Intra prediction using template matching with adaptive illumination compensation

Modern video coding standards such as H.264/AVC use intra prediction for efficient coding of Intra pictures. These usually exploit local directional signal correlations. More recently, intra prediction modes using non-local signal information have been introduced. A very popular approach is the so called template matching prediction (TMP), which uses template based texture synthesis for signal prediction. This, combined with regular directional prediction, significantly improves intra coding efficiency compared to H.264/AVC. However, current TMP techniques have trouble synthesizing picture data with non-uniform illumination characteristics. They assume that similar picture regions resemble at the same time in structure and illumination, which is often not the case. In order to solve this, we propose a template matching technique with locally adaptive illumination compensation. The proposed technique is based on a linear compensation model with a scaling and an offset parameters to compensate for contrast and brightness disparities respectively. The model parameters are calculated by solving an auto-regressive Least Square problem during the template search for TMP. This permits to synthesize signal structures while capturing the local characteristics of illumination without needing extra side information. The total improvement in intra coding efficiency with respect to H.264/AVC can be of up to 18%.