JPH03166882A - Digital noise reduction circuit in optical video disk player - Google Patents

Abstract

PURPOSE:To apply noise reduction processing by providing a limiter outputting a signal of an optional or smaller level from an output of a band pass filter and a subtractor subtracting the output from a reproduced video signal. CONSTITUTION:A reproduction video signal is converted by an A/D converter 1 and the converted signal is inputted to a BPF 2 and a delay element 5. The BPF 2 is a digital filter outputting a signal of a frequency band including a noise component from the A/D-converted reproduced video signal. An output of the BPF 2 is inputted to a limiter 3 shown in lower Figure. The output of the BPF 2 in the limiter 3 is compared with a constant C at a comparator 7. The comparator circuit 7 outputs 0 as an output of a selector 8 when the input signal is the constant C or over and outputs the input signal as it is when the input signal is less than the constant C. The output of the limiter 3 is subjected to subtraction at a subtractor 4 with the reproduced video signal delayed by a time for processing of the BPF 2 and the limiter 3 through a delay element 5 and noise reduce processing of the reproduced video signal is implemented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a noise reduction circuit for removing noise contained in a reproduced video signal of an optical video disc player. (Prior Art) FIG. 3 shows the basic configuration of a noise reduction circuit for a conventional optical video disc player. In FIG. 3, 12 is a band pass filter (hereinafter referred to as BPF) for extracting a frequency band containing noise components contained in the reproduced video signal of the optical video disk player;
l3 is a limiter that outputs a small amplitude signal of the output of BPF 12, 14 is a subtracter that subtracts the output of limiter 13 from the input signal, and 15 is a subtracter that corrects the delay time generated by the processing of BPF 12 and limiter 13, and reproduces it in the subtracter. This is a delay element that adjusts the time between the video signal and the limiter output. Next, the operation of the noise reduction circuit of the conventional optical video disc player will be described. In FIG. 3, the reproduced video signal of the optical video disc player inputted from the input terminal is inputted to the BPF 128 on one side and the delay element 15 on the other side. BPFl2 extracts a frequency band signal containing noise components from the input reproduced video signal. The output signal of this BPF12 is limiter 1
3, and the limiter 13 outputs a signal having an amplitude below a certain level, regarding it as noise. The output of this limiter 13 is input to a subtracter l4, where it is subtracted by a delay element l5 from the reproduced video signal delayed by the time delay caused by the processing of the BPF 12 and limiter 13, thereby performing noise reduction processing. .

(Problem to be Solved by the Invention) However, the noise reduction circuit of the conventional optical video disk player described above is composed of an analog circuit, and phase rotation occurs due to the analog element of the BPF, and delay time adjustment using the delay element occurs. However, the problem was that the image quality of the reproduced video signal deteriorated. The present invention solves the above-mentioned conventional problems, and aims to provide a noise reduction circuit for a video disc player that does not cause phase shift and allows easy delay time adjustment. (Means for Solving the Problems) In order to achieve the above object, the present invention configures a noise reduction circuit with a digital circuit, and adds an A/D converter to convert an input reproduced video signal into a digital signal. After conversion, noise reduction processing is performed by digital signal processing.

(Function) With the above-described configuration, the present invention prevents phase rotation due to the BPF, and makes time adjustment simple using a delay element, thereby making it possible to perform noise reduction processing without attempting to improve image quality deterioration of the reproduced video signal. It is something that can be done. (Example) Fig. 1 shows the structure of a noise reduction circuit in an embodiment of the present invention, and Fig. 2 shows the structure of a limiter of the noise reduction circuit in an embodiment of the invention. . In FIG. 1, 1 is an A/D converter, 2 is a BPF, 3 is a limiter, 4 is a subtracter, 5 is a delay element, and 6
is a D/A converter. Further, in FIG. 2, 7 is a comparator, 8 is a selector, and C is a constant.

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

In FIG. 1, a reproduced video signal of an optical video disc player inputted from an input terminal is converted into a digital signal by an A/D converter 1, and inputted to a BPF 2 and a delay element 5. BPF2 is a digital filter that outputs a signal in a frequency band containing some noise from the A/D converted reproduced video signal. The output of BPF2 is input to limiter 3 shown in FIG. With this limiter 3,
The output of BPF2 is compared in magnitude with constant C by comparator 7. Depending on the comparison result, the comparator 7 sets the output of the selector 8 to 0 if the input signal is greater than or equal to the constant C, and outputs the input signal as it is if the input signal is less than the constant C.
The output of this limiter 3 is transmitted to BPF2 by delay element 5.
The subtracter 4 performs subtraction processing on the reproduced video signal delayed by the time processed by the limiter 3 and the reproduced video signal to perform noise reduction processing. The output of the subtracter 4 is restored to an analog signal by the D/A converter 6 and output from the output terminal. In this noise reduction processing, since the BPF 2, limiter 3, and delay element 5 are composed of digital circuits, there is no phase shift in the BPF 2 that can occur in an analog circuit, and the input video signal is strictly controlled by the delay element 5. Delay time management can be easily performed, and noise reduction processing can be performed without impairing the quality of the reproduced video signal.

(Effects of the Invention) As is clear from the above embodiments, the present invention provides a band-pass filter for extracting an arbitrary frequency component of an optical video disc player converted into a digital signal, and a band-pass filter for extracting an arbitrary frequency component of an output of the band-pass filter. To perform noise reduction processing without impairing the quality of a reproduced video signal of an optical video disk player by comprising a limiter that outputs a signal below the level and a subtracter that subtracts the output of the limiter from the reproduced video signal. It has the effect of being able to.

[Brief explanation of the drawing]

Figure 1 is a block configuration diagram of a noise reduction circuit in an embodiment of the present invention, Figure 2 is a configuration diagram of the limiter in Figure 1, and Figure 3 is the basics of a noise reduction circuit for a conventional optical video disc player. FIG. 1...A/D converter, 2,12...Band pass filter, 3,13...Limiter, 4,14...
・Subtractor, 5, l5...Delay element, 6...D/A
Converter, 7... Comparator, 8... Selector.

Claims (1)

[Claims] a bandpass filter that extracts an arbitrary frequency component of a reproduced video signal of an optical video disc player that has been converted into a digital signal; a limiter that outputs a signal below an arbitrary amplitude level of the output of the bandpass filter; and the limiter and a subtracter for subtracting the output of the reproduced video signal from the reproduced video signal.