root/modules/videoio/src/cap_gstreamer.cpp

DEFINITIONS

1. init
2. init
3. close
4. grabFrame
5. retrieveFrame
6. isPipelinePlaying
7. startPipeline
8. stopPipeline
9. restartPipeline
10. setFilter
11. removeFilter
12. newPad
13. open
14. getProperty
15. setProperty
16. cvCreateCapture_GStreamer
17. init
18. close
19. filenameToMimetype
20. open
21. writeFrame
22. cvCreateVideoWriter_GStreamer
23. toFraction
24. handleMessage

/*M///////////////////////////////////////////////////////////////////////////////////////
//
//  IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING.
//
//  By downloading, copying, installing or using the software you agree to this license.
//  If you do not agree to this license, do not download, install,
//  copy or use the software.
//
//
//                        Intel License Agreement
//                For Open Source Computer Vision Library
//
// Copyright (C) 2008, 2011, Nils Hasler, all rights reserved.
// Third party copyrights are property of their respective owners.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
//   * Redistribution's of source code must retain the above copyright notice,
//     this list of conditions and the following disclaimer.
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// (including, but not limited to, procurement of substitute goods or services;
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// and on any theory of liability, whether in contract, strict liability,
// or tort (including negligence or otherwise) arising in any way out of
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//
//M*/

/*!
 * \file cap_gstreamer.cpp
 * \author Nils Hasler <hasler@mpi-inf.mpg.de>
 *         Max-Planck-Institut Informatik
 * \author Dirk Van Haerenborgh <vhdirk@gmail.com>
 *
 * \brief Use GStreamer to read/write video
 */
#include "precomp.hpp"
#include <unistd.h>
#include <string.h>
#include <gst/gst.h>
#include <gst/gstbuffer.h>
#include <gst/video/video.h>
#include <gst/app/gstappsink.h>
#include <gst/app/gstappsrc.h>
#include <gst/riff/riff-media.h>
#include <gst/pbutils/missing-plugins.h>

#define VERSION_NUM(major, minor, micro) (major * 1000000 + minor * 1000 + micro)
#define FULL_GST_VERSION VERSION_NUM(GST_VERSION_MAJOR, GST_VERSION_MINOR, GST_VERSION_MICRO)

#if FULL_GST_VERSION >= VERSION_NUM(0,10,32)
#include <gst/pbutils/encoding-profile.h>
//#include <gst/base/gsttypefindhelper.h>
#endif


#ifdef NDEBUG
#define CV_WARN(message)
#else
#define CV_WARN(message) fprintf(stderr, "warning: %s (%s:%d)\n", message, __FILE__, __LINE__)
#endif

#if GST_VERSION_MAJOR == 0
#define COLOR_ELEM "ffmpegcolorspace"
#elif FULL_GST_VERSION < VERSION_NUM(1,5,0)
#define COLOR_ELEM "videoconvert"
#else
#define COLOR_ELEM "autovideoconvert"
#endif

void toFraction(double decimal, double &numerator, double &denominator);
void handleMessage(GstElement * pipeline);


static cv::Mutex gst_initializer_mutex;

/*!
 * \brief The gst_initializer class
 * Initializes gstreamer once in the whole process
 */
class gst_initializer
{
public:
    static void init()
    {
        gst_initializer_mutex.lock();
        static gst_initializer init;
        gst_initializer_mutex.unlock();
    }
private:
    gst_initializer()
    {
        gst_init(NULL, NULL);
//        gst_debug_set_active(1);
//        gst_debug_set_colored(1);
//        gst_debug_set_default_threshold(GST_LEVEL_INFO);
    }
};

