JPH08140102A - Blanking device with color killer circuit - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention relates to a blanking device using a color killer circuit for blanking when switching images in a television receiver or the like, and switching between different color systems or the same color system. In addition, it corresponds to the switching of black and white and the video signal of black and white broadcasting, and blanking is applied only for the minimum necessary time. [Configuration] The microcomputer 111 has a video amplifier circuit 103 for switching a color broadcast video signal for a minimum time required for switching depending on the state of the color killer circuit 106, and for switching a black and white broadcast video signal for a fixed time by a timer circuit 112. A configuration in which the color demodulation circuit 108 is controlled to block the video signal and the display device 110 is blanked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blanking device for temporarily interrupting a video signal when a video signal of a TV is switched so as to prevent the screen from being disturbed.

[0002]

2. Description of the Prior Art In the prior art, the actual construction of Sho 62-39
No. 837, a mute circuit for reproduced video signals is mentioned. This is to perform the mute operation according to the state of the reproduced video signal because the reference for determining whether or not the mute is necessary is the sync signal in the reproduced video signal. In the present invention, unlike the above-mentioned prior art, when the video signal is switched, such as when switching channels, the presence or absence of a color burst signal is detected from the carrier color signal obtained from the reception signal of the terrestrial broadcast radio wave, and the color synchronization circuit is set. A color killer circuit that detects whether the reference sub-carrier frequency matches the color system of the received signal and controls the band amplification circuit is used to optimize the blanking length. The invention is clearly different from the above-mentioned prior art.

Next, general prior art will be described from the viewpoint of a television receiver. Television receivers (hereinafter TV) in the European market are PAL, SEC
It is necessary to be able to receive the broadcast format of each color system such as AM and NTSC. Further, since it is necessary to set the color system independently for each position, the types of the color system are often switched. During this switching process, the screen is generally disturbed for several hundred milliseconds to one second. For this reason, conventionally, depending on the market, it is necessary to block the video signal at the time of signal switching so that the disturbance on the display screen cannot be seen. The conventional blanking of a video signal will be described with reference to FIG. The intermediate frequency signal 201 from the tuner is subjected to intermediate frequency amplification and video detection by the IF signal processing circuit 202, becomes a color video signal, and enters the video amplification circuit 203. Here, the video signal is also distributed to the color processing circuit group, is processed, and then enters the color output circuit 209.
It is displayed on the display device 210 after being amplified together with the luminance signal from the video amplifier circuit 203. The video signal is blocked by controlling the video amplifier circuit 203 and the color demodulation circuit 208 using a microcomputer 211 or the like in order to prevent noise from being seen on the display device 210 when the video signal is disturbed when the channel is switched or when the input source is switched. Conventionally, the control is performed only by the timer circuit 212 for a certain period of time. Further, since the time required for switching between the color systems is different, the time of the timer 212 is set to match the time required for switching between the color systems which takes the longest time.

[0004]

When the blanking is performed in accordance with the switching time between the color systems which takes the longest time as in the prior art, it is possible to switch between different color systems in a short time and between the same color systems. There is a lot of time wasted in switching. For example, when switching from a TV PAL signal to a video NTSC signal, the image is disturbed for about 800 milliseconds, but when switching from the TV PAL signal to the same PAL signal, it is disturbed for only about 200 milliseconds. Conventionally, only the timer circuit was used to adjust to the longest disturbance time, so when switching between the same color systems, blanking took about 4 times longer than the required time. Depending on the type of color system that is switched in this way,
There is a problem that blanking of an unnecessary length is applied.

[0005]

In order to solve the above problems, according to the present invention, since the color burst signal changes when the color system is switched, the color burst signal is constantly monitored to detect the presence or absence of the color burst signal. Also, it has a color killer circuit that detects whether the reference sub-carrier frequency set in the color synchronization circuit matches the color system of the received signal and controls the band amplification circuit, and that blanking is applied when receiving a monochrome broadcast. A timer circuit is provided to prevent such a situation, and a microcomputer for monitoring the states of the color killer circuit and the timer circuit is provided to enable the necessary minimum blanking.

