JPS6016789B2 - Shadow key signal generation circuit - Google Patents

Description

[Detailed description of the invention] The present invention is used when inserting character signals (hereinafter referred to as super signals) such as time and commercials into video signals (hereinafter referred to as base signals) in television broadcasting (hereinafter referred to as super signals). The present invention relates to a shadow key signal generation circuit.

In order to make the super signal more visible when inserting the super signal into the base signal, there is a method of lowering the level of the base signal and adding a shadow to it, which uses digital technology. Because the device is simple, it is often used.

As a technique for inserting a super signal into a base signal, there is a technique described in Japanese Tokkoku Seki No. 50-69922.

In other words, after the super signal is digitized and stored in memory, it is read out with a delay time of several fields, and at the same time, a certain amount of time relationship in the vertical and horizontal directions is subtracted based on the digitized and represented digital super signal. Alternatively, a pulse signal having the added width is obtained, and the pulse signal is further shaped to obtain a contour signal which is a trapezoidal wave, and the level of the video signal is lowered by this contour signal. At this time, the level of the video signal is lowered more deeply as it approaches the super signal. Now, when creating a digital super signal from a super signal, a clock signal is used, but depending on the relative positional relationship between the clock 0 signal and the super signal, the digital super signal may lag behind the super signal by a maximum of one clock period. When a contour signal is created based on this digital super signal, the level of the base signal is lowered by the contour signal, and the super signal is inserted, there are the following drawbacks. For example, even if the level of the base signal is lowered to some extent by the contour signal, if the energy of the color signal component included in the base signal is large, the influence of the color signal component included in the base signal will be inserted later. There is a drawback that the super signal appears in the base signal which is 0 and is colored, or if the super signal is colored, the color changes due to the influence of the color signal component of the base signal. Furthermore, even if the level of the base signal is sufficiently lowered by the contour signal to remove the influence of the color signal components contained in the base signal, it will not match completely with the super signal added later, so The drawback is that black areas may appear. Of course, if the clock frequency when digitizing the super signal is increased, this drawback will be reduced, but the number of parts used in the mounting will rapidly increase, which is disadvantageous from the point of view of economy and stability. Therefore, an object of the present invention is to generate a shadow key signal with a simple configuration, in which a super signal inserted later is not affected by color signal components included in a base signal, and a black part is not formed on the side of the super signal. It is to provide a vessel.

Next, the present invention will be described in detail with reference to the drawings showing one embodiment of the present invention. Referring to FIG. 1, an embodiment of the present invention includes a shadow key signal generator 10 and a mixed key block Taifu device that inserts a super signal from an input terminal 11 into a video signal (base signal) from an input terminal 21. It is equipped with 20.

The shadow key signal generator 10' receives a super signal A (FIG. 2A) representing a character to be inserted from the input terminal 11.
Clock pulses B (FIG. 2B) are supplied from terminals 12, respectively. The super signal A is digitized by an analog-to-digital converter (A/D converter) 13 based on the rising edge of the clock signal B, and is converted into a digital super signal C (second
Figure C). Digital supersignal C is stored in memory 14 in response to clock pulse B. The digital super signal C is read out after being delayed by about one field in the field memory 14, and is sent to the pulse generating circuit 15. The pulse generating circuit 15 generates a pulse signal D (see Fig. 2D
). This pulse signal D is sent to the waveform shaping circuit 16. The waveform shaping circuit 16 shapes the pulse signal D in order to add a slope to the pulse signal D at a time point corresponding to the periphery of the super signal to obtain a trapezoidal shadow signal E (FIG. 2E). In the conventional device, this trapezoidal shadow signal E
is added directly to the mixing keyer amplifier as a shadow key signal, and the mixing keyer amplifier is controlled so as to attenuate the base signal by 100% at the top of the trapezoidal wave E. Therefore, an output waveform as shown in FIG. 2F is obtained at the output of the mixed key amplifier. Conventional devices are, for example,
Since it is described in detail in the No. 922 publication, a detailed explanation will be omitted. As mentioned above, depending on the positional relationship between super signal A and clock signal B, digital super signal C may lag behind super signal A by a maximum of one clock period. As shown in Figure 2, the right part f of super signal A
becomes a black level and becomes very unsightly. Furthermore, if the positional relationship of the super signal A with respect to the clock pulse B changes, the width of the portion f changes, making the screen even more difficult to see. Furthermore, if the attenuation rate of the base signal at the top part e of the trapezoidal wave E is lower than 100%, for example 30%, when the super signal A is mixed with the attenuated base signal, the color signal component of the base signal There may be a color change in the super signal. In the present invention, this trapezoidal wave E is fed to a non-additive mixing circuit 18, and the super signal A is mixed non-additively to produce a shadow key signal G. That is, the super signal A is clamped to a fixed voltage at the vedestal level by the clamp circuit 17, and is combined with the trapezoidal wave E by the non-addition mixing circuit (NAM circuit) 18 to obtain the shadow key signal G. At this time, a crank pulse synchronized with the super signal A is supplied from the terminal 19 to the clamp circuit 17. In the shadow key signal G, the shard portion p has a forehead slant, and the closer it is to the super signal, the lower the level of the base signal is, so the super signal becomes easier to see. Moreover, since the level of the portion of the base signal into which the super signal is inserted later is completely lowered by the punched portion q, the color signal component contained in the base signal does not affect the super signal. The rate lowered by the shard part is 3
Since it is about 0%, the sides of the super signal do not turn black on the screen, and the delay of the digital super signal C when digitizing the super signal A is not noticeable on the screen because it is a shadow. The shadow key signal G obtained by the shadow key signal generator 10 is sent to the mixed key amplifier 20.
The super signal A and the base signal supplied from the terminal 11 are combined. Figure 2 shows the output of the mixed key amplifier circuit. In this embodiment, a more precise image can be obtained by scanning the field memory with a frame memo. Further, the trapezoidal wave and super signal synthesis circuit does not necessarily have to be a non-adder circuit, and a combination of an analog gate circuit and an adder circuit is sufficient in practice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
It is a waveform of each part of the example shown in the figure. In the figure, 10...shadow key signal generator, 13...
...A/○ converter, 14...Memory, 15.
... Pulse generation circuit, 16 ... Waveform shaping circuit, 17 ... Clamp circuit, 18 ... Non-adding mixing circuit, 20 ... Mixing keyer amplifier. Figure 1 Figure 2

Claims (1)

[Claims] 1. A clamp circuit that clamps a super signal representing a character signal, etc. to be inserted, and a peripheral portion of the super signal in the vertical and horizontal directions is expanded with an inclination so that the maximum value of the signal level is the super signal from the clamp circuit. A shadow key signal generation circuit comprising: means for generating a shadow signal smaller than the signal level of the signal level; and mixing means for non-additively mixing the shadow signal and the super signal from the clamp circuit to obtain a shadow key signal. .