Synchronizing 5 cameras with arduino uno generator
Answered
Hi
I am setting up a motion capture system using a series of CM3 cameras. They are being triggered using an Arduino generator for synchronization. I have set the code to generate a square wave pulse wherein it is high for 10ms and low for 10ms.
The frame rate in my programme's trigger settings I have as such set to 50 frames per second and the exposure settings to <0.02 seconds.
However, their recordings are not synchronized and do not behave the way that they are supposed to.
Sometimes, although rarely, they all have identical durations and play the video in real time.
Sometimes some of them are half the duration of others and play the recording as if fast forwarded 2 x.
Sometimes even some of them play the video as if it is slowed down by 1/2.
I think it has something to do with the exposure settings or the frame rate that I am using on my mocap software or even the square wave frequency on my Arduino IDE but I am not surebecause I tried using a relay board for opto-isolation and connected two cameras. Although the two recordings were the same length, they were still sped up 2x.
Do you have any ideas on how to treat this problem? And how I can arrange this system for 3D motion capture using around 5 cameras?
Thank you in advance.
Varun
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Official comment
Hello Varun,
Trigger Overlap is not about synchronized images, but it allows you to trigger at the full framerate.
TriggerOverlap should be available on all the cameras. If one of your cameras doesn't show it, maybe check your firmware or ensure you are actually in trigger mode.
Instead of decreasing your framerate, I suggest you just reduce your max exposure time. Then, you can still get 50Hz, just ensure your exposure is shorter than 20ms.
Demos
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Hi Varun,
It sounds like you are using at 50 fps (10ms high, 10ms low = rising edge every 20ms). If you are exposure time is also set to 20ms, I believe you are seeing sometimes half framerate because the trigger is being missed because you are still exposing. To test this, please set a shorter exposure time or slow down your trigger rate to see if everything stays in sync.
Are you using Spinnaker or Flycapture2 to work with your CM3 cameras?
Demos
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Hi Demos,
Thank you for this. I have had some preliminary successes in trials of 3 cameras by using a lower trigger rate. I plan to try and increase the number of cameras to help me do this some more.
I am actually not using either one of those softwares. I am working with an experimental programme developed from Python specifically for markerless motion capture called JARVIS MOCAP.
It was actually developed specifically for use with FLIR machine vision cameras.
https://jarvis-mocap.github.io/jarvis-docs/manual/3_acquisitiontool_setup/
Sometimes on this the trigger overlap option doesn't appear for at least one of the cameras connected. I am starting to think that this could be a reason for problems.
Do you know if its possible to get synchronised videos without using 'Trigger overlap'? E.g. what would be the way used for those camera models that don't support it ?
Regards,
Varun
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