Interlaced scan is an old technique where each video frame is split into two half-frames called fields — one with odd horizontal lines (1, 3, 5…), one with even (2, 4, 6…) — captured a sixtieth of a second apart and displayed alternately. The trick was clever: engineers in the 1940s halved the radio bandwidth needed to broadcast television, and on chunky CRT TVs the eye stitched the two fields together into something that looked like motion.
The price is paid on modern flat-panel displays. Because the two fields are from different moments in time, anything that moved between them produces visible jagged horizontal lines — the "combing" artefact you might recognise from old VHS tapes or sports broadcasts. To play interlaced video properly on a modern screen, the player must run a deinterlacing step that recombines fields into proper progressive frames; good deinterlacers use motion analysis, cheap ones just blend lines and soften the image.
For a content business in 2026, interlaced is purely a legacy concern. You'll see it in broadcast TV archives, old DVDs, satellite feeds in some regions, and some surveillance cameras. Anything you produce today should be progressive. If you ingest interlaced material, deinterlace it once at the start of your pipeline — not on the fly during playback.
