JPH04192978A - Image display controller - Google Patents

Abstract

PURPOSE:To prevent the erroneous discrimination of attendance and non-attendance occurring in the noise level at the time of the unattended signal reception of satellite broadcasting by changing over the operation of a synchronizing signal extraction circuit and a synchronizing signal discrimination circuit according to a selection instruction signal. CONSTITUTION:The discrimination of the attendance and non-attendance of the received video signals by the ground broadcasting and satellite broadcasting inputted from terminals T1, T11 is executed by changing over the operations of the synchronizing signal extraction circuit 12 and the synchronizing signal discrimination circuit 13 according to the selection instruction signal inputted from a terminal T10. The discrimination processing at the time of reception of the satellite broadcasting is executed by the circuit 12 which changes over an integrating circuit for extracting the horizontal synchronizing signal and an integrating circuit for extracting the vertical synchronizing signal by connecting a capacitor C11 in parallel to the capacitor C1 of the above-mentioned integrating circuit by a switching circuit 11 as well as the circuit 13 which changes over the count values for discriminating the attendance in accordance with the signal extracted by the circuit 12. The discrimination is thus synchronously executed. Even if the noise of a large level exists in the synchronizing signal at the time of the non-attended signal reception, this noise is absorbed by the circuit 12 and the erroneous discrimination of the synchronous discrimination processing based on the noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to image display control of a video device equipped with a satellite broadcast receiving device in addition to a terrestrial broadcast video signal receiving device. The present invention relates to an image display control device that performs tuning control by determining whether a station is present or not based on a synchronization signal, and performs suitable image mute control when determining whether a station is present or not.

(b) Conventional technology The image display control of video equipment with a built-in tuner selection device determines whether a station is present or not based on the horizontal synchronization signal in the received video signal, and uses this determination signal and a tuning instruction signal output from the tuner. Tuning control is performed by this, and image display control is performed by switching the monitor output between a monitor video signal and an image mute signal.

Generally, when determining whether a station is present, the tuner is instructed to select a station (fixed tuning) using tuning control based on a tuning instruction signal output from the tuner, and a monitor video signal is output using image display control. The channel selection instruction (sweep instruction) is used to control the selection to the desired station, and the image display control changes the output from the monitor video signal to the image mute signal (
For example, it has been a popular practice to mute the noise screen when there is no station by switching to a blue back signal and outputting it.

FIG. 2 shows a conventional example of image display control in a video device incorporating a terrestrial broadcast video signal receiving tuner.

In FIG. 2, T1 is a terminal for inputting a received video signal from a tuner (not shown), T2 is a terminal for inputting a tuning instruction signal (AFT-5 times number) from the tuner, and T3 is a terminal for instructing the tuner to select a channel. A terminal that outputs a signal (fixed tuning when there is a station, sweep instruction when there is no station), T4 is a terminal that inputs a monitor video signal detected by the tuner and processed as a playback signal, and T5 is selected by image display control. This is a terminal for monitoring and outputting signals.

A received video signal input from the tuner to terminal T1 is separated into a composite synchronization signal by a synchronization separation circuit 1, and a synchronization signal extraction circuit 2 removes noise components contained in the composite synchronization signal and extracts a horizontal synchronization signal. Ru. Specifically, it is an integrating circuit composed of an RC circuit including a resistor (R1) and a capacitor (C1), and the resistor R1 has one end connected to the output of the synchronous separation circuit and the other end connected to the capacitor C.
The horizontal synchronizing signal from which noise has been removed is taken out from the connection point between R1 and 01. The extracted horizontal synchronization signal is then input to the synchronization signal discrimination circuit 3, which counts the horizontal synchronization signals in a predetermined period, and uses the count value to determine whether the received video signal is stationed or not. is output. Specifically, this value (10, 31) is set because it can be determined that a station is present if the count value of the horizontal synchronization signal is 10 times or more and 31 times or less in 1 millisecond. Then, the above-mentioned signal for determining whether the station is present or not is inputted to the tuning control circuit 4 together with the tuning instruction signal outputted from the tuner, and the circuit 4 determines whether the received video signal is within the tuning range of the station or not. It is determined whether there is no station included. Based on this determination, a tuning instruction signal (an instruction signal to maintain the tuned state when tuning to a station, a sweep instruction signal at other times) is output to the tuner, and an image control signal is output. Then, the image display control circuit 6 selects the image mute signal (for example, a blue back signal) generated by the image mute signal generation circuit 5 and the monitor received video signal based on the image control signal, and outputs the selected signals to the monitor from the terminal T5. .

