Comparison between median filtering and vertical edge controlled interpolation for flicker reduction

A vertical-temporal median filter and adaptive vertical-edge-controlled interpolation are described, using a field frequency doubled to 100 Hz (120 Hz). The filter is found to have good properties for flicker reduction in TV systems, but it produces additional disturbing alias components and movement defects in the vertical direction. A major advantage of the adaptive filter over the median filter is the ease with which alias components are suppressed. Furthermore, vertical-edge-controlled interpolation is insensitive to noise and the subcarrier in standard TV receivers, since these disturbances can be prevented by pre- and postfiltering within the edge detector. The filter and interpolation hardware is limited to one field memory for a noninterlace conversion, or two field memories when the field frequency is doubled. By comparison, a satisfactory motion-adaptive filter using frame delays needs three field memories and an additional one for converting the field frequency