Frame rate control (FRC) is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.
Most TN panels represent colors using only 6 bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, they use a dithering method that combines adjacent pixels to simulate the desired shade.
FRC is a form of temporal dithering which cycles between different color shades with each new frame to simulate an intermediate shade. This can create a potentially noticeable 30 Hz flicker. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible.
8 bit TN+film panels with dithering are sometimes advertised as having "16.2 million colors".
Some panels now render HDR10 content with an 8-bit panel using frame rate control.