Assertion failed while using findEssentialMat()

edit

I am using findEssentialMat() function so I can later recover the relative pose (translation and rotation) between two following frames of a webcam with recoverPose(). However, I get an asserion failed error:

OpenCV Error: Assertion failed(!fixedType() && !fixedSize()) in create, file /home/patrchri/opencv/modules/core/src/matrix.cpp, line 2297

To be more specific, I have written the following in a while loop which reads the following frames :

 vector<KeyPoint> kpointsframe1;
 vector<KeyPoint> kpointsframe2;
 vector<Point2f> pointsframe1;
 vector<Point2f> pointsframe2;
 vector<Point2f> velocityvect;
 vector<uchar> status;
 vector<float> err;
 Size winSize = Size(21,21);
 TermCriteria termcrit = TermCriteria(TermCriteria::COUNT+TermCriteria::EPS,30,0.01);
 Mat Essential,R,T;
 capture.read(frame1);
 capture.read(frame2);
 undistort(frame1,frame1undist,CameraMatrix,distCoeffs);
 undistort(frame2,frame2undist,CameraMatrix,distCoeffs);
 cvtColor(frame1undist,frame1gray,CV_BGR2GRAY);
 cvtColor(frame2undist,frame2gray,CV_BGR2GRAY);
 //goodFeaturesToTrack(frame1gray,corners,500,qualityLevel,minDistance,Mat(),blockSize,useHarrisDetector);
 FAST(frame1gray,kpointsframe1,THRESHOLD_DIFFERENCE,false,FastFeatureDetector::TYPE_9_16);
 for(int i=0;i<kpointsframe1.size();i++)    pointsframe1.push_back(kpointsframe1.at(i).pt);
 calcOpticalFlowPyrLK(frame1gray,frame2gray,pointsframe1,pointsframe2,status,err,winSize,3,termcrit,0,0.001);
 int ind = 0;
 for( int i=0; i<status.size(); i++){
    Point2f pt = pointsframe2.at(i- ind);
        if ((status.at(i) == 0)||(pt.x<0)||(pt.y<0)){
              if((pt.x<0)||(pt.y<0)){
                status.at(i) = 0;
              }
              pointsframe1.erase(pointsframe1.begin()+(i-ind));
              pointsframe2.erase(pointsframe2.begin()+(i-ind));
              ind++;
        }

 }
 Point2d pp(320,240);
 double focal = 9.5327626068874099e+02;
 Essential = findEssentialMat(pointsframe1,pointsframe2,CameraMatrix,RANSAC,0.999,1,Mat());
 recoverPose(Essential,pointsframe1,pointsframe2,CameraMatrix,R,T,Mat());

I have declared the CameraMatrix outside this while loop.

The issue arises from the findEssentialMat() but I am confused on what is wrong with it. I searched for similar assertion failures but I couldn't find something that it would be helpful. Surely the error comes from the sizes of the Mats used. What could be wrong with it?

Thank you for your answers and for your time in advance,

Chris

1st EDIT:

The CameraMatrix has been declared as follows after the callibration of the webcam:

 double data[3][3];
 data[0][0] = 9.5327626068874099e+02;
 data[0][1] = 0.0;
 data[0][2] = 320.;
 data[1][0] = 0.0;
 data[1][1] = 9.5327626068874099e+02;
 data[1][2] = 240.0;
 data[2][0] = 0.0;
 data[2][1] = 0.0;
 data[2][2] = 1.0;
 double avg_reprojection_error = 3.5640854681839190e-01;
 Mat CameraMatrix(3,3,CV_64F,&data);

2nd EDIT:

The full printscreen of the error is the following:

If I follow the trace I see that it comes from:

void _OutputArray::create(int d, const int* sizes, int mtype, int i,
                          bool allowTransposed, int fixedDepthMask) const
{
    int k = kind();
    mtype = CV_MAT_TYPE(mtype);

    if( k == MAT )
    {
        CV_Assert( i < 0 );
        Mat& m = *(Mat*)obj;
        if( allowTransposed )
        {
            if( !m.isContinuous() )
            {
                --->CV_Assert(!fixedType() && !fixedSize());<---- (That is line 2297)
                m.release();
            }

            if( d == 2 && m.dims == 2 && m.data &&
                m.type() == mtype && m.rows == sizes[1] && m.cols == sizes[0] )
                return;
        }

        if(fixedType())
        {
            if(CV_MAT_CN(mtype) == m.channels() && ((1 << CV_MAT_TYPE(flags)) & fixedDepthMask) != 0 ...