Low-level features vs.
 High-level Features
nLow-level features (color, edge, texture…):
ntend to be unstable and unreliable in representing semantics
nAlso, hard to relate a query to suitable low level features
nFor example: “Find shots with people holding banner”
nHigh-level features
nDetectors of varying accuracy are available. For example, face, car, boat, commercial, sports, etc
nProvide partial semantics to ASR and queries
nHave been shown to be effective in TRECVID 2005
nCan be easily incorporated into text-based retrieval systems