Color frame sequence

In video engineering, the color frame sequence is the sequence of fields in an analog composite video signal through which the video frame timing and chrominance subcarrier signal timing—in particular, that of the color burst—cycle through all possible phase relationships. The process of maintaining this alignment through the process of analog composite video recording, editing and broadcast was known as color framing.

The exact nature of the color frame sequence depends on the video standard being used. In the case of the two main composite video standards, both of which use analog quadrature amplitude modulation for the chrominance signal, PAL has an 8-field (4 frame) color frame sequence, and NTSC has a 4-field (2 frame) color frame sequence. Because it uses frequency modulation for the chrominance subcarrier, SECAM does not have the subcarrier phase sensitivity problems of NTSC or PAL, but a field phase sequence was usually imposed to reduce visible artifacts on monochrome receivers.