NTSC vs PAL

NTSC color encoding is used with the M format, which consists of 29.97 interlaced frames of video per second. Each frame consists of a total of 525 scanlines, of which 486 make up the visible raster. The remainder (the vertical blanking interval) are used for synchronization and vertical retrace. Originally designed to be blank to allow for the simple analog circuits and slow vertical retrace of early TV receivers, some of these lines now can contain other data such as closed captioning and vertical interval timecode (VITC). In the complete raster (ignoring half-lines), the even-numbered or 'lower" scanlines (lines 21 to 263 in the video signal) are drawn in the first field, and the odd-numbered or "upper" (signal lines 283 to 525) are drawn in the second field, to yield a flicker-free image at the field refresh frequency of approximately 59.94 Hertz (actually 60 Hz/1.001). For comparison, PAL uses 625 lines (576 visible), and so has a higher vertical resolution, but a lower temporal resolution of 25 frames or 50 fields per second.