JPH04183184A - Image display controller - Google Patents

Abstract

PURPOSE:To improve a strange phenomenon and instantaneous flickering that appear on a monitor screen during a transient period of selecting a channel and that spoil the view by latching a display changeover signal in synchronous with a vertical synchronous signal and by controlling image mute based on eatching output. CONSTITUTION:When starting selection of a channel, a display changeover signal of high level based on a channel select operating signal is input to the D input of D-F.F.81, and to a tuner.IF circuit 2 a TU channel select opening signal is supplied by a delay circuit 78, so to the output Q of the D-F.F.81 a control signal in synchronous with a vertical synchronous signal is output to connect a switch S81 to the NO side. When terminating channel selection, a channel select state discriminating section 76 outputs a channel presence discriminating signal, and the tuner channel select action of the tuner.IF circuit 2 terminates, while, at the same time, to D input of D-F.F.81 a display changeover signal of low level is input, and by inputting a vertical synchronous signal to the input of C, to the output of Q a control signal in synchronous with the vertical synchronous signal is output, thereby connecting the switch S81 to the NO side.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial field of application The present invention provides a video equipment equipped with a tuner, in which there is no television broadcast signal during the transition period when switching between no stations and stations during the tuning operation. The present invention relates to an image display control device that controls a status monitor screen to make it easier to view.

(b) Conventional technology In circuits that supply received video signals to video equipment on the receiving side (for example, monitor devices), it is often necessary to turn the video signals on and off, or to make the monitor screen easier to see in a single color. exist. In this case, if the video signal is simply turned off to completely block the video signal and no signal is output, noise will occur in the video equipment on the supplied side and the monitor screen will become an eyesore.

2) When the video signal is off, the monitor screen is made easier to see by replacing the noise image with a noise image created by the video equipment on the supplied side, or by supplying another video signal, such as a synchronization signal or a predetermined signal. .

In other words, it is recommended to forcibly mute the image to prevent noise from appearing on the monitor screen when detecting no station in the TV redirect and during the transition period between available stations during the channel selection operation. .

The monitor screen display control that is commonly used with the above-mentioned image muting technology is, for example, when selecting a channel from a channel being received to another channel, the transition period of the channel selection is displayed using an image mute.
- View. Furthermore, when selecting another stationed broadcast from the stationed broadcast that is being received via a non-stationed broadcast, the image is muted during the transition period between the stationed broadcast and the station selection period.

The image mute screen is set to a so-called blue bank monitor screen, which is a single color except when receiving station broadcasts, in order to distinguish between the presence of stations, the absence of stations, and the transitional period of tuning. This is screen display control.

However, in this case, with the above technology, when switching between the video signal of the station broadcasting and the image mute signal, there is no synchronization during the tuning operation 1t; A synchronization hole occurs due to a mismatch between the two signals, and a black band-shaped vertical synchronization signal section appears on the monitor screen. Furthermore, there is a drawback that the momentary flickering of colors on the monitor screen due to image muting is obtrusive and gives a strange feeling to non-electronic devices.

(C) Impositions to be solved by the invention The present invention has been made in view of the above-mentioned drawbacks, and the vertical synchronization signal section that appears on the monitor screen due to the synchronization mismatch between the image mute signal and the received video signal causes an unsightly and strange feeling. To provide an image display control device that aims to improve momentary color flickering.

(d) Means for Solving the Problems Therefore, in the present invention, in an image display control device that mutes a received video signal during a TV broadcast channel selection operation, one of the features is a selection method based on a channel selection operation. a display switching signal generation circuit whose output is controlled by the station operation signal and the station presence determination signal of the received video signal; and launching the display switching signal output from the display switching signal generation circuit in synchronization with a vertical synchronization signal; Based on the output of the latch 8, the output state of the received video signal changes from the output state of the received video signal to the output state of the predetermined DC level in response to the tuning start operation, and the output state of the received video signal changes from the output state of the predetermined DC level in response to the end of tuning. The present invention is characterized in that it includes an image display circuit that switches between the states.

Secondly, the station presence determination signal is determined based on a count value of horizontal synchronization signals detected in a predetermined period and a tuning instruction signal.

Thirdly, at the start of the tuning, the tuning operation signal is delayed by at least one vertical interval and then supplied to the tuner IF circuit.

(E) Effect According to the above-described configuration, the display switching signal is latched in synchronization with the vertical synchronization signal, and the image mute is controlled based on the launch output, so that the video signal of station broadcasting and the image mute signal are synchronization will not be disrupted when switching between

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described in detail. FIG. 1 is a circuit diagram of the implementation fkl.

