JPS62299181A - Noise reduction system for television signal - Google Patents

Abstract

PURPOSE:To attain noise reduction even at a moving image by providing the first noise reducing means to reduce the noise by a field or frame correlation, the second noise reducing means to reduce the noise by the line correlation, and a selecting means. CONSTITUTION:When the movement of a video signal impressed to an input terminal is large, a detecting device 20 detects that the action is large, and a feedback coefficient generating device 22 sets small a feedback coefficient (k). Here, when (k) is set to a special value or below, the improvement factor of an SN ratio comes to be a line correlation noise reduction circuit 6 or below, and thus, bu supervising the output to the feedback coefficient generating device 22, the movement detecting device 20 detects that the feedback (k) is set. At such time, the movement detecting device 20 controls a switch control circuit 34 and a switch control circuit 34 connects a switch 8 to a line correlation noise reduction circuit 6 side by such control.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (11 Field of Use in Piracy) The present invention is directed to a method for reducing noise in television signals (b). There is a noise reducer that uses field correlation.

Regarding this noise reducer, please refer to ``Image Digital Signal Processing'' published by Nikkan Kogyo Shimbun, May 25, 1981.
pages 115 to 118, and Special Publication No. 59-2227
No., and J, SMPTE T.

1.87 No-31) P, 129-1l29-13
3 (1978) rA digital noise
o reaucer for encoa
ea NTSO signals” and is notoriously well known.

This noise reducer can be considered as a noise low-pass circuit using frame correlation (or field correlation). In other words, TV 9/1/1 takes advantage of the fact that there are many parts with strong frame correlation, and noise is generated randomly. In order to operate well even in moving images, it is equipped with a motion detection circuit (subtraction circuit) and a feedback coefficient generation circuit, and changes the feedback rate coefficient FK+ according to the motion. , changes so that it is close to "1" for still images and close to "0" for videos.
The relationship between the degree of improvement of the N ratio and the return coefficient (Kl) is expressed by the following equation.

A (aB)=20-jog((1+k)/(1-k
))? 4 Problems to be solved by the invention By the way, in moving images, the frame correlation becomes small, and the coefficient (Kl approaches "0". Therefore, the improvement degree body) also decreases with Q.
approaching dB. For this reason, the effect of improving the SN ratio is worse than that using a low-noise circuit using line correlation (for example, Japanese Patent Publication No. 59-2228).

B) Means for Solving the Problems The present invention provides a first noise reduction means for reducing noise by field or frame correlation, a second noise low frequency means for reducing noise by line correlation, and a motion detection means for reducing noise by υ. ” control signal causes the first. a selection means for selectively outputting the television signal from the second noise low M means;
This is a noise reduction method for television signals.

(E) 1 Effect Since the present invention has the above-described configuration, noise reduction is performed by line correlation in the case of a moving image with small frame correlation.

(f) Embodiment An embodiment of the present invention will be described with reference to FIG. 1st
In the figure, (21 is an input terminal for a video signal.

(4) is a feedback noise reducer (cyclic noise reducer) that reduces noise by frame correlation.

(61 is a line correlation noise reduction circuit that performs noise reduction by line correlation. (8) is the output of this line correlation noise reduction circuit (6) and the feedback type noise reducer (4).
) and output.

(1 (I is the output terminal of the video signal.

In the feedback noise reducer (4), Q7J is a multiplier and α4 is an original calculator. The decoy is a frame memory that constitutes a one-frame delay circuit. The alpha barrel is a multiplier. ■
is a motion detector that detects motion by comparing (H calculation) an undelayed video signal and a video signal delayed by one frame. 2z is a feedback coefficient generator which determines the coefficient (1-k)lkl of the 1 multiplier n in accordance with the output from the motion detector (2).

In the line correlated noise reduction circuit (6), C4) is 1
This is a 1-line memory that constitutes an H delay circuit. Four is lI
& calculator, ■ is an amplitude limiter. ('3C is a decorrelation detector, and when the output from the correlation calculator (g) is large.

It is determined that there is no line correlation, and the output of the amplitude side (U unit 2 & It is a calculator.

A switch control circuit controls the switch (8). In the feedback type noise reducer, when the feedback rate is -5-2'J, the SN ratio improvement is about 34B, which is the same as the improvement in the line correlation noise low-band circuit (6).

Therefore, -m I t&'-)lDJi6tel'11. ,
! When the temperature falls below 1ffiitkL5 (!"'1ll
rThis publication uses the switch (8) as a feedback noise reducer (4).
) side to the line correlation noise reduction circuit (6) side.

The above V1 production will be explained.

The operation of the feedback noise reducer (4) will be explained.

The video signal applied to the input terminal (2) is combined with the coefficient (1-k) determined by the feedback coefficient generator and the multiplier q21.
Multiplied by Furthermore, the output of this multiplier qz is
The output of the frame memory αθ is multiplied by the feedback coefficient tkl Y multiplier (X81), and the adder Q41 adds the output. This output is input to the frame memory (161, delayed by a frame, and output. Detector(
) and the feedback coefficient generator ■ are designed to minimize the image quality deterioration caused by the loss of frame correlation in a moving image and to maximize the noise reduction effect. It is determined by applying a certain function to the difference between

Next, the operation of the line correlated noise low band circuit (6) will be explained. The video signal applied to the input terminal (2) is
The signal delayed by 1H by the JC241 is calculated by the calculator 4. This true value output is a noise component signal in a video signal with line correlation. This output is then subjected to an amplitude limiter +281-c amplitude limit. The undelayed video (signal is processed by the calculator C33, where the noise component (amplitude limiter output) is removed, improving the 3N ratio. Note that when the output of the θ & calculator ■ is large, there is no line correlation, which means there is no line correlation. Detector G detects this and closes the amplitude limiter to cut off the output of this amplitude limiter.

