JPS62252285A - Character signal multiplexing adapter - Google Patents

Abstract

PURPOSE:To generate a character signal even when a video signal is absent by using a signal absence detecting circuit to detect the presence and absence of the video signal, a signal changing-over circuit controlled by the circuit and a synchronizing signal generating circuit connected to a character signal generating circuit at the time fo the signal absence. CONSTITUTION:When a video signal is not inputted to an input terminal 1, a signal changing-over circuit 7 is changed-over to a B side by a signal absence detecting circuit 3. Consequently, to a character signal generating circuit 8, a synchronizing signal 12 prepared by a synchronizing signal generating circuit 5 is inputted and a stable character signal 13 is generated. The synchronizing signal 12 enters a replacing circuit 9 through a level shifting circuit 6 and a signal changing-over circuit 7. When the character signal is absent, an output 14 of the replacing circuit 9 comes to be one black color. Consequently, when the video signal is absent, the signal waveform to overlap a white character to a black background is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a character signal multiplexing adapter for superimposing a character signal onto a video signal.

[Conventional technology]

For a single frame of an image shot by a video camera, or a single frame of a video signal sent via an antenna to a television set, information such as the date, title, or channel number may be recorded on a video tape recorder, etc. If a device (hereinafter referred to as a single KVTR) can record simultaneously, it would be very convenient to save one picture (hereinafter referred to as a program) and to grasp the contents of the program.

In particular, when using a video camera, in order to insert characters such as the date and title into the program when producing a program, it is necessary to take a picture of a board with these characters written on it at the beginning of the filming, or to use a video captioner. This required the use of special equipment called .

In addition, recently, multifunctional video cameras with text display and recording functions have been developed.1 However, by incorporating such functions, the video cameras become larger, making them difficult to use as video cameras for general users. There is a problem that mobility is impaired0 In order to deal with these problems, for example, the
As described in No. 750, one video signal source and V
It has been proposed to insert a character signal multiplex adapter (Character Generator Adapter: CGA) between the TR and superimpose the necessary character signals on the video signal of the program. Applying this to a video camera In this case, as shown in FIG.
It was necessary to bind to l'R23.

The use of CGA in this way allows the necessary text signals to be included in the video signal regardless of the functionality of the video camera, and the video insert function can be used to insert text signals into the program after filming. [Problems to be Solved by the Invention] However, this CGA has the problem that it cannot superimpose character signals when no video signal is input from the outside.Objective of the Invention solves the problems of the conventional technology mentioned above,
The purpose of the above is to provide a character signal multiplexing adapter that can generate a character signal even when there is no video signal using a CGA. A no-signal detection circuit detects the presence or absence of ``!'', a signal switching circuit controlled by the no-signal detection circuit, and a character signal generation circuit when there is no signal. t
This is achieved by using a synchronization signal generation circuit connected in series.

[Effect]

When the external video signal disappears, the no-signal detection circuit operates, switches the signal switching circuit, and switches the synchronous signal generation circuit to
Connect to character signal generation circuit.

As a result, a character signal is generated from the character signal generation circuit, and even when there is no signal, the character signal can be generated at 1 tatami.

〔Example〕

Hereinafter, embodiments of the present invention will be described using one aspect.

FIG. 1 is a block diagram showing an embodiment of a character signal multiplex adapter according to the present invention.

In the figure, 1 is an input terminal for a composite video signal input from a video signal source such as a video camera, 2 is a buffer amplifier, 3 is a no-signal detection circuit that detects the absence of a video signal, and 4 is a no-signal detection circuit. 5 is a sync signal generation circuit, 6 is a level shift circuit, 7 is a signal switching circuit that switches the signal source to the sync signal generation circuit side when there is no signal, and 8 is a sync separation circuit that separates a sync signal from a video signal. Character signal generation circuit, 9
is a permutation circuit.

In addition, FIG. 2(a) is a signal waveform diagram of each part in FIG. 1 when the video signal is supplied from input terminal 1, and FIG. FIG. 2 shows signal waveform diagrams of various parts in FIG. 1 in a no-signal state. Figure 2 (a
) e (1)) (11) to (14) are the first
This is a signal waveform at the position shown in the figure.

First, we will explain the operation of the circuit in Figure 1 when a video signal is supplied. #l!r5 and the 0 free code detection circuit 5 inputted to the synchronization separation circuit 4 function to switch the signal switching circuit 7 to the A side when there is a video signal.

Therefore, the synchronization signal (12) separated from the video signal by the synchronization separation circuit 4 enters the character signal generation circuit 8 through the signal switching circuit 7, and the character signal (12) synchronized with the video signal is input to the character signal generation circuit 8.
5). This character signal (13) is transmitted to the replacement circuit 9
The original video signal (which is input to the buffer amplifier 2° and passed through the signal switching circuit 7) is replaced with a character superimposed portion.

The output (14) of the replacement circuit 9 is a video signal with white characters superimposed on it, and is supplied from the output terminal 10 to the VTR and recorded.When no video signal is input to the input terminal 1, The signal switching circuit 7 is switched to the B side by the no-signal detection circuit 3. Therefore, the synchronization signal generated by the synchronization signal generation circuit 5 shown in (12) in FIG. 2 is input to the character signal generation circuit 8, and a stable character signal (13) is generated. Furthermore, the synchronization signal (12) is the level shift signal (12).
1r6 and the signal switching circuit 7 to enter the replacement circuit 9.

When there is no character signal, the output (14) of the replacement circuit 9 is solid black. Therefore, when there is no video signal, white characters are superimposed on a black background, resulting in a good signal waveform.

〔Effect of the invention〕

According to the present invention, even when there is no video signal, it is possible to print one character signal in one tatami kamama.

In addition, although the explanation of the operation in this example uses the case where the video signal disappears, functions such as intentionally cutting the video signal and inserting text on a plain screen can be easily performed using the present invention. It is obvious that this can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a character signal multiplexing adapter according to the present invention, FIG. 2 is a signal waveform diagram at the valley part of FIG. 1,
FIG. 3 is a conceptual diagram illustrating the connection of character signal length 1 adapters. DESCRIPTION OF SYMBOLS 1...Composite video signal input terminal, 2...Battery anchor, 3...No signal detection circuit, 4...Synchronization separation circuit,
5... Synchronization signal generation circuit, 6... Level shifter, 7
...Signal switching circuit, 8...Character signal generation circuit, 9°
°°Replacement circuit. ),

Claims (1)

[Claims] 1. A character signal multiplexing adapter that superimposes a character signal on a composite video signal from a video signal source, comprising means for detecting the presence or absence of the composite video signal, and a signal controlled by the output signal of the means. and a synchronization signal generation circuit that is connected to the character signal generation circuit by the signal switching means when there is no signal, and when there is no signal, the synchronization signal output from the synchronization signal generation circuit is connected to the character signal generation circuit. A character signal multiplexing adapter characterized in that a character signal is generated by supplying a character signal, and the character signal can be superimposed even when there is no signal. 2. When a video signal is input, a synchronization signal extracted from the composite video signal is supplied to the character signal generation circuit via the signal switching means. Character signal multiplex adapter.