Here are the data structures with brief descriptions:

C_xtract_amp_tracker
C_xtract_frame_tracker
C_xtract_function_descriptor	Data structure containing useful information about functions provided by LibXtract
C[struct].algo
C[struct].data
C[struct].argv
C[union].result
C[struct].result.scalar
C[struct].result.vector
Cxtract_mel_filter_	An array of pointers to functions that perform the extraction