/*!
 * \brief The CvCapture_GStreamer class
 * Use GStreamer to capture video
 */
class CvCapture_GStreamer : public CvCapture
{
public:
    CvCapture_GStreamer() { init(); }
    virtual ~CvCapture_GStreamer() { close(); }

    virtual bool open( int type, const char* filename );
    virtual void close();

    virtual double getProperty(int) const;
    virtual bool setProperty(int, double);
    virtual bool grabFrame();
    virtual IplImage* retrieveFrame(int);

protected:
    void init();
    bool reopen();
    bool isPipelinePlaying();
    void startPipeline();
    void stopPipeline();
    void restartPipeline();
    void setFilter(const char* prop, int type, int v1, int v2 = 0);
    void removeFilter(const char *filter);
    static void newPad(GstElement *myelement,
                       GstPad     *pad,
                       gpointer    data);
    GstElement*   pipeline;
    GstElement*   uridecodebin;
    GstElement*   color;
    GstElement*   sink;
#if GST_VERSION_MAJOR > 0
    GstSample*    sample;
    GstMapInfo*   info;
#endif
    GstBuffer*    buffer;
    GstCaps*      caps;
    IplImage*     frame;
    gint64        duration;
    gint          width;
    gint          height;
    double        fps;
};

/*!
 * \brief CvCapture_GStreamer::init
 * inits the class
 */
void CvCapture_GStreamer::init()
{
    pipeline = NULL;
    uridecodebin = NULL;
    color = NULL;
    sink = NULL;
#if GST_VERSION_MAJOR > 0
    sample = NULL;
    info = new GstMapInfo;
#endif
    buffer = NULL;
    caps = NULL;
    frame = NULL;
    duration = -1;
    width = -1;
    height = -1;
    fps = -1;
}

/*!
 * \brief CvCapture_GStreamer::close
 * Closes the pipeline and destroys all instances
 */
void CvCapture_GStreamer::close()
{
    if (isPipelinePlaying())
        this->stopPipeline();

    if(pipeline) {
        gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_NULL);
        gst_object_unref(GST_OBJECT(pipeline));
        pipeline = NULL;
    }

    duration = -1;
    width = -1;
    height = -1;
    fps = -1;
}

/*!
 * \brief CvCapture_GStreamer::grabFrame
 * \return
 * Grabs a sample from the pipeline, awaiting consumation by retreiveFrame.
 * The pipeline is started if it was not running yet
 */
bool CvCapture_GStreamer::grabFrame()
{
    if(!pipeline)
        return false;

    // start the pipeline if it was not in playing state yet
    if(!this->isPipelinePlaying())
        this->startPipeline();

    // bail out if EOS
    if(gst_app_sink_is_eos(GST_APP_SINK(sink)))
        return false;

#if GST_VERSION_MAJOR == 0
    if(buffer)
        gst_buffer_unref(buffer);

    buffer = gst_app_sink_pull_buffer(GST_APP_SINK(sink));
#else
    if(sample)
        gst_sample_unref(sample);

    sample = gst_app_sink_pull_sample(GST_APP_SINK(sink));

    if(!sample)
        return false;

    buffer = gst_sample_get_buffer(sample);
#endif

    if(!buffer)
        return false;

    return true;
}

/*!
 * \brief CvCapture_GStreamer::retrieveFrame
 * \return IplImage pointer. [Transfer Full]
 *  Retreive the previously grabbed buffer, and wrap it in an IPLImage structure
 */
IplImage * CvCapture_GStreamer::retrieveFrame(int)
{
    if(!buffer)
        return 0;

    //construct a frame header if we did not have any yet
    if(!frame)
    {
#if GST_VERSION_MAJOR == 0
        GstCaps* buffer_caps = gst_buffer_get_caps(buffer);
#else
        GstCaps* buffer_caps = gst_sample_get_caps(sample);
#endif
        // bail out in no caps
        assert(gst_caps_get_size(buffer_caps) == 1);
        GstStructure* structure = gst_caps_get_structure(buffer_caps, 0);

        // bail out if width or height are 0
        if(!gst_structure_get_int(structure, "width", &width) ||
                !gst_structure_get_int(structure, "height", &height))
        {
            gst_caps_unref(buffer_caps);
            return 0;
        }

        int depth = 3;
#if GST_VERSION_MAJOR > 0
        depth = 0;
        const gchar* name = gst_structure_get_name(structure);
        const gchar* format = gst_structure_get_string(structure, "format");

        if (!name || !format)
            return 0;

