JPS62137976A - Noise suppressing circuit - Google Patents

Abstract

PURPOSE:To make the switching operation visually inconspicuous by providing a time constant circuit and changing the quantity of suppression of picture noise divisionally several times by switching due to a control signal. CONSTITUTION:A time constant circuit 9 outputs a noise suppression characteristic control address E to a fixed storage device 6 in accordance with the control signal inputted from an input terminal 7 and a vertical synchronizing pulse inputted from an input terminal 8. In this case, when the control signal is switched from the high level to the low level or from the low level to the high level, the output control address E is switched stepwise by the circuit 9. Then, the noise suppression characteristic is changed stepwise. That is, two upper bits of a differential signal D from a subtracting circuit 4 are substituted with the address E, and the noise suppression characteristic is switched to a maximum of 4 stages. Thus, the noise suppression characteristic is switched at a slow gradient to make the switching operation of the noise suppression characteristic visually inconspicuous.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise suppression circuit that suppresses noise from a transmission signal in a MUSE decoder that demodulates a MUSE high-definition television signal.

[Conventional technology]

Regarding the MUSE decoder mentioned above, it is described in the material published in NHK Giken Monthly Report, Vol. 27, No. 7 (July 1983 issue) "New Transmission Method for High Definition Television (MUSE) J." According to this. In the MUSE method, Table 1
A control signal as shown in is transmitted together with the video signal and acoustic signal. The noise reducer control of this control signal allows the receiving side to switch noise suppression on and off.

FIG. 2 shows a circuit in which a control signal input is added to the conventional noise suppression circuit shown in, for example, Japanese Patent Publication No. 59-17580 ``Noise Suppression Apparatus for Television Signals''. In the figure, 1 is an input terminal into which a digital television signal is input, 2 is a frame memory for delaying the noise-suppressed digital television signal, and 3 is a downstream digital circuit for transmitting the noise-suppressed digital television signal. This is an output terminal that outputs to. 4 is a subtraction circuit that subtracts the digital television signal A input from the input terminal 1 and the digital television/vision signal B output from the frame memory 2; 5 is the television signal A input from the input terminal 1 and a noise suppression correction circuit; Addition circuit that adds signal Z, 6 is subtraction circuit 4
A fixed storage device receives the difference signal outputted from the fixed storage device and outputs the noise suppression correction signal Z. Reference numeral 7 designates a control signal input terminal to which the control signal Noise Reduce Control is input.

Next, the operation will be explained.

The television signal A input from the input terminal 1 is input to the subtraction circuit 4 together with the television signal B output from the frame memory 2. The subtraction circuit 4 outputs the difference signal D C
=A-B). This difference signal is stored in the fixed storage device 6.
is input as an address signal. Various values are recorded in each address of the fixed storage device 6, and a noise suppression correction signal Z is outputted with characteristics as shown in FIG. 3, for example, in response to each address signal. The address signal requires a positive address and a negative address depending on the polarity of the difference signal. Therefore, negative addresses are processed using complement representation. Also, the noise suppression correction output Z for this address signal is τ in complement representation for the correct address.
, for negative addresses, outputs Z in real number representation. Next, 0 is recorded at an address where the absolute value of the difference signal is greater than a certain constant number D0. This is the absolute value ID of the difference signal
This is because a television signal in which I is greater than Do is determined to be a moving image portion. In other words, in the case of a still image with little movement in the image played back on a TV, the deterioration of image quality due to noise is difficult to ignore, but when the image is in motion, the deterioration of the image quality is not visually noticeable. There is no problem. Therefore, the noise suppression correction signal Z output from the fixed storage device 6 becomes O, and the input signal A is directly output as the noise suppression television signal Y which is the output of the adding circuit 5.

On the other hand, when the absolute value of the difference signal is close to 0 (less than Do), when D is positive (A>B), a negative stored content (complement) T is output from the fixed storage device 6. Therefore, the output of the adder circuit 5 is Y = A + - Z, that is, -2 from the value of A.
The absolute value of − is eliminated. Moreover, when A<B, the above operation is reversed. The output of the noise suppression correction signal Z in response to the input of the difference signal in FIG.
Alternatively, the characteristic is linear until the value of Z max is reached. Therefore, if the noise suppressed television signal Y during this period is expressed as the television signals A and B using a constant K (K is a coefficient whose absolute value is less than 1), it becomes Z--K (A-B), and Y- (1-K)A+KB For example, in the case of -0,5, the above formula is 1/2 (
A+B), and the average of A and B is taken out as the output signal. As a result, random noise components are suppressed.

