Rotary special effects generator

Abstract

A special effects generator for use in video switching produces a wide variety of rotational wipes, fades, and special effects. The generator functions by mixing together controlled amounts of horizontal and vertical sawtooth waveforms and DC potentials. The resultant signal is then fed into a comparator, and the comparator output is used to control one or more electronic video switches. The special effects are controlled by varying the strengths of the waveforms which are summed through the use of potentiometers or variable resistors. Rotational special effects are achieved through the use of a 360 degree circular potentiometer having multiple taps. Provision is made for multiple image special effects. Also disclosed are circuits for preserving the integrity of the switch output signal during synchronizing intervals and for equalizing the DC levels of all the video signals which are mixed together.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. An apparatus for combining first and second incoming video signals so as to produce a composite video signal that produces a composite image containing portions of the incoming signals separated by straight-line boundaries which boundaries may be rotated, said apparatus comprising: a source of one or more horizontal sawtooth waveforms;   a source of one or more vertical sawtooth waveforms;   signal mixing means coupled to said sources and having an output at which is presented a mixture of one horizontal sawtooth waveform with one vertical sawtooth waveform, said mixing means including externally operable control means for setting the proportions of the mixture and for determining which waveforms are included in the mixture;   comparator means having an input connected to the output of said mixing means for generating a binary output signal indicating whether the comparator means input signal is above or below a reference level; and   video switching means into which the first and second incoming video signals are fed and out of which the composite video signal flows for switching between the incoming signals under the control of the output signals generated by the comparator means in such a manner that the first video signal becomes the composite video signal when the binary output signal is in one state and the second video signal becomes the composite output signal when the binary output signal is in the other state.   
     
     
       2. An apparatus in accordance with claim 1 wherein the signal mixing means comprises a potentiometer having one end terminal connected to a source of horizontal sawtooth waveform, having another end terminal connected to a source of vertical sawtooth waveform, and having a movable tap connecting to a comparator means input. 
     
     
       3. An apparatus in accordance with claim 1 wherein the signal mixing means comprises a potentiometer having end terminals connected between sources of normal and inverted sawtooth waveforms of one variety (horizontal or vertical), having a center tap terminal connected to a sawtooth waveform of the other variety, and having a movable tap connecting to a comparator means input. 
     
     
       4. An apparatus in accordance with claim 1 wherein the signal mixing means comprises a 360° rotational potentiometer having four fixed taps spaced at 90° intervals, wherein sources of normal and inverted horizontal sawtooth waveforms are connected respectively to a first tap and to a second tap positioned 184° from the first tap; wherein sources of normal and inverted vertical sawtooth waveforms are connected respectively to a third tap and to a fourth tap spaced 180° away from the third tap, and said potentiometer having a first movable tap which connects to a first comparator means input. 
     
     
       5. An apparatus in accordance with claim 1 wherein the signal mixing means comprises a 360° rotational potentiometer having four fixed taps spaced at 90° intervals, wherein sources of normal and inverted vertical sawtooth waveforms are connected respectively to a first tap and to a second tap positioned 180° from the first tap; wherein sources of normal and inverted vertical sawtooth waveforms are connected respectively to a third tap and to a fourth tap spaced 180° away from the third tap, and said potentiometer having a first movable tap which connects to a first comparator input and a second movable tap mounted 90° away from the first movable tap which connects to a second comparator input. 
     
     
       6. An apparatus in accordance with claim 1 wherein one or more of the waveforms generated by the sources include a substantial direct current component that shifts the center of rotation away from the center of the composite image towards an edge or corner of the composite image. 
     
     
       7. An apparatus in accordance with claim 1 wherein the signal mixing means mixes a horizontal waveform with a vertical waveform, and wherein biasing means are provided for effectively D.C. biasing the horizontal and vertical waveforms in opposite directions sufficiently so that the center about which rotation occurs is a corner of the video image, whereby a 90° corner wipe effect is achieved. 
     
     
       8. An apparatus in accordance with claim 1 wherein the signal mixing means includes control means which, when actuated in one direction, first mixes a waveform of one type (horizontal or vertical) with a waveform of the other type and then mixes the waveform of the other type with an inverted waveform of the one type, said mixing means presenting the waveform of one type to the comparator means when the control means is in one extreme position, said mixing means presenting the inverted waveform of the one type when the control means is in the other extreme position, and said mixing means presenting the waveform of the other type when said control means is halfway between the respective extreme positions, whereby a 180° rotation of a boundary is achieved. 
     
     
       9. An apparatus in accordance with claim 8 wherein the normal and inverted waveforms of the one type are DC biased to shift the center of rotation to the center of an edge of the composite image, thereby giving a 180° wipe effect. 
     
     
       10. An apparatus for combining two or more incoming video signals so as to produce a composite video signal that produces a composite image containing portions of the incoming signals separated by straight-line boundaries which boundaries may be rotated, said apparatus comprising: a source of one or more horizontal sawtooth waveforms;   a source of one or more vertical sawtooth waveforms;   signal mixing means coupled to said sources and having at least two outputs to each of which are presented a mixture of one horizontal sawtooth waveform with one vertical sawtooth waveform, said mixing means including externally operable control means for setting the proportions of the mixture and for determining which waveforms are included in the mixture;   two comparators having respective inputs connected to the outputs of said mixing means and each generating binary output signals, wherein said two binary output signals when considered together have four possible states; and   video switching means into which the video signals and binary output signals are fed and out of which the composite video signal flows, comprising means for supplying a particular one of the incoming signals as the composite video signal during each of the four possible states of the two binary output signals generated by the comparators.   
     