        // we support 3 types of data:
        //     video/x-raw, format=BGR   -> 8bit, 3 channels
        //     video/x-raw, format=GRAY8 -> 8bit, 1 channel
        //     video/x-bayer             -> 8bit, 1 channel
        // bayer data is never decoded, the user is responsible for that
        // everything is 8 bit, so we just test the caps for bit depth

        if (strcasecmp(name, "video/x-raw") == 0)
        {
            if (strcasecmp(format, "BGR") == 0) {
                depth = 3;
            }
            else if(strcasecmp(format, "GRAY8") == 0){
                depth = 1;
            }
        }
        else if (strcasecmp(name, "video/x-bayer") == 0)
        {
            depth = 1;
        }
#endif
        if (depth > 0) {
            frame = cvCreateImageHeader(cvSize(width, height), IPL_DEPTH_8U, depth);
        } else {
            gst_caps_unref(buffer_caps);
            return 0;
        }

        gst_caps_unref(buffer_caps);
    }

    // gstreamer expects us to handle the memory at this point
    // so we can just wrap the raw buffer and be done with it
#if GST_VERSION_MAJOR == 0
    frame->imageData = (char *)GST_BUFFER_DATA(buffer);
#else
    // the data ptr in GstMapInfo is only valid throughout the mapifo objects life.
    // TODO: check if reusing the mapinfo object is ok.

    gboolean success = gst_buffer_map(buffer,info, (GstMapFlags)GST_MAP_READ);
    if (!success){
        //something weird went wrong here. abort. abort.
        //fprintf(stderr,"GStreamer: unable to map buffer");
        return 0;
    }
    frame->imageData = (char*)info->data;
    gst_buffer_unmap(buffer,info);
#endif

    return frame;
}


/*!
 * \brief CvCapture_GStreamer::isPipelinePlaying
 * \return if the pipeline is currently playing.
 */
bool CvCapture_GStreamer::isPipelinePlaying()
{
    GstState current, pending;
    GstClockTime timeout = 5*GST_SECOND;
    if(!GST_IS_ELEMENT(pipeline)){
        return false;
    }

    GstStateChangeReturn ret = gst_element_get_state(GST_ELEMENT(pipeline),&current, &pending, timeout);
    if (!ret){
        //fprintf(stderr, "GStreamer: unable to query pipeline state\n");
        return false;
    }

    return current == GST_STATE_PLAYING;
}

/*!
 * \brief CvCapture_GStreamer::startPipeline
 * Start the pipeline by setting it to the playing state
 */
void CvCapture_GStreamer::startPipeline()
{
    CV_FUNCNAME("icvStartPipeline");

    __BEGIN__;

    //fprintf(stderr, "relinked, pausing\n");
    GstStateChangeReturn status = gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_PLAYING);
    if (status == GST_STATE_CHANGE_ASYNC)
    {
        // wait for status update
        GstState st1;
        GstState st2;
        status = gst_element_get_state(pipeline, &st1, &st2, GST_CLOCK_TIME_NONE);
    }
    if (status == GST_STATE_CHANGE_FAILURE)
    {
        handleMessage(pipeline);
        gst_object_unref(pipeline);
        pipeline = NULL;
        CV_ERROR(CV_StsError, "GStreamer: unable to start pipeline\n");
        return;
    }

    //printf("state now playing\n");
    handleMessage(pipeline);
    __END__;
}


/*!
 * \brief CvCapture_GStreamer::stopPipeline
 * Stop the pipeline by setting it to NULL
 */
void CvCapture_GStreamer::stopPipeline()
{
    CV_FUNCNAME("icvStopPipeline");

    __BEGIN__;

    //fprintf(stderr, "restarting pipeline, going to ready\n");
    if(gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_NULL) ==
            GST_STATE_CHANGE_FAILURE) {
        CV_ERROR(CV_StsError, "GStreamer: unable to stop pipeline\n");
        gst_object_unref(pipeline);
        pipeline = NULL;
        return;
    }
    __END__;
}

