Camera calibration segfault when displaying images from thread

[pieleric]

Running the camera calibration (mono or stereo) with git head (indigo) fails with this errors:

QObject::moveToThread: Widgets cannot be moved to a new thread
QObject::setParent: Cannot set parent, new parent is in a different thread
Segmentation fault (core dumped)

That's on a Ubuntu 14.04 64-bits (x86).

My understanding is that it's due to the move to OpenCV2, which uses QT, which doesn't allow to draw on the window from a different thread than the original thread that created the window.

I'm not sure what's the right way to fix it. As a workaround, I've moved the window init code to its own function, and add a call to that function from the init of the ConsumerThread (passed as a 3rd argument).
But I had to disable the stereo thread.

It looks more or less like that:

class ConsumerThread(threading.Thread):
    def __init__(self, queue, function, init):
        threading.Thread.__init__(self)
        self.queue = queue
        self.function = function
        init()
:
class CalibrationNode:
    :
    mth = ConsumerThread(self.q_mono, self.handle_monocular, self.initWindow)
:
class OpenCVCalibrationNode(CalibrationNode):
    :
    def __init__(self, *args):
        CalibrationNode.__init__(self, *args)

    def initWindow(self):
        cv2.namedWindow("display", cv2.WINDOW_NORMAL)
        cv2.setMouseCallback("display", self.on_mouse)
        cv2.createTrackbar("scale", "display", 0, 100, self.on_scale)

[vrabaud]

I have Indigo on the same configuration and I do not have that problem (other persons are using this code without errors too).
Do you get that error every time ? With my Kinect, I just run:

rosrun camera_calibration cameracalibrator.py image:=/camera/rgb/image_raw

Anything else you are running ?
Can you also please try that branch at https://github.com/vrabaud/image_pipeline/tree/indigo . I created it to solve another problem but it might work for you.

[pieleric]

Strange... anyway, I've tried with your branch but it gave the same result.

Actually, from time to time, instead of segfaulting, it gives this output, and blocks there:

OK
init done 
opengl support available 
QMetaMethod::invoke: Unable to invoke methods with return values in queued connections

I don't know whether it's helpful, or more confusing ;-)

I run camera calibration with a simple webcam, like that:

roslaunch ar_pose ar_pose_single.launch  # part of ar_tools, to start a camera node
rosrun camera_calibration cameracalibrator.py --size 9x6 --square 0.25 image:=/camera/image_raw  camera:=/camera

Let's try to be more precise on the libraries:

libopencv-core2.4:amd64       2.4.8+dfsg1-2ubuntu
libqtgui4:amd64 4:4.8.5+git192-g085f851+dfsg-2ubuntu4

[vrabaud]

I have both kubuntu and ubuntu installed ... I guess I need a pure Ubuntu. I'll try to get a big enough USB key to get that going.
My OpenCV is slightly newer: 2.4.8+dfsg1-2ubuntu1

[delmic]

I think the OpenCV version is the same, it's just the last character that got dropped in my copy/pasting ;-)

[vrabaud]

please, try this out and tell me if it works for you. Thx

[pieleric]

Almost :-)

The __init__() of the Thread object is done in the original thread, so you have to move the window init to the run() function:

    def __init__(self, queue, opencv_calibration_node):
        threading.Thread.__init__(self)
        self.queue = queue
        self.opencv_calibration_node = opencv_calibration_node

    def run(self):
        cv2.namedWindow("display", cv2.WINDOW_NORMAL)
        cv2.setMouseCallback("display", self.opencv_calibration_node.on_mouse)
        cv2.createTrackbar("scale", "display", 0, 100, self.opencv_calibration_node.on_scale)
        while True:
   :

Also, there is a typo in redraw_stereo():

self.queue.display.put(display) --> self.queue_display.put(display)

[vrabaud]

I had fixed the typo, I guess I did not push at the right moment. And does that work for you with those 2 changes ?

[pieleric]

With these 2 small fixes, yes it works fine :-)