JPS6364494A - Feedback type noise reducer - Google Patents

Abstract

PURPOSE:To eliminate noise in response to the characteristic of a luminance signal and a chrominance signal by varying feedback quantity independently as to each of the luminance and chrominance signal in an input video signal. CONSTITUTION:A video signal SV fed from an input terminal 1 and a signal fed from a synthesis circuit 12 are subtracted by a subtractor 2. That is, the noise component of the luminance signal and chrominance carrier signal is subtracted from the signal SV and a video signal SV* whose noise component is subtracted is outputted at an output terminal 4. Through the constitution above, the characteristic of limiters 9Y, 9C of the luminance signal system and carrier signal system and gain adjustment circuits 10Y, 10C is made different and the feedback quantity of the chrominance carrier signal is made larger than that of the luminance signal. Thus, the reduction rate in the noise component of the chromiance carrier signal is higher than the reduction rate of that of the luminance signal. Thus, the noise rejection in response to the brightness is applied.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

8. Field of industrial application B Summary of the invention C Prior art D Problem to be solved by the invention E Means for solving the problem F Effect G Embodiment G1 Description of the first embodiment (Fig. 1) G2 Explanation of the second embodiment (Figure 3) G3 Explanation of the third embodiment (Figure 4) G4 Explanation of the fourth embodiment (Figure 6) H Effect of the invention A Industrial application field book The present invention relates to a feedback type noise reducer used to reduce noise components in a video signal.

B. Summary of the Invention The present invention provides a feedback J (lJ noise reducer ζ, The amount of feedback can be changed i1J independently for each of the luminance signal and chrominance signal sequence in the video signal.1. By doing this, noise removal can be performed according to the characteristics of the luminance signal and chrominance signal, as shown in a). This is what I did.

C. Prior Art As a noise reducer used to reduce noise components in a video signal, one that utilizes autocorrelation between frames of a video signal is known. FIG. 7 shows an example of such a noise reducer.

In the figure, (11 is an input terminal, and a composite video signal SV of the NTSC system, for example, is supplied to this input terminal (1). This video signal S is sent to a subtracter (2).
and (3).

Further, an output terminal (4) is derived from the output side of the subtracter (2), and the output signal of this subtracter (2) is connected to a luminance signal via a delay line (5) having a delay time of one frame. The signal is supplied to a separation circuit (6) that separates it from the progressive color signal.

The luminance signal Y' from this separation circuit (6) is sent to the synthesis circuit (7).
), and the carrier color signal C' from the separation circuit (6) is phase-inverted by an inverter (8) and then supplied to a synthesis circuit (7).

Further, the video signal from the synthesis circuit (7) is supplied to a subtracter (3), and in this subtracter (3), an input terminal 11
Subtraction is performed between the video signal SV supplied from the synthesizer circuit (7) and the video signal of the previous frame supplied from the synthesis circuit (7). The output signal of this subtracter (3) is regarded as a noise component. Here, the reason why the phase of the carrier color (N4) is inverted by the inverter (8) is that in the case of the NTSC system, the phase of the color subcarrier signal is inverted between adjacent frames. This is because the output signal of ) contains the carrier color signal component.

In addition, the output signal of the subtracter (3) is sent to the subtracter (2) via a series circuit of a limiter (9) and a gain adjustment circuit (10).
and this subtractor (2) smell ζ is supplied to the input terminal I
The video signal SV supplied from ll and the gain adjustment circuit (1
0) is subtracted from the signal supplied by 0).

That is, the noise component is subtracted from the video signal Sv, and the video signal sv'' with the noise component subtracted by 11 is output to the output terminal (4).

Here, the limiter (9) is configured to turn off a characteristic in which the output level becomes zero when the input level increases beyond a certain level, as shown in FIG. 8, for example. Therefore, when the output signal of the subtracter (3) becomes larger than a certain level, the signal subtracted from the video signal S■ in the subtracter (2) becomes zero. In other words, the output signal of the subtracter (3) at this time is not a noise component, but is considered to be a signal obtained because there is no correlation.

