Read & write C3D mocap files



This is a small library for reading and writing C3D binary files. C3D files are a standard format for recording 3-dimensional time sequence data, especially data recorded by a 3D motion tracking apparatus.


Install with pip:

pip install c3d

Or if you'd like to use the bleeding-edge version, just clone the github repository and build and install using the normal Python setup process:

git clone
cd py-c3d
python install



This package includes a script for converting C3D motion data to CSV format (c3d2csv) and an OpenGL-based visualization tool for observing the motion described by a C3D file (c3d-viewer).


To use the C3D library, just import the package and create a Reader or Writer depending on your intended usage:

import c3d

with open('data.c3d', 'rb') as handle:
    reader = c3d.Reader(handle)
    for i, (points, analog) in enumerate(reader.read_frames()):
        print('Frame {}: {}'.format(i, points.round(2)))

You can also get and set metadata fields using the library; see the package documentation for more details.


This library is minimally effective, in the sense that the only motion tracking system I have access to (for testing) is a Phasespace system. If you try out the library and find that it doesn't work with your motion tracking system, let me know. Pull requests are also welcome!

Also, if you're looking for more functionality than just reading and writing C3D files, there are a lot of better toolkits out there that support a lot more file formats and provide more functionality, perhaps at the cost of increased complexity. The biomechanical toolkit is a good package for analyzing motion data.