How to Synchronize 3-D Data with video data in Vicon Nexus?

[Gannon White]

Re: How to Synchronize 3-D Data with video data in Vicon Nexus?

I'm curious what version of Polygon are you working in? We have 3.5.1 but have upgraded to 4 which seems much easier. But we are waiting for the Bonita ref camera to come out so I haven't had to deal with the syncing issue yet.

[Andrew Lewis]

Re: How to Synchronize 3-D Data with video data in Vicon Nexus?

There a slightly clumsy work around for synchronising video with 3D data in Polygon by changing the length of your video file. I had a video of normal walking that had been cropped to a shorter length than the 3D data from the c3d file. Cropping the video file had, of course, reset the time coding so it started from zero at the new 1st frame. Polygon’s synchronisation was then thrown off it matches the two files using their time coding.

You can’t crop the c3d file as the time coding isn’t reset but you can alter the length of the video file. The easiest way I found to do this was using MicroSoft MovieMaker which is often a standard piece of software on PCs. You can take a snapshot of the video’s 1st frame and then add this as a prolonged “still” at the start of the video to offset the actual video frames to the appropriate time to match with the c3d data (my file needed 1.2s delay as judged by looking at Polygon time-bar). MovieMaker seems to only export to WMV format so you may have to use a subsequent mpg converter before Polygon can read it. This whole process may be much easier in more sophisticated video editing packages.

Why Polygon doesn’t have a video offset synchronisation tool, like both Workstation and Nexus do, is anyone’s guess!

Hope that helps,
Andy Lewis

Dear all,

I am wondering how to synchronised the 3-D data captured in Nexus with the video, because when you are reporting in polygon, the video data did not matched with the 3-D data and graphs.

It would be great if some body help me.

Regards

Syed

[Gaspar Morey Klapsing]

Re: How to Synchronize 3-D Data with video data in Vicon Nexus?

Dear Syed,

I'm assuming you are capturing your video data with NEXUS and that your DV cam is NOT triggered by the MX-System (if it was, everything should be synchronised).
When not triggered (camera running free), there is no frame by frame synchronisation (only simultaneous start and stop). To overcome this, NEXUS provides the "Delay compensation" slider in DV properties.
You should setup an overlay view in NEXUS and then play with the slider until you get a synchronised image. Then you save it generating the c3d. If you than make your Polygon report, the video should be synchronised.
It could happen then it is not synchronised the first time you play it, but it should be on the second time and subsequent ones.

I hope this helped. Good luck,

Gaspar

[At Hof]

Re: How to Synchronize 3-D Data with video data in Vicon Nexus?

Dear all,

I am wondering how to synchronised the 3-D data captured in Nexus with the video, because when you are reporting in polygon, the video data did not matched with the 3-D data and graphs.

It would be great if some body help me.

Regards

Syed

Dear Syed,
If your video cameras are driven by the Nexus software, they are synchronized. In Polygon, the sync can be off one or two frames, but this error is constant, and cannot be remedied as it seems.
Yours,
At Hof

[Syed Wasim]

Dear all,

I am wondering how to synchronised the 3-D data captured in Nexus with the video, because when you are reporting in polygon, the video data did not matched with the 3-D data and graphs.

It would be great if some body help me.

Regards

Syed