This prevents, for example, a moving image from being subtracted as a noise component and causing blurring.

The gain adjustment circuit (10) is configured to have a characteristic as shown, for example, in FIG. The amount, that is, the amount of feedback is adjusted,
The rate of reduction of noise components is limited.

In the example shown in FIG. 7, the video signal SV supplied to the input terminal (1) is A, the video signal sv output to the output terminal (4) is 01, and the output signal of the delay line (5) is B= CZ-”,
Furthermore, if the gain between subtractors (3) and (2) is G,
The operation of this example in FIG. 7 is shown by the following equation.

A (1-G) = C (1-GZ-”) ...
+11 Figure 2 also shows an example of a noise reducer that utilizes the autocorrelation between frames of a video signal.

In the figure, (21) is an input terminal, and a composite video signal SV of, for example, the NTSC system is supplied to this input terminal (21). This video No. 10 SV is passed through a coefficient value (1-K) coefficient unit (22) to an adder (23).
).

Further, an output terminal (24) is derived from the output side of the adder (23), and the output terminal η of this adder (23) is connected via a delay line (25) having a delay time of one frame. It is supplied to a separation circuit (26) which separates the luminance signal and carrier color signal. Luminance signal Y' from this separation circuit (26)
is supplied to the combining circuit (27), and the conveyed color No. 14 C' from the separating circuit (26) is supplied to the inverter (28).
), and then supplied to a combining circuit (27).

In addition, the video signal from the synthesis circuit (27) has a coefficient value (K)
is supplied to the adder (23) via the coefficient unit (29).

In addition, the video signal Sv from the input terminal (21) is sent to a subtracter (
30), and this subtracter (30) has a synthesis circuit (
27) is supplied. This subtractor (30
), subtraction is performed between the video (fi SV) and the video signal of the previous frame supplied from the synthesis circuit (27).The output signal of this subtractor (30) is regarded as a noise component. ζ, the output signal of this subtracter (30) is supplied to a control circuit (31) that controls the values of the coefficient units (22) and (29).In this case, the coefficient unit (22)
The value of (29) is changed in accordance with the magnitude of the output signal of the subtractor (30), and when the output signal of the subtractor (30) is larger than a certain level, the value is small; For example, it is controlled to be zero.

In the example in Fig. 9, a type of integrator whose time constant changes depending on the value of K is used (operates). Assuming that the output signal of the video signal SVX of the C1 delay line (25) is B=CZ-1, the operation of the example shown in FIG. 9 is broken down by the following equation.

A (1-K) = C (1-KZ-”) ...
Comparing Equation (2) in (2) with Equation (11), which represents the operation of the example shown in Figure 1, it can be seen that the equations have the same form. ) Example smell -
(Similar to the example in FIG. 7, the video signal SVx with reduced noise components is output to the output terminal (24). Also, the coefficient (2
2) When the value of (29) is changed, the reduction rate of the noise component is determined to be large, and the size of the output array of the subtractor (30) is increased to a certain extent. When , the l< value is made small, so that in the case of a moving image, for example, IL is prevented from reducing the motion component as a noise component and causing blur.

However, the noise resolution and 1-sa that appear in this example in Figure 9 are as follows.
For example, U.S. Patent No. 4,064,530, JP
It is described in 4-121823.

D. While the invention is trying to solve Ml door 1 (in this way,
The noise component of the video signal can be reduced to 1 by the noise reducer shown in the example of FIG. 7 and the example of FIG. 9. However, in these noise reducers, since both the luminance signal and the carrier color signal pass through the same path, there is a drawback that noise reduction cannot be performed in accordance with the characteristics of each signal. For example, if the noise component of the carrier color signal is large,
When the noise component of the luminance signal is small, the amount of feedback is increased in order to sufficiently remove the noise component of the carrier color signal.
), the motion component of the luminance signal is also removed, and the blur in the moving image becomes noticeable.

