The POINT:RATE parameter is a single floating-point value that records the 3D sample rate of the data contained within the C3D file in samples per second.  Note that this is not the necessarily the same as the original data sample rate.  For instance if the 3D data points were recorded on a 60 Hz system, then RATE should be set to 60.  If the C3D file only contains 3D sample data for every fourth sample then the POINT:RATE value will be 15.  This parameter is used to calculate times for the 3D data samples.

The RATE parameter value can also be found stored in floating-point format in words 11-12 of the C3D file header.  The POINT:RATE header value should always be identical to the value stored in the parameter section.

The same POINT:RATE value applies to all 3D samples – the C3D file format requires that all 3D points be recorded at a single rate.  This means that if the C3D file is used to store 3D data from a variety of different sources, all 3D points (even fixed points) must be sampled at the rate required by the fastest moving 3D point.