JPS6048945B2 - special effects waveform generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a special effects waveform generator for use in television special effects.

Traditionally, the sawtooth wave, which is the fundamental wave of special effects waveform generators,
In order to obtain triangular waves, parabolic waves, etc., these digital signals are generated by digital calculation, and a fundamental wave is created from this digital signal by converting it into an analog signal using a digital-to-analog (D/A) converter. It was hot.

In this case, the stepwise changing signal output from the digital-to-analog converter was passed through a low-pass filter to obtain a smooth fundamental wave. However, this low-pass filter requires a large number of elements and is relatively complex in order to have good pulse response characteristics.

Also, it is advantageous to increase the calculation speed of the digital calculation circuit, but increasing the calculation speed of the digital calculation element used, D/
There were disadvantages in terms of increased power consumption of the A converter, etc. Therefore, an object of the present invention is to provide a special effect waveform generator that can obtain a smooth fundamental wave without using a high-performance low-pass filter. According to the special effect waveform generator according to the present invention, a special effect waveform generator can be obtained which is provided with a waveform shaping circuit that makes fine step-like changes in the converted output after the 5D/A converter. Next, the present invention will be described in detail with reference to the drawings showing one embodiment of the present invention.

FIG. 1 is a block diagram of an embodiment of the present invention, in which a data selector 1 sets the slopes of horizontal and vertical special effect fundamental waves, respectively.

The set data is sequentially added by the horizontal digital arithmetic circuit 2 and the vertical digital arithmetic circuit 3. In the horizontal harmonic signal generation circuit 4, the horizontal synchronization signal supplied from the terminal 5 is multiplied (for example, by a factor of 7), and becomes a clock signal for timing calculations in the horizontal digital calculation circuit 2. The calculation timing of the vertical digital calculation circuit 3 is performed at the timing of the horizontal synchronization signal.

D/A converters 6 and 7 are each horizontal digital arithmetic circuit 2
and the vertical digital arithmetic circuit 3 are converted into analog signals. The waveform shaping circuits 8 and 9 are for making the step-like changes in the output of the D/A converter finer, and will be explained later.

The outputs of the waveform shaping circuits 8 and 9 are mixed in a mixing circuit 10. The mixed output is compared with the fader control voltage from the terminal 12 in a comparator circuit 11 to obtain a special effect waveform for switching the screen. Other than waveform shaping circuits 8 and 9, patent application No. 52-3254
No. 2 (Japanese Unexamined Patent Publication No. 117325/1989) describes this in detail, so the explanation will be omitted.

Next, the configuration and operation of the waveform shaping circuits 8 and 9 will be explained.

FIG. 2 is a diagram showing an example of a waveform shaping circuit, and FIG. 3 is a waveform diagram for explaining the operation. An output waveform S from the D/A converter is supplied to an input terminal 13 of the waveform shaping circuit.

The waveform S is assumed to be a waveform as shown, which changes by an analog amount A every period T. The waveform S, is the impulse amplifier 14
The signal is then applied to a series circuit of a resistor 15 and a delay line 16, and a resistor 17 connected in parallel with the series circuit.

The delay amount of the delay line 16 is T,/2, and the resistance value is made equal to the characteristic impedance of the delay line 16. At this time, on the input side of the impulse amplifier 18, a voltage with an amplitude of A/2 of 4.times. is first generated, and after a time T,/2, a waveform S becomes the amplitude of A. appears. For this reason, the input impedance of the impulse amplifier 18 is set to be sufficiently high. When the output of the boosting amplifier 18 is further applied to a series circuit of a resistor 19, a delay line, and 20, and a resistor 21 connected in parallel with the series circuit, the output of the boosting amplifier 22 produces a signal having a waveform S3. is obtained.

At this time, the delay amount of the delay line 20 is selected to be T1/4, and the resistance value is selected to be equal to the characteristic impedance of the delay line 20. The boosting amplifiers 14, 18, and 22 are all used with high input impedance and low output impedance.

Therefore, an analog signal obtained by further subdividing the stepped output signal of the D/A converter 7 is obtained as the output of the waveform shaping circuit.

In this way, by combining the waveform shaping circuit that subdivides the input stepwise signal and the low-pass filter that removes relatively high frequency components, a smooth waveform can be obtained without increasing the digital calculation speed. For example, if a horizontal harmonic signal generation circuit generates a signal that is 256 (?) times the horizontal synchronization signal, and this signal is used to perform calculations in the horizontal digital calculation circuit 2, the delay line in the waveform shaping circuit 8 The delay amount is 124 ns for the first stage, 62 ns for the second stage, and 31 ns for the third stage when there are three stages.

In this case, a smooth analog signal can be obtained.
Note that the same process can be performed in the stages subsequent to the vertical digital arithmetic circuit 3.
It is also possible to omit one of the waveform shaping circuits 8 and 9, especially the vertical waveforming circuit 9.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a configuration diagram of a waveform shaping circuit, and FIG. 3 is a waveform diagram for explaining the operation of the waveform shaping circuit. Digital data selector, 2... horizontal digital arithmetic circuit, 3...
Vertical digital arithmetic circuit, 4...Horizontal harmonic signal generation circuit, 6, 7...D/A conversion circuit, 8, 9...Waveform shaping circuit, 10...Mixing circuit, 11...Comparison circuit,
14, 18, 22... Encouragement amplifier, 16, 20
...delay line.

Claims (1)

[Claims] 1 A data selector that can set first and second data and outputs first and second digital data corresponding to the first and second data, respectively, and a horizontal synchronization signal that multiplies the first data. a first digital arithmetic circuit that sequentially adds or subtracts the second data at the timing of a signal obtained by multiplying the vertical synchronization signal or a second digital arithmetic circuit that sequentially adds or subtracts the second data at the timing of a signal obtained by multiplying the vertical synchronization signal or a horizontal synchronization signal; , a first digital-to-analog (D/A) converter that converts the output of the first digital arithmetic circuit into an analog signal, and a second D/A converter that converts the output of the second digital arithmetic circuit into an analog signal. A special effect waveform comprising an A converter, a mixing circuit that mixes the outputs of the first and second D/A converters, and a comparison circuit that compares the output level of the mixing circuit with the level of a fader control signal. In the generator, the first and second D/A
the D at least on one side between the converter and the mixing circuit;
A waveform shaping circuit is provided to subdivide the staircase of the staircase waveform of the output of the D/A converter, and the waveform shaping circuit has a delay of 1/2 of the staircase period with respect to the staircase waveform of the output of the D/A converter. A special effect waveform generator comprising: means for creating a delayed waveform having time; and means for adding the stepped waveform output from the D/A converter and the delayed waveform.