FIG. 10 shows an example of a reproduction system of a VTR. In the same figure, rotating magnetic heads (51^) and (51B)
Signals reproduced from the magnetic tape (52) are supplied to fixed terminals on the A side and B side of the head changeover switch (54) via reproduction amplifiers (53^) and (53B), respectively. An RF switching pulse Psta is supplied to this changeover switch (54), and the changeover switch (54) is sequentially switched to the input side and the B side. The 1-ba signal output from this changeover switch (54) is fed to both the bypass fill (55) and the low-pass fill (56).

The FM luminance signal YFM outputted from the bypass filter (55) is supplied to the FM demodulator (57), and the luminance (M1+Y) obtained from the 1.M demodulator (57) is supplied to the combining circuit (58). In addition, a low-pass filter (5
The low frequency conversion color CL obtained from 6) is supplied to the frequency converter ([io) via the 80C circuit (59),
The carrier color signal C produced by this frequency converter ((io), l, i4/is supplied to a combining circuit (5).
For example, an NTSC combo I-video sequence S■ is obtained at the terminal (old) derived from the synthesis circuit (58).

This figure 10 example shows the raw silk odor (rotating nitric gas 1")
51^), (51B) weight! If there is a difference of 1", 41" is added to the general color feed signal every time the head is switched, causing so-called chroma flicker. For example, to perform the Roma Friso power like this,
1-It is necessary to increase the weight of the noise reducer mentioned above and remove the noise component sufficiently, but if you do this, the motion component of the luminance signal will also be removed, and the blur in the video will be eye-catching. It becomes a constant thing.

In view of this point, the present invention enables noise removal to be performed in accordance with the characteristics of the luminance signal and color signal.

E. Means for Solving the Problems The present invention provides a feedback system that reduces noise components in the human-powered video signal by delaying the human-powered video signal by at least one field, returning it to the input side, and combining it with the human-powered video signal. This assumes a type noise reducer. The feedback amount can be changed independently by r+J for each of the luminance signal and color signal in the input video signal.

F. In the configuration described above, for example, the amount of feedback can be set independently for each of the luminance signal and chrominance signal in the human-powered video signal.This allows noise removal to be performed according to the characteristics of each of the luminance signal and chrominance signal. For example, if the noise is noticeable
The amount of feedback is set small for a luminance signal where blurring due to motion is more noticeable, while the amount of feedback is set larger for a color signal where noise is more noticeable and blurring due to motion is less noticeable.

G Example G1 Description of the first example The first example of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the same figure, the luminance signal Y' from the separation circuit (6) is supplied to the subtracter (3Y), and this separation circuit (6)
The carrier color signal C' from is inverted in phase by an inverter (8) and then supplied to a subtracter (3C).

Further, the video signal Sv supplied to the terminal (1) is supplied to a separation circuit (11) that separates a luminance signal and a carrier color signal. The luminance signal Y from this separation circuit (11) is supplied to a subtracter (3Y), and the carrier color signal C from this separation circuit (11) is supplied to a subtracter (3C).

In the subtracter (3Y), subtraction is performed between the luminance signal Y and the luminance signal Y' of one frame before. This subtractor (3
The output signal of v) is regarded as a noise component of the luminance signal, and the output signal of this subtracter (3Y) is supplied to the synthesis circuit (12) via a series circuit of a limiter (9Y) and a gain adjustment circuit (IOY). be done. Here, the limiter (9v) and the gain adjustment circuit (IOY) are each configured to have characteristics as shown in FIGS. 2A and 2C, for example.

Further, in the subtracter (3C), subtraction is performed between the carrier color signal C and the carrier color signal C' of one frame before. The output signal of this subtracter (3C) is regarded as a noise component of the carrier color signal, and the output signal of this subtracter (3C) is passed through a series circuit of a limiter (9C) and a gain adjustment circuit (IOC) to a synthesis circuit. (12). Here, the limiter (9C) and the gain adjustment circuit (IOC) are each configured to have characteristics as shown in FIGS. 2B and 2D, for example. In this case, the characteristics of limiters (9Y) and (9C) are such that the output becomes zero when the input level increases beyond a certain level, but limiter (9c)
The characteristics of the limiter (9V) are such that the input level at which the output level becomes zero is greater than the characteristics of the limiter (9V). Furthermore, the characteristics of the gain adjustment circuit (IOc) are such that the output level is greater than the characteristics of the gain adjustment circuit (IOY).

