Determining a movement of an object may include obtaining an event stream corresponding to a scene over time, wherein the event stream includes events associated with detected changes in brightness, wherein each event includes a pixel location, a timestamp, and a brightness indication; selecting a first subset of pixels from the plurality of pixels corresponding to an object for a first time period; determining a first movement of the object based on the brightness indications and timestamps for the first subset of pixels; determining that the first movement is insufficient to generate a velocity measure; selecting, based on the first movement, a second subset of pixels associated with the object for a second time period; determining an updated movement of the object based on the brightness indications and timestamps for the second subset of pixels and the first movement; and generating a velocity measure based on the updated movement.