JPH027677A - Noise canceller - Google Patents

Abstract

PURPOSE:To attenuate even a noise component of an edge part by substracting an output signal of the 2nd signal path from an output signal of the 1st signal path, detecting an output signal level of a high pass filter in the 2nd signal path and controlling a switching circuit. CONSTITUTION:A high frequency component is extracted from a reproduced luminance signal including noise (n) by a high pass filter 2, a level detection circuit 8 detects whether an output signal level of the high pass filter 2 is larger than the noise level (a) or smaller to control a switching circuit 7. Moreover, a slice circuit 9 slices the output signal of the high pass filter 2 at the edge noise level (b) of a large amplitude and the noise component is fed to an adder 10. The adder 10 adds a noise component of the flat part of the reproduced luminance signal and the noise component of the edge part with a large amplitude, gives an output to a low pass filter 4, the low pass filter 4 decides the noise band to be attenuated and gives an output to a subtractor 5. Thus, the noise component of the edge part with a large amplitude in the reproduced luminance signal is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a noise canceller device for removing noise from a reproduced signal of a magnetic recording/reproducing device (hereinafter abbreviated as VTR) capable of recording and reproducing video signals. It is related to.

BACKGROUND OF THE INVENTION A conventional noise canceller device will be described below with reference to the drawings.

FIG. 2 shows a block diagram of a conventional noise canceller device. In FIG. 2, 1 is an input terminal into which a reproduced luminance signal is input, 2 is a high-pass filter that extracts all high-frequency components from the reproduced luminance signal input from input terminal 1;
3 is a limiter circuit, 4 is a low-pass filter that limits the noise band, 6 is a subtracter, and 6 is an output terminal.

First, a reproduced luminance signal of a VTR containing noise n=i is inputted from the input terminal 1 as shown in FIG. 3A. The high-pass filter 2 extracts all high-frequency components from the signal shown in FIG. 3A, and outputs a signal as shown in FIG. 3B. The limiter 3 extracts all minute noise components below the limiter level a from the signal shown in FIG. In subtractor 5,
The output signal of the low-pass filter 4 is subtracted from the reproduced luminance signal shown in FIG.

This output signal is shown in FIG.

Problems to be Solved by the Invention However, with the above configuration, noise components in large amplitude edge portions with poor S/N and visually unsightly in the reproduced luminance signal cannot pass through the limiter 3, so they are removed. I can't.

Furthermore, as shown in FIG. 3C, there is a problem that the signal at the edge portion is missing and the waveform becomes dull.

In view of the above-mentioned problems, the present invention can remove noise in flat parts and large amplitude edge parts of a reproduced luminance signal, and
Furthermore, it is an object of the present invention to provide a noise canceller device in which signals at edge portions are not dulled.

Means for Solving the Problems In order to solve the above problems, the noise canceller device of the present invention has an input terminal into which a luminance signal is input, and a first... a second signal path, a subtracter that subtracts the output signal of the second signal path from the output signal of the first signal path, a high-pass filter provided in the second signal path, and the high-pass filter The present invention is characterized by comprising a level detection circuit for detecting the level of the output signal and controlling a switching circuit provided in a circuit from the high-pass filter to the subtracter.

Further, the present invention is characterized by the addition of a slice circuit into which the output signal from the high-pass filter is input, and an adder that adds the output signal from the slice circuit and the output signal from the switching circuit.

Effect of the Invention According to the present invention, only the signal below the noise level in the output signal of the high-pass filter can be extracted using the level detection circuit and the switching circuit. Therefore, it is possible to completely remove the noise components in the large-amplitude edge portions of the reproduced luminance signal, which cannot be removed by conventional devices, have a high noise level, and are visually very unsightly. Also,
By passing the output signal of the high-pass filter through a slicing circuit, it is possible to extract edge components with large amplitudes, so the signal components at the edges, which were lost with conventional devices, are not lost, and the waveform remains unchanged. It's never full.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a noise canceller device of the present invention. In FIG. 1, the same reference numerals as those in FIG. 2 are the same or corresponding parts, so the explanation will be omitted. 7
is a switching circuit, 8 is a level detection circuit, 9 is a slice circuit,
1o is an adder.

The operation of the noise canceller device configured as described above will be explained below.A reproduced luminance signal containing noise as shown in FIG. As shown in Figure 3, its high frequency components are extracted. The level detection circuit 8 determines whether the output signal level of the high-pass filter 2 is thicker than the noise level a as shown in the opening of FIG.
The switching circuit T is fully controlled so that the signal does not pass through the switching circuit 7 when it is greater than the noise level a, and so that the signal passes through the switching circuit 7 when it is smaller than the noise level a. The switching circuit 7 supplies a signal as shown in FIG. 3 to the adder 1o. The slicing circuit 9 slices the output signal of the high-pass filter 2 as shown in the opening of FIG. Supply to 1o. The adder 1o completely adds the noise component of the flat part of the reproduced luminance signal as shown in FIG. Output. The low-pass filter 4 determines the entire noise band to be attenuated and outputs it to the subtracter 5. The subtracter 5 selects a low-pass filter 4 from the noise-filled reproduced luminance signal as shown in FIG. 3A.
The output signal is subtracted from the reproduced luminance signal as shown in FIG.

Effects of the Invention As described above, the noise canceller device of the present invention has an input terminal into which a luminance signal is input, and a first... a second signal path; a subtracter that subtracts the output signal of the second signal path from the output signal of the first signal path; a high-pass filter provided in the second signal path; Since it is equipped with a level detection circuit that detects all output signal levels of the filter and controls all switching circuits provided in the circuit from the high-pass filter to the subtracter, it is possible to eliminate noise levels that could not be detected with conventional devices. It is also possible to attenuate large, unsightly, large-amplitude edge portion noise components.

Furthermore, since it is equipped with a slicing circuit that slices the output signal of the high-pass filter and an adder that adds the output signal from this slicing circuit and the output signal of the switching circuit, the signal of the edge portion that was lost in the conventional device is provided. This has the advantage that the waveform is not lost and waveform rounding does not occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the noise canceller circuit of the present invention, FIG. 2 is a block diagram of a conventional noise canceler circuit, and FIG. 3 is a signal waveform diagram of each part. 1...Input terminal, 2...High pass filter, 4...Low pass filter, 5...Subtractor, 6...Output terminal, 7... ...Switching circuit, 8
...Level detection circuit, 9...Slice circuit, 1o River...Adder. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 1 Atsushi Heto

Claims (2)

[Claims] (1) an input terminal into which a luminance signal component of a video signal is input, and first and second signal paths connected to this input terminal;
a subtracter that subtracts the output signal of the second signal path from the output signal of the first signal path; a high-pass filter provided in the second signal path; and detecting an output signal level of the high-pass filter. and a level detection circuit that controls a switching circuit provided in a circuit from the high-pass filter to the subtracter. (2) Claim 1, characterized in that it is provided with a slicing circuit that slices the output signal from the high-pass filter, and an adder that adds the output signal of the slicing circuit and the output signal of the switching circuit. Noise canceling device as described.