Further, the output signal of the combining circuit (12) is supplied to a subtracter (2).

The rest of the structure is the same as the example shown in FIG.

In this example, the subtracter (2) subtracts the video signal Sv supplied from the input terminal (1) and the signal supplied from the composite amount +-&(12). That is, the video signal S
The brightness signal and the noise component of the carrier color (number N) are subtracted from V, and a video signal SV8 with reduced noise components is output to the output terminal (4). Limiter (9v) and gain adjustment circuit 11 (I
The characteristics of the carrier color signal system limiter (9C) and the gain aliI rectifying circuit (1 (lc)) are made different, and the feedback amount of the carrier color signal is made larger than the feedback amount of the luminance signal. Therefore, compared to the reduction rate of the noise component of brightness (No. 4), the reduction rate of the noise component of 11! color transfer and other ゛■- is higher.

In this way, according to this example, the reduction rate of the noise component of a luminance signal where noise is less noticeable and blur caused by motion is more noticeable is low, while noise is more noticeable and blur caused by motion is more noticeable.
4: Since the reduction rate of the noise component of the carrier color signal is quotient, it is necessary to remove noise according to the characteristics of each of the luminance signal and the color carrier signal.

G2 Description of Second Embodiment Next, FIG. 3 shows a second embodiment of the present invention, in which a video signal is input separated into a luminance signal Y and a carrier color signal 0. It is. In FIG. 3, parts corresponding to those in FIG.

In the same figure, a luminance signal Y is supplied to an input terminal (IY), and this luminance signal Y is supplied to a combining circuit (13) and is also supplied to a subtracter (3v). (1C) is supplied with the IM color feeding signal C, and this carrier color signal C is supplied to the combining circuit (13) and is also supplied to the subtracter (3C).
) is fed to a subtracter (2).

The rest of the structure is the same as the example shown in FIG.

The example in FIG. 3 differs from the example in FIG. 1 only in the input format. Therefore, the example shown in FIG. 3 operates in the same way as the example shown in FIG. 1, and can obtain the same functions and benefits.

G3 Description of the third embodiment Next, FIG.
4), and as a video signal, the 10th Hikari 54-1. J
In this example, -y, the red A' signal RY, and the blue difference signal [-Y are input alternately for a predetermined period. In this figure 4, the parts corresponding to figure 1 are the same and the numbers are 4.
=J' L, '(Boshi ζ is there.

In the same figure, the input terminal (1) is connected to the luminance signal Y and the red color difference signal)≧-'/, +' as shown in box 4 in Figure +i.
The i No. B - Y is repeated to the father +jl at a predetermined period, and the X-deviated video signal SVt is supplied. This video signal S
Vt is supplied to the subtractor (2) and also to the subtractor (3).

In addition, the video signal svt' from the slow line (5) is sent to the subtracter (
3). In this subtracter (3), subtraction is performed between the video signal SVt and the video of one frame before (M number svt').The output signal of this subtracter (3) is regarded as a noise component, and in this case, the video signal SVt is Corresponding to the luminance signal Y portion of the signal SVt, it becomes a noise component of the luminance signal Y,
Corresponding to the color difference signal R-Y, +3-Y portion, °( is a noise component of the color difference signal R-Y, B-Y.

