Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon.
When someone watches interlaced video on a progressive monitor with poor (or no) deinterlacing, they can see "combing" in movement between two fields of one frame.
Phase Alternating Line (PAL) is a colour encoding system for analog television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields per second, and associated with CCIR analogue broadcast television systems B, D, G, H, I or K. The articles on analog broadcast television systems further describe frame rates, image resolution, and audio modulation.
Un-decoded PAL image, showing chroma information as fine patterns chroma dots (click to zoom) overlapping the luma signal
Decoded PAL image, with chroma fully recovered. Some minor artifacts (see dot crawl) are present across transition areas (click to zoom)
A waterfall display showing a 20ms long interlaced PAL frame with high FFT resolution
Analyzing a PAL signal and decoding the 20ms frame and 64µs lines
