KR940002329B1 - Frequency processing method - Google Patents

Abstract

The method of unfolding a frequency adapting the folding or unfolding of frequency includes a frequency shifter for shifting the high-frequency component of a video signal to the original frequency band, a frequency folding/unfolding discriminator for deciding the folding or unfolding of the input signal, a switch for selecting the output of the frequency shifter for the frequency-folded input, and selecting a non-signal for the frequency-unfolded input, an adder for adding a video input signal to be reproduced to the switch output to form a signal of the full-bandwidth, and a low-pass filter for removing noise, thereby increasing picture quality.

Description

How to adjust frequency by adapting the presence or absence of frequency folding

1A is a frequency structure of a video signal.

1b shows a partial detail according to FIG. 1a.

2 is a frequency structure of a video signal without frequency folding.

3A shows a frequency structure of a video signal obtained by frequency folding.

3b is a partial detail according to FIG. 3a.

Figure 4a is a system configuration of a conventional frequency power system.

4b is a frequency structure of a signal in which the signal of FIG. 2 is reproduced by applying FIG. 4a.

Figure 5a is a system configuration diagram of the frequency spreading method adapted to the presence or absence of the frequency folding in the present invention.

5b is a frequency structure of a signal in which the signal of FIG. 2 is reproduced by applying the present invention.

Fig. 5c is a frequency structure of a signal reproducing the signal of Fig. 3a according to the present invention.

5d is an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10: video input 20: frequency shifter

30: adder 40: low pass comb filter

50: Reproduced video result 60: Frequency folding judgment

70: switch, NAND gate 100: high pass filter

110: high pass comb filter 120: comparator

The present invention relates to a method of applying the presence or absence of frequency folding to the frequency band in order to improve the image quality while having compatibility with the existing VHS system and software.

In a video signal processor such as VHS, the processing frequency band is limited to around 3MHZ. Since the frequency band of video signal transmitted from NTSC TV system is about 5MHZ, it is a trend to develop high quality VTR that can reproduce video signal of 3MHZ or more. This is achieved by frequency folding technique.

The frequency folding technique is a method of narrowing and recording a frequency band by folding a high frequency component into a low frequency region using characteristics of an image signal, and is intended to achieve software compatibility by making the frequency band similar to that of a conventional VHS.

Frequency 폄 technology is a technique of returning the folded frequency components to the original state when recording, and is a method of moving the high frequency components folded in the low frequency region to the high frequency region.

When a VHS tape is reproduced in a system that reproduces a high-definition video signal using such a high frequency folding and zooming method, a part of the low frequency components of the video signal is forcibly moved to a high frequency region in the process of frequency shifting information without a frequency folding. High frequency noise is generated, resulting in deterioration of image quality.

In order to solve the deterioration of the image quality which is a problem in the conventional frequency folding and powering techniques described above, the present invention provides a method for passing different processing paths according to the state of a recorded input signal.

1A-B are diagrams showing the frequency structure of the video signal, and FIG. 2 is a diagram showing the frequency structure of the video signal without frequency folding.

FIG. 3 shows the frequency structure of the image signal with frequency folding. In case of recording information with frequency folding, the frequency 폄 causes the high frequency component folded into the low frequency region to move back to the high range to obtain a good image quality. have.

However, even when the input state is information without frequency folding as shown in FIG. 2, the frequency 강제 is forcibly forced to move a part of the low frequency components to the high frequency region by the frequency 에도 even though there is no high frequency component in the input signal. Will be.

As described above, as shown in Figs. 4A-B, high frequency components in a frequency region higher than the folding frequency f _F correspond to high frequency noise, and this noise degrades image quality.

5a-d are diagrams of the present invention's frequency power system, and FIG. 5a is a diagram illustrating a method of frequency spreading in accordance with the presence or absence of frequency folding presented in the present invention.

Here, the frequency shifter 20 moves the frequency of the input signal 10 to the high frequency region as a whole, and the frequency characteristic is symmetrical with the frequency characteristic of the input signal 10 with respect to the folding frequency f _F.

In addition, the frequency folding or not judging unit 60 adjusts the switch 70 by determining whether the input signal 10 is information without frequency folding as shown in FIG. 2 or information with frequency folding as shown in FIG. By selecting the output result of the frequency shifter 20 or the signal-free state according to the result of the frequency folding / undetermining unit 60, it is added to the input signal through the adder 30.

The output of the adder 30 is input to the low pass filter 40 to remove the noise trapped between the bands.

The result of the com-filtering of the signal is as shown in FIG. 5C, and FIG. 5B is a reproducing output signal for the input signal as shown in FIG. 2 without the frequency folding.

In this case, the high frequency noise shown in FIG.

FIG. 5C shows the characteristics of the reproduction output signal with respect to the recording input signal as in FIG. 3 with frequency folding.

In this case, the high frequency component folded in the low range is moved back to the high range, so that the clear image of the original signal before recording can be reproduced.

Figure 5d is an embodiment of the frequency 에 according to the present invention whether the frequency folding, the frequency folding and judging unit 60 is composed of a high pass filter 100, a high pass comb filter 110 and a comparator 120 It is.

Here, the high pass filter is intended to extract only the portion where the frequency overlap occurs when the frequency is folded, and the high pass comb filter passes only the frequency folded component.

The components that pass through the high pass filter and the high pass comb filter are generated only when there is a frequency folding. The output value of the comparator is "1" when there is a frequency folding and "0" when there is no frequency folding. do.

The outputs "0" and "1" of the comparator are inputted to the NAND gate serving as a switch to transmit or block a signal passing through the frequency shifter to the adder.

As described above, it is possible to determine whether or not the frequency input of the recorded input signal is reproduced with the maximum image quality of the signal regardless of the frequency folded state of the recorded signal, and achieve software compatibility.

Claims (2)

The frequency shifter 20 shifts the frequency band of the video input signal 10 to be reproduced to the high frequency region to move the high frequency components of the video signal before recording to the original frequency band, and the video input signal to be reproduced has a frequency fold. The output of the frequency shifter is selected for the image input with the frequency folding according to the output of the frequency folding or not judging device 60 and the frequency folding or not judging device which judges whether the information is the information or the information without the frequency folding. And a switch 70 for selecting and outputting a non-signal having a value of zero for a video input signal without a frequency fold, and a video input signal to be played back and a video before recording containing a low frequency component of the video signal before recording. The video signal before recording is added by adding the switch outputs containing the high frequency components of the signal. Presence or absence of frequency folding, characterized in that it consists of an adder (30) for producing a full-band signal and a low pass comb filter (40) for removing noise from frequency folding across the entire band from the output of the adder (30). How to adjust your frequency. The frequency folded signal is determined when the frequency folded signal when the frequency folded with the high pass filter 100 that passes only the high band near the frequency folding frequency f _F where the signal overlapping occurs strongly. It is composed of a high pass comb filter 110 that passes only the existing band and a comparator 120 indicating that there is a frequency folding only when the amount of the frequency folded signal is greater than or equal to a predetermined value. Way.