/*!
 * \brief CvCapture_GStreamer::restartPipeline
 * Restart the pipeline
 */
void CvCapture_GStreamer::restartPipeline()
{
    handleMessage(pipeline);

    this->stopPipeline();
    this->startPipeline();
}


/*!
 * \brief CvCapture_GStreamer::setFilter
 * \param prop the property name
 * \param type glib property type
 * \param v1 the value
 * \param v2 second value of property type requires it, else NULL
 * Filter the output formats by setting appsink caps properties
 */
void CvCapture_GStreamer::setFilter(const char *prop, int type, int v1, int v2)
{
    //printf("GStreamer: setFilter \n");
    if(!caps || !( GST_IS_CAPS (caps) ))
    {
        if(type == G_TYPE_INT)
        {
#if GST_VERSION_MAJOR == 0
            caps = gst_caps_new_simple("video/x-raw-rgb", prop, type, v1, NULL);
#else
            caps = gst_caps_new_simple("video/x-raw","format",G_TYPE_STRING,"BGR", prop, type, v1, NULL);
#endif
        }
        else
        {
#if GST_VERSION_MAJOR == 0
            caps = gst_caps_new_simple("video/x-raw-rgb", prop, type, v1, v2, NULL);
#else
            caps = gst_caps_new_simple("video/x-raw","format",G_TYPE_STRING,"BGR", prop, type, v1, v2, NULL);
#endif
        }
    }
    else
    {
#if GST_VERSION_MAJOR > 0
        if (! gst_caps_is_writable(caps))
            caps = gst_caps_make_writable (caps);
#endif
        if(type == G_TYPE_INT){
            gst_caps_set_simple(caps, prop, type, v1, NULL);
        }else{
            gst_caps_set_simple(caps, prop, type, v1, v2, NULL);
        }
    }

#if GST_VERSION_MAJOR > 0
    caps = gst_caps_fixate(caps);
#endif

    gst_app_sink_set_caps(GST_APP_SINK(sink), caps);
    //printf("filtering with %s\n", gst_caps_to_string(caps));
}


/*!
 * \brief CvCapture_GStreamer::removeFilter
 * \param filter filter to remove
 * remove the specified filter from the appsink template caps
 */
void CvCapture_GStreamer::removeFilter(const char *filter)
{
    if(!caps)
        return;

#if GST_VERSION_MAJOR > 0
    if (! gst_caps_is_writable(caps))
        caps = gst_caps_make_writable (caps);
#endif

    GstStructure *s = gst_caps_get_structure(caps, 0);
    gst_structure_remove_field(s, filter);

    gst_app_sink_set_caps(GST_APP_SINK(sink), caps);
}

/*!
 * \brief CvCapture_GStreamer::newPad link dynamic padd
 * \param pad
 * \param data
 * decodebin creates pads based on stream information, which is not known upfront
 * on receiving the pad-added signal, we connect it to the colorspace conversion element
 */
void CvCapture_GStreamer::newPad(GstElement * /*elem*/,
                                 GstPad     *pad,
                                 gpointer    data)
{
    GstPad *sinkpad;
    GstElement *color = (GstElement *) data;

    sinkpad = gst_element_get_static_pad (color, "sink");
    if (!sinkpad){
        //fprintf(stderr, "Gstreamer: no pad named sink\n");
        return;
    }