[0006]

According to the present invention, before the color video signal output from the video amplifier circuit is input to the display device such as a cathode ray tube, when switching the video signal of the color broadcast, the color killer circuit minimizes the time required. The blanking is applied, and the blanking is controlled by the timer circuit when the video signal of the black and white broadcast is switched to prevent the blanking from remaining. The microcomputer performs blanking control depending on the states of the color killer circuit and the timer circuit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A blanking device using this color killer circuit will be described below with reference to the illustrated embodiment.

In FIG. 1, an intermediate frequency signal 101 of an image taken out from a channel selection section such as a tuner is subjected to intermediate frequency amplification and image detection by an IF signal processing circuit 102 to become a color image signal, which enters a video amplification circuit 103. Here, the color video signal is distributed, one is sent to the band amplification circuit 104, and one is sent to the color output circuit 109 as a luminance signal. The band amplification circuit 104 extracts a carrier color signal including a color burst signal from the received color video signal,
It is sent to the color demodulation circuit 108 and the burst amplification circuit 105. The color demodulation circuit 108 generates a color difference signal based on the carrier color signal received from the band amplification circuit and the reference subcarrier from the color synchronization circuit 107, and sends it to the color output circuit 109. Color output circuit 1
09 is the luminance signal received from the video amplification circuit 103,
The color difference signal received from the color demodulation circuit 108 is amplified and sent to the display device 110 for image reception. The burst amplifier circuit 105 extracts a color burst signal from the carrier color signal, amplifies it, and sends it to the color synchronization circuit 107 and the color killer circuit 106. The color synchronizing circuit 107 generates a reference width carrier wave by the oscillator having the received color burst signal and the reference subcarrier frequency corresponding to each color system, and the color demodulation circuit 20.
Send to 8. The color killer circuit 106 detects the presence or absence of a color burst signal, and the microcomputer 11
It is detected whether the reference sub-carrier frequency set in the color synchronization circuit 107 by 1 or the like matches the color system of the received signal, and during black-and-white broadcasting or when the reference sub-carrier frequency does not match the color system of the received signal. The band amplification circuit 104 is controlled so as not to generate color noise, and whether or not the color killer operation is performed is sent to the microcomputer 111 as data. The timer circuit 112 measures a fixed time under the control of the microcomputer 111.

At the start of the color video signal switching process due to a tuning operation or the like, the microcomputer 111 controls the video amplification circuit 103 and the color demodulation circuit 108 in order to prevent the display video on the display device 110 from being disturbed. , Shut off the video signal. Here, not only is the blanking time set to a fixed time by the timer circuit 112 for black and white broadcast reception, but also the color killer circuit 106 determines whether or not the color killer is operating, that is, whether or not the screen is properly colored. When the color killer operation is completed, that is, when the screen can be colored correctly, the microcomputer 111 controls the image amplification circuit 103 and the color demodulation circuit 108 to immediately cancel the blanking. , Apply blanking for the minimum required time. In the timer circuit 112, the maximum time necessary for switching the color video signal is set by the microcomputer 111 at the start of switching the video signal.

