interlace (scan)

The alternating display of the two fields of each frame of a television picture -- all the odd numbered lines followed by all the even numbered lines of one frame, followed by all the odd then even numbered lines of the next frame, and so on. Scan formats are indicated as either interlaced (e.g. 1080i) or progressive (1080p). Interlacing improves the display of motion, reduces picture flicker with no increase in picture rate, and no increase in bandwidth or data rate. On the downside, interlacing reduces the vertical definition of moving images compared to progressive scans and can create dithering in horizontal picture detail.