JPS59207032A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To prevent the degradation of picture quality due to dubbing by disconnecting a specific noise reduction means from a video signal reproducing circuit system at a dubbing time to by-pass the video signal. CONSTITUTION:Switches 18 and 19 interlocking with each other are connected to contacts (b) at a dubbing time, and a 1H correlation noise reduction circuit 9, a noise erasing circuit 10, and a comb line filter 16 are disconnected from the reproducing circuit system, and the specific noise reduction means which is a cause of the degradation of picture quality by dubbing is disconnected from the reproducing circuit system. The circuit 9 uses the line correlation of a reproduced luminance signal of 1H before and amplifies the differential output of both signals and eliminates a high-level component in a limiter and mixes the result with the original reproduced luminance signal. The circuit 10 takes out a high- band component of the reproduced luminance signal by an HPF and takes out a components having a certain level or higher by a slice circuit and superposes the result onto the original reproduced luminance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a video signal reproducing device, such as a home VTR (video tape recorder), which is equipped with various noise reduction means.

(Background of the Invention) Conventionally, home VTRs in particular have been equipped with various noise reduction means. Household V equipped with this noise reduction means
When dubbing with ``T'R,'' some types of noise reduction methods not only reduce noise, but also have a negative effect on the original video signal, resulting in a significant drop in image quality. There was a problem.

For example, home VTRs use many noise reduction means such as double limiter FM system, video emphasis, burst level up, IH correlation noise reduction, various noise cancellers, and color crosstalk cancellers. Of these, if IH correlated noise reduction, various noise cancellers, and color crosstalk cancellers are activated during dubbing, the image quality will deteriorate significantly as described below. Utilizing the line correlation with the IH delay signal, the difference between the two is amplified by a differential amplifier circuit, and the low level portion of the output is extracted by a limiter circuit.
Since it is mixed with the original luminance signal, the horizontal luminance signal will affect the lower horizontal luminance signal in sequence every time dubbing is performed, so the horizontal contours of the image may become blurred downwards. , or especially when dubbing multiple times, the high-frequency components of the luminance signal are lost, resulting in a loss of screen sharpness.
Image quality deteriorates.

Each glaze noise canceler typically extracts the high-frequency components of the reproduced luminance signal using a bypass filter, removes the low-level components using a slice circuit, and superimposes only the high-level components on the original reproduced luminance signal. In addition, during the superposition, the high-frequency signal is raised to a slightly higher level to emphasize and sharpen the contours of the double-differential method, and the high-frequency component of the reproduced luminance signal is extracted using a bypass filter, and the high-frequency component is increased to a higher level. There are methods such as removing the low-level noise with a limiter, reversing the polarity of only the low-level noise, and superimposing it on the original reproduced brightness signal. The high-frequency components of the signal are lost, the entire screen becomes blurred, and, for example, the details of the hair in a close-amplified image of a person are removed, resulting in a flat image with reduced image quality.

The color crosstalk canceller is], 'S (Ph
aseShaft) method or p■('Phase 1
:nvert) method, the reproduced color signal after phase restoration is delayed by 1H using a comb filter, etc., and then added. Therefore, each time dubbing, the horizontal color signal is sequentially added to the lower horizontal color. It will affect the signal and go. Therefore, the colors appear to be blurred toward the bottom of the screen, the sharpness of the screen is lost, and the image quality is degraded.

Therefore, FM-
When considering adopting the FM dubbing method or the luminance signal/chroma signal separation dubbing method, the servo system of the recording device must be synchronized with the input signal during dubbing. Extract the synchronization signal and use it as the reference signal for the servo system, but ■(
゛In the 4-FM dubbing method, it is difficult to extract the synchronization signal from the input FM signal, so it is necessary to supply a video signal to extract the synchronization signal from a separate playback device, or to separately input the synchronization signal from the outside to the playback and recorder. If the circuit system becomes complicated or the number of terminals increases, problems may arise.Also, in the separate dubbing method for Luminance Shinmail and Chroma, there is a need to operate the Dubbing only.
It is necessary to provide separate output systems for W signal and chroma signal.
However, there are problems in that the circuit system becomes complicated and the number of edges increases. Home VTR
, because the frequency fluctuation of Colorim is large, AP, C (-8 automatic Pha
It is necessary to perform frequency correction such as (se Control), but this frequency correction cannot be easily performed with both of the above methods. Therefore, it is difficult to employ both of the above-mentioned methods in home V'l'R, etc.