    gst_pad_link (pad, sinkpad);
    gst_object_unref (sinkpad);
}

/*!
 * \brief CvCapture_GStreamer::open Open the given file with gstreamer
 * \param type CvCapture type. One of CV_CAP_GSTREAMER_*
 * \param filename Filename to open in case of CV_CAP_GSTREAMER_FILE
 * \return boolean. Specifies if opening was successful.
 *
 * In case of CV_CAP_GSTREAMER_V4L(2), a pipelin is constructed as follows:
 *    v4l2src ! autoconvert ! appsink
 *
 *
 * The 'filename' parameter is not limited to filesystem paths, and may be one of the following:
 *
 *  - a normal filesystem path:
 *        e.g. video.avi or /path/to/video.avi or C:\\video.avi
 *  - an uri:
 *        e.g. file:///path/to/video.avi or rtsp:///path/to/stream.asf
 *  - a gstreamer pipeline description:
 *        e.g. videotestsrc ! videoconvert ! appsink
 *        the appsink name should be either 'appsink0' (the default) or 'opencvsink'
 *
 *  When dealing with a file, CvCapture_GStreamer will not drop frames if the grabbing interval
 *  larger than the framerate period. (Unlike the uri or manual pipeline description, which assume
 *  a live source)
 *
 *  The pipeline will only be started whenever the first frame is grabbed. Setting pipeline properties
 *  is really slow if we need to restart the pipeline over and over again.
 *
 *  TODO: the 'type' parameter is imo unneeded. for v4l2, filename 'v4l2:///dev/video0' can be used.
 *  I expect this to be the same for CV_CAP_GSTREAMER_1394. Is anyone actually still using v4l (v1)?
 *
 */
bool CvCapture_GStreamer::open( int type, const char* filename )
{
    CV_FUNCNAME("cvCaptureFromCAM_GStreamer");

    __BEGIN__;

    gst_initializer::init();

    bool file = false;
    bool stream = false;
    bool manualpipeline = false;
    char *uri = NULL;
    uridecodebin = NULL;
    GstElementFactory * testfac;
    GstStateChangeReturn status;

    if (type == CV_CAP_GSTREAMER_V4L){
        testfac = gst_element_factory_find("v4lsrc");
        if (!testfac){
            return false;
        }
        g_object_unref(G_OBJECT(testfac));
        filename = "v4lsrc ! " COLOR_ELEM " ! appsink";
    }
    if (type == CV_CAP_GSTREAMER_V4L2){
        testfac = gst_element_factory_find("v4l2src");
        if (!testfac){
            return false;
        }
        g_object_unref(G_OBJECT(testfac));
        filename = "v4l2src ! " COLOR_ELEM " ! appsink";
    }


    // test if we have a valid uri. If so, open it with an uridecodebin
    // else, we might have a file or a manual pipeline.
    // if gstreamer cannot parse the manual pipeline, we assume we were given and
    // ordinary file path.
    if(!gst_uri_is_valid(filename))
    {
        uri = realpath(filename, NULL);
        stream = false;
        if(uri)
        {
            uri = g_filename_to_uri(uri, NULL, NULL);
            if(uri)
            {
                file = true;
            }
            else
            {
                CV_WARN("GStreamer: Error opening file\n");
                close();
                return false;
            }
        }
        else
        {
            GError *err = NULL;
            uridecodebin = gst_parse_launch(filename, &err);
            if(!uridecodebin)
            {
                fprintf(stderr, "GStreamer: Error opening bin: %s\n", err->message);
                return false;
            }
            stream = true;
            manualpipeline = true;
        }
    } else {
        stream = true;
        uri = g_strdup(filename);
    }

    bool element_from_uri = false;
    if(!uridecodebin)
    {
        // At this writing, the v4l2 element (and maybe others too) does not support caps renegotiation.
        // This means that we cannot use an uridecodebin when dealing with v4l2, since setting
        // capture properties will not work.
        // The solution (probably only until gstreamer 1.2) is to make an element from uri when dealing with v4l2.
        gchar * protocol = gst_uri_get_protocol(uri);
        if (!strcasecmp(protocol , "v4l2"))
        {
#if GST_VERSION_MAJOR == 0
            uridecodebin = gst_element_make_from_uri(GST_URI_SRC, uri, "src");
#else
            uridecodebin = gst_element_make_from_uri(GST_URI_SRC, uri, "src", NULL);
#endif
            element_from_uri = true;
        }else{
            uridecodebin = gst_element_factory_make("uridecodebin", NULL);
            g_object_set(G_OBJECT(uridecodebin), "uri", uri, NULL);
        }
        g_free(protocol);

