opencv stereo correspondence "OpenCV Error: Bad argument (Unknown array type) in cvarrToMat"

edit

I'm trying to compute depth using stereo correspondence but keep getting the error in the title of this question. I don't really know how to debug this.

Code:

        void imageprocess::get_depth()
        {
            Size size = bridge[0]->image.size();
            Mat imgl, imgr, disp;

            cvtColor(bridge[0]->image, imgl, CV_RGB2GRAY, 1);
            cvtColor(bridge[1]->image, imgr, CV_RGB2GRAY, 1);

            CvStereoBMState* state = cvCreateStereoBMState(0, 16);
            cvFindStereoCorrespondenceBM(&imgl, &imgr, &disp, state);
            cvReleaseStereoBMState(&state);

            imshow(WINDOWM, disp);
            waitKey(3);

        }

Unless my C++ is a lot rustier than I thought, I think I'm using the functions correctly. Which is why I don't see any problem with my code.

It works fine without:

cvFindStereoCorrespondenceBM(&imgl, &imgr, &disp, state);

and the function decleration is:

cvFindStereoCorrespondenceBM(const CvArr* left, const CvArr* right, CvArr* disparity, CvStereoBMState* state)

Edit: I also tried from http://stackoverflow.com/questions/11027574/convert-cvmat-to-const-cvmat-or-cvmat:

    Size size = bridge[0]->image.size();
    Mat imgl, imgr;

    cvtColor(bridge[0]->image, imgl, CV_RGB2GRAY, 1);
    cvtColor(bridge[1]->image, imgr, CV_RGB2GRAY, 1);

    CvMat cvimgl, cvimgr, cvdisp;

    cvimgl = imgl;
    cvimgr = imgr;

    CvStereoBMState* state = cvCreateStereoBMState(0, 16);
    cvFindStereoCorrespondenceBM(&cvimgl, &cvimgr, &cvdisp, state);
    cvReleaseStereoBMState(&state);