1.125 MHz

This is a common frequency that can be derived from 625/50 PAL (and 525/60 NTSC) that runs through SD, HD and UHD digital television standards using 4:4:4 or 4:2:2 sampling, including 1080-line HD and UHD at 25, 30, 60 Hz frame rates. It can be created from the old analog (PAL or NTSC) black-and-burst signal. Because 1.125 MHz is a common frequency, black and burst was widely used as a timing reference signal in the early days of HD.

See also: 13.5, Tri-level sync