JPS6288485A - Video switching device - Google Patents

Abstract

PURPOSE:To prevent the storing information of a memory from being outputted before controlling the switching of a video switching circuit, by performing the switching control of the video switching circuit which inputs the output signal of a picture image memory by fairly delaying the input-output transmission time of the memory. CONSTITUTION:A case where input videos from an input terminal 2 are selected at a switching circuit 3 and switching control is made at another switching circuit 5 from a state where input videos from the input terminal 2 are selected to another state where output videos from a picture memory 4 are selected is considered as an example. The switching circuits 3 and 5 are simultaneously actuated when a phenomenon which becomes a main cause of the switching control occurs, but the occurrence of the switching control of the circuit 3 is detected by a detecting circuit 6. When the occurrence is detected, a switching control signal inputted from a terminal 8 is transmitted to the video switching circuit 5 after delaying the signal by means of a delaying circuit 7 until the signal inputted to the picture memory 4 from the input terminal 2 through the switching circuit 3 is outputted from the memory 4. The switching control is performed by the signal transmitted to the video switching circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television video switching device, and more particularly to a switching control circuit for a video switching device.

[Conventional technology]

Conventionally, video switching control of a video switching device including an image memory such as a frame synchronizer in the thread path has been performed simultaneously in all video switching circuits in response to the occurrence of an event that activates video switching.

[Problem that the invention seeks to solve]

As mentioned above, control of the video switching circuits inside a conventional video switching device having an image memory is performed simultaneously on all video switching circuits in the device depending on the event that causes the video switching. When switching control occurs from a video system that does not go through the image memory to a video system that goes through the image memory, the video switching circuit selects the output video of the image memory. There is a drawback that the image recorded in the image memory before the video switching control occurs appears for a period corresponding to the transmission delay between the input and output of the image memory after the occurrence of the video switching control.

[Means for solving problems]

A video switching device according to the present invention includes a means for detecting the occurrence of switching control of a video signal to an image memory, and a means for detecting the occurrence of switching control of a video signal to an image memory, and a means for detecting the switching control of a video switching circuit that receives an output signal from the image memory. It also has means for considerable delay.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a video system diagram of an embodiment of the present invention.

1 and 2 are video signal input terminals, 3 is an input video switching circuit for an image memory that selects and switches video signals from input terminals 1 and 2, 4 is an image memory, and 5 has an output video of the image memory as an input. Video switching circuit, 6 is video switching circuit 3
7 is a control delay circuit that delays the switching control signal input from the terminal 8 according to the signal detected by the detection circuit 6, and 9 is a video signal output terminal.

Next, the operation of the video switching device according to the present invention will be described.

First, when the video switching device is controlled not to go through the image memory, the video switching circuit 3 is connected to the input terminals 1 and 2.
Neither of the input video signals is selected, and an undefined image is recorded in the image memory. FIG. 2 shows this state, in which the video signal from the input terminal 2 is output to the output terminal 9.

From this state, input video from input terminal 2 is transferred to image memory 4.
When a video switching control that requires no transmission to the output terminal 9 occurs, the state after the video switching control is completed is as shown in FIG.

The video switching control from FIG. 2 to FIG. This is switching control from a state in which a video is selected to a state in which an output video signal from the image memory 4 is selected.

These two are activated simultaneously by the occurrence of an event that causes switching control, but according to the present invention, the detection circuit 6 detects the occurrence of switching control acting on the switching circuit 3, and the switching control is activated from the input terminal 2. Until the video signal input to the image memory 4 via the circuit 3 is output from here, the switching control input from the terminal 8 is delayed in the delay circuit 7 and then transmitted to the video switching circuit 5. Perform switching control.

〔Effect of the invention〕

As explained above, the present invention detects the occurrence of input video switching control to the image memory, and controls the video switching circuit that has the output video from the image memory as an input by controlling the transmission delay time between the input and output of the image memory. Due to the considerable delay, it is possible to switch to the desired video without causing the video that was recorded in the video memory before the input video switching control to the video memory to appear at the output terminal of the video switching device. There is an effect that can be done.

[Brief explanation of drawings]

Claims (1)

[Claims] A first step for inputting and selecting at least two input video signals.
a video signal switching circuit, an image memory for inputting the video signal selected by the first video signal switching circuit, and a second video signal switching circuit for inputting and selecting the video signal from the image memory and the input video signal. a control detection circuit that sends the output of the first switching circuit to the image memory and detects that the second video signal switching circuit has selected the video signal from the image memory; It is characterized by comprising a control delay circuit which inputs a control signal to the video signal switching circuit and transmits the signal with a delay equal to the video transmission delay time between input and output of the image memory according to the detection signal of the control detection circuit. Video switching device.