1. A system for determining a summary feature set comprising: a processor configured to: select a plurality of subsegments of a first segment, wherein the plurality of subsegments have variable lengths; for each subsegment, compute a plurality of values by applying a set of functions to each subsegment; and from all the values computed for all the subsegments, select a first subset of values; and a memory coupled with the processor and configured to provide the processor with instructions.