Real Time Processing with sampleBuffer (AVFoundation)

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Hi,

I am trying to process the real-time camera images on iOS. In the didOutputSampleBuffer-Method of AVCaptureVideoDataOutputSampleBufferDelegate I am creating a matrix out of a sampleBuffer (which works without any problems). But when performing certain methods, such as cv::GaussianBlur, the app crashes because of "exc_bad_access code=1, address = 0x10......"

cv::Mat matrix(bufferHeight, bufferWidth, CV_8UC4, baseAddress);

cv::GaussianBlur(matrix, matrix, cvSize(5,5), 0); // Crahes here

My other question is: how can I update the "camera-view" with points returned from the open-cv-processing function? Currently, I am detecting rectangles and return the four points (one for each point). But when setting these as coordinates for a label, they are not refreshed immediately (takes a very long time...).

I hope my question is understandable :) Thanks for any help!