JP2503620B2 - Digital superimpose device - Google Patents

Description

The present invention relates to a device for superimposing a character signal or the like on a television signal, and more particularly to a digital superimposing device for digitally processing this.

[Prior Art] Conventionally, as a superimposing device of this kind, a device for switching both a video signal and a character signal in an analog signal state, and when a digital character signal is white or black, a digital character is added to an analog video signal. There is a device that mixes or switches signals and outputs them. There is also a simple switching superimposing device that switches both the video signal and the character signal in a digital state.

[Problems to be Solved by the Invention] The above-described superimposing device in which the video signal and the character signal are analog does not cause a problem because the video signal is not sampled, but it is necessary to use a sample for a special effect or a still image. If it has been converted, it is necessary to convert both the video signal and the character signal to analog, and a D / A converter and an encoder are required for both signal systems. Therefore, the circuit is complicated and large-scaled.

When the character signal has color information, the video signal is once color-separated into baseband signals (Y, I, Q, etc.), the character signal is converted into the same area as the baseband signal, and then synthesized. , D / A conversion and encoder were used to convert to standard television signals. For this reason, there is a drawback that the circuit becomes complicated and image quality is deteriorated by once performing color separation.

Also, in the case of only the switch in the digital domain,
Since the switching portion changes abruptly, switching noise causes overshoot and undershoot, and there is a drawback that the color of the character is not faithfully reproduced.

[Means for Solving the Problems] An object of the present invention is to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a digital superimposing device that can easily switch between a video signal and a character signal with digital data as it is, thereby reproducing a video signal with less noise and capable of multicolor expression.

The present invention has achieved the above-mentioned object, and includes a video signal sampled at a frequency N times the subcarrier frequency of a standard television signal, and a red, green, and blue signal composed of a dot number N times the subcarrier frequency. In a superimposing apparatus for switching and synthesizing coded character signals of three primary colors, it has a sampling frequency 1 / N counter, and inputs this counter output signal and the coded red green blue signal, Digital encoder that generates a character signal that has become a standardized television video signal, an adder that adds the encoder output and the sampled video signal, and the adder output and the sampled video signal and It is characterized by including a switching device that switches between a digital encoder output and a D / A converter that converts the switching device output into an analog television signal. To.

[Embodiment] Next, a digital superimposing apparatus of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a digital superimposing apparatus according to the present invention.

In this embodiment, the video signal is a coded signal sampled at a frequency four times as high as the subcarrier, and the red, green and blue character signals each have 1 bit.

Reference numeral 101 is an encoded video signal input terminal, 102 to 104 are encoded red, green, and blue input terminals, respectively, and 105 is a sampling frequency input terminal. Further, 1 is a counter that sets the sampling frequency to 1/4, and indicates the phase relationship between the sampling frequency and the subcarrier with a 2-bit output. This counter 1
Must be synchronized with the burst signal of the video signal, and are thus phase-synchronized with the reset signal input from the reset signal input terminal 106. Reference numeral 2 outputs a signal indicating whether there is a character signal and a character signal, which is a standard television format signal encoded for each sampling frequency, from the red, green, and blue signals and the output of the counter 1. It is a digital encoder. An adder 3 adds the character signal and the video signal. 4 is a video signal, a character signal, and an adder 3
It is a switcher that outputs any of the data whose output is 1/2. A switch controller 5 controls the switch 4. 6
Is a D / A converter that converts the switched signal into an analog signal. 107 is a standard television signal output terminal.

By the way, the standard television signal SCTS is expressed by the following equation.

SCTS = EY + EQsin (ωt + 33 °) + EIcon (ωt + 33 °)
(1) EY = 0.29ER + 0.59EG + 0.11EB} EI = 0.60ER-0.28EG-0.32EB} (2) EQ = 0.21ER-0.52EG + 0.31EB} That is, the encoder 2 outputs red, green, Blue input terminal
From the inputs from 102 to 104 and the output of counter 1, (1)
Then, the equation (2) may be calculated. First, the equation (2) is calculated from the inputs from the red, green, and blue input terminals 102 to 104, and this is substituted into the equation (1). The ωt term in the equation (1) indicates the n-th dot position in the horizontal direction, but since the dot lock is 4 times the subcarrier, ωt = n / 4 · 2π, and ωt = 0,
One of π / 2, π, 3π / 2. Therefore, it is possible to know in which phase the output is from 2 bits of the 1/4 counter 1 of the sampling frequency. Further, since the character signal is switched with the video signal, it is necessary to match the color phase of the video signal, so that the color phase synchronization is maintained by the reset signal input from the terminal 106. Than these things,
Since the formula (1) can be calculated and the calculated data may be stored in the ROM in advance, the digital encoder 2 can be composed of one ROM. The output of the digital encoder 2 is added to the video signal by the adder 3, and the adder output is halved and supplied to the switch 4.

The switch 4 receives a video signal, a character signal, and a signal obtained by adding these two signals, and switches and outputs these signals.

First, as shown in FIG. 2, a character signal is output in the character signal portion, a video signal is output in the video signal portion, and an added signal is output at the switching point between the character signal and the video signal. To do. As a result, the discontinuity at the transition between the video signal and the character signal can be reduced.
A control signal is supplied from the switching controller 5 so that the switching device 4 operates as described above.

As described above, the digital video signal in which the video signal and the character signal are combined is converted into an analog television signal by the D / A converter 6, and then output from the output terminal 107 as a standard television signal. .

In the above description, the sampling frequency phase is 0, π
Although / 2, π, and 3π / 2 are used, it is necessary to match the phase relationship of the video signal. To do this, ωt in equation (1) is changed to ωt = 2π
・ It is possible to match the color phase by setting n / 4 + α and changing the value of α. Also, by configuring each one bit of red, green, and blue with a larger number of bits, it is possible to reproduce multicolor characters.

[Effects of the Invention] As described above, according to the present invention, by selecting the sampling frequency to be N times the subcarrier, a digital encoder that can be easily configured with a 1 / N counter and a ROM, and a video signal. By switching between the adder for adding the character signal and the output of this adder, and the video signal and the character signal, it becomes possible to easily switch the digital data as it is. This has the effect of reproducing a video signal that can be expressed.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a digital superimposing apparatus according to the present invention. FIG. 2 is a timing chart showing the switching timing in the digital superimposing apparatus of FIG. 1 ... Counter 2 ... Digital encoder 3 ... Adder 4 ... Switcher 5 ... Switching controller 6 ... D / A converter

Claims (1)

(57) [Claims] 1. A coded character signal of three primary colors of red, green, and blue, which is composed of a video signal sampled at a frequency N times as high as the subcarrier frequency of a standard television signal and a number of dots N times as high as the subcarrier frequency. In a superimposing device for switching and synthesizing, having a sampling frequency 1 / N counter, the counter output signal and the encoded red green blue signal are input,
A digital encoder that generates a character signal that has become an encoded standard television video signal, an adder that adds the encoder output and the sampled video signal, and the adder output and the sampled video A digital superimpose characterized by comprising a switching device for switching between a signal and a digital encoder output, and a D / A converter for converting the switching device output into an analog television signal. apparatus.