A single, complete picture in a video or film. A video frame is made up of two interlaced fields of either 525 lines (NTSC) or 625 lines (PAL). Full-motion video for NTSC runs at 30 frames per second (fps); for PAL, 25 fps. Film runs at 24 fps. For progressive scan (non-interlaced) video, the frame is written through successive lines that start at the top left of the picture and finish at the bottom right.