Orb_slam2: OpenCV Error:

[Gasethata]

This is what I get while trying to use the ROS Example running monocular node.

Input sensor was set to: Monocular
OpenCV Error: Unknown error code -49 (Input file is empty) in cvOpenFileStorage, file /tmp/binarydeb/ros-kinetic-opencv3-3.2.0/modules/core/src/persistence.cpp, line 4422
terminate called after throwing an instance of 'cv::Exception'
what(): /tmp/binarydeb/ros-kinetic-opencv3-3.2.0/modules/core/src/persistence.cpp:4422: error: (-49) Input file is empty in function cvOpenFileStorage

Aborted (core dumped)

Can someone please help me out on this one.
Thanks in advance.

[YuehChuan]

@Gasethata
Same Issue! What's is your envionment
I'm using raspberry pi3 with ubuntuMATE16.04.3, ROS kinetic, and with OpenCV-3.3.0(newest one) installed
I guess is OpenCV version problem. ORB_SLAM2 just support toup to OpenCV-3.2.0

[YuehChuan]

I;m using ros package usb_cam and run mono camera demo with command
rosrun ORB_SLAM2 Mono Vocabulary/ORBvoc.txt Examples/Monocular/head_camera.yaml /camera/image_raw:=/usb_cam/image_raw

[YuehChuan]

relate to
https://github.com/HKUST-Aerial-Robotics/VINS-Mono/issues/31

[YuehChuan]

quite wired, i already delete opencv-3.3.0 from /usr/local/lib /usr/local/include
then compile everything make sure it is configured with kinetics opencv-3.2.0 using find_package(OpenCV 3.2.0 REQUIRED) , also open GUI for ubnutuMATE
still same issue
DBoW2, ORB_SLAM2 ros, ORB_SLAM2

[Gasethata]

I have managed to solve the problem.
The problem was the settings file that contained my camera calibration parameters.
Do check it.

But from that being fixed, new problem came.

After running this command:
rosrun ORB_SLAM2 Mono /home/vip/ORB_SLAM2/Vocabulary/ORBvoc.txt /home/vip/ORB_SLAM2/Examples/ROS/ORB_SLAM2/SettingsFiles/microsoftWebcam.yaml /camera/image_raw:=/usb_cam/image_raw

I get a black window stating that its "WAITING FOR IMAGES"
I think its got something to do with ROS.

Can someone please help me out here.

[Gasethata]

Hi everyone
I managed to solve the "WAITING FOR IMAGES" issue.
This is what i did:

1. roscore
2. roslaunch usb_cam-test.launch (make sure that you are in the .launch file directory)
   
   
   
   • for my case, usb_cam is the topic I'm using.
   
   
3. rosrun ORB_SLAM2 Mono /home/vip/ORB_SLAM2/Vocabulary/ORBvoc.txt /home/vip/ORB_SLAM2/Examples/ROS/ORB_SLAM2/SettingsFiles/microsoftWebcam.yaml /camera/image_raw:=/usb_cam/image_raw

[BBlackB]

Hi @Gasethata, I have the same problem("OpenCV Error").
could you please talk about the details that how you solve the "OpenCV Error" problem?
Thanks in advance.

[BBlackB]

I got it.
It is wrong style of yaml file that cause the problem.
Thanks for all guys!

[konnpaku-youmu]

@BBlackB Yeah, you are right! Thanks!

[zivAstra]

Can you be more specific as to what fixes the yaml problem?
Thanks

[braineniac]

If anybody else stumbles upon this problem, this is how you change the yaml file

[heshanchuan]

I fixed same problem. It's all about the YAML grammar.
I find there is a blank space before %YAML:1.0
So I delete the blank space.