JPH03283878A - Video non-addition mixer - Google Patents

Abstract

PURPOSE:To reproduce a signal part less than a pedestal level by generating offset coefficients in accordance with first and second fader control signals at first and second offset coefficient circuits, respectively, and subtracting those offset coefficients from video signals after multiplication. CONSTITUTION:The first and second offset coefficient circuits 5, 6 generate first and second offset coefficients based on the first and second fader control signals inputted from fader control signal input terminals 13, 14, and first and second offset subtraction circuits 7, 8 subtract the first and second offset coefficients from the output of first and second multiplier circuits 3, 4. The output are inputted to a non-addition mixing circuit 9, and the pedestal level is added on them at a pedestal adder circuit 10, and a signal is outputted as a mixing output signal with the same pedestal level as that of an original video signal. In such a way, it is possible to reproduce a video input signal with fidelity even when the signal with level less than the pedestal level is included in it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video non-addition mixing device used for fade processing and the like when switching between two video signals.

[Prior Art] Conventionally, a circuit shown in FIG. 4 is known as this type of video non-addition mixing device.

This device inputs first and second video input signals through a fader.
Non-additive mixing is performed at a predetermined mixing ratio based on a control signal.

That is, the first and second video input signals are input to the first pedestal subtractor 1 and the second pedestal level subtraction circuit 2 via video input terminals 11 and 12, respectively. First and second pedestal level subtraction circuits 1 and 2 subtract values corresponding to the pedestal levels from the first and second video input signals, respectively, and produce level-shifted video signals whose pedestal levels become O level. Output.

The outputs of the first and second pedestal level subtraction circuits 1.degree.2 are input to one input end of the first multiplication circuit 3 and the second multiplication circuit 4, respectively. Further, at the other input terminals of the first and second multiplier circuits 3.4, first and second fader control signals whose values change according to the mixing ratio, as shown in FIG. Fader control signal input terminal 13.14
is entered via. first and second multiplication circuits 3;
4c, 1st and 2nd with pedestal level subtracted respectively
The video input signal is multiplied by the first and second fader control signals to generate a video signal to be mixed.

The outputs of these first and second multiplication circuits 3 and 4 are input to a non-addition mixing circuit 9. The non-addition mixing circuit 9 compares the levels of the outputs of both the multiplication circuits 3 and 4, selects and outputs the signal with the higher level. The output of this non-addition mixing circuit 9 is input to a pedestal level addition circuit 10. The pedestal level addition circuit 10 adds the pedestal level to the output of the non-addition mixing circuit 9 and outputs the result from the video output terminal 15.

In the non-additive mixing device configured in this way, the first and second fader control signals input to the first and second multiplier circuits 3 and 4 are controlled by the non-additive mixing ratio, as shown in FIG. The first fader control signal takes a value of 1 from the first video input signal cutoff point to the midpoint of the mixing ratio, and from the midpoint to Second
It gradually decreases from 1 to O toward the video input signal cutoff point of . Moreover, the second fader control signal, on the contrary, gradually increases from O to 1 from the first video input signal cutting point to the intermediate point, and increases from O to 1 from the intermediate point to the second video input signal cutting point. Takes a value of 1 up to the point.

Therefore, at the first video input signal cut-off point, the output of the second multiplier circuit 4 becomes 0 level, and at the second video input signal cut-off point, the output of the first multiplier circuit 3 becomes level, and at these points, , the first or second video input signal is input as is to the non-addition mixing circuit 9. Also, in the middle of both cutoff points, both video input signals are
The gain is adjusted according to the control signal and output.

Then, the non-addition mixing circuit 9 selects and outputs the signal with a higher level among both signals, thereby obtaining a mixed and added output of both signals.

[Problems to be Solved by the Invention] By the way, for example, a composite video signal may include a signal that is below the pedestal level, that is, has a negative polarity, such as a blue portion of a color par.

On the other hand, at the first and second video input signal cutoff points, one of the two video input signals is transmitted to the multiplier circuit 3.
or fixed at the pedestal level by 4.

