Segmentation Fault When OpenCV Program run as a Video Filter Plugin for VLC

asked 2016-04-29 01:17:02 -0500

Pawan gravatar image

I Downloaded the OpenCV 3.1 source code and compiled it using MinGW. Make Files are generated using CMake. I also turned on the CMake_GNUtoMS option CMake so that .lib files are generated along with .a files.

Now i have written a VLC OpenCV filter which conatins Code for FaceDetection (reference). This filter compiles fine (linked to opencv_world310.lib) but when i run a test program which tells VLC to use this Filter i get a Segmentation Fault at cv::CascadeClassifier::load(cv::String const&). I have tried running it after linking this Filter against opencv_world310.dll.a but the same Error persists.

Filter code:

using namespace cv;

struct filter_sys_t
{
    CascadeClassifier detector;
};


static int  OpenFilter ( vlc_object_t * );
static void CloseFilter( vlc_object_t * );

static picture_t *Filter( filter_t *, picture_t * );

vlc_module_begin ()
    // Set vlc Description, Shortname, Capability, Category .etc
    set_callbacks( OpenFilter, CloseFilter )
vlc_module_end ()


static int OpenFilter( vlc_object_t *p_this )
{
    filter_t *p_filter = (filter_t*)p_this;

    filter_sys_t *p_sys;

    /* Allocate the memory needed to store the decoder's structure */
    if( ( p_filter->p_sys = p_sys =
          (filter_sys_t *)malloc(sizeof(filter_sys_t)) ) == NULL )
    {
        return VLC_ENOMEM;
    }

    //init the video_filter_event_info_t struct

    //create the VIDEO_FILTER_EVENT_VARIABLE


    cv::String f = "C:\\OpenCV\\sources\\data\\haarcascades\\haarcascade_frontalface_alt.xml";

    msg_Dbg(p_filter, "going to load detector");

    bool loaded = p_sys->detector.load(f);

    msg_Dbg( p_filter, "detector loaded %d", loaded);

    if (!loaded)
    {
        return VLC_EGENERIC;
    }

    return VLC_SUCCESS;
}

/*****************************************************************************
 * CloseFilter: clean up the filter
 *****************************************************************************/
static void CloseFilter( vlc_object_t *p_this )
{
    filter_t *p_filter = (filter_t*)p_this;
    filter_sys_t *p_sys = p_filter->p_sys;

    free( p_sys );

    var_Destroy( p_filter->p_libvlc, VIDEO_FILTER_EVENT_VARIABLE);
}

/****************************************************************************
 * Filter: Check for faces and raises an event when one is found.
 ****************************************************************************/
static picture_t *Filter( filter_t *p_filter, picture_t *p_pic )
{
    msg_Dbg( p_filter, "Entered Filter()");
    int groundThreshold = 2;
    double scaleStep = 1.1;
    Size minimalObjectSize(80, 80);
    Size maximalObjectSize(200, 200);

    IplImage** p_img = NULL;
    filter_sys_t *p_sys = p_filter->p_sys;

    if ((!p_pic) )
    {
        msg_Err( p_filter, "no image array" );
        return NULL;
    }

    //cast the picture_t to array of IplImage*
    p_img = (IplImage**) p_pic;

    //check the image array for validity
    if ((!p_img[0]))    //1st plane is 'I' i.e. greyscale
    {
        msg_Err( p_filter, "no image" );
        return NULL;
    }
    msg_Dbg( p_filter, "Going to convert iplImage to MAT");
    Mat img = cvarrToMat(p_img);
    Mat image_grey;
    // Convert input to greyscale 
    cvtColor(img, image_grey, CV_BGR2GRAY);

    //perform face detection
    std::vector<Rect> found;

    msg_Dbg( p_filter, "Going to detect face");
    //// Detect faces
    p_sys->detector.detectMultiScale(image_grey, found, scaleStep, groundThreshold, 0 | 2, minimalObjectSize,maximalObjectSize);

    ////// Draw the results into mat 
    if (found.size() > 0) {
        msg_Dbg( p_filter, "Faces Found: %d", found.size());
            for (int i = 0; i <= found.size() - 1; i++) {

                    rectangle(img, found[i].br(), found[i].tl(), Scalar(0, 255, 0), 1, 8, 0);

            }
    }
    return p_pic;
}

BUT when i run the FaceDetection Code as a independent program (linked against the same .lib/.a and Using Same opencv_world310.dll) it Works Good.

ERROR that i get:

Program received signal SIGSEGV, Segmentation fault.
0x0c300bcd in cv::CascadeClassifier::load(cv::String const&) ()
   from C:\Windows\SysWOW64\libopencv_world310.dll
(gdb) bt
#0  0x0c300bcd in cv::CascadeClassifier::load(cv::String const&) ()
   from C:\Windows\SysWOW64\libopencv_world310.dll
#1  0x088593a8 in ?? ()
#2  0x6a7bef8a in module_need ()
   from C:\test\libvlccore.dll
#3  0x0925a2c1 in vlc_entry_license__1_1_0g ()
   from C:\test\libopencv_wrapper_plugin.dll
#4  0x00000001 in ...
(more)
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