Video Force Vector Analysis

[Biswas Lohani V K]

Hello Everyone,

I would like to request for your valuable suggestion and ideas to overly force data taken from force plate in C3D format and the video in .avi format recorded at the same time with a simple Sony video camera. if possible please suggest me how can I do this in Matlab or if this is not applicable I would like to request for your ideas.

I have force data or the force plate data in C3D file format and video in .AVI format. now I want to perform video vector analysis in real time.

Hope for your positive response.

Thanking you in advance.

Your Sincerely,

Biswas

[Manvendra Singh]

Re: Video Force Vector Analysis

Use Mokka software https://b-tk.googlecode.com/svn/web/mokka/index.html

[Tim Wrigley]

Re: Video Force Vector Analysis

Hi Biswas
You say you want to do this in real-time, so the fact that your force plate data is stored in C3D format would be irrelevant would it not ? You want to generate the force vector overlay in real-time, as it occurring, correct ? Note that some mocap systems now have facilities for this built-in.
But for a custom system, you need access to the force platform data directly from the analog-to-digital converter. Matlab supports many ADCs.
Software access to video in real-time is also possible from some cameras, although digital video has ironically sometimes made this more difficult than analog video used to be. You will have to determine what interfaces your camera has, and whether Matlab can access them in real-time (probably requiring the Image Acquisition Toolbox).
Once you have access to the basic signal sources in real-time, overlay of the two requires that they use the same 3D coordinate system. So the video camera calibration (intrinsic and extrinsic parameters) needs to be known. Matlab's Computer Vision System Toolbox provides a tool for this, or there are free public domain toolboxes (if your camera is positioned directly orthogonal to the force plate, there are simpler solutions that do not require a full camera calibration).
Your calculated 3D force plate data (COP and vector) is then projected onto the 2D space of the video camera.
Programming-wise, a simple polling loop should be adequate to generate the overlay in real-time, as fast as it can handle the incoming data.
If you don't want to do it all in real-time, putting it all together from stored C3D and AVI files is much easier. You only need the camera calibration and a way of time-synchronizing the two data sources. Some ideas here:

http://www.sciencedirect.com/science/article/pii/S096663620600378X

Tim Wrigley
University of Melbourne

[Biswas Lohani V K]

Re: Video Force Vector Analysis

Use Mokka software https://b-tk.googlecode.com/svn/web/mokka/index.html

Hello msingh 27,

Thank you very much for the link that you provided is very use full for the analysis of acquisition data including C3D format.

moreover, I have got many ideas from the MOKKA, a perfect open source and cross platform software application for the analysis of gait. thank you for the link again.

However, the problem is I am working out to design the same type of system not exactly with all the features but only the force data from C3D file in the graphical image format with force vector as MOKKA also does with line vector and in place of the trajectory movement skeletal data I want to include the video frame so that I can superimpose two frame and put them together in one place. I am also sending you the attached example what I am interested to know about how we can do that with Matlab code or any other easy method.

I just want to extract the force data from the c3D file and convert that data in the force vector form with arrow in head in sequence and at the same time extract frame from the .avi videos in certain time and put them together.

hope for your more suggestion ideas.

best regards,

Biswas

[Manvendra Singh]

Re: Video Force Vector Analysis

This is doable in Mokka but would require manual efforts to align video frame with GRF data on common time scale. I presume GRF and Video frames are synched together at the time of recording. You can import video files as well as GRF data in C3D file.
BR,
Manvendra

[Biswas Lohani V K]

Re: Video Force Vector Analysis

Dear Tim Sir,

Thank you very much for your suggestion and ideas. I did review your literature that you provided in the link based on your own research work and highly appreciate for providing that link. it is not compulsory to make it real so may be this will work. now only the thing is need to see practically how I can go . In the mean time if I have any question, I do appreciate your valuable feedback and suggestion.

Hope for your positive response.

Thanking you in advance.

Your Sincerely,

Biswas Lohani V K

[Biswas Lohani V K]

Re: Video Force Vector Analysis

Hello Sir,

I did extract the Video frames from the video in avi with the Matlab code but still struggling to extract the ground reaction force from the C3D file. If i could calculate the resultant force vector from the C3D file and visualize it in the graphical form i can synchronized it. If you provide me some ideas how can i work only with force data in each force plate among the four that stored in the C3D file that would be so helpful. I also did tried C3DServer but doesn't work.

Hope for your more suggestion and ideas.

Thanking you in advance.

Regards,

Biswas Lohani V K