In FIG. 1, first, the color system is PA.
A case of changing from L to SECAM will be described. P
To receive AL correctly, microcomputer 1
Reference numeral 11 sets the reference subcarrier frequency of PAL to the color synchronization circuit 107. At this time, the color can be demodulated normally and the color is properly added to the screen. The color killer circuit 106 detects that the reference subcarrier frequency is correct and that there is a color burst signal, and since the timer circuit 112 is not operating, the microcomputer 111 blocks the video amplification circuit 103 and the color demodulation circuit 108. Do not indicate ranking. When changing to SECAM reception, the microcomputer 111 first controls the image amplification circuit 103 and the color demodulation circuit 108 to perform blanking before performing the actual switching process. When the switching process starts, the color burst signal disappears and the color killer circuit 106 turns the band amplification circuit 104 into a signal.
To control the color killer. When this switching process ends and the video signal becomes stable, the SECAM color burst signal is detected again. However, the microcomputer 111 determines that the received signal is SECAM, and the reference subcarrier frequency of SECAM is set to the color synchronization circuit 107.
The color killer circuit continues the color killer operation because colors are not applied correctly until it is set to. When the microcomputer 111 determines that the received signal is SECAM and correctly sets the reference subcarrier frequency of SECAM in the color synchronization circuit 107, the color killer circuit 106 stops the color killer operation and correct color demodulation is performed. The microcomputer 111 receives the suspension of the color killer operation as data, and the image amplification circuit 103 and the color demodulation circuit 1 are received.
08 is instructed to cancel blanking. In response to this, the video amplification circuit 103 and the color demodulation circuit 108 cancel the blanking and the correctly colored image is displayed on the display device 11.
Appears at 0. When the microcomputer 111 receives the clock signal from the timer circuit 112 and remains blanked for a certain period of time, the video amplifier circuit 10
3. Instruct the color demodulation circuit 108 to cancel the blanking.

Next, the case of receiving a monochrome broadcast will be described. Before the microcomputer 111 actually starts the switching process, the timer circuit 112 is set so as to measure a fixed time, and the video amplification circuit 103 and the color demodulation circuit 1 are set.
08 is controlled and blanking is applied. Even after the switching is completed and the video signal is stable, the color killer circuit 106
Does not detect a color burst signal, the color killer operation remains performed. As a result, the microcomputer 111 cannot issue a blanking cancellation command only with the signal from the color killer circuit 106, so that the timer circuit 112 detects the elapse of a certain period of time and blanks the image amplification circuit 103 and the color demodulation circuit 108. Command release. In response to this, the video amplification circuit 103 and the color demodulation circuit 108 release the interruption of the video signal, and a black and white screen appears on the display device 110. The time required for blanking the black and white screen is set to the longest time required for the microcomputer 111 to correctly determine whether the color system of the received signal is PAL / SECAM / NTSC when switching the color screen. To do.

[0012]

As described above, according to the blanking device using the color killer circuit of the present invention, the same color system can be completed in a short time even when switching the video signal between different color systems which takes a long time. Even if you switch between them, you can apply a blanking of the minimum necessary length by monitoring the color killer operation of the color killer circuit, and also in the case of black and white broadcast reception, by using the timer circuit together, It is possible to prevent the blanking from remaining.

[Brief description of drawings]

FIG. 1 is a block diagram of a blanking device configuration using a color killer circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a blanking device configuration using only a conventional timer circuit.

[Explanation of symbols]

 101 intermediate frequency signal 102 IF signal processing circuit 103 image amplification circuit 104 band amplification circuit 105 burst amplification circuit 106 color killer circuit 107 color synchronization circuit 108 color demodulation circuit 109 color output circuit 110 display device 111 microcomputer 112 timer circuit 201 intermediate frequency signal 202 IF signal processing circuit 203 Video amplification circuit 204 Band amplification circuit 205 Burst amplification circuit 206 Color killer circuit 207 Color synchronization circuit 208 Color demodulation circuit 209 Color output circuit 210 Display device 211 Microcomputer 212 Timer circuit

Claims (1)

[Claims] 1. A band amplification circuit is controlled by detecting the presence or absence of a color burst signal from a carrier color signal, and detecting whether a reference sub-carrier frequency set in a color synchronizing circuit matches a color system of a received signal. A signal having a color killer circuit, a timer circuit for measuring a fixed time, and a microcomputer for receiving the output signals of the color killer circuit and the timer circuit and instructing a video blanking circuit to a video amplification circuit and a color demodulation circuit. A blanking device using a color killer circuit, which not only blanks a timer for a certain period of time when switching, but also blanks depending on the presence or absence of a color burst signal and whether or not the reference subcarrier frequency is correct.