 For framerate conversions and zooming it would mostly be ideal to line-double each field to produce a double rate of progressive frames, resample the frames to the desired resolution and then re-scan the stream at the desired rate, either in progressive or interlaced mode.Interlace introduces a potential problem called interline twitter, a form of moiré.This aliasing effect only shows up under certain circumstances—when the subject contains vertical detail that approaches the horizontal resolution of the video format.