Therefore, if one of the video input signals contains the above-mentioned negative polarity signal at the video output terminal,
In the negative polarity portion, the comparison result in the non-addition mixing circuit 9 is clamped to the pedestal level (O level), making it impossible to reproduce the signal portion below the pedestal level. As a result, there is a problem that the video input signal is not correctly reproduced at the video input signal cutoff point.

The present invention has been made in view of such problems, and it is possible to reproduce information below the pedestal level included in the video input signal even at the point where the video input signal is cut off.
It is an object of the present invention to provide a video non-additive mixing device that is capable of performing appropriate mixing processing according to the mixing ratio.

[Means for Solving the Problems] A video non-addition mixing device according to the present invention includes a first pedestal level subtraction circuit that subtracts a value corresponding to the pedestal level from a first video signal, and a second video signal. a second pedestal level subtraction circuit that subtracts a value corresponding to the pedestal level from the pedestal level, and a first pedestal level subtraction circuit that inputs the output of the first pedestal level subtraction circuit and the first fader control signal and multiplies them. a multiplier circuit, a second multiplier circuit that receives the output of the second pedestal level subtraction circuit and the second fader control signal and multiplies the two; a first offset coefficient circuit that generates an offset coefficient according to the value; a second offset coefficient circuit that receives the second fader control signal and generates an offset coefficient according to the value;
a first offset subtraction circuit that subtracts the offset coefficient generated by the first offset coefficient circuit from the output of the first multiplication circuit; and a first offset coefficient circuit that subtracts the offset coefficient generated by the first offset coefficient circuit from the output of the second multiplication circuit. a second offset subtraction circuit for subtracting the generated offset coefficient; a non-addition mixing circuit for non-additive mixing the outputs of the first and second offset subtraction circuits; and a pedestal level for the output of the non-addition mixing circuit. It is characterized by having a pedestal level addition circuit for adding.

[Operation] According to the present invention, offset coefficients corresponding to the first and second fader control signals are generated from the first and second offset coefficient circuits, respectively, and the offset coefficients are generated from the video signal after being multiplied by the offset coefficients. Subtraction is performed in the first and second offset subtraction circuits. Therefore, even if the mixing ratio of two video input signals is set as the signal cutoff point, the signal level of one is fixed at a value shifted to the negative side than the pedestal level, so the signal portion below the pedestal level is This means that the same video output signal as the video input signal can be obtained at the signal cutoff point.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of a video non-additive mixing device according to an embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 4 are given the same reference numerals, and detailed explanations of the overlapping parts will be omitted.

The device shown in FIG. 1 differs from the device shown in FIG. 4 in that first and second offset coefficient circuits 5 and 6 are provided, and first and second offset subtraction circuits 7 and 8 are provided. This is the point that is provided.

The first and second offset coefficient circuits 5 and 6 each have a first
and a second fader control signal to generate first and second offset coefficients, which will be described later.

The first and second offset subtraction circuits 7 and 8 each have a first
and the outputs of the second multiplier circuits 3 and 4 to the first and second multipliers.
Subtract the offset factor of . The output thereof is then input to a non-addition mixing circuit 9.

Next, the operation of the video non-additive mixing device according to the present embodiment configured as described above will be explained.

FIG. 2 is a waveform diagram of each part showing the operation of this device.

The first and second video input signals are 8-bit digital signals and take values from 0 to 255, as shown in FIG. 2(a). Here, the pedestal level is 60, and the lowest level in the synchronization signal portion is 4.

These video input signals are subtracted by 60 in the first and second pedestal level subtraction circuits 1 and 2 so that the pedestal level becomes 0 level, as shown in FIG. 2(b).

Subsequently, the outputs of these pedestal level subtraction circuits 1.2 are multiplied by a fader control signal determined according to the mixing ratio in first and second multiplication circuits 3.4, and the outputs are multiplied by fader control signals determined according to the mixing ratio. ), the amplitude level is adjusted around the 0 level.

