Improved video effect recall technique

Abstract From the Canadian patent

A video switcher (10) advantageously affords the capability of executing a video effect following recall that avoids visible artifacts upon transitioning from one effect to another. At the outset the switcher identifies active , elements within the video effect the comprising those elements that undergo a change during execution of the video effect as opposed to those that remain , inert during effect execution. The switcher then dynamically calculates offset for application to an initial key frame value for the video effect to avoid any change in value to active elements upon initial effect recall. The offset value is applied to each subsequent interpolation of the video effect …