JPH03165185A - Video noise reduction circuit - Google Patents

Abstract

PURPOSE:To realize prescribed noise reduction sufficiently without unsharpening leading and trailing of a video signal by turning off the noise reduction operation for the leading and trailing period of the video signal. CONSTITUTION:A video noise reduction circuit has a noise detection circuit 2, an inverting circuit 3, an adder circuit 4, an integration circuit 6, a subtraction circuit 7 and a switch circuit 8 and detects the leading and trailing period of the video signal to turn off the noise reduction operation for the detection period. For the leading and trailing period of the video signal, the noise reduction operation is turned off to add only the noise component of the video signal except that for the leading and trailing period of the video signal to the input video signal. Thus, production of unsharpened portion at the leading and trailing period of the video signal is prevented while applying prescribed noise reduction sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video noise reduction M path configured to remove noise components in a video signal in a color television receiver.

[Prior Art] Fig. 3 is a block diagram showing the configuration of a conventional video noise reduction circuit, in which (1) is an input terminal for a video signal, (2) is a noise detection circuit, and - the above terminal (
1) Detect noise components in the input video signal. (3) is an inversion circuit that inverts the noise component detected by the noise detection circuit (2).

(4) is an adder circuit which adds the inverted noise component to the input video signal to cancel the noise component in the input video signal. (5) is an output terminal for the noise-cancelled video signal.

Next, the operation of the above configuration will be explained.

The video signal input from the terminal (+) has a waveform as shown in FIG. 4 [a] and includes a noise component (n). By inputting such a video signal (a) to the noise detection circuit (2), a noise component signal having a waveform as shown in FIG. The rising part (Ll) and the falling part (t2
) are also detected as noise components (nl) and (nl).

Next, the above noise component signal (b) is transferred to the inverting circuit (3).
The signal is inputted into the inverted noise component signal as shown in FIG. 4(C).

Next, the inverted noise component signal (C) is sent to the adder circuit (
4) and is added to the input video signal (a) here to cancel the noise component and produce the fourth signal.
A noise canceling video signal as shown in Figure (d) is output to the terminal (5).

[Problems to be Solved by the Invention] Since the conventional video noise reduction circuit is configured as described above, the rising and falling portions of the video signal are also detected as noise components. )
As shown in FIG. 2, although the noise component can be canceled, there is a problem in that the rising and falling parts of the video signal itself become dull and the outline of the image becomes blurred.

This invention was made in order to solve the above-mentioned problems, and it is possible to sufficiently reduce the noise in the video signal, and also to produce a video that does not cause distortion in the falling and falling portions of the video signal itself. The purpose is to provide noise reduction operation.

[Means for Solving the Problems] A video noise reduction circuit according to the present invention is characterized in that it is configured to detect the rising and falling periods of an input video signal, and turn off the noise reduction operation during the detection period. shall be.

[Operation] According to the present invention, by turning off the noise reduction operation during the rising and falling periods of the video signal, only the noise components excluding the rising and falling portions of the video signal are added to the input video signal. This makes it possible to sufficiently perform a predetermined noise reduction while preventing the occurrence of dullness in the rising and falling portions of the video signal.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a video noise reduction circuit according to an embodiment of the present invention. In the diagram, (1) to (5) are the same as the conventional example shown in FIG.
The same reference numerals are given to the corresponding parts, detailed explanation thereof will be omitted, and only the added parts will be explained.

In FIG. 1, (6) is an input video signal integration circuit, (
7) is a subtraction circuit, and these two circuits (6) and (7) constitute a detection circuit that detects the rising and falling periods of the input video signal by subtracting the signal obtained by integrating the input video signal from the input video signal. are doing. (8) is a switch circuit which is turned off by the absolute value of the output signal of the subtraction circuit (7) and outputs only the noise component.

Next, the operation of the above configuration will be explained.

From terminal (1), the waveform is as shown in Fig. 2 (a).

When a video signal containing a noise component (n) is input, the noise detection circuit (2) detects a noise component signal having a waveform as shown in FIG. 2(b).

Here, a rising portion (tl) and a falling portion (t2) of the input video signal (a) are also detected as noise components (nl) and (n2) at the same time.

Next, this noise component signal (b) is input to the inversion circuit (3) to become an inverted noise component signal as shown in FIG. 2 (C), which is input to one input terminal of the switch circuit (8). .

On the other hand, the video signal (a) containing the noise component input to the terminal (1) is also input to the integrating circuit (6) and is integrated.
The signal shown in FIG. 2(d) is output. Next, in the subtraction circuit (7), the integral signal (
By subtracting d), a signal having pulses (pl) and (p2) at the rising portion (tl) and falling portion (t2) of the video signal (a) is obtained as shown in FIG. 2(e). can get.

Next, by controlling the switch circuit (8) to turn off via the absolute value of the signal (e), that is, the boundary pulses (pi) and (P2) of the video signal,
A signal containing only a noise component (n) as shown in FIG. 2 (f'') is outputted to the output end of this switch circuit (8).

Next, this noise component signal (f) is added to the addition circuit (4).
By adding the noise component to the input video signal (a) containing the noise component at ) is output.

In the above embodiments, the circuit for detecting the rising and falling periods of the video signal is constructed of an integrating circuit that integrates the video signal and a subtraction circuit that subtracts the integrated signal from the original video signal. However, the rising and falling periods of the video signal may be detected by first-order differentiation, or the contour signal of another video signal may be used to turn off the noise reduction circuit. be effective.

[Effects of the Invention] As described above, according to the present invention, by turning off the noise reduction operation during the rising and falling periods of the video signal, the noise reduction operation can be performed without dulling the rising and falling portions of the video signal. A predetermined noise reduction can be sufficiently achieved, and blurring of the outline of an image can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a video noise reduction circuit according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part, and FIG. 3 is a block diagram showing the configuration of a conventional video noise reduction circuit. FIG. 4 is a signal waveform diagram of each part of the conventional example. (1)...Noise detection circuit, (3)...Inversion circuit,
(4)...Addition circuit, (6)...Integrator circuit, (7)
...Subtraction circuit, (8)...Switch circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) An image equipped with a noise detection circuit that detects a noise component in an input video signal, an inversion circuit that inverts the detected noise component, and an addition circuit that adds the inverted noise component to the input video signal. A video noise reduction circuit comprising: a detection circuit that detects rising and falling periods of the input video signal; and a switch circuit that turns off noise reduction operation during the detected periods.