In a normal C3D file it happens that the parameters start at the 2nd record but this is not a requirement. The first word of a parameter file has the same format of the first word in a C3D file. Parameter data is stored contiguously following the parameter file header and may overlap 512 byte record boundaries. Each parameter and group identifier starts with a header, the format of which is common between the two. Group identifiers are assigned a negative group number in the group header.
Parameters indicate which group they belong to by a positive group number in the parameter header.
Group identifiers and parameters may appear in any order in the file. This web site is maintained by Motion Lab Systems, Inc. , as a service to the gait and biomechanics community.