal, and the curve b indicates the group delay (G
ROUPE / DELAY), and the curve c shows the f (frequency) characteristic of the output amplitude with respect to the input.

By setting the resonance frequency of the LC parallel resonance circuit near the chroma frequency band and causing the resonance circuit to resonate,
The resistor R3 connected between the LC parallel resonant circuit and the ground is in parallel with the resistor R2. That is, the resistance value at the time of non-resonance is R2 ÷ (R1 + R2), while at the time of resonance, the following equation is obtained.

[0031]

[Equation 1]

Therefore, the resistance value at the time of resonance decreases, the f (frequency) characteristic of the output amplitude decreases at the resonance frequency as shown in FIG. 3, and the group delay (GRO
UP / DELAY) rises sharply. By using the band in which this group delay rises (set so that the band of the chroma signal is exactly in this region), the delay time of the chroma signal is adjusted to correspond to each color television system, and the predetermined delay Get three types of chroma delay circuits with time.

Next, a case where the video tape recorder receives a broadcast signal of each color television system will be described. First, when the channel selected by the video tape recorder is, for example, the M / NTSC system, the microcomputer 24 identifies the M / NTSC system. And the microcomputer 24 is M / NTS
A system selection control signal indicating the C system is sent to the first switch 9 and the second switch 19.

As a result, the first switch 9 selects the M-system Y delay circuit 6 and the second switch 19 selects the M-system chroma delay circuit 16. Therefore, the luminance signal passes through the M-system Y delay circuit 6, is pre-emphasized by the pre-emphasis circuit 10, and then is overshot and preshoot on the white peak and dark sides by the W / D (white / dark) clip circuit 11. FM is clipped after
The modulation circuit 12 performs FM modulation. Then, after the low-frequency band component is removed by the HPF (high-pass filter) circuit 13, the low-frequency band component is supplied to the Y / C.

On the other hand, the chroma signal passes through the M-system chroma delay circuit 16, and the chroma level is adjusted by the ACC (Automatic Chroma Level Control) circuit 20. Then, the low-frequency conversion circuit 21 performs low-frequency conversion, the LPF (low-pass filter) circuit 22 removes high-frequency components other than the low-frequency conversion chroma signal component, and then the Y / C / MIX (luminance / chroma / mixing) circuit 23. Is supplied to a recording / amplifying circuit (not shown) as a color composite signal after being mixed with the luminance signal. As a result, there is no time delay between the luminance signal and the chroma signal, and a recorded video signal with a timed timing is output.

Next, when the channel selected by the video tape recorder is the B / PAL or G / PAL system, the microcomputer 24 discriminates the B / PAL or G / PAL system, and the B / PAL or G / PAL system is selected. A system selection control signal indicating the PAL system is sent to the first switch 9 and the second switch 19. As a result, the first switch 9 selects the B and G system Y delay circuit 7, and the second switch 19 selects the B and G system chroma delay circuit 17. Subsequent operations and functions of signals are the same as those described above, and will be omitted.

Similarly, when the channel selected by the video tape recorder is the I / PAL, D / PAL or K / PAL system, the microcomputer 24 controls the I / PAL or D / PAL system.
Identifies the PAL and K / PAL system, and I / PA
The first switch 9 and the second switch 19 send a system selection control signal indicating the L, D / PAL, K / PAL system.
To send to. As a result, the first switch 9 selects the I, D, K system Y delay circuit 8, and the second switch 19 selects I, D, K.
The K system chroma delay circuit 18 is selected. Subsequent operations and functions of signals are the same as those described above, and will be omitted.

Next, another embodiment will be described with reference to FIG. Those having the same functions as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 4, the output terminal of the AMP circuit 5 is connected to the common contact 9d of the first switch 9. The first contact 9a of the first switch 9 is an M type Y
The second contact 9b is connected to the input terminal of the delay circuit 6 by the B, G method Y.
The third contact 9c is connected to the input terminal of the delay circuit 7 and the input terminal of the I, D, and K system Y delay circuit 8, respectively.
The switching control terminal 9e of the first switch 9 is connected to the microcomputer 24. The output terminals of the three Y delay circuits 6, 7 and 8 are all connected to the input terminal of the pre-emphasis circuit 10.

