Block-Based Gradient Descent for Local Backlight Dimming and Flicker Reduction

Local backlight dimming technology is a two-fold improvement for LED backlit LCD screens that allows to reduce power consumption and increase visual quality. This paper presents a fast version of an iterative backlight dimming algorithm based on gradient descent search. The speed is increased by exploiting the local uniformity of backlight to reduce the complexity for determining the optimal backlight of a given image. The algorithm is adapted to video sequences by using the backlight of the previous frame as a starting point to calculate the backlight for the current frame. Fast variations of backlight dimming over time can produce a visually annoying flicker artifact. To avoid this artifact, a control mechanism is also proposed.