Further, the output of the adder circuit 5 is outputted from the output terminal 3 as a noise suppressed television signal Y, and is also inputted to the frame memory 2. This input Y is used in order to calculate the noise suppression correction signal Z in the next frame of television (ij No. B and No. 7).

Next, a noise reduction control signal is inputted to the control signal input terminal 7 and 2 to control the output of the fixed storage device 6. (Con) When the human power at the a-low input terminal 7 is at H level, all noise suppression correction signals Z are output as 0 regardless of the difference signal value 4m, and the operation of the noise suppression circuit is turned off. Further, when the input of control number 8 input terminal 7 is at a high level, the above-mentioned operation is performed and the noise suppression circuit is turned on.

[Problem that the invention seeks to solve]

The conventional noise suppression circuit is configured as described above, and the operation of the noise suppression circuit is turned on and off by a control signal. Therefore, the noise suppression is turned on because the noise suppressed television signal Y (= to Z) and the input television signal are instantly switched.

Off is visually noticeable. Furthermore, if a large number of these operations occur in a short period of time, there may be problems such as an image that appears to flicker due to the presence or absence of image noise on the entire screen.

This invention was made in order to solve the above-mentioned problem, and it is possible to change the amount of image noise suppression several times by switching with the control gogo. From 15 to 1. To obtain a noise suppression circuit that can make the switching operation visually inconspicuous [1.6 [Means for solving the problem] Noise suppression circuit according to the present invention When the operation of the δtan I(F circuit is switched from the on state to the off state or from the off state to the on state by the control signal, the switching operation is temporarily prolonged, that is, the noise suppression characteristics change. For example, a time constant circuit is added to the 6th place in Philbee so that it changes with a time constant in the time direction.

[Effect]

In this invention, by adding a time constant circuit, the noise suppression characteristic changes, which used to change sharply depending on the control signal, are now changed in several stages, and the characteristic changes are changed over time. Switching occurs at a gentle slope, making the switching operation force 9 of the noise suppression characteristic visually unnoticeable.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is an input terminal into which digital television Shinsatsu A is input, 2 is a frame memory;
It outputs a frame-delayed digital television signal B. 3 is an output terminal for outputting a digital television signal to a subsequent digital circuit. 4 is a subtraction circuit that subtracts the television signal A manually input from the input terminal 1 and the television signal B output from the frame memory 2; 5 is the television signal A input from the input terminal 1;
and the noise suppression correction signal Z, and 6 is an addition circuit that adds the noise suppression correction signal Z by the difference signal output from the subtraction circuit 4.
It is a fixed storage device that outputs . In addition, 7 is a control signal input terminal for manually controlling the control signal noise reduction, and 8 is a vertical synchronization signal (VD pulse).
9 is the control signal input from the control signal input terminal 7 and the VD input terminal 8 is input.
This is a time constant circuit that outputs a noise suppression characteristic control address signal of the fixed storage device 6 based on the input VD pulse.

Next, the operation will be explained.

A television signal A manually input from an input terminal 1 is input to a subtraction circuit 4 together with a television signal B output from a frame memory 2. From the subtraction circuit 4, the difference signal D
(=A-B) is output, and this difference signal is input as an address signal of the fixed storage device 6. Various values are recorded in each address of the fixed storage device 6, and a noise suppression signal Z is outputted with the characteristics shown in the third section, for example, for each address signal. The address signal requires a positive address and a negative address depending on the polarity of I]. Therefore, negative addresses are processed using complement representation. Further, the noise suppression correction output Z for this address signal is -z-1 in complement representation for a positive address, and 7 in real number representation for a negative address.

Furthermore, 0 is recorded at an address where the absolute value of the difference signal value is greater than a certain constant number D0. This is the absolute value IDi of the difference signal. This is because a larger television signal is determined to be a moving image part, so the noise suppression correction signal Z output from the fixed storage device 6 becomes 0, and the addition circuit 5
The output of the noise suppressed television signal Y is directly output to the input signal.

