JPH09233447A - Picture quality improving method for catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve video whose picture quality is not high so much because of flickering or noise generation on the side of center and to transmit the video to a viewer. SOLUTION: When picture quality is degraded by generating the flicker or noise of image in a TV signal to be transmitted, at the center of a CATV system, the video signal of the TV signal is separated into a brightness signal (Y signal) and a chrominance signal (C signal), the signal levels of either one or both of the luminance signal and the chrominance signal are dropped for suitable quantity, afterwards, the video signal is reproduced while mixing both the signals, and the TV signal is transmitted to the transmission line of the CATV system by using the video signal. The level of the brightness signal or the chrominance signal is controlled inside a TV modulator 1 at the center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention retransmits TV broadcasts received at the headend, and transmits V broadcasts at the headend.
The present invention relates to a method of improving image quality in a CATV system that allows a viewer to see a TV image that is not too bad even if the image quality of the image to be transmitted is bad in the CATV that transmits the TR image.

[0002]

2. Description of the Related Art In a CATV system, when a TV broadcast wave is received and retransmitted, if the reception condition of the broadcast wave is poor, the retransmitted image may flicker or generate noise, which may cause a viewer May be annoying. In this case, the viewer sees the flicker video as it is, or the viewer operates a video mode switch called living mode or theater mode of the TV receiver at home,
The brightness (brightness) of the screen displayed on the V receiver is lowered to make the flicker and noise of the image inconspicuous. Video flicker and noise occur not only when a TV broadcast is retransmitted but also when a VTR video reproduced from a video tape that has been repeatedly reproduced many times in the past and whose quality has deteriorated. Therefore, in a CATV that retransmits and uses a VTR a lot, flicker and noise may occur in an image as compared with a general TV broadcasting station that often transmits an image captured by its own station.

[0003]

In the center of a CATV system, when a video image with flicker or noise is transmitted, the screen becomes difficult for the viewer to see. This is not preferable in commercial broadcasting even if the video source is bad. However, in the past, the center side did not have any means for improving the video when the video source was bad, so it is the actual situation that the viewer side is entirely responsible for dealing with video with poor image quality, and this improvement has been demanded. .

An object of the present invention is to provide an image quality improving method in a CATV system capable of transmitting a flicker, noise, etc., which is not so good in image quality and which can be transmitted on the center side while making the flicker, noise, etc. less noticeable. To provide.

[0005]

As shown in FIG. 1, a method of improving image quality in a CATV system according to claim 1 of the present invention deteriorates the image quality by causing image flicker or noise in a TV signal to be transmitted. In the center of the CATV system, the video signal of the TV signal is separated into a luminance signal (Y signal) and a color signal (C signal), and either or both of the luminance signal and the color signal have an appropriate signal level. After dropping, both signals are mixed to reproduce a video signal, and the TV signal is transmitted to the transmission path of the CATV system by using this video signal.

According to the second aspect of the present invention, in the image quality improving method in the CATV system, as shown in FIG. 2, the level adjustment of the luminance signal and the chrominance signal is executed in the TV modulator 1 of the center.

[0007]

First Embodiment FIG. 1 shows an embodiment of an image quality improving method in a CATV system of the present invention. In this image quality improving method, the head end H. E. FIG. The TV modulator 1 installed in the computer has an image quality improving function. The TV modulator 1 can input a video signal and an audio signal separated from the TV signal. With respect to the video signal, the Y / C separation circuit 11 outputs a Y signal (luminance signal) and a C signal (color signal). For the Y signal, the luminance of the Y signal can be adjusted in the luminance processing circuit 12, the adjusted Y signal and the unadjusted C signal are mixed to reproduce a video signal, and then the video signal is reproduced. The signal can be modulated by the modulator 13 and output to the transmission line. In FIG. 1B, the processing unit for the input video signal is similar to that of the conventional TV modulator and is omitted.

The brightness processing circuit 12 is an adjusting volume (not shown) for adjusting the brightness of the Y signal.
And a pass switch (not shown) for allowing the Y signal to pass through without being adjusted, and the adjustment volume and the pass switch can be relatively easily operated by a worker. Worker is TV modulator 1
When the state of the video signal input to is good, the pass switch is set to through so as not to adjust the brightness of the Y signal. When the state of the video signal input to the TV modulator 1 is bad, the pass switch is set to The brightness of the Y signal is adjusted by operating the switch and the adjustment knob, respectively. This adjustment is performed, for example, while monitoring the image output from the TV modulator 1 so that flicker and noise are not noticeable in the image on this monitor finally.

The TV modulator 1 includes a headend H.264.
E. FIG. In addition to inputting video and audio signals of TV signals received by the receiving antenna 14 of VTR (commercial VTR,
It is possible to input a video signal and an audio signal from a home VTR (VHS, SVHS, 8 mm video, 6 mm digital video, beta). Further, it is possible to input a video signal and an audio signal from an LD (laser disk), which does not deteriorate in image quality, and it is also possible to input other sources.

In the image quality improving method in the CATV system of the present invention, the luminance of the Y signal is not lowered, but C
It may be possible to reduce the color density of the signal, or Y
It is also possible to use the signal brightness adjustment and the C signal density adjustment together. When adjusting the C signal or adjusting the Y signal and the C signal together, a color density processing circuit that separately processes the C signal to make the color density variable can be provided in Y / Y of FIG. It is provided on the C signal output side of the C separation circuit 11.

Further, in the image quality improving method in the CATV system of the present invention, the adjustment of the Y signal and the adjustment of the C signal are not performed in the TV modulator 1, and the head end H.264 signal is not generated. E. FIG.
It is also possible to do it in the circuit inside or other circuits (please let the inventor know if you can give a specific name). In short, if the system configuration is such that the video signal of the TV signal to be transmitted can be processed on the center side and the video signal has flicker or noise, the Y signal and C signal can be adjusted to such an extent that the flicker or noise can be made inconspicuous. good.

[0012]

According to the image quality improving method in the CATV system of the present invention, when the image to be transmitted is deteriorated, it can be improved and provided to the viewer at the center side. You can see relatively beautiful images without operating the machine.

[Brief description of drawings]

1A and 1B are diagrams showing an embodiment of an image quality improving method in a CATV system of the present invention, FIG. 1A is a schematic diagram showing a configuration of an entire center, and FIG. 1B is a portion showing a configuration of a TV modulator. Block diagram.

[Explanation of symbols]

 1 TV modulator

Claims (2)

[Claims] 1. When the image quality of a transmitted TV signal is deteriorated due to image flicker, noise or the like, the image signal of the TV signal is changed to a luminance signal (Y signal) and a color signal (in the center of the CATV system). C signal), the signal level of either or both of the luminance signal and the chrominance signal is reduced by an appropriate amount, and then both signals are mixed to reproduce a video signal, and the TV signal is used as a CATV signal by using this video signal. A method for improving image quality in a CATV system, characterized in that transmission is performed on a transmission path of the system. 2. A method for improving image quality in a CATV system according to claim 1, wherein the level adjustment of the luminance signal and the color signal is executed in the TV modulator (1) at the center.