        if(!uridecodebin) {
            //fprintf(stderr, "GStreamer: Error opening bin: %s\n", err->message);
            close();
            return false;
        }
    }

    if(manualpipeline)
    {
        GstIterator *it = NULL;
#if GST_VERSION_MAJOR == 0
        it = gst_bin_iterate_sinks(GST_BIN(uridecodebin));
        if(gst_iterator_next(it, (gpointer *)&sink) != GST_ITERATOR_OK) {
            CV_ERROR(CV_StsError, "GStreamer: cannot find appsink in manual pipeline\n");
            return false;
        }
#else
        it = gst_bin_iterate_sinks (GST_BIN(uridecodebin));

        gboolean done = FALSE;
        GstElement *element = NULL;
        gchar* name = NULL;
        GValue value = G_VALUE_INIT;

        while (!done) {
          switch (gst_iterator_next (it, &value)) {
            case GST_ITERATOR_OK:
              element = GST_ELEMENT (g_value_get_object (&value));
              name = gst_element_get_name(element);
              if (name){
                if(strstr(name, "opencvsink") != NULL || strstr(name, "appsink") != NULL) {
                  sink = GST_ELEMENT ( gst_object_ref (element) );
                  done = TRUE;
                }
                g_free(name);
              }
              g_value_unset (&value);

              break;
            case GST_ITERATOR_RESYNC:
              gst_iterator_resync (it);
              break;
            case GST_ITERATOR_ERROR:
            case GST_ITERATOR_DONE:
              done = TRUE;
              break;
          }
        }
        gst_iterator_free (it);


        if (!sink){
            CV_ERROR(CV_StsError, "GStreamer: cannot find appsink in manual pipeline\n");
            return false;
        }
#endif
        pipeline = uridecodebin;
    }
    else
    {
        pipeline = gst_pipeline_new(NULL);
        // videoconvert (in 0.10: ffmpegcolorspace, in 1.x autovideoconvert)
        //automatically selects the correct colorspace conversion based on caps.
        color = gst_element_factory_make(COLOR_ELEM, NULL);
        sink = gst_element_factory_make("appsink", NULL);

        gst_bin_add_many(GST_BIN(pipeline), uridecodebin, color, sink, NULL);

        if(element_from_uri) {
            if(!gst_element_link(uridecodebin, color)) {
                CV_ERROR(CV_StsError, "GStreamer: cannot link color -> sink\n");
                gst_object_unref(pipeline);
                pipeline = NULL;
                return false;
            }
        }else{
            g_signal_connect(uridecodebin, "pad-added", G_CALLBACK(newPad), color);
        }

        if(!gst_element_link(color, sink)) {
            CV_ERROR(CV_StsError, "GStreamer: cannot link color -> sink\n");
            gst_object_unref(pipeline);
            pipeline = NULL;
            return false;
        }
    }

    //TODO: is 1 single buffer really high enough?
    gst_app_sink_set_max_buffers (GST_APP_SINK(sink), 1);
    gst_app_sink_set_drop (GST_APP_SINK(sink), stream);
    //do not emit signals: all calls will be synchronous and blocking
    gst_app_sink_set_emit_signals (GST_APP_SINK(sink), 0);

#if GST_VERSION_MAJOR == 0
    caps = gst_caps_new_simple("video/x-raw-rgb",
                               "bpp",        G_TYPE_INT, 24,
                               "red_mask",   G_TYPE_INT, 0x0000FF,
                               "green_mask", G_TYPE_INT, 0x00FF00,
                               "blue_mask",  G_TYPE_INT, 0xFF0000,
                               NULL);
#else
    // support 1 and 3 channel 8 bit data, as well as bayer (also  1 channel, 8bit)
    caps = gst_caps_from_string("video/x-raw, format=(string){BGR, GRAY8}; video/x-bayer,format=(string){rggb,bggr,grbg,gbrg}");
#endif
    gst_app_sink_set_caps(GST_APP_SINK(sink), caps);
    gst_caps_unref(caps);

