cv::imshow seems to corrupt some memory areas

Question

I use both OpenCV library and C++ NAOqi API in my code. In particular, I need to use the method setAngles() to set the head joints of the robot. Executing these lines:

//(1) set desired joint values on the desired joint names
pan = 0.0;
tilt = 0.0;
AL::ALValue names = AL::ALValue::array(PAN_JOINT,TILT_JOINT);
AL::ALValue angles = AL::ALValue::array(pan,tilt);
cout << "pan: " << pan << endl;
cout << "tilt: " << tilt << endl;
motionPtr->setAngles(names,angles,0.1f);

//(2) capture image from subscribed camera
AL::ALValue img = cameraPtr->getImageRemote(cameraClient);
imgHeader.data = (uchar*) img[6].GetBinary();
cameraPtr->releaseImage(cameraClient);

//(3) show image
imshow("test",imgHeader);
waitKey(30);

results into a crash with the following error:

terminate called after throwing an instance of 'AL::ALError' what(): ALMotion::setAngles ALBroker::methodCall: method: setAngles, params: [["HeadYaw", "HeadPitch"], [0, 0], 0] ALMotion::setAngles ALMotion::setAngles fractionMaxSpeed: Expected a fraction of max speed between 0.0 and 1.0

i.e. it says that the third argument of setAngles() is not a value between 0.0 and 1.0 as expected. Actually, it reads it as a 0 (maybe casted to int?). Of course, this is not true, as you can see from the code. The "funny" aspect is that, if I comment the cv::imshow(), the code normally works and no errors are raised.

Does anybody knows a possible reason why this could happen? Apparently, there are no connections between the operations of setting angles on the robot and displaying the image through OpenCV. Can you help me? Thanks

UPDATE: Maybe I forgot to say that this code is inside a while loop. Anyway, using the post attribute of NAOqi proxies objects, I made the method setAngles run in background in a parallel thread. In this way the image is properly shown and no errors are raised. However, the robot joints are not set, and the robot is still. Again, this does not happen if the cv::imshow is not called. Here is the full function where the whole while loop is contained.

//these are member variables of a class
double pan = 0.0;
double tilt = 0.0;
Mat imgHeader = Mat(320,240,CV8UC3);
bool headset = false;

//main loop
while(!headset){

    motionPtr->setStiffnesses("Head", 1.0f);
    int dtilt, dpan;
    int res;
    /**** Get inputs from joystick ***/
    res = joy->readEv();
    if(res != -1){
        if(jse->type & JS_EVENT_BUTTON){
            if((int)jse->number == X_BUTTON){//tilt down
                dtilt = -1;
            }
            else if((int)jse->number == TRIANGLE_BUTTON){//tilt up
                dtilt = 1;
            }
            else if((int)jse->number == START_BUTTON){//tilt down
                (firstKeyIgnored) ? (headset = true) : (firstKeyIgnored = true) ;
            }
            else{
                dtilt = 0;
            }
        }

        updateTilt(dtilt); //<-- it just changes the value of the member variable `tilt`

    }


    AL::ALValue names = AL::ALValue::array(PAN_JOINT,TILT_JOINT);
    AL::ALValue angles = AL::ALValue::array(pan,tilt);
    int id;
    id = motionPtr->post.setAngles(names,angles,0.1f);


    //capture image from subscribed camera
    ALimg = cameraPtr->getImageRemote(cameraClient);
    imgHeader.data = (uchar*) ALimg[6].getObject();
    imshow("test",imgHeader);
    waitKey(30);//*/
}

i guess, your imgHeader Mat is invalid after `cameraPtr->releaseImage(cameraClient);` , since you only do a shallow assignment of the pixels pointer . try a `imgHeader = imgHeader.clone();` before releasing the camera image — berak, Feb 18 '16 at 11:17
Actually, `releaseImage` should be useless with `getImageRemote`, as said [here](http://doc.aldebaran.com/1-14/naoqi/vision/alvideodevice-api.html#ALVideoDeviceProxy::releaseImage__ssCR) . I tried to remove it, but the problem still occurs. — Marco Ferro, Feb 18 '16 at 11:29
And even so, this does not look like to be the point. The crash is on `setAngles()` method, because it sees a wrong third argument. — Marco Ferro, Feb 18 '16 at 11:48
Is `imgHeader` an opencv `Mat`? Have you setup the width, height, datatype, step, etc. correctly before the `imgHeader.data` assignment? I would consider creating the `Mat` using the constructor of the form: `Mat(int rows, int cols, int type, void* data, size_t step)` after `getImageRemote`. — Douglas Dawson, Feb 18 '16 at 20:54
Problem semi-solved. I'm on Ubuntu 14.04 and I'm using Naoqi 1.14, that seems to have support until to 12.04. Passing on Ubuntu 12.04 actually prevents this error to occur. Thanks to all — Marco Ferro, Feb 29 '16 at 14:56

score 0 · Accepted Answer · answered Feb 29 '16 at 14:57

0

Problem semi-solved. I'm on Ubuntu 14.04 and I'm using Naoqi 1.14, that seems to have support until to 12.04. Passing on Ubuntu 12.04 actually prevents this error to occur. Maybe I should try using Naoqi 2.1 to check if running on Ubuntu 14.04 is ok.

answered Feb 29 '16 at 14:57

Marco Ferro

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cv::imshow seems to corrupt some memory areas

1 Answers1