In FIG. 1, ■ is a TV signal input terminal into which TV broadcasts are input, and 2 is a receiving state judgment circuit (to be described later) that supplies a TU channel selection start signal and a station presence judgment signal, and detects the TV broadcast signal into a video signal. At the same time, a signal CA F T for instructing the video signal and the tuning point of the video signal.
- Tuner/IF circuit that outputs S curve signal, 1, 3
Reference numeral 1 denotes a signal processing circuit that outputs the received video signal as a monitor; 4 a monitor device that displays the monitor output from the signal processing circuit on a screen; and 5 determines the synchronization signal of the video signal and detects the synchronization signal. a synchronization separation circuit that separates and extracts a horizontal synchronization signal and a vertical synchronization signal from the components; 6;
is an input terminal for a tuning operation signal that instructs a tuning operation, and ヱ is a reception state that determines the reception state based on the tuning operation signal, the horizontal synchronization signal, and the AFT=S curve signal, and outputs a display switching signal. This is a discrimination circuit.

Here, the function of the reception state determination circuit 7 will be further explained. 71 is a counter that counts the horizontal synchronization signal output from the synchronization separation circuit 5; 72 is a timer that sets a predetermined period of 01 milliseconds to specify the counted value of the counter; and 73 is a device that determines whether a station is present based on the counted value. This is a reference value memory in which reference values are set. Specifically, if the count value of the horizontal synchronization signal during the predetermined period is 10 times or more and 31 times or less, it can be determined that the station is present, so this value i:1
0.31) is set. 74 is the timer 72
a comparator that detects presence of a station when the count value of the counter 71 during a predetermined period set in is within a reference value set in the memory 73, and detects no station when it is outside the reference value; 75 is a window comparator which receives the AFT-S curve signal output from the tuner/IF circuit 2 and creates a signal (AFT-5 signal) indicating the tuning point of the station; A tuning state determination unit 77 receives the station presence detection signal and outputs a station presence determination signal indicating that a station is present and the tuning point of the station; Depending on both inputs, Tadami,
78 is a display switching signal generation circuit that outputs a display switching signal in which the tuning operation signal has priority over the station identification signal; 78 is a delay circuit that is set to delay the tuning operation (IE double signal by at least 61 vertical synchronization periods); It is.

The display switching signal and the vertical synchronization signal are input to the nose, and the received video signal is output in synchronization with the vertical synchronization signal according to the state of the display switching signal (i.e., station present, station selection in progress, or no station). This is an image display circuit that switches between outputting a signal at a predetermined DC level and outputting a no signal at a predetermined DC level.

To further explain the image display circuit, 81 inputs a display switching signal to the D (data) input and inputs a vertical synchronization signal to the C (clock) input, and its output (Q) outputs a signal in synchronization with the vertical synchronization signal. The well-known D-F, F, (
D type flip-flop). Further, 82 is a circuit for setting a predetermined DC level, and S81 is the above-mentioned D-F, F
, 81, which connects the DC level setting circuit output to the terminal No. (normally open) side and connects the received video signal to the terminal NC (normally open) side, The switch output is output to the monitor device 4.

Next, the switch control operation using the display switching signal and the vertical synchronization signal will be explained based on the channel selection operation with reference to the timing chart of FIG.

The switch control operation during station reception is as follows. That is, the display switching signal generation circuit 77 inputs the signal (Lo
- A level display switching signal is input, and the D-F, F,
By inputting the vertical synchronization signal from the synchronization separation circuit 5 to the C input of 81, a low-level switch control signal is output to the output (Q) of the D-F, F, and 81, and the switch 581 is switched to the NC side. Connect to. In this case, the switch control signal is maintained at a low level because a vertical synchronization signal that continues periodically is input during station reception, and the signal processing circuit 3
A received video signal inputted from the monitor device 4 is outputted to the monitor device 4 .

The switch control operation at the time of starting tuning by tuning operation is as follows. That is, based on the channel selection operation signal from the display switching signal generation circuit 77, <H
At the same time, the high level display switching signal is input, and the T signal delayed by the delay circuit 78 is input to the tuner/IF circuit 2.
Since the U tuning start signal is supplied, the vertical synchronization signal is generated at least once during the delay period, and the D-, F, F,
The output (Q) of 81 is a high signal synchronized with the vertical synchronization signal.
The h level switch control signal is output and the switch S81
Connect to the No side. As a result, the received video signal is set to a predetermined DC level, and is output to the monitor device 4 after being switched to a no signal without an intervening signal.