The output (No. 4) of this subtracter (3) is supplied to the fixed terminal on the A side of the changeover switch (14) via a series circuit of a limiter (9Y) and a gain 1 & I rectifying circuit (IOY), and is also supplied to the fixed terminal on the A side of the changeover switch (14). 9C) and a gain adjustment circuit (IOC) to the fixed terminal on the B side of the changeover switch (14). It is controlled by °C in relation to the signal SVt.That is, the luminance signal Y part of the video signal SVt is connected to the A side, while the color difference signals RY and 13-Y part of the eye image signal SVi are connected to the A side. The corresponding one is connected to the B side.The output signal of the FJJ conversion switch (14) is supplied to the subtracter (2).

The rest of the structure is the same as the example shown in FIG.

In this example, the subtracter (2) has input terminals fit, 1
, the video signal SVj that is supplied with the relay and the 1 changeover switch (
14) Subtraction is performed with the signal supplied by Immediately I5
, the luminance signal Y portion of the video signal SVj and the color MfliS1
N, -y.

The noise component of the luminance signal Y and the noise component of the color difference signals RY and B-Y are subtracted by a difference t7 from the +3-Y portion, respectively, and the output terminal (4) receives the video signal SV with reduced noise components.
t'' is output. Also, in this example, ゛( is the luminance signal system limiter (9Y) and the gain all+!
Characteristics of ll5 (IOY) and color difference signal thread limiter (!
Ic) and the characteristics of the gain adjustment circuit (IOC) are made to be I), and the feedback amount of the chrominance fi signal is made larger than the feedback amount of the luminance signal, so the noise component of the luminance signal is reduced. The reduction rate of the noise component of Iroax False-J is higher than the rate.

In this way, according to the example in Fig. 4, the reduction rate of the noise component of the luminance signal where noise is less noticeable and blur caused by motion is more noticeable is low (on the other hand, the noise component of the color difference signal where noise is more noticeable and blur caused by motion is less noticeable) is low. Since the reduction rate of is a quotient, noise removal according to the characteristics of each of the luminance signal and color difference signal becomes +1 function.

G4 Description of the Fourth Embodiment Next, FIG. 6 shows the fourth embodiment of the present invention. In FIG. 6, portions corresponding to those in FIG.

In the figure, a video signal SV supplied to an input terminal (21) is supplied to a separation circuit (3) that separates a luminance signal and a carrier color signal.
2) Iha is paid. The luminance signal Y from this separation circuit (32) is supplied to the adder (23Y) via the coefficient unit (22Y) of the coefficient value (IKY).
The output signal of Y) is supplied to a combining circuit (33). In addition, the conveyed color f C coefficient value (] from the separation circuit (32)
, Kc) through the coefficient unit (22G) of the adder (2
3C), and the output signal of this W adder (23C) is supplied to a combining circuit (33).

In addition, from the output side of the synthesis circuit (33), the output terminal (24)
is derived, and the output signal of this composite 1111 path (33) is a slow line (25) having a delay time of one frame.
The signal is supplied to the separation circuit (26) via.

The luminance signal Y' from this separation circuit (26) has a coefficient value (K
Adder (2:1v) via coefficient unit (29Y) of
1iIIIllllI circuit (2
The carrier color signal C' from 6) is phase-inverted by an inverter (28) and then sent to a coefficient multiplier (29G) with a coefficient ftN (Kc).
The signal is supplied to the adder (23C) via the adder (23C).

In addition, the luminance tn Y from the separation circuit (32) is transmitted through a subtracter (
30Y), and this subtracter (30v) is supplied with the luminance signal Y' from the separation circuit (26).

In this subtracter (30Y), luminance No. 14 Y and 1
Subtraction with the luminance signal Y' of the previous frame is performed.

The output signal of this subtracter (30Y) is regarded as a noise component of the luminance signal 1iJ. And this subtraction R: 4 (30
Y) output (N coefficient unit (22Y), (
It is supplied to the control circuit (38") that controls the KY value of the coefficient unit (22v), (29Y).
) The Ky value of the subtracter (30Y) is changed in accordance with the magnitude of the output signal of the subtracter (30Y).
When the output signal (0Y) is larger than a certain level, the KY value is controlled to be small, for example, zero.