(Object of the Invention) It is an object of the present invention to provide a video signal reproducing apparatus equipped with a noise reduction means that does not significantly deteriorate image quality even when dubbing is performed.

(Summary of '8 Ming) The technical point of the present invention is to separate a specific noise reduction means from the video signal generating circuit system during dubbing and to enable or disable the video signal.

(Embodiment) 1f'gl+ is a block diagram showing an embodiment of the present invention, in which 1 is a video signal, 2 is a preamplifier that amplifies the reproduced video signal from the video signal 1, and 3 is a preamplifier for amplifying the reproduced video signal from the video signal.゛A bypass filter that takes out the Δ4 luminance signal, a double limiter circuit that prevents reversal during reproduction of the 4-digit luminance signal, 5 a dropout compensation circuit that compensates for signals lost due to scratches on the magnetic tape, etc., 6 FM'F4 FM demodulation circuit for demodulating the FM demodulation circuit 6 (a low-pass filter for extracting the endogenous luminance (M signal) from the output of the FM demodulation circuit 6, 8
9 is a tie-enance circuit that returns the brightness to the brightness that emphasized high frequencies by a pre-emphasis circuit during recording, and 9 is an i
, 114 correlation noise reduction circuit that utilizes the line correlation of the reproduced luminance signal before H, amplifies the differential output of both, removes the high level part with a limiter, and mixes it with the original reproduced luminance signal, 10 is a noise canceller, for example, the high-frequency component of the reproduced luminance signal is extracted with a high-frequency filter, and the high-frequency component of the reproduced luminance signal is extracted with a slice circuit and superimposed on the original reproduced luminance signal.The high-frequency component of the reproduced luminance coefficient is bypassed. There are methods such as extracting the signal with a filter, extracting the lower part of the signal with a Riminok circuit, inverting the signal, and superimposing it on the original reproduced luminance signal. Reference numeral 11 denotes a synthesis circuit that synthesizes the reproduced luminance No. 1b and the reproduced color signal to generate a reproduced luminance signal, and 12 denotes an ACC (Automatic Co1or Con-
13 is a frequency conversion circuit that converts the reproduced low frequency conversion color signal (for example, 688.l<I4 y, in N'l'SC) to a carrier color signal (3.58 to [lz in NTSC), 14 is level up (e.g. 5dBup)
The burst newsletter was released in Level Town (6tjBdown
15 is a bandpass filter for extracting the carrier color signal from a balanced modulated color signal; 16 is a S method or PI method for removing color crosstalk between adjacent channels; In the final processing step, the 111 raw color signal after the phase afterlight and the IH-delayed color signal are subjected to f-7,11 calculation using a comb filter, 17
is the output circuit for impedance conversion, 18.1
Reference numeral 9 denotes switch circuits that interlock with each other, and are normally connected to the contact a side, and by operating to connect to the contact side during dubbing, for example, the IH correlation noise reduction circuit 9, the noise canceller 10, and the comb are connected. The configuration is such that the shaped filter 16 can be separated from the reproduction circuit system and the signal can be bypassed.

With such a configuration, when dubbing, by operating the switch circuits 18 and 19 and connecting them to the contact side, a specific noise reduction means that may cause deterioration of image quality due to dubbing is separated from the reproduction circuit system.

(Effects of the Invention) As described above, according to the present invention, a specific noise reduction means can be separated from the video signal reproduction circuit system during dubbing, so that the image quality does not deteriorate significantly due to dubbing. Further, the noise that cannot be removed by bypassing the circuit by the playback machine during dubbing can be removed immediately when the dubbed tape is run on a normal playback machine to play back the image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. (Explanation of the number in the main part) 9...1] I phase [↓゛] Noise reduction circuit 10... Noise canceller 16... Comb shape), f filter] 8. 19...Switch circuit 1 old 1, 1 person Nippon Kogaku Co., Ltd. agent Takao Watanabe

Claims (1)

[Scope of Claims] 1. A video signal reproducing device comprising a video signal noise reduction means and a switching means that allows the noise reduction means to be arbitrarily separated from the video signal reproduction circuit system. 2. A plurality of the noise reduction means are provided, and the switching means is capable of switching off a specific noise reduction means that degrades the video signal due to dubbing from the video signal reproduction circuit system, among the plurality of noise reduction means. A video signal reproducing device according to claim 1.