Method and System for Detecting Global Brightness Change for Weighted Prediction in Video Encoding

A video encoder configured to encode a coding unit of a digital video sequence using weighted prediction, the video encoder comprising:

• a memory configured to store a reference coding unit to be used in encoding the coding unit;
• a brightness change estimation component configured to detect whether there is global brightness change in the coding unit by
• computing a brightness measure for each region in a plurality of regions in the coding unit, wherein the brightness measure indicates a relative brightness between the region in the coding unit and a corresponding region in the reference coding unit,
• determining a number of regions in the plurality of regions with significant brightness change by comparing each brightness measure to a region brightness change threshold;
• and
• detecting whether there is global brightness change in the coding unit by comparing the number of regions to a global brightness threshold;
• and
• a weighted prediction factors computation component configured to compute weighted prediction factors when global brightness change is detected, the weighted prediction factors to be used for weighted prediction in encoding the coding unit.

A digital system configured to encode a coding unit of a digital video sequence using weighted prediction, the digital system comprising:

• means for storing a reference coding unit to be used in encoding the coding unit;
• means for computing a brightness measure for each region in a plurality of regions in the coding unit, wherein the brightness measure indicates a relative brightness between the region in the coding unit and a corresponding region in the reference coding unit,
• means for determining a number of regions in the plurality of regions with significant brightness change by comparing each brightness measure to a region brightness change threshold;
• and
• means for detecting whether there is global brightness change in the coding unit by comparing the number of regions to a global brightness threshold;
• and
• means for computing weighted prediction factors when global brightness change is detected, the weighted prediction factors to be used for weighted prediction in encoding the coding unit