     
       11. An apparatus in accordance with claim 10 wherein four incoming signals are fed into the video switching means, a particular one of the four signals becoming the composite video signal during each of the four possible states of the binary output signals. 
     
     
       12. An apparatus for producing 90° rotational wipes between two video signals comprising: sources of horizontal and of vertical sawtooth waveforms;   mixing means connecting to both said sources and having an output at which a mixture of said waveforms appear, the proportions of said waveforms present at said output varying linearly with the actuation of control means within the mixing means;   comparator means having an input connected to said mixing means output and having binary output;   signal switching means into which said two video signals and said binary output are fed, said signal switching means having an output at which appears one or the other of the video signals in accordance with the state of the binary signal.   
     
     
       13. An apparatus in accordance with claim 12 in which some of the waveforms are DC biased with respect to the comparator means. 
     
     
       14. An apparatus in accordance with claim 13 wherein the DC bias is adjusted to cause a 90° corner wipe effect. 
     
     
       15. An apparatus for producing 180° rotational wipes between two video signals comprising: sources of horizontal and vertical sawtooth waveforms;   mixing means including externally actuatable control means having a first range corresponding to half of the control means motion during which a varying mixture of one type of waveform (horizontal or vertical) with the other type is produced at an output, the one type being produced when the control means is at one extreme end of its first range and the other type being produced when the control means is at the other extreme end of its first range and at the middle of its overall range; said control means having a second range corresponding to the reamining half of the control means motion during which a varying mixture of the other type of waveform with an inverted waveform of the one type is produced at the output, the inverted waveform of the one type being produced when the control means is at one extreme and of its second range and the other type being produced when the control means is at the other extreme end of its second range and at the middle of its overall range;   comparator means having an input connected to the mixing means output and generating an output control signal; and   video switching means into which said two video signals and said output control signal are fed for switching between the two video signals under the control of the comparator means output control signal.   
     
     
       16. An apparatus in accordance with claim 15 in which some of the waveforms are DC biased with respect to the comparator means. 
     
     
       17. An apparatus in accordance with claim 15 wherein DC bias is applied to the one type of waveform and to the inverted waveform of the one type so as to produce a 180° wipe effect about the center of one edge of the resultant video image. 
     
     
       18. An apparatus for producing rotational special effects comprising: sources of normal and inverted horizontal and vertical sawtooth waveforms;   mixing means connecting to all of said sources and including rotational control means for generating at least one output signal that at any given moment is a mixture of no more than one horizontal and one vertical waveform, said rotational control means causing every possible mixture of said horizontal with said vertical waveforms to be produced during each complete rotation of the control means, said output signals presenting in sequence a horizontal sawtooth waveform, a vertical sawtooth waveform, an inverted horizontal sawtooth waveform, and an inverted vertical sawtooth waveform, and said output signals presenting smoothly varying mixtures of the waveforms in between generations of the pure waveforms;   comparator means connected to each output of said mixing means and generating one or more switching control signals; and   video switching means controlled by the switching control signals.   
     
     
       19. An apparatus in accordance with claim 18 wherein the mixing means is a 360° rotary potentiometer having taps at 90° intervals connected in sequence to the horizontal, vertical, inverted horizontal, and inverted vertical waveforms and having at least one slider connecting to comparator means and supplying an output signal to the comparator means. 
     
     
       20. An apparatus in accordance with claim 18 wherein the potentiometer has two sliders mounted 90° from one another each generating an output signal for each of two comparator means, wherein the comparator means generate switching signals having four states, and wherein the video switching means passes a predetermined one of two or more video signals for each of the four states. 
     
     
       21. In a special effects generator including video switching means controlled by comparators having inputs connected to sawtooth waveforms, an apparatus for preventing switching from occurring during the transmission of synchronizing pulses, said apparatus comprising: logical OR means for combining horizontal and vertical synchronizing pulses into a single waveform;   a disable input terminal to each comparator for forcing the comparator output to a predetermined state when a signal is supplied to said disable input; and   circuit means connecting the single waveform generated by the logical OR means to the comparator disable input terminals.   
     
     
       22. An apparatus in accordance with claim 21 wherein the disable input to the comparators is a comparator input that is normally held at a fixed potential while another comparator input is supplied with sawtooth waveforms. 
     
     
       23. An apparatus in accordance with claim 21 and further including one-shot multivibrator means for extending the length of horizontal synchronizing pulses to encompass the color burst signal as well as the horizontal synchronizing pulses. .Iadd. 24. An apparatus for combining first and second incoming video signals so as to produce a composite video signal that produces a composite video image containing portions of the incoming signals separated by substantially straight boundaries, which boundaries may be rotated, said apparatus comprising: a source of one or more horizontal sawtooth waveforms;   a source of one or more vertical sawtooth waveforms;   signal mixing means coupled to said sources and having an output at which is presented a mixture of one horizontal sawtooth waveform and one vertical sawtooth waveform, said mixing means including externally operable control means for setting the proportions of the sawtooth waveforms forming the mixture;   means into which said first and second video signals are fed and out of which the composite video signal flows for determining the composition of the composite video signals, said composition determining means being responsive to a control signal for altering the composition of the composite video signal; and   means electrically coupling the output of said signal mixing means to said composition determining means thereby to provide said control signal to said composition determining means. .Iaddend.