Next, the outputs of these multiplier circuits 3 and 4 are
In offset subtraction circuits 7 and 8, the offset coefficient is subtracted. As shown in FIG. 3, this offset coefficient is inversely proportional to the fader control signal and takes values from 0 to 56. That is, when the fader control signal is O, the offset coefficient is 56. This corresponds to the synchronization signal level of the quantization level shown in FIG. 2(a).

Now, assuming that this offset coefficient is a, by subtracting this offset coefficient from the outputs of the multiplier circuits 3 and 4, the outputs of the offset subtraction circuits 7 and 8 are as shown in FIG.
As shown in d), the signal is level-shifted so that the pedestal level becomes -a. Here, if the mixing ratio in FIG. 5 is the first video output signal cutoff point, the second fader control signal is 0, so the second
The output of the offset subtraction circuit 8 is at a constant level of -56, as shown in FIG. 2(e). Also, at this time,
Since the output of the first offset subtraction circuit 7 is a signal as shown in FIG. 2(b), the output signal resulting from the level comparison in the non-addition mixing circuit 9 is
The signal is exactly as shown in FIG.

The output of this non-addition mixing circuit 9 is added with a pedestal level by a pedestal level adding circuit 10, and is output as a mixed output signal whose pedestal level becomes the same level as the original video signal.

In this way, according to the apparatus of this embodiment, even if the video input signal contains a signal below the pedestal level, it can be faithfully reproduced.

[Effects of the Invention] As described above, according to the present invention, offset coefficients corresponding to the first and second fader control signals are generated in the first and second offset coefficient circuits, respectively, and the offset coefficients are generated in the first and second offset coefficient circuits. By subtracting from the multiplied video signal in the first and second offset subtraction circuits, the signal portion below the pedestal level can be reproduced even when the mixing ratio of the two video input signals is set as the signal cutoff point. This has the effect that the same video output signal as the video input signal can be obtained at the signal cut-off point.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a video non-addition mixing device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of the device, and FIG. 3 is a diagram showing offset coefficients and fader control signal levels in the device. FIG. 4 is a block diagram of a conventional video non-addition mixing device, and FIG. 5 is a graph showing the relationship between the non-addition mixing ratio and the fader control signal. 1; first pedestal level subtraction circuit; 2; second pedestal level subtraction circuit; 3; first multiplication circuit; 4; second pedestal level subtraction circuit;
multiplication circuit, 5; first offset coefficient circuit, 6; second
offset coefficient circuit, 7; first offset subtraction circuit, 8; second offset subtraction circuit, 9; non-addition mixing circuit, 10; pedestal level addition circuit

Claims (2)

[Claims] (1) a first pedestal level subtraction circuit that subtracts a value corresponding to the pedestal level from the first video signal;
A second pedestal level subtraction circuit subtracts a value corresponding to the pedestal level from the second video signal, and the output of the first pedestal level subtraction circuit and the first fader control signal are inputted, and the multiplication of both is performed. a second multiplier circuit that receives the output of the second pedestal level subtraction circuit and the second fader control signal and multiplies them; and a second multiplier circuit that receives the first fader control signal. a first offset coefficient circuit that generates an offset coefficient according to the value of the fader; a second offset coefficient circuit that receives the second fader control signal and generates an offset coefficient according to the value; a first offset subtraction circuit that subtracts the offset coefficient generated by the first offset coefficient circuit from the output of the multiplication circuit;
a second offset subtraction circuit that subtracts the offset coefficient generated by the first offset coefficient circuit from the output of the multiplication circuit; and a non-additive mixture that non-additively mixes the outputs of the first and second offset subtracting circuits. 1. A video non-addition mixing device comprising: a circuit; and a pedestal level addition circuit that adds a pedestal level to the output of the non-addition mixing circuit. (2) The first and second offset coefficient circuits output first and second offset coefficients at levels inversely proportional to the levels of the first and second fader control signals, respectively. The video non-additive mixing device according to claim 1.