JPH08331579A - Video signal processing device - Google Patents

Abstract

(57) [Abstract] [Purpose] The delay lines in the luminance system and the chroma system can be shared, and the circuit scale can be reduced. [Structure] The delay line 5 is also used as a 1H delay line for dropout compensation, a delay line for line correlation type YNR, and a line correlation type CNR. Adder 2 connected to the input side of delay line 5
3, the luminance signal whose band is limited by the trap circuit 25 and the chroma signal from the subtracter 14 are supplied. The luminance signal from which the noise has been removed from the subtractor 11 is taken out to the output terminal 12, and the chroma signal from which the noise has been removed from the band pass filter 24 is taken out to the output terminal 22.

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 device applied to a format, for example, a Hi8VTR, in which a band of a reproduced luminance signal is deeper than a band of a reproduced chroma signal.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the configuration of a conventional S / N improving circuit provided in a reproduction signal system of a VCR (video cassette recorder). The configuration of FIG. 5 is applied when the luminance signal band extends into the band of the chroma signal. here,
The first delay line 5 is used exclusively for the luminance signal, and the second delay line 15 is used exclusively for the chroma signal.

In FIG. 5, FM is reproduced from tape.
A luminance signal obtained by processing such as demodulation is supplied from the input terminal 1 to the delay line 5, the subtractor 6 and the delay circuit 10 via the terminals bc of the switch circuit 2. The output signal of the delay line 5 is supplied to the subtractor 6 and also to one input terminal a of the switch circuit 2. The switch circuit 2 is controlled by the dropout detection signal Sd, and when the dropout is detected, the input terminal b and the output terminal c
And are connected and the dropout is compensated by the output of the delay line 5. The output signal of the subtractor 6 is supplied to the subtractor 11 via the fsc trap circuit 7, the limiter 8 and the coefficient unit 9. The output signal of the delay circuit 10 is supplied to the subtractor 11. The output luminance signal from which the noise from the subtractor 11 is removed is taken out to the output terminal 12. The delay line 5, the subtractor 6 and the subtractor 11 constitute a Y signal comb type filter, and the delay line 5 is also used for dropout compensation.

The chroma signal reproduced from the tape and having the original carrier frequency fsc by frequency conversion is supplied from the input terminal 13 to the subtractor 14. Also,
The signal selected by the switch circuit 20 is supplied from the output terminal c to the subtractor 14. The output signal of the subtractor 14 is supplied to the delay line 15, the subtractor 16 and the adder 17. The output signal of the delay line 15 is supplied to the subtractor 16 and the adder 17. The output signal of the adder 17 (that is, the noise component and the color non-correlation component) is supplied to the subtractor 14 via the bandpass filter 18, the coefficient unit 19 and the terminals ac of the switch circuit 20. The switch circuit 2 is controlled by the decorrelation detection signal Sc, and when there is no correlation, the input terminal b and the output terminal c
(Fixed voltage) is connected. The output chroma signal from which the noise from the subtractor 16 has been removed is taken out to the output terminal 22.

FIG. 6 shows a conventional configuration in a format (8 mm system, VHS system, etc.) in which the luminance signal does not spread to the chroma band. In this case, a common delay line may be used for the luminance signal and the chroma signal. In FIG. 6, the luminance signal is supplied from the input terminal 1 to the delay circuit 10, the subtractor 6 and the adder 23 via the terminals bc of the switch circuit 2. Also, the subtractor 14
Is supplied to the adder 23. Here, since the luminance input signal is in a state of not interfering with the chroma signal in terms of frequency, on the input side of the delay line 5,
It is not necessary to dispose a band limiting filter or the like before the adder 23 for mixing the luminance signal and the chroma signal.

The output signal of the adder 23 is supplied to the delay line 5, the subtractor 16 and the adder 17. The output signal of the delay line 5 is supplied to the fsc trap circuit 4, the subtractor 6, the adder 17, and the subtractor 16. fsc
The output signal of the trap circuit 4 is supplied to the input terminal a of the switch circuit 2. The output signal of the subtractor 6 is passed through the fsc trap circuit 7, the limiter 8 and the coefficient unit 9 to the subtractor 11
Is supplied to. The output signal of the delay circuit 10 is supplied to the subtractor 11. The dropout is compensated and the noise-removed output luminance signal is taken out from the subtractor 11 to the output terminal 12.

The chroma signal is input from the input terminal 13 to the subtractor 14
Is supplied to. Further, the signal selected by the switch circuit 20 is supplied from the output terminal c to the subtractor 14. Subtractor 1
The output signal of 4 is supplied to the adder 23. The output signal of the adder 17 is supplied to the subtractor 14 via the bandpass filter 18, the coefficient unit 19 and the terminals ac of the switch circuit 20. The output signal of the subtractor 16 is supplied to the bandpass filter 24. The output chroma signal from which the noise from the bandpass filter 24 is removed is taken out to the output terminal 22.

