1. A gesture recognition method comprising: receiving, at a processor, an input stream of image frames depicting an articulating entity; computing instance level features from individual ones of the image frames and sending the computed features to a trained machine learning system; and receiving in response at least one gesture class from a plurality of possible gesture classes; wherein the trained machine learning system comprises at least one multiple decision boundary classifier comprising a plurality of decision boundaries arranged to divide an instance level feature space into a plurality of regions, at least one region being associated with a gesture primitive; and wherein the instance level features are calculated from one or more instances where the instances are temporally non-sequential subsets of frames depicting a complete gesture of the gesture class made by the articulated entity.