This distortion is present if a signal’s chrominance phase is affected by chrominance amplitude. These phase errors are a result of the system’s inability to uniformly process all amplitudes of high-frequency chrominance information. Chrominance nonlinear phase distortion is expressed in degrees of shift of subcarrier phase. This parameter should be measured at different APL (Average Picture Level); the worst result is quoted as the amount of distortion. Chrominance nonlinear phase distortion will cause picture hue to shift as color saturation increases.

A modulated pedestal signal is used to measure this distortion. The modulated pedestal signal consists of three chrominance packets with the same phase and luminance level but each chrominance packet has increasing amplitudes of 20, 40, and 80 IRE.