[0008]

However, the above-mentioned conventional configuration shown in FIG. 5 requires two delay lines for the luminance signal and the chroma signal. Further, the configuration shown in FIG. 6 cannot be used when the luminance signal band extends into the chroma signal band. For example, in the state where the band of the reproduction luminance signal such as the Hi8 format is more than the chroma signal band, the YNR is set by the reproduction system.
(Line correlation luminance signal S / N improvement circuit) processing and CNR
When simultaneously realizing (line correlation type chroma signal S / N improvement circuit) processing, 1H (horizontal period in NTSC system) / 2H for luminance signal and chroma signal respectively
(Horizontal period in PAL system) A delay line is required, and it is impossible to use a single delay line as in the case of the 8 mm format, which can be used for both the luminance system and the chroma system.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a video signal processing device in which the delay lines in the luminance system and the chroma system can be made common and the circuit scale can be reduced.

[0010]

According to the present invention, there is provided a line correlation type luminance signal S / N improving circuit having a delay line and a path constituted by a limiter circuit, a coefficient unit and a subtractor, a delay line and an addition circuit. A line-correlation type chroma signal S / N improvement circuit having a feedback loop composed of a converter, a switch circuit and a subtractor, and adding the luminance signal and the chroma signal band-limited to the extent that the band of the chroma signal is not applied. , A delay line input, and the output of the delay line is divided into a luminance signal and a chroma signal by filtering, and the luminance signal generated by the division and the original luminance signal not subject to band limitation are line-correlated luminance signal S / The video signal processing device is characterized in that it is supplied to an N improvement circuit.

[0011]

Even if the luminance signal band is wider than the chroma signal band, the band of the luminance signal sent to the common delay line is limited in advance so as not to interfere with the chroma band. Therefore, by performing comb filter processing on the luminance signal only in the band of 0 to 3 MHz where noise is visually noticeable and limiting the bandwidth of the luminance signal due to the dropout processing to the chroma signal band or less, the delay in the luminance system and the chroma system is reduced. The line can be shared.

[0012]

An embodiment of the present invention will be described below. FIG. 1 shows the configuration of an S / N improvement circuit provided in a VCR reproduction signal system according to an embodiment of the present invention. First, the luminance signal system will be described. The luminance signal reproduced from the tape and obtained by processing such as FM demodulation is supplied from the input terminal 1 to the delay circuit 10 via the terminals bc of the switch circuit 2 and the trap circuit 25.

As shown in the frequency spectrum of FIG. 4A, the luminance signal has a high frequency band extending beyond the band of the chroma signal. The switch circuit 2 is controlled by the dropout detection signal Sd. When the dropout is detected, the input terminal b and the output terminal c are connected and the dropout is compensated by the output of the delay line 5. The trap circuit 25 uses the subtractor 14 to add the adder 2
The luminance signal is band-limited so that it does not interfere with the chroma signal supplied to the third frequency band. Trap circuit 25
Is supplied to the adder 23 and the subtracter 6
Is supplied to. Further, the output signal of the subtractor 14 which constitutes the CNR is supplied to the adder 23.

As shown in FIG. 4B, the output signal of the adder 23 is a frequency-multiplexed low-frequency component of the luminance signal, a chroma signal, and a high-frequency component of the luminance signal. This adder 2
The output signal 3 is supplied to the delay line 5. The output signal of the delay line 5 is supplied to the fsc trap circuit 4, the subtractor 6, the adder 17, and the subtractor 16. This f
The output signal of the sc trap circuit 4 is supplied to the input terminal a of the switch circuit 2. Therefore, when a dropout of the luminance signal occurs, the output signal of the delay line 5 via the fsc trap circuit 4 (a signal that is 1H before the dropout portion and has not been dropped out) is output from the switch circuit 2. It is selected instead of the input luminance signal via terminals ac. As described above, the luminance signal for the dropout process does not include a band that overlaps with the chroma signal, and at the same time, the fsc trap circuit 4 causes the chroma signal to output the luminance signal at the output terminal 12 during the dropout compensation. Can be prevented from remaining in.

On the other hand, in the subtractor 6, the output signal of the delay line 5 is subtracted from the output signal of the trap circuit 25. As a result, the output signal of the subtractor 6 has a noise component,
There are line direction decorrelation components and chroma components of the luminance signal. The output signal of the subtractor 6 is supplied to the fsc trap circuit 7, and the fsc trap circuit 7 removes the chroma signal component. From the fsc trap circuit 7,
Only noise and uncorrelated components are output.

