SU1677876A1 - Device for suppressing video signal noise - Google Patents

Abstract

The invention relates to a television technique, a magnetic video recording technique and can be used in a household video recorder. The purpose of the invention is to reduce video signal distortion, simplify the design of the device. The device contains a subtracting unit 1, a controlled high-pass filter 2 (HPF), a unit 3 for extracting the absolute value of the signal, a limiter 4 for the minimum. The output of the high pass filter is subtracted from the input video signal. The cut-off frequency of the HPF is proportional to the level of the high-frequency components of the video signal. 2 Il.

Description

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The invention relates to television technology, magnetic video recording technology and can be used in the playback channel of a video recorder.

The aim of the invention is to reduce distortion while simplifying the device,

Figure 1 shows a block diagram of a device for suppressing noise in a video signal; 2 shows video signal diagrams with noise and distortion.

The device consists of a subtracting unit 1, the first input of which is connected to the input of the device, and the output is the output of the device, a controlled high-pass filter 2 (HPF), the input of which is connected to the input of the device and the output to the second input of the subtracting unit 1. K the output of the controlled highpass filter 2 is connected in series with the absolute value extraction unit 3 and the limiter 4 at a minimum, the output of the latter being connected to the control input of the highpass filter 2.

The device works as follows

The output video signal containing noise (Fig. 2a) is fed simultaneously to the first input of the subtractive unit 1 and the input of the controlled HPF 2. FVCh 2 (Fig. Highlight noise and video signal peaks (Fig. 2b), which are fed to the second input of the subtractive unit 1 (FIG. 1) are subtracted from the input video signal, as a result of which the video signal is cleared of noise (FIG. 2e).

The output signal of the controlled highpass filter 2 (Fig. 26) passes through the series-connected absolute magnification separation blocks (Fig. V, to form a unipolar control signal (Fig. 2b) and limiter 4 at a minimum, the threshold of which is selected above the noise level This thereby eliminates the effect of noise on the control signal, which is a unipolar peaks corresponding to differences in the input video signal (Fig. 2d).

The cut-off frequency of the controlled HPF 2 is proportional to the amplitude of the control signal (Fig. 2d), therefore its values corresponding to the flat sections

video signal containing noise, and differences in video signal are different, which allows, on the one hand, to suppress noise in a wide frequency band, and on the other hand, to reduce

to minimize distortion of the video signal. The minimum cut-off frequency of the controlled high-pass filter 2 must be chosen from the condition of suppressing the main part of the high-frequency noise (for a domestic VCR, this is approximately 500 KHz). The maximum cut-off frequency is chosen outside the frequency spectrum occupied by the video signal (for a domestic video recorder, more than 3-4 MHz).

Thus, the proposed device reduces video signal distortion by reducing the peak duration, which is subtracted from the input video signal and causes its distortion, and also provides effective noise suppression in a wider frequency band as a result of the possibility of choosing a lower cut-off frequency of the controlled high-pass filter .

The proposed device, simply by design, provides processing of video signals having various parameters by automatically tracking their spectra.

Claims (1)

A device for suppressing noise in a video signal comprising a subtracting unit, a high-pass filter, a serially connected absolute value selection unit and a minimum signal stop, the first input of the subtracting unit being a device, the high-pass filter output is connected to 0 with the second input of the subtracting unit, characterized in that, in order to reduce distortion while simplifying the device, the first input of the high-pass filter is connected to the input of the device, the output 5 of the high-pass filter is connected to the input of the absolute value selection unit of the signal, the output of the signal limiter is at minimum connected to the second input of the high-pass filter, and the output of the subtracting unit 0 is the output of the device. WWVWtH ftWVWV A WWWiW IMWWVWVW VWWB VSVr Mmm