Abstract: In the generation of a digital special effect boundary signal for mixing or fading television signals with a wipe movement, the boundary position is determined by the state of a counter controlled by a clock pulse oscillator coupled to the line frequency. In order to prevent a visible staircase effect on the moving boundary, a progressive phase shifting of the clock signal for clocking the counter is provided by a control signal derived from the digital data of the special effect boundary signal. For that purpose a variable delay line is interposed ahead of the clock input of the counter and the delay is controlled, line by line, by a digital ramp signal processed in a multiplier and other stages. The counter is loaded with data supplied during the horizontal blanking interval from another output of the digital multiplier.

Abstract: Horizontal and vertical wipe signals are additively modified to vary the boundary between an inserted picture to be faded in and the previously displayed picture to be faded out as part of the fading transition. The resulting modified wipe signals are compared with a zero voltage reference signal to determine intervals, respectively in horizontal and vertical scan, during which the substituted picture is to be switched in. The picture switching signal is also used to substitute, during that same interval, an inverted wipe signal instead of the non-inverted wipe signal. The composite wipe signal thus produced is then compared with a border width control voltage to produce horizontal and vertical border-defining pulses respectively centered on the flanks of the picture switching pulse. The horizontal and vertical border defining pulses are multiplicatively combined to produce the ultimate border defining pulse for inserting the border between the two picture contents.

Abstract: A steady or slowing changing analog signal affected with noise is sampled and held at the sampling rate of a following analog to digital converter and has a rectangular a.c. signal superimposed on it before it is supplied to the converter. This is done in such a way that when the analog signal is in the middle range between quantization steps, the least significant bit (LSB) is well defined. When the analog signal is close to a quantization threshold, the superimposed rectangular pulses change the LSB values back and forth and comparison of successive values is used to suppress changes in LSB value. On the other hand, if the analog signal is changing more rapidly through quantization steps, the circuit does not interfere with digital output changes. The system can be used during the vertical blanking intervals of a television signal for digitizing an analog voltage corresponding to a blending voltage for a video signal.

Abstract: Special effect television picture transitions in which the new picture grows from a point on the television screen to occupy the entire screen, displacing the old picture, can be made to originate at any point of the television screen and to bring the picture to occupy precisely the entire television screen under control of a single actuating lever moved to produce the entire transition. The special effect picture size voltages which conventionally control the size of the special effect picture are inverted and multiplied by the corresponding picture shift voltages (horizontal and vertical) to produced inputs to the conventional function generators controlling the position of the special effects picture.

Abstract: Method and apparatus for creating control signals which, when applied to a special effects mixer determine the shape and position of a geometric figure during a wipe transition. The control signals are formed by a combination of input signals synchronized to either the horizontal or vertical synchronization frequency and having amplitudes which vary as a predetermined function of time. A DC voltage having an amplitude corresponding to the setting of a potentiometer or variable resistor is inserted into at least one of the input signals and is preserved when the one input signal, such as a sawtooth signal is processed (squared) to create a second input signal (parabolic signal). The position of the figure on the screen changes with changing amplitude of the so-inserted DC voltage.