It has been a challenge to apply the above-described conventional image display control function during a channel selection operation to video equipment equipped with a terrestrial broadcast receiving device that is added to the terrestrial broadcast receiving device.

However, when there is no station due to satellite broadcasting reception, the noise level of the signal input to the synchronization separation circuit is almost twice as high as when there is no station due to terrestrial broadcasting reception.
Noise components leak into the synchronization separation circuit and its output. Therefore, the noise component is regarded as a synchronization signal by the synchronization signal discrimination circuit 3, and the presence of a station is determined. According to the discrimination signal, even though the actual satellite broadcasting is receiving no station, the image display control determines that the noise component is present. When receiving satellite broadcasts, the above-mentioned image display control may occur due to noise caused by noise during satellite broadcast reception, such as output of a monitor received video signal based on station discrimination. Had to stop muting the image.

(c) Problems to be Solved by the Invention The present invention has been made to solve the above-mentioned problems with the prior art. The objective is to solve the drawbacks of image display control based on synchronous signal discrimination between stations and non-stations, such as erroneous station discrimination.

(d) Means for Solving the Problems Therefore, the present invention provides an image display control device that mutes an image based on a no-station determination based on a synchronization signal of a received video signal of a video device equipped with a satellite broadcast receiving device. synchronization signal extraction means for extracting a horizontal synchronization signal from a composite synchronization signal separated from the received video signal; and a synchronization device for discriminating the extracted synchronization signal and outputting a signal indicating whether the received video signal is stationed or not. a signal determining means, selectively inputting the received video signal to the synchronization signal extracting means in response to a selection instruction signal for selecting a received video signal by terrestrial broadcasting and a received video signal by satellite broadcasting; synchronous signal extraction means,
The system is configured to switch the discrimination criteria of the synchronization signal discriminating means for horizontal synchronization signal extraction when receiving terrestrial broadcasting and for vertical synchronization signal extraction when receiving satellite broadcasting, depending on the selected received video signal, as follows. The channel selection state is determined based on the output of the synchronization signal determining means.

(E) As a result, in the present invention, the received video signal selected in response to the selection instruction signal is synchronously separated, and the synchronization signal corresponding to the selection instruction signal is extracted. Then, since the extracted synchronization signal is determined to be synchronized between station and non-station according to the selection instruction signal, even if there is a high level noise in the synchronization signal when receiving a non-station, it will be absorbed by the synchronization signal extraction circuit. Misjudgment in synchronization discrimination processing based on noise does not occur.

(F) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1, but the same parts as in FIG.

FIG. 1 shows an embodiment of the present invention, which performs image display control to monitor and output an image mute signal to a terrestrial broadcasting tuner when determining whether there is no station during tuning operation, and also performs image display control to monitor and output an image mute signal to a terrestrial broadcasting tuner. The configuration is such that similar image mute control is performed even when the image is muted.

