JPS61214877A - Video signal processor - Google Patents

Abstract

PURPOSE:To suppress low the luminance of the edge part of character information when the luminance signal of the video signal exceeds the prescribed electric potential and to decode easily character information in case of any character information by setting a character outline part of an on-screen signal to an optical electric potential. CONSTITUTION:At a horizontal synchronizing separator circuit 1 of a video signal processor, a horizontal synchronizing signal (b) is extracted from a video signal (a), and a vertical synchronizing signal (c) is outputted from a vertical synchronizing separator circuit 2 with a signal (b) as an input. The synchronizing signals (b) and (c) are inputted into a character generating device 3 provided with an oscillating circuit and at the video signal period of the signal (a), a character signal (d) is inputted. Signals (a) and (b) are applied to a clamping circuit 4, and the pedestal electric potential of the signal (a) is clamped to the constant electric potential. Further, the signal (d) is overlapped by an adder circuit 5 to a clamped video signal (e) and a differential pulse is generated by the signal (d) from a differential circuit 6. A signal with an outline part of the on-screen character as a prescribed electric potential is outputted in accordance with the differential pulse from a substracting circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal processing device capable of inserting character signals into a video signal.

Conventional technology When inserting character information into a video signal, as shown in FIG.
is separated and input to a character generator 3 to generate a character signal d. Next, when character signal d is inserted into video signal a, the DC potential varies depending on the luminance signal of the color of the video signal, so the clamp circuit 4 sets the pedestal potential of video signal a to 0 as shown in FIG. 5e. [Ma] is fixed, and as shown in FIG. 6, a character signal d is inserted into a video signal a by an adder circuit 6 to produce an on-screen signal.

In FIG. 5, the horizontal synchronization signal S output from the horizontal synchronization separation circuit 1 is differentiated to become a signal b1, and a threshold value vth is provided for the signal b1 to generate a pulse with a constant width between times t and t2. b2 is obtained and input to the clamp circuit 4.

As shown in FIG. 7(fL) and (b), the video signal a
The luminance signal of is +1.2 [ma] and the character signal d is +1.4
[:T:1, the luminance difference between both signals is 0.2[v
] Therefore, it is possible to decipher the textual information. For example, the luminance signal of the video signal color and the character signal d are both at the same potential (+
1, 4 [ma]), it was difficult to decipher the character information as shown in FIGS. 7(C) and (d).

Problems to be Solved by the Invention In view of the above-mentioned problems, an object of the present invention is to provide a video signal processing device that can easily decode text information no matter what potential the luminance signal of the video signal is at.

Means for Solving the Problems In order to solve the above problems, the present invention detects the change point of the character signal and uses it as a differential pulse, and after combining the video signal and the character signal, uses the differential pulse to extract the character information. The edge portion is fixed at an arbitrary potential of the luminance signal.

According to the above-described structure, the present invention suppresses the brightness of the edges of character information to a low level when the brightness signal of the video signal exceeds a predetermined potential, thereby emphasizing the outline of the character and making it easier to decipher the character information.

Embodiment FIG. 1 is a block diagram showing an embodiment of the video signal processing apparatus of the present invention. In FIG. 1, 1 is a video signal a
A horizontal synchronization separation circuit extracts the horizontal synchronization signal BL from the horizontal synchronization signal, 2 a vertical synchronization separation circuit that extracts the vertical synchronization signal C from the horizontal synchronization signal, and 3 inputs the horizontal synchronization signal and the vertical synchronization signal C to the video signal period. A character generator 4 that generates a predetermined character signal d sets the pedestal potential of the video signal color to, for example, 0 [
5 is a clamp circuit that fixes the pedestal potential to O.
[Ma] is an addition circuit that inserts a character signal di into a fixed video signal e to produce an on-screen signal f; 6 is a differentiation circuit that detects a change point in the character signal d and generates a differential pulse g; 7 is a video This is a subtraction circuit that fixes the outline of the character signal d to an arbitrary potential using a differential pulse from the on-screen signal f in which the character signal d is inserted into the signal e.

The differentiating circuit 6 is composed of logic elements as shown in FIG. 2, for example, and obtains the differential pulse g shown in FIG. 3 (IL). The subtraction circuit 7 is constituted by a transistor circuit, for example, as shown in FIG. 2, and obtains the on-screen signal f shown in FIG. 3 (IL). The contour potential of the character signal d can be arbitrarily controlled by the collector potential of the transistor of the subtraction circuit 7.

However, in this embodiment, the differential pulse g is applied only in the horizontal direction.
As a result, the vertical contour is emphasized as shown in Figure 3(b), but if a vertical differential pulse is generated using a 1-line delay element for the horizontal synchronization signal, as shown in Figure 3(b), As shown in (C), an outline can be obtained over the entire character.

Effects of the Invention As described above, according to the present invention, by setting the character outline of the on-screen signal to an arbitrary potential, even when the difference between the video signal potential of the video signal and the character signal potential is small, the character Information is easy to decipher.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a video signal processing device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of main parts of the present invention, and FIG.
FIG. 3(IL) is a time chart showing the operation of each part of the present invention, FIGS. 3(b) and 3(C) are state diagrams showing the same image state, and FIG. 4 is a block diagram showing a conventional video signal processing device. Fig. 6 is a time chart showing the operation of each part of the same device, Fig. 6 is a circuit diagram of the main part of the same device, Fig. 7 (IL), (0) is a time chart showing the operation of each part of the conventional example, Fig. 7 During)
, ((1) is a state diagram showing the same image state. 1...Horizontal sync separation circuit, 2...Vertical sync separation circuit, 3...Character generator , 4...
...Clamp circuit, 5... Addition circuit, 6...
...differentiation circuit, 7...subtraction circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person i1
figure,? Figure 2 Figure 3 Figure 4 Figure 50 Figure 6 b2 S V Figure 7

Claims (1)

[Claims] A horizontal synchronization separation circuit that inputs a video signal and extracts a horizontal synchronization signal, a vertical synchronization separation circuit that inputs a horizontal synchronization signal and generates a vertical synchronization signal, and an internal oscillation circuit that generates a vertical synchronization signal and a horizontal synchronization signal. a character generator that inputs the video signal and generates a predetermined character signal during the video signal period of the video signal; a clamp circuit that inputs the video signal and the horizontal synchronization signal and sets the pedestal potential of the video signal to a constant potential; An addition circuit that superimposes a character signal on a signal to produce an on-screen signal, a differentiation circuit that generates a differential pulse at a change point of the character signal, and a subtraction circuit that uses the differential pulse to set the potential of the outline of an on-screen character to a predetermined value. A video signal processing device comprising: