4. The method of claim 3 wherein the frame-level audio features from a plurality of audio frames are aggregated to determine clip-level features.
4. The method of claim 3 wherein the frame-level audio features from a plurality of audio frames are aggregated to determine clip-level features. 5. The method of claim 4 wherein the frame-level audio features are aggregated by computing frame-level preliminary semantic concept detection values responsive to the frame-level audio features and then determining clip-level preliminary semantic concept detection values by determining an average or a maximum of the frame-level preliminary semantic concept detection values.