Two sample C3D files produced by NaturalPoint.  

05/21/2009  07:32 AM         1,829,888 Facial-Sing.c3d
05/21/2009  07:35 AM         4,320,800 OptiTrack-IITSEC2007.c3d

These files contain no analog data and are poorly formatted as they lack both
the ANALOG and FORCE_PLATFORM groups which are needed to tell applications opening
the file that there is no analog or force platform data in the file.  These files
are provided to allow programmers to test that their applications function correctly
when C3D files contain minor errors.

Two sample C3D files generated by NaturalPoint processed with their ARENA motion 
capture software. The files contain point data only.