The switch control operation at the end of tuning by tuning operation is as follows. That is, the station selection state determination section 76 outputs a station presence determination signal, and the tuner selection operation of the tuner/IF circuit 2 is completed by the station presence determination signal. A Loa level display switching signal based on the station identification signal is inputted from the display switching signal generation circuit 77 to the input, and a vertical synchronization signal is inputted from the synchronization separation circuit 5 to the C inputs of the D-F, F, and 81. As a result, a low-level switch control signal synchronized with the vertical synchronizing signal is output from the D-F, F, and 81 (Q), and the switch/V switch 581 is connected to the NC side. ,
A predetermined DC level is set, and a no signal without a synchronizing signal is switched to a received video signal and output to the monitor device 4.

In addition, FIG. 3 shows a monitor screen transition diagram of image muting by image display control in the channel selection operation of the embodiment.
FIG. 3A shows a conventional example of the image display control, and FIGS. 3B and 3C show the image display control according to the present invention.

In the conventional example shown in FIG. 3A, the transition period (N) between stations is when a target station (C) is selected from one station (A) via another station (B). ), color flickering occurs due to momentary switching between the image of the received video signal and the single color mute image, and the synchronization signal occurs due to a mismatch in the vertical synchronization signal between the video signal and the single color image mute signal. A large number of parts appear on the monitor screen, creating an unsightly and strange sensation. Furthermore, color noise or the like may occur in the synchronization signal portion during the process of stabilizing the vertical synchronization.

In the example of the channel selection operation according to the present invention shown in FIG. 4B,
The transition period when selecting a target station (c) from another station (via lower) (2) is the predetermined DC level created from the image of the received video signal and the image display control stage. Since the mute image with no signal set to is switched in synchronization with the vertical synchronization signal of the movie image signal, the above-mentioned color flicker and synchronization signal portion do not appear on the monitor screen.

Also, in another example of the channel selection operation according to the present invention shown in FIG. , In order to switch to a mute image with no signal set at a predetermined DC level during the channel selection transition period (d) and when there is no station (e), the monitor screen will display flickering colors and The sync signal section does not appear.

(G) Effects of the Invention As described above, according to the present invention, the reception status is automatically determined based on the channel selection operation signal when the channel selection operation starts, and when the channel selection operation ends. Based on the determined channel selection control signal, the image display control of the video signal when a station is received and the image mute signal during the non-station period including the channel selection transition period is switched to the vertical synchronization signal at the same time. For this reason, a black band-shaped vertical synchronization signal portion appears on the monitor screen due to synchronization mismatch due to the transition period of channel selection, such as switching between available stations and switching from non-station to available station, etc. due to the tuning operation. It can prevent strange feeling. Furthermore, since the image mute signal is replaced with a no signal at a predetermined DC level, it is possible to easily eliminate momentary color flickering on the monitor screen due to the transitional period of channel selection. Moreover, the present invention can be implemented with a simple configuration and has great effects.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the switch control operation for image display control, and FIG. 3 is an image obtained by channel selection control in the channel selection operation of the embodiment. A transition diagram of the mute monitor screen is shown. 2-=--Tuner/IF circuit, 5-----One synchronization separation circuit, 6,--11 Station operation 1 and signal input terminal, 7-----Intrusion status determination circuit, 76------
1 station status determination unit, 77 ------- display switching signal generation circuit, 78 ------- 1 delay circuit, and 1-
--Value image display circuit, 81 ---7 lip 70 amplifiers, 82 --- Stream level setting circuit, S 81
-11~----Switch.

Claims (3)

[Claims] (1) In an image display control device that mutes a received video signal during a tuning operation, a display switching signal whose output is controlled by a tuning operation signal based on a tuning operation and a station presence determination signal of the received video signal. and a display switching signal generating circuit that latches the display switching signal output from the display switching signal generating circuit in synchronization with the vertical synchronization signal, and determines the output state of the received video signal in response to a channel selection start operation based on the latch output. An image display control device comprising: an image display circuit that switches from an output state of a predetermined DC level to an output state of a received video signal in response to completion of channel selection. (2) The image display control device according to claim 1, wherein the station presence determination signal is determined based on a count value of a horizontal synchronization signal detected during a predetermined period and a tuning instruction signal. (3) The image display control device according to claim 1, wherein at the start of the tuning, the tuning operation signal is delayed by at least one vertical synchronization period and then supplied to the tuner/IF circuit.