question: private static int selectTrack ( MediaExtractor extractor ) { int numTracks = extractor . getTrackCount ( ) ; for ( int i = 0 ; i < numTracks ; i ++ ) { MediaFormat format = extractor . getTrackFormat ( i ) ; String mime = format . getString ( MediaFormat . KEY_MIME ) ; if ( mime . startsWith ( "video/" ) ) { if ( VERBOSE ) { Log . d ( TAG , "Extractor selected track " + i + " (" + mime + "): " + format ) ; } return i ; } } return - 1 ; }
target:  Selects the video track, if any.