On the other hand, the output terminal of the AMP circuit 15 is connected to the common contact 19d of the second switch 19. The first contact 19a of the second switch 19 is the M type chroma delay circuit 1
6, the second contact 19b is an input terminal of the B and G type chroma delay circuit 17, and the third contact 19c is I, D, K.
They are connected to the input terminals of the system chroma delay circuit 18, respectively. The switching control terminal 19 of the second switch 19
e is connected to the microcomputer 24. The output terminals of the three chroma delay circuits 16, 17, and 18 are both connected to the input terminal of the ACC circuit 20.
The delay processing for the luminance signal and the chroma signal and the description of the operation of both signals are the same as those of the luminance signal and chroma signal time alignment circuit in FIG.

[0040]

As described above, the time adjustment circuit for the luminance signal and the chroma signal according to any one of claims 1 to 4 of the present invention uses one receiver for the broadcast wave of each color television system. When receiving, the video signal after detecting the IF signal is separated into a luminance signal and a chroma signal, and a delay circuit corresponding to each color television system is provided on the luminance signal side and the chroma signal side. The respective delay circuits are appropriately switched, and the luminance signal and the chroma signal are time-aligned. Since this delay circuit can be configured with a simple circuit using inexpensive parts, it can be provided at a low price, and it is effective in reducing cost, improving reliability, and improving image quality.

The luminance signal and chroma signal time adjusting circuits according to the second to fourth aspects of the present invention are suitable for mass production because they are compatible with the color television system adopted in many regions of the world. Cost reduction effect can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal processing circuit to which a time alignment circuit for a luminance signal and a chroma signal of the present invention is applied.

FIG. 2 is a chroma delay circuit diagram of a time alignment circuit for a luminance signal and a chroma signal according to the present invention.

FIG. 3 is a frequency characteristic diagram of a chroma delay circuit.

FIG. 4 is a block diagram of a video signal processing circuit to which a time alignment circuit for a luminance signal and a chroma signal according to another embodiment of the present invention is applied.

FIG. 5 is a block diagram of a conventional video signal processing circuit.

[Explanation of symbols]

 1a Antenna 1b Tuner circuit 2 IF processing circuit 3 AGC circuit 4 LPF circuit 5 AMP circuit 6 M system Y delay circuit 7 B, G system Y delay circuit 8 I, D, K system Y delay circuit 9 First switch 10 Pre-emphasis circuit 11 W / D circuit 12 FM modulation circuit 13 HPF circuit 14 BPF circuit 15 AMP circuit 16 M system chroma delay circuit 17 B, G system chroma delay circuit 18 I, D, K system chroma delay circuit 19 Second switch 20 ACC circuit 21 Low-frequency conversion circuit 22 LPF circuit 23 Y / C / MIX circuit 24 Microcomputer

Claims (4)

[Claims] 1. A video signal processing circuit, comprising a Y / C separation circuit for separating a luminance signal and a chroma signal of a video signal, for performing a video signal processing by separating the luminance signal and the chroma signal. A plurality of luminance signal delaying means for receiving the luminance signal output of the separation circuit and delaying the luminance signal for a time suitable for a predetermined color television system, and selecting one from the plurality of luminance signal delaying means, The predetermined color television system receiving the luminance signal output of the Y / C separation circuit, the first switching means connecting to the selected luminance signal delay means, and the chroma signal output of the Y / C separation circuit. A plurality of chroma signal delaying means for delaying the chroma signal for a time corresponding to, and selecting one from the plurality of chroma signal delaying means,
A second switching means for connecting the chroma signal output of the Y / C separation circuit to the selected chroma signal delay means; and one color television system selected from the predetermined color television systems. A luminance signal, comprising: a control means for outputting a control signal to the first switching means and the second switching means so as to select the luminance signal delay means and the chroma signal delay means adapted to the color television system. And chroma signal time adjustment circuit. 2. The luminance signal and chroma according to claim 1, wherein one of the luminance signal delay means and the chroma signal delay means is a pair of delay means adapted to the M / NTSC system. Signal time adjustment circuit. 3. A set of the luminance signal delay means and the chroma signal delay means is a B / PAL system or a G / PAL system.
2. The time adjustment circuit for the luminance signal and the chroma signal according to claim 1, wherein the time adjustment circuit is a set of delay means adapted to the system. 4. One of the luminance signal delay means and the chroma signal delay means is an I / PAL system or a D / PAL system.
2. The time adjustment circuit for the luminance signal and the chroma signal according to claim 1, wherein the time adjustment circuit is a set of delay means adapted to the K.PAL system or the K / PAL system.