Opencv video writer only writes 128byte files (os x el capitan) - c++

Question

So i tried several pieces of code now, all more or less similar, and they all only produce a 128 byte file. I want to record the webcam stream to file.
I don't believe this is a codec issue, i tried all of them and i still get only 128 bytes. Anyone know what the problem here is ? So far i only tried it on MacOS X.
For example below code:
#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
int main( int argc, char** argv ) {
CvCapture* capture;
capture = cvCreateCameraCapture(0);
assert( capture != NULL );
IplImage* bgr_frame = cvQueryFrame( capture );
CvSize size = cvSize(
(int)cvGetCaptureProperty( capture,
CV_CAP_PROP_FRAME_WIDTH),
(int)cvGetCaptureProperty( capture,
CV_CAP_PROP_FRAME_HEIGHT)
);
cvNamedWindow( "Webcam", CV_WINDOW_AUTOSIZE );
CvVideoWriter *writer = cvCreateVideoWriter( "vidtry.AVI",
CV_FOURCC('A','V','C','1'),
30,
size
);
while( (bgr_frame = cvQueryFrame( capture )) != NULL )
{
cvWriteFrame(writer, bgr_frame );
cvShowImage( "Webcam", bgr_frame );
char c = cvWaitKey( 33 );
if( c == 27 ) break;
}
cvReleaseVideoWriter( &writer );
cvReleaseCapture( &capture );
cvDestroyWindow( "Webcam" );
return( 0 );
}