Next, the operation of the switch (8) will be explained.

When there is little movement in the video signal that is applied to the input terminal (2) (when it is close to a still image), the motion detector ■ detects that there is little movement compared to the flavor-delayed video signal and the non-delayed signal. Detect. The feedback coefficient generator uses the signal from the motion detector 2 to set the feedback p coefficient (kl to 1-k
) and (kl. Also, the fact that the movement is small is also output to the switch control circuit copper), and the switch control circuit r3i
J is the switch (8) on the feedback type noise reducer (4) side
Connect.

Also, when the motion of the video signal input to the input terminal (2) is large (when the motion is a moving image with large motion), the motion detector (2) detects that the motion is large in the same manner as described above.

Then, the feedback coefficient 1kl of the feedback coefficient generator is set to a small value. Here, if [kl is set below =s-zn, the degree of improvement in the S/N ratio is determined by the line correlation noise reduction circuit (6)
The following is true. In this way, the itl'l detector detects that the return coefficient (kl) is set to less than ±1 by monitoring the output of the feedback coefficient generator.

At this time, the motion detector controls the switch control circuit G. Through this control, the switch egg control circuit (34) controls the switch (8) on-line correlated noise low test circuit (6).
) side.

If the motion of the video signal input to the input terminal (2) is large, and the video at this time has no correlation in the vertical direction, the switch (8) will switch to the line correlation noise low range in the same way as above. The output of the amplitude limiter Q8 becomes zero due to the non-correlation detector C1.

In this case, the signal from the input terminal (2) is sent directly to the output terminal O.
Output from Q.

In the above embodiment, the feedback type noise reducer reduces noise by using a frame delay, but it will not work even if it uses a field delay. Also, the line correlation noise reduction circuit can be used as a feedback type.

It is also applicable to chroma signals and composite video signals. Furthermore, in the above embodiment, the switch control circuit θ is connected to the motion detector.
The field was controlled by the output of the feedback coefficient generator 23.

FIG. 2 shows a second embodiment of the invention. This example is
This is an example of use in a magnetic reproduction bag (2) for a video tape recorder, etc., and is used to compensate for dropouts in video signals such as drop-acts. In the second factor, the same parts as in FIG. 1 are given the same reference numerals.

terminal (weak is drop out, pulse input terminal,
For example, a high level pulse of 7t is supplied during the drop-a-wat compensation period including the period in which a drop act occurs.

When a high level pulse signal is applied to this terminal C(8), this signal is transmitted to the feedback coefficient generator (n).The feedback coefficient generator 1221 is forced to have a feedback coefficient of 1kl while this pulse signal is input. is set to "1".As a result, the contents of the frame memory (161) circulate through a loop consisting of the 1 multiplier [1g + the square multiplier I, and the drop-act portion is compensated for.

In addition, the pulse signal of the terminal is output to the second switch (1■3rd switch (port).
(4Z is 1 normally received as shown in FIG. 2, but during pulse signal input, 1 is switched to the opposite side.

The 1H delayed video signal from the block 1H memory u4J circulates through the second switch αC and is transmitted to the switch (8) through the sixth switch (43).

In addition, the pulse signal of the terminal μs is sent to the switch control circuit (b).
is output to. An example of a switch control circuit is the state of the switch (8) during the input of this pulse signal and just before this pulse 1 word is input! keep.

FIG. 3 shows an example of the α71 converter used when the above embodiment is applied to a composite video signal.

In other words, in the NTSC television signal, the phase of the color difference 1Δ is reversed for each frame or line, so it is necessary to correct this.

In FIG. 3, ``shun'' is a frame memory or 1H memory, and corresponds to (lflilt241 in FIGS. 1 and 2).

(52) i-1, YC separation circuit (4 units/color signal separation circuit) consisting of a filter, (54) a phase inverter, (56)
is an adder. Therefore, the color signal component from the output terminal (58) is output with its phase inverted.

FIG. 4 shows a third embodiment of the invention. In addition, in FIG. 4, the same parts as in FIG. 1 are given the same reference numerals. (60)
is the head of a video tape recorder.

(62) is a reproduction amplifier, (64) is a demodulation circuit that demodulates the FM modulated reproduction signal into a normal television signal, and (66) is a dropout that detects the envelope of the reproduction signal to detect dropouts. This is a detection circuit.

(68) is when the pulse signal is input from the drop act detection circuit (66).

The fourth switch (68) switches to the output 11 in contrast to the state shown in FIG. 4, and this switch (68) forms a drop-act compensation circuit. In this circuit, the input to the feedback noise reducer (4) is placed after the fourth switch (68) and before the IH mesori (two switches).

(e) Effects of the Invention As described above, according to the present invention, it is possible to reduce noise in the low range even in moving images.

[Brief explanation of the drawing]

Fig. 1 shows a first embodiment of the present invention, Fig. 2 shows a second embodiment of the invention, and Fig. 6 shows a chroma inverter! The figure shown in FIG. 4 is a diagram showing a third embodiment of the present invention. (4)...Feedback type noise reducer (first noise reduction means), (61...Line correlation noise low frequency circuit (
(2nd noise reduction means), C'l)...Motion detector (motion detection means), (8)...Switch (selection means).

Claims (1)

[Claims] (1) A first noise reduction means that performs noise reduction by field or frame correlation, a second noise reduction means that performs noise reduction by line correlation, and the first and second noise reduction means according to a control signal from the motion detection means. A method for reducing noise in a television signal, comprising: selection means for selectively outputting a television signal from a television signal.