GStreamer Plugin using OpenCV corrupts Video and Images

[Mandar Joshi]

Hello everyone,
I am writing a simple GStreamer element that converts incoming frame
into grayscale using OpenCV. The relevant part of the *tranform (*
function is
-------------------------------------------------------------------------------------------------------
    GstMytest *filter = GST_MYTEST (trans);

    guint bufsize;
    gchar *outbuf;

    GstMapInfo map;
    if (gst_buffer_map (in, &map, GST_MAP_READ) == FALSE) {
        g_print ("gst_buffer_map failed\n");
        exit (1);
    }
    Mat image(Size(640,480), CV_8UC3, (char*)map.data, Mat::AUTO_STEP);
    Mat edges;

    cvtColor(image, edges, CV_BGR2GRAY);
    unsigned char *processedData = (unsigned char*)edges.data;

    imwrite("snapshot.png",edges);
    gst_buffer_fill(out, 0, processedData, 640*480*1);
    gst_buffer_unmap (in, &map);
    return GST_FLOW_OK;
-------------------------------------------------------------------------------------------------------------
This gives me an output like this http://imgur.com/LQDEPRH
It is live video but it's corrupted somehow.
Replacing cvtColor with edges=image and setting 640*480*3 in
gst_buffer_fill gives me untouched live video. Doing processing with
cvtColor seems to be causing the problem.

The pipeline I use is
GST_PLUGIN_PATH=. gst-launch-1.0 -v videotestsrc !
video/x-raw,height=480,width=640,format=BGR ! videoconvert !  mytest !
xvimagesink sync=false

For compiling this plugin are:
g++ gstmytest.c -fPIC -c -o gstmytest.o `pkg-config --cflags
gstreamer-1.0  gstreamer-base-1.0 gstreamer-video-1.0 opencv`
g++ -shared -o libgstmytest.so gstmytest.o `pkg-config --libs
gstreamer-1.0  gstreamer-base-1.0 gstreamer-video-1.0 opencv`

I am using
gstreamer1-1.6.2-1.fc23.x86_64
opencv-2.4.12.3-1.fc23.x86_64

I've attached the source. Please have a look

Regards
Mandar Joshi
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