The output signal of the fsc trap circuit 7 is supplied to the limiter 8. The limiter 8 removes large-amplitude uncorrelated components. This has a role of preventing the reproduced image from being visually blurred. The output signal of the limiter 8 is supplied to the coefficient unit 9. The signal supplied to the coefficient unit 9 is a band-limited minute luminance signal non-correlation component and a noise component. This signal is attenuated by being multiplied by a coefficient smaller than 1 by the coefficient unit 9.

The output signal of the coefficient unit 9 is supplied to the subtractor 11. Further, the output signal of the delay circuit 10 is supplied to the subtractor 11. The delay circuit 10 has a delay amount equal to the delay amount generated in the trap circuit 25, the subtractor 6, the limiter 8 and the coefficient unit 9. Thus, by performing delay compensation, an accurate comb-shaped characteristic can be obtained. The subtractor 11 subtracts the output signal of the coefficient multiplier 9 from the luminance signal that is not band-limited through the delay circuit 10. The dropout is compensated and the noise-removed output luminance signal is taken out from the subtractor 11 to the output terminal 12. Therefore, the extracted luminance signal is one in which noise in the luminance signal system other than the chroma signal band as shown in FIG. 4C is removed. That is, the broken line portion in FIG. 4C indicates the region subjected to the comb-shaped processing, and the depth of the comb-shaped characteristic changes depending on the luminance amplitude.

Next, the chroma signal system will be described. The original carrier frequency fsc is reproduced from the tape and frequency-converted.
The chroma signal determined to have the following is supplied from the input terminal 13 to the subtractor 14. Further, the output signal from the output terminal c of the switch circuit 20 is supplied to the subtractor 14. The switch circuit 2 is controlled by the dropout detection signal Sd. When the dropout is detected, the input terminal b and the output terminal c are connected, and the output of the delay line 5 compensates the dropout. The subtraction components of the subtractor 14 are the chroma signal crosstalk component and the noise component.

The output signal of the subtractor 14 is supplied to the adder 23. The adder 23 adds the output signal of the subtractor 14 and the band-limited luminance signal from the trap circuit 25. As can be seen from the frequency spectrum of the output signal of the adder 23 (FIG. 4B), the chroma signal and the luminance signal do not interfere with each other. The output signal of the adder 23 is supplied to the delay line 5, the adder 17, and the subtractor 16.

In the adder 17, the output signal of the adder 23 and the output signal of the delay line 5 are added. Then, in the output signal of the adder 17, a chroma macrostalk component, a chroma noise component, a chroma line direction non-correlation component, and a band-limited luminance signal component remain. The output signal of the adder 17 is supplied to the bandpass filter 18 (the function is similar to that of the bandpass filter 24). By the bandpass filter 18, the chroma macrostalk component, the chroma noise component, and the chroma line direction non-correlation component,
The components included in the chroma band are selectively output.

The output signal of the bandpass filter 18 is supplied to the coefficient multiplier 19. Then, it is attenuated by the coefficient unit 19. The output signal of the coefficient unit 19 is the switch circuit 2
0 is selected and supplied to the subtractor 14 via the terminals ac. The subtractor 14 calculates a coefficient unit 1 from the input chroma signal.
The output signal of 9 is subtracted. Then, it is attenuated by being multiplied by a coefficient smaller than 1 by the coefficient unit 19. The coefficient unit 19 determines the amount of noise to be subtracted.

On the other hand, the subtractor 16 subtracts the output signal of the delay line 5 from the output signal of the adder 23,
There are chroma components and chroma signals from which crosstalk has been removed, and luminance non-correlation components and luminance signal noise components that do not interfere in a band. The output signal of the subtracter 16 is supplied to the bandpass filter 24 (bandpass filter for extracting only the signal component in the chroma band). The bandpass filter 24 extracts the chroma signal.
The chroma signal from which the noise from the bandpass filter 24 has been removed is taken out to the output terminal 22.

The chroma noise component and the crosstalk component are subtracted by the subtractor 14, the adder 23, the delay line 5, the adder 17, the bandpass filter 18, and the coefficient unit 19.
By circulating the feedback loop constituted by the switch circuit 20 and the switch circuit 20, the effect of removing them is further enhanced.

The above-described embodiment of the present invention is the same as that shown in FIG.
In addition to the configuration shown in (1), the common delay line 5 is provided by newly disposing the trap circuit 25 in the luminance signal system.
In addition, the luminance signal and the chroma signal can coexist without interfering with each other in the frequency band. As a result, the comb-shaped characteristic band of the luminance signal (that is, the band in which noise can be removed) is
It is outside the chroma signal band. However, what is most noticeable on the screen as a noise component is a low frequency band of 3 MHz or less. Further, since the noise components in the high frequency band are small, even if they are present to some extent, they are less noticeable than the low frequency band components. Therefore, the noise improving effect can be enhanced by performing the comb-type processing of the luminance signal in a region other than the chroma band.