In FIG. 1, T10 is an input terminal to which a selection instruction signal for instructing reception of television broadcasting by satellite broadcasting is input, Tll is a terminal to which a video signal is inputted from a satellite broadcast reception tuner (not shown), and T12 is a terminal to which a video signal is inputted from a satellite broadcast reception tuner (not shown). A terminal to which a tuning instruction signal is input from the broadcast reception tuner, T13 is a terminal that outputs a tuning instruction signal (fixed tuning when there is a station, a tuning instruction when there is no station) to the satellite broadcast reception tuner, and T14 is a terminal for outputting a tuning instruction signal to the satellite broadcast reception tuner. A terminal for inputting a monitor video signal detected by a broadcast reception tuner and subjected to playback signal processing; S10 is a switch for switching between terrestrial broadcasting video signal input and satellite broadcasting video signal input according to the selection instruction signal; 11 is the selection It is a switch circuit that switches its output according to an instruction signal.When there is a selection instruction signal (for example, High level), the switch circuit turns on and its output is grounded, and when there is no selection instruction signal (for example, Low level), the switch circuit turns on. turns off and releases its output. 12, a horizontal synchronization signal is obtained from the composite synchronization signal obtained by synchronously separating the video signal when receiving terrestrial broadcasting, and a vertical synchronizing signal from the composite synchronization signal obtained by synchronously separating the video signal when receiving satellite broadcasting, This is a synchronization signal extraction circuit that extracts each synchronization signal according to the output of the switch circuit. Specifically, a capacitor C1l is connected in parallel with C1 of a horizontal synchronizing signal extraction circuit made up of a resistor R1 and a capacitor C1, and
The combined capacitance of I and C1l is set to be capable of extracting a vertical synchronizing signal, and one end of the capacitor C1l is connected to the output of the switch circuit to form an integrating circuit that extracts the vertical synchronizing signal by turning on the switch circuit. 13
The determination process is performed by changing the reference signal for determining whether a station is present or not according to the selection instruction signal, and if there is a selection instruction signal (
For example, when there is no selection instruction signal, the vertical synchronization signal is counted during a predetermined period (for example, High level), and when there is no selection instruction signal, for example, Low level.
This is a synchronization determination processing circuit that counts horizontal synchronization signals in a predetermined period (level) and determines whether each received video signal is stationed or not based on the count. Specifically, the determination process when receiving satellite broadcasting takes into consideration the influence of electrostatic noise, and if the count value of the vertical synchronization signal is 2 or more times in 2 frames (approximately 62.5 milliseconds), the station is detected. This value is set because it can be judged as the status. In addition, in the determination process when receiving terrestrial broadcasting, the count value of the horizontal synchronization signal is conventionally 10.
If it was more than 31 times, it was considered to be stationed.
According to the embodiment of the present invention, it has been found through experiments that when a noise component is converted into a synchronization signal in a weak electric field, there are inconveniences such as not being able to control the image display by optimal station presence determination, and counting the horizontal synchronization signal in 1 millisecond. The above-mentioned inconvenience can be solved by synchronization determination processing in which it is determined that the station is in a stationed state if the value is 6 times or more and 26 times or less. Reference numeral 14 is an image display control circuit which receives the above-mentioned station/non-station discrimination signal and the above-mentioned tuning instruction signal, creates a channel selection instruction signal and an image control signal, and sends the image control signal to the satellite broadcasting tuner with the channel selection instruction signal. This is a satellite broadcasting channel selection control circuit that outputs the respective satellite broadcasting signals, and is selected by a selection instruction signal from the terrestrial broadcasting video signal channel selection control circuit.

(G) Effects of the Invention As described above, according to the present invention, the synchronization signal extraction circuit and the synchronization signal discrimination circuit operate according to the selection instruction signal to determine whether the received video signal by terrestrial broadcasting or satellite broadcasting is stationed or not. The synchronous signal extraction circuit switches between an integrating circuit that extracts the horizontal synchronous signal and an integrating circuit that extracts the vertical synchronous signal by connecting a capacitor in parallel with the capacitor of the integrating circuit using a switch. Since synchronization is determined by switching the station presence determination count value based on the signal extracted by the signal extraction circuit, it is possible to solve the drawbacks of image display control when satellite broadcasting is added based on conventional synchronization determination processing. The present invention has the advantage that image display control when receiving a satellite broadcasting signal, similar to when receiving a terrestrial broadcasting signal, can be performed using a simple circuit configuration, and has great practical effects.

[Brief explanation of the drawing]

FIG. 1 shows a circuit block diagram according to an embodiment of the present invention, and FIG.
The figures each show a conventional circuit block diagram.

Claims (1)

[Claims] (1) In the image display control device, which determines the channel selection state from the received video signal, controls the tuning according to the determination, and mutes the image based on the no-station determination, the video signal is separated from the received video signal. comprising a synchronization signal extraction means for extracting a horizontal synchronization signal from a composite synchronization signal, and a synchronization signal discrimination means for discriminating the extracted synchronization signal and outputting a signal indicating whether the received video signal is stationed or not; In response to a selection instruction signal for selecting a received video signal by terrestrial broadcasting and a received video signal by satellite broadcasting, the received video signal is selectively input to the synchronization signal extraction means, and the synchronization signal extraction means is The method is configured to switch the discrimination criteria of the synchronization signal determining means for extracting a horizontal synchronization signal when receiving a broadcast, and for extracting a vertical synchronization signal when receiving a satellite broadcast, depending on the selected received video signal. An image display control device characterized in that a channel selection state is determined based on the output of a synchronization signal determining means.