Assertion failure with call to cv::calcOpticalFlowPyrLK(...) (ANSWERED)

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Greetings all,

I am having trouble integrating a call to cv::calcOpticalFlowPyrLK(...) into my (C++) code. Ultimately, I wish to create a video stabilization routine.

I get the following assertion error with the call to cv::calcOpticalFlowPyrLK(...):

OpenCV Error: Assertion failed ((npoints = prevPtsMat.checkVector(2, CV_32F, true)) >= 0) in cv::calcOpticalFlowPyrLK, file C:\...\opencv\modules\video\src\lkpyramid.cpp, line 593

As far as I can tell, my code follows the example L-K optical flow code in sources\samples\cpp. My code follows. The assertion error occurs with the call directly following the "// PROBLEM OCCURS WITH THIS CALL TO THE L-K OPTICAL FLOW CODE!!!" comment.

If it makes any difference, I am using OpenCV 2.4.7 with Microsoft Visual Studio 2012. I can routinely compile and run other code that utilizes OpenCV.

#include "ConjoinImages.h"

#include "opencv2/calib3d/calib3d.hpp"
#include "opencv2/core/core.hpp"
#include "opencv2/video/video.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/videostab/videostab.hpp"

#include <iostream>
#include <string>
#include <time.h>


int _tmain(int argc, _TCHAR* argv[]) {

   std::string videoFilename= "my_video.mp4";

   // Open input video.
   std::cout<< "Attempting to open input video file:  "<< videoFilename<< std::endl;
   cv::VideoCapture videoIn;
   videoIn.open( videoFilename);
   if( !videoIn.isOpened())
      throw "Error when reading stream!";
   std::cout<< "Video input file open."<< std::endl;

   // Run everything through the stabilizer...
   cv::Mat frame;
   cv::Mat stabilizedFrame;
   bool initialized= false;

   for( unsigned int ii= 0; ii< 30; ++ii) {
      videoIn.read( frame);
   }

   unsigned int frameNum= 0;
   time_t tstart= time( 0);
   while( videoIn.read( frame)) {

      // need to grayscale the image
      if( frame.type()!= CV_8U)
         cv::cvtColor( frame, frame, cv::COLOR_BGR2GRAY);

      // Get the features that need to be tracked.
      int maxCorners= 30;
      cv::vector< cv::Point2f> frameFeatures;
      cv::goodFeaturesToTrack( frame, frameFeatures, maxCorners, 0.01, 30);
      cv::vector< cv::Point2d> prevFeatures;
      cv::goodFeaturesToTrack( stabilizedFrame, prevFeatures, maxCorners, 0.01, 30);

      if( frameFeatures.size()== prevFeatures.size()) {
         // Calculate the Lucas-Kanade optical flow between the two frames.
         cv::vector< uchar> status;
         status.reserve( maxCorners);
         cv::vector< float> errors;
         errors.reserve( maxCorners);

         // PROBLEM OCCURS WITH THIS CALL TO THE L-K OPTICAL FLOW CODE!!!
         cv::calcOpticalFlowPyrLK( stabilizedFrame, frame, prevFeatures, frameFeatures, status, errors);

         // Find the homography transformation between the frames.
         cv::Mat H= cv::findHomography( prevFeatures, frameFeatures);

         if( !H.empty()) {
            // Warp the current frame to match the previous frame.
            cv::warpPerspective( frame, stabilizedFrame, H, frame.size(), cv::INTER_NEAREST| cv::WARP_INVERSE_MAP);
         }
         else {
            stabilizedFrame= frame;
         }
      }
      else {
         stabilizedFrame= frame;
      }

      // Display.
      cv::Mat output;
      ConjoinImages::TwoSideBySide( frame, stabilizedFrame, output);
      cv::imshow( "stabilization", output);
      cv::waitKey( 1);

      ++frameNum;
   }

   return 0;
}

Thank you very much for your time,

-Nate