Cameras are not connected through mutual observations

[ns15417]

when running kalibr_calibrate_cameras i encountered a problem which is listed below:
`timestamp cam0 cam1
1575683268.01 84 -
1575683268.06 - 56
1575683268.27 108 -
1575683268.32 - 71
1575683268.81 - 72
1575683269.02 52 -
1575683269.07 - 71
1575683269.26 103 -
1575683269.32 - 123
1575683269.51 108 -
1575683269.56 - 101
1575683269.77 124 -

Cameras are not connected through mutual observations, please check the dataset. Maybe adjust the approx. sync. tolerance.
Traceback (most recent call last):
File "/home/shinan/Project/kalibr_workspace/devel/bin/kalibr_calibrate_cameras", line 15, in
exec(compile(fh.read(), python_script, 'exec'), context)
File "/home/shinan/Project/kalibr_workspace/src/kalibr-master/aslam_offline_calibration/kalibr/python/kalibr_calibrate_cameras", line 447, in
main()
File "/home/shinan/Project/kalibr_workspace/src/kalibr-master/aslam_offline_calibration/kalibr/python/kalibr_calibrate_cameras", line 204, in main
graph.plotGraph()
File "/home/shinan/Project/kalibr_workspace/src/kalibr-master/aslam_offline_calibration/kalibr/python/kalibr_camera_calibration/MulticamGraph.py", line 308, in plotGraph
edge_label=self.G.es["weight"],
KeyError: 'Attribute does not exist'
`
above is part of the log, I am not sure what is the exact reason of this bug, but according to the bold log, it is said that the cameras are not synchronous. i guess the reason must be that i set my camera frame rate to 4HZ which leads to the two cameras cannot get images at the same time. I think the timestamp also tells the same thing.

I solved this by changing the frame rate of both cameras to 20HZ.
Just list this here, if anyone have other explanation please tell me.

[kannidekan]

execuse me, do you know how could i get the IMU YAML file of the requirements in the camera-imu calibration? #341

Thanks very much!

[AbnerCSZ]

Comment this code on line 201 of src/Kalibr/aslam_offline_calibration/kalibr/python/kalibr_calibrate_cameras to solve your problem:

    if not graph.isGraphConnected():
        obsdb.printTable()
        print "Cameras are not connected through mutual observations, please check the dataset. Maybe adjust the approx. sync. tolerance."
        graph.plotGraph()
        sys.exit(-1)

[huonggiangdhtn]

@ns15417 thank you, I had the same propblem, and I changed to 20Hz, it is ok. But I got error at plotGraph

[goldbattle]

Please try PR #515 to see if you still get this issue. If so, please provide a bag file this fails on.