In the final output signal such as VCR,
When the luminance signal and the chroma signal are added and output, the chroma component remaining in the luminance signal in the recording system and the reproduced chroma component may interfere with each other to generate a beat. Therefore, it is necessary to appropriately attenuate the luminance component of the portion corresponding to the chroma band of the luminance signal before the addition. However, this is necessary regardless of the presence or absence of the present invention, and is no different from the conventional case.

Further, the band of the output signal when the luminance signal is dropped out is narrowed by the fsc trap circuit 4 as compared with the conventional case. However, the signal component for dropout compensation does not necessarily require the entire band, and if it has the above-mentioned band, there is no visual problem.

FIG. 2 shows the configuration of the S / N improving circuit provided in the reproduction signal system of the VCR according to another embodiment of the present invention. Figure 2
As shown in FIG. 6, unlike the other embodiments, the trap circuit 25 is arranged immediately before the adder 23 in the other embodiments. In this case, the delay time on the path supplied to the subtractor 6 via the delay line 5 increases by the amount of the delay generated in the trap circuit 25. Therefore, it is necessary to dispose the delay circuit 26 having a delay amount corresponding to this between the output terminal c of the switch circuit 2 and the subtractor 6. Since the description of the configuration of the other embodiments is the same as that of the first embodiment,
Omitted for simplicity.

In FIG. 2, the difference in delay amount between the luminance signal system and the chroma signal system can be adjusted by the bandpass filter 24. Further, a dropout compensation loop for the luminance signal (switch circuit 2, trap circuit 25, adder 23, delay line 5 and fsc trap circuit 4
System), the loop lengthens by the delay of the trap circuit 25. The delay amount of this system is ideally 1H (horizontal period) in the low range of the luminance signal, but it is visually permissible even if it increases a little. And the trap circuit 2
In the case of 5, this delay amount can be suppressed to a range where it does not matter.

FIG. 3 shows still another embodiment of the present invention. Still another embodiment is applied to the case where the delay line 5 can be easily divided like a digital processing system. As shown in FIG. 3, the luminance signal sent to the adder 23 is band-limited by the low-pass filter 28.
The low-pass filter 28 has a low-pass characteristic so that the maximum band can be secured within the range where it does not interfere with the chroma signal. When the delay amount increases, the low-pass filter 28 cannot allow the deviation of the entire delay amount of the luminance signal dropout compensation loop with respect to 1H.

Therefore, in still another embodiment, the delay line 5 and the delay circuit 27 are divided into two, and the 1H delay signal for the comb filter processing is taken out from the output signal of the delay circuit 27 and the dropout compensation is performed. For 1H
The delay signal is sent from the delay line 5 to the fsc trap circuit 4.
Is supplied to. Here, the delay amount of the delay circuit 27 is set to fsc.
Trap circuit 4, switch circuit 2, low-pass filter 2
By making the delay amount added by 8 and the adder 23 equal, the delay amount of the dropout compensation loop can be set to 1H, and accurate compensation can be realized. In addition,
The low pass filter 28 may be of a trap circuit type as in other embodiments.

Note that the configurations of the YNR and CNR in the above-described embodiments are examples, and the present invention is not limited to these configurations.

[0032]

According to the present invention, the cost can be reduced because the delay line and its peripheral circuits can be eliminated. Since the power consumption can be reduced by reducing the circuit, the battery drive time can be extended by applying it to the camera integrated VCR. Further, since it leads to reduction of power consumption, there is an advantage that the heat generation amount can be reduced.

Further, according to the present invention, since the number of parts can be reduced, the reliability of the product can be improved by reducing the defective parts and the defective mounting. Furthermore, since the board area can be reduced by reducing the number of parts, the size can be further reduced and the product can be easily carried.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of still another embodiment of the present invention.

FIG. 4 is a schematic diagram showing characteristics of frequency bands of respective parts.

FIG. 5 is a block diagram showing a conventional configuration.

FIG. 6 is a block diagram showing a conventional configuration.

[Explanation of symbols]

 5 Delay line 10, 26, 27 Delay circuit 25 Trap circuit 28 Low pass filter

Claims (2)

[Claims] 1. A line correlation type luminance signal S / N improvement circuit having a delay line and a path constituted by a limiter circuit, a coefficient unit and a subtractor, the delay line, an adder, a switch circuit and a subtractor. And a line correlation type chroma signal S / N having a feedback loop composed of
An improvement circuit is provided, and the luminance signal whose band is limited to such an extent that it does not fall within the band of the chroma signal and the chroma signal are added, input to the delay line, and the output of the delay line is filtered to obtain the luminance signal and the chroma signal. And a luminance signal generated by the division and the original luminance signal not subjected to band limitation are supplied to the line correlation type luminance signal S / N improving circuit. apparatus. 2. The video signal processing apparatus according to claim 1, wherein the dropout of the brightness signal is compensated by the band-limited brightness signal of the output of the delay line. apparatus.