Abstract: A video signal mixer with a parabolic signal mixing function, especially useful in scene-by-scene color correction systems and “blue screen” video masking applications. The mixer effects mixing two independent signal sources while smoothly controlling the rate of change during mixing. An input stage receives a first video signal and a second video signal. The mixing circuit mixes the first video signal with the second video signal based on a predetermined parabolic function. An aperture signal circuit in the mixer allows a degree of operator control over the parabolic function. An output stage provides a parabolized output signal. The output signal, which comprises the mixture of the first video signal and the second video signal, eliminates discontinuities in regions of the signal which would otherwise produce discontinuities in prior art types of video signal mixers.

Abstract: A digital processing system for providing spectral headroom to accommodate harmonic distortion components resulting from non-linear processing of digitized samples of video signals is shown. A standard set of video signal samples are all upsampled and filtered so that they have a common sampling rate. These are filtered to provide spectral headroom. Non-linear operations are then performed on the upsampled and filtered sequences. After processing, the processed upsampled signals are filtered to remove the harmonic components, and then the signals are decimated to reestablish their original sampling rates. This provides non-linear processing for signal sequences which were originally band limited, yet avoids the appearance of aliased frequencies in the output that normally result from harmonic distortion components generated by non-linear processing.