On the other hand, when the absolute value of the difference signal is close to O5 (less than Do), when D is positive (A>B), a negative stored content (complement) T is output from the fixed storage device 6. Therefore, the output of the adder circuit 5 is Y=A+Z-1, that is, the value of A minus the absolute value of T. Further, when A<b, the above operation is reversed. In this way, random noise will be suppressed.

Further, the output of the adder circuit 5 is output from the output terminal 3 as a noise suppressed television signal Y 7 and is also input to the frame memory 2. This input signal Y is used as the next frame's television signal B as a noise suppression correction signal Z.
used to calculate.

Next, 5, the noise reduce control is input to the control signal input terminal 7, and the vertical equal amount signal VD pulse is input to the VD input terminal 8. As a result, when the noise reduction control is switched from H level to ■7 level or from L level to I (1/bell), the time constant circuit 9 changes the noise suppression characteristic control address E of the output in stages, The suppression characteristics are switched in stages. For example, in FIG. 4, the difference signal D, that is, the upper two bits of the address signal, is replaced with the noise suppression characteristic control address E, and the noise suppression characteristics are changed in four stages from 0 to the maximum. Noise suppression characteristics when the control address E is "oo", S when the control address E is "01", Q when the control address is "01", Q when it is "10", and P when the control address E is "11". Take the characteristics of.

When the control signal input terminal 7 is in a steady state of level,
The noise suppression control address E becomes "00", all Z outputs take a characteristic S of O, and the noise suppression circuit is turned off. In addition, when the control input terminal 7 is in a steady state of L level, the noise suppression control address E
becomes "11", the noise suppression characteristic takes the maximum characteristic P, and the noise suppression circuit is turned on.

On the other hand, Fig. 5 shows the switching of the noise suppression control address E when the control signal input terminal 7 switches from the steady state of H level to the L level, and when the control signal input terminal 7 switches from the steady state of - level to the H level. It shows.

When the control signal input terminal 7 switches from the steady state of the H level to the L level, the time constant circuit 9 sets the time that is an integer multiple of the vertical synchronizing signal VD as the value time, and the noise suppression control address E is set to "00". to 11'', that is, the noise suppression characteristic is switched stepwise from O(S) to maximum (P). Further, when the control input terminal 7 is switched from the steady state of the L level to the level, the above operation is reversed.

In this manner, in this embodiment, the characteristic change of the noise suppression circuit is switched with a gentle slope, and the on/off operation of noise suppression becomes visually inconspicuous.

〔Effect of the invention〕

As described above, according to the present invention, a time constant circuit is provided in which the noise suppression characteristics are switched in stages when the noise suppression circuit is switched on and off by a control signal. The noise suppression characteristic can be switched in a gentle slope around 1, whereas the suppression characteristic was previously switched, and there is an effect that the switching operation of the noise suppression characteristic can be made visually inconspicuous.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a noise suppression circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional noise suppression circuit, FIG. 3 is a diagram showing conventional noise suppression characteristics, and FIG. 4 is a block diagram of the present invention. FIG. 5 is a diagram showing the noise suppression characteristics according to an embodiment of the present invention, and FIG. 5 is a diagram showing the transition of the noise suppression control address by the control signal. 1...Input terminal, 2...Frame memory, 4...
Subtraction circuit, 5... Addition circuit, 6... Fixed storage device,
7... Control signal input terminal, 8... VD input terminal, 9... Time constant circuit. Note that the same or corresponding symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A noise suppression circuit that adds a predetermined correction signal to an input television signal to suppress the noise component of the input television signal, the circuit comprising: the input television signal and the noise that is input before the signal and which has already been suppressed; a difference circuit that takes a difference from a processed television signal; a correction signal output means that outputs a correction signal for suppressing noise with a predetermined noise suppression characteristic based on the difference value; and a correction signal output means for turning on a noise suppression operation. , and a time constant circuit for causing the correction signal output means to output an output obtained by changing the noise suppression characteristic in stages when switching on and off by a control signal indicating OFF. suppression circuit.