JPH04176277A - Picture mute circuit - Google Patents

Abstract

PURPOSE:To enable the switching of video without noises or synchronization disturbance by switching signals while taking video mute during the vertical blanking period of the former video signal and releasing the video mute during the vertical blanking after the next picture signal is stabilized. CONSTITUTION:At the time of picture switching input, a mute command signal (d) is inputted to a picture mute circuit 1 by a key/remote control processing part 2. Simultaneously, a picture changeover signal (b) is outputted to a picture selection circuit 3 by delaying some 10m sec, and the input signal is switched. The picture selection circuit 3 outputs a post selection signal (a) to a picture output circuit 4, and transmits a vertical synchronizing pulse (c) to a picture mute circuit 1 at all times. The picture mute release is released after 100 to 200m sec after the picture changeover, and a picture mute output pulse (f) and a vertical synchronizing pulse (c) are synchronized to be released after the release. Thus, the quality at the time of switching the picture which is often overlooked can be improved during the advancement of technology in sound and image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video micort circuit for switching video signals.

BACKGROUND OF THE INVENTION Generally, when switching TV channels, the open signal for several tens to hundreds of m5ec is lost until the tuning voltage of the tuner stabilizes, and a screen with noise and synchronization appears. In addition, the synchronization of television broadcast signals differs for each station, and the synchronization of TVs, TRs, video discs, etc. also differs for each device, so when switching signals, you may see a momentary out-of-sync screen. There is.

Furthermore, conventionally, even when video muting is applied at the time of signal switching, the start and end of muting could be seen in the middle of one screen.

Problems to be Solved by the Invention In such conventional video mute circuits, when switching between video signals with different synchronization, muting may not be applied at the start or end of a screen in the middle of one screen.

The present invention is intended to solve these problems, and it is an object of the present invention to provide a video mute circuit that can eliminate synchronization error and noise and improve image quality when switching signals. .

Means for Solving the Problems In order to achieve the second object, the present invention mutes the video signal during the vertical blanking period of the previous video signal to switch the signal, and after the next video signal becomes stable, the vertical blanking period The circuit is configured to release the video mu I- during the blanking period.

The present invention has the above-mentioned configuration, which eliminates the noise caused by conventional signal switching, synchronization errors, and the fact that the beginning and end of muting can be seen on the screen even when muting the conventional video. However, it is possible to perform a high-quality Shingetsu switch that eliminates all of these problems.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1, 2, and 3.

FIG. 1 shows a video mute circuit 1 of the present invention, in which the video mute generator 1-1 receives a mu I command signal d at the time of signal switching, generates a video mu 1 pulse e,
The synchronization section 1-2 is configured to generate a video mute output pulse f in synchronization with the vertical synchronization pulse C.

FIG. 2 shows the entire circuit including the video mute circuit 1 of the present invention, and FIG. 3 shows the timing of the input/output lines of FIG. 2 in the vertical line 1-.

Below, FIG. 2 will be explained together with the timing diagram of FIG. 3. Note that the input/output lines in FIG. 2 and the timing chart in FIG. 3 are shown with the same numbers.

First, when a video switching power saw is input using a key or remote control, the key/remote control processing unit 2 inputs a mute command signal d to the video mute circuit 1, and at the same time, several tens of m5
The video selection circuit 3 delays the ec and outputs the video switching signal.
output to the input signal and switch the input signal. The video selection circuit 3 outputs the selected signal a to the video output circuit 4, and also always sends a vertical synchronization pulse C to the video mute circuit 1.

Also, video mu I/cancellation is 100~2 after video switching.
The video mute output pulse f is configured to be released in synchronization with the vertical synchronization pulse C even after release.

By applying the above-described video mute output pulse f to the video output circuit 4, the video output waveform can be switched without noise or synchronization deviation, as can be seen from FIG. 3g.

Note that the part 5 in FIG. 2 can be performed using a microcomputer or the like.

Effects of the Invention As is clear from the above embodiments, the video mute circuit of the present invention incorporates simple timing processing to improve the quality of video switching, which is often overlooked amid technological trends toward higher sound quality and higher image quality. It is possible to provide a video muting circuit that can increase the performance of video signals and that does not cause problems such as disturbances in synchronization or periods in which muting is not applied even when switching between video signals with different synchronization signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the video mute circuit of the present invention, FIG. 2 is a diagram of the entire configuration including the video mute circuit of FIG. 1, and FIG. 3 is a timing diagram of each input/output terminal. 1...Video mute circuit, 1-1...
Video mute generation section, 1-2...Synchronization section, C.
...Vertical synchronization pulse, d...Mute command signal, e...Video mute pulse, r...
...Video mute output pulse.

Claims (4)

[Claims] (1) video mute signal generating means for outputting a video mute signal when switching channels of a television receiver;
A video mute circuit comprising: synchronization means for synchronizing the video mute signal with a vertical synchronization signal. (2) The video mute circuit according to claim 1, wherein the rising edge of the video mute signal occurs during a vertical blanking period of the video signal. (3) The video mute circuit according to claim 1, wherein the falling edge of the video mute signal is a vertical blanking period of the video signal. (4) When switching video signals with different synchronization, the video mute signal rises during the vertical blanking period of the video signal before switching, and falls during the vertical blanking period of the video signal after switching. The video mute circuit according to claim 1, characterized in that: