Rate-Distortion Theory for Affine Global Motion Compensation in Video Coding
Holger Meuel, Stephan Ferenz, Yiqun Liu, Jörn Östermann · 2018
In this work, we derive the rate-distortion function for video coding using affine global motion compensation. We model the displacement estimation error during motion estimation and obtain the bit rate after applying the rate-distortion theory. We assume that the displacement estimation error is caused by a perturbed affine transformation. The 6 affine transformation parameters are assumed statistically independent, with each of them having a zero-mean Gaussian distributed estimation error. Based on that, the joint p.d.f. of the displacement estimation errors is derived and related to the prediction error. Using the ratedistortion theory, we calculate the bit rate in dependence of the perturbation of the affine transformation parameters. Comparing with a translational motion model in video coding standards like HEVC, we determine accuracy boundaries for the affine transformation, with which a gain can be achieved.