Also, separation episode 1#! The carrier color signal C from (32) is supplied to a subtracter (30C), which is supplied with the carrier color signal C' from the inverter (28).

This subtracter (30G) performs subtraction between the carrier color signal C and the carrier color signal C' of one frame before. The output signal of this subtracter (30C) is regarded as a noise component of the carrier color signal. Then, °ζ, the output signal of this subtracter (30C) is Kc of the coefficient unit (22C), (29C)
It is supplied to a control circuit (31C) that controls the value. In this case, a coefficient unit (22C).

The Kc value of (29C) is changed by °ζ corresponding to the magnitude of the output signal of the subtracter (31C>), and when the output signal of this subtractor (30G) is larger than a certain level, the Kc value is small, for example, zero. In this way, the Kc of the coefficient units (22C) and (29C)
The values are also ``dual coefficient multiplier<22V), (2!I
is controlled similarly to the KY value of the subtractor (3(I
subtracter G (QC) than the KY value for the output signal of L)
The Kc value for the output signal is controlled to be larger.

The rest of the structure is the same as the example shown in FIG.

In the example in Fig. 6, the return path is divided into the luminance signal line and the carrier color signal system, but the basic principle is the same as in the example in Fig. 9, and the output terminal (24) is , the noise components of the luminance signal and the carrier color signal (1(reduced video signal sv”)
is output. In addition, in this example, the subtracter (30Y
) subtracter (30G) than the KY value for the output signal of
The Kc value for the output signal of the carrier color signal is controlled to be larger than the feedback amount of the luminance signal.
Since the amount of power increases, the reduction rate of the noise component of the carrier color signal is higher than the reduction rate of the noise component of the luminance signal.
It becomes.

In this way, according to this example, the reduction rate of the noise component of the luminance signal, where noise is noticeable and blur caused by movement is difficult to notice, is low, while the noise component of the carrier color signal, where noise is noticeable and blur caused by motion is difficult to notice, is low. The reduction rate of the noise component is 11f
Therefore, the same effect as the example in FIG. 1 can be obtained.

In the above-mentioned practical hIIi example, (1) the frame-delayed video signal is fed back to the input terminal; It is also possible to adopt a configuration in which M signals (average signal of video signals extended over a horizontal period i!l!) are returned to the input side.

Furthermore, in the above embodiment, an NTSC video signal is supplied, but in the case of a PAL format,
For example, a similar configuration can be achieved by arranging a 2-frame delay line instead of the 1-frame delay line (51, (25)).

In addition, in the first embodiment, ′ζ is configured such that the feedback amount of the chrominance signal is larger than that of the luminance signal feedback (2).
It is not limited to this. The present invention independently increases the feedback P by +1 for each of the luminance signal and color signal in the video signal.
Each change has its own characteristics.

■(Effects of the Invention) According to the present invention, since it is possible to independently change the amount of attribution i+J for each of the luminance signal and chrominance signal in the video@! signal, the luminance (No. 8 and color Noise removal can be performed according to the characteristics of b4'iJ-.

[Brief explanation of drawings]

vJI diagram is a block diagram of one embodiment of the present invention, FIG. 2 is a human output characteristic diagram for explaining the same, and FIGS. The configuration diagram, Figure 5 is the 4th block diagram.
Figures 1 and 9 are configuration diagrams of conventional examples, Figures 1 and 9 are input/output characteristic diagrams for explaining examples 1 and 10 are VTR This is a configuration diagram of the reproduction system. fl+ is an input terminal, (21, (3Y) and (3C) are subtracters, (4) is an output terminal, (5) is a delay line, (6) and (11) are Separation circuit, (8) is an inverter, (9v) and (9C) beams, (IOY) and (IOC) are gain w! rectifier circuits, and (12) is a synthesis circuit.

Claims (1)

[Claims] In the feedback type noise reducer, the input video signal is delayed by at least one field, returned to the input side, and combined with the video signal to reduce the noise component in the video signal. and a feedback type noise reducer that can independently vary the amount of feedback for each of the color signals.