valder's profile - activity

@berak, I"m having a hard time extracting frames from a video. Can you show me what you did to do this? All the frames I extract come out all garbled. I'm not sure what is wrong. Any help would be appreciated.

Did you get any help on this? I'm in the same boat.

Hello, I've been trying to port a C library into Java for my Android project. I'm not making a whole lot of progress. I'm taking in a video file and trying to do some analysis on the frames. I'm able to get all the way up to the point where I call Video.calcOpticalFlowPyrLK(). At this point the code just never returns. No exception is thrown or any messages printed to the log. Any suggestions? I've included some code snippets .

Thanks,

void DetectFrame(Mat currFrame)
{
    TermCriteria termcrit = new TermCriteria(TermCriteria.MAX_ITER | TermCriteria.EPS, 20, 0.03);
    Size subPixWinSize = new Size(10,10), winSize = new Size(31,31);

    Imgproc.cvtColor(currFrame, curr_, Imgproc.COLOR_BGR2GRAY);
    Imgproc.goodFeaturesToTrack(curr_, initialPoints, max_corners, 0.01, 10);

    Log.d(MotionTracker.class.getCanonicalName(), "features found: " + initialPoints.total());

    nextPoints = new MatOfPoint2f( initialPoints.toArray() );
    Log.d(TAG, "Number of features found : " + nextPoints.total());

    if(nextPoints.total() != 0) //Some weird problem that causes features to be found !!!
    {
        Size zeroZone = new Size(-1, -1);
        Imgproc.cornerSubPix(curr_, nextPoints, subPixWinSize, zeroZone, termcrit);
        Log.d(TAG, "sub pixel count: " + nextPoints.total());

        if(prev_.empty())
        {
            swapMatOfPoint2f();
            swapMat();
        }
    }
    else {
        Log.d(TAG, "No features found !");
    }
}


public boolean TrackFrame(Mat trackedFrame) {
    int i=0, k;
    MatOfPoint2f pt;
    TermCriteria termCriteria = new TermCriteria(TermCriteria.EPS | TermCriteria.MAX_ITER, 20, 0.03);
    Size subPixWinSize = new Size(10,10);
    Size winSize = new Size(5,5);
    if (prevPoints.empty() || (frame_count_ % 12) == 0) {
        DetectFrame(trackedFrame);
    }
    else {
        try {
             Imgproc.cvtColor(trackedFrame, curr_, Imgproc.COLOR_BGR2GRAY);
              Video.calcOpticalFlowPyrLK(prev_, curr_, prevPoints, nextPoints, status_, err_);

        } catch (Exception ex) {
            // do something with the exception
             ......
        }

Hello, I'm having a hell of a time trying to get this to work. When I try Mat_to_vector_Point2f I get the following error in my log file (Android)

error()﹕ OpenCV Error: Assertion failed (channels() == CV_MAT_CN(dtype)) in void cv::Mat::copyTo(cv::OutputArray) const, file /home/reports/ci/slave_desktop/50-SDK/opencv/modules/core/src/copy.cpp, line 212

Here's my code that sets up the call:

vector<cv::Point2f> points1, points2;
cv::Mat& previousMatPoints = *(cv::Mat *)addrInputPointsVector;
cv::Mat& nextMatPoints = *(cv::Mat *)addrOutputPointsVector;
Mat_to_vector_Point2f(previousMatPoints, points1);
Mat_to_vector_Point2f(nextMatPoints, points2);

I'm totally stumped. The Java code passes in the long values generated from the .getNativeObjAddr() calls