    // For video files only: set pipeline to PAUSED state to get its duration
    if (file)
    {
        status = gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_PAUSED);
        if (status == GST_STATE_CHANGE_ASYNC)
        {
            // wait for status update
            GstState st1;
            GstState st2;
            status = gst_element_get_state(pipeline, &st1, &st2, GST_CLOCK_TIME_NONE);
        }
        if (status == GST_STATE_CHANGE_FAILURE)
        {
            handleMessage(pipeline);
            gst_object_unref(pipeline);
            pipeline = NULL;
            CV_ERROR(CV_StsError, "GStreamer: unable to start pipeline\n");
            return false;
        }

        GstFormat format;

        format = GST_FORMAT_DEFAULT;
#if GST_VERSION_MAJOR == 0
        if(!gst_element_query_duration(sink, &format, &duration))
#else
        if(!gst_element_query_duration(sink, format, &duration))
#endif
        {
            handleMessage(pipeline);
            CV_WARN("GStreamer: unable to query duration of stream");
            duration = -1;
        }

        GstPad* pad = gst_element_get_static_pad(color, "src");
#if GST_VERSION_MAJOR == 0
        GstCaps* buffer_caps = gst_pad_get_caps(pad);
#else
        GstCaps* buffer_caps = gst_pad_get_current_caps(pad);
#endif
        const GstStructure *structure = gst_caps_get_structure (buffer_caps, 0);

        if (!gst_structure_get_int (structure, "width", &width))
        {
            CV_WARN("Cannot query video width\n");
        }

        if (!gst_structure_get_int (structure, "height", &height))
        {
            CV_WARN("Cannot query video heigth\n");
        }

        gint num = 0, denom=1;
        if(!gst_structure_get_fraction(structure, "framerate", &num, &denom))
        {
            CV_WARN("Cannot query video fps\n");
        }

        fps = (double)num/(double)denom;

         // GST_DEBUG_BIN_TO_DOT_FILE(GST_BIN(pipeline), GST_DEBUG_GRAPH_SHOW_ALL, "pipeline");
    }
    else
    {
        duration = -1;
        width = -1;
        height = -1;
        fps = -1;
    }

    __END__;

    return true;
}

/*!
 * \brief CvCapture_GStreamer::getProperty retreive the requested property from the pipeline
 * \param propId requested property
 * \return property value
 *
 * There are two ways the properties can be retreived. For seek-based properties we can query the pipeline.
 * For frame-based properties, we use the caps of the lasst receivef sample. This means that some properties
 * are not available until a first frame was received
 */
double CvCapture_GStreamer::getProperty( int propId ) const
{
    GstFormat format;
    gint64 value;
    gboolean status;

#if GST_VERSION_MAJOR == 0
#define FORMAT &format
#else
#define FORMAT format
#endif

    if(!pipeline) {
        CV_WARN("GStreamer: no pipeline");
        return false;
    }

    switch(propId) {
    case CV_CAP_PROP_POS_MSEC:
        format = GST_FORMAT_TIME;
        status = gst_element_query_position(sink, FORMAT, &value);
        if(!status) {
            CV_WARN("GStreamer: unable to query position of stream");
            return false;
        }
        return value * 1e-6; // nano seconds to milli seconds
    case CV_CAP_PROP_POS_FRAMES:
        format = GST_FORMAT_DEFAULT;
        status = gst_element_query_position(sink, FORMAT, &value);
        if(!status) {
            CV_WARN("GStreamer: unable to query position of stream");
            return false;
        }
        return value;
    case CV_CAP_PROP_POS_AVI_RATIO:
        format = GST_FORMAT_PERCENT;
        status = gst_element_query_position(sink, FORMAT, &value);
        if(!status) {
            CV_WARN("GStreamer: unable to query position of stream");
            return false;
        }
        return ((double) value) / GST_FORMAT_PERCENT_MAX;
    case CV_CAP_PROP_FRAME_WIDTH:
        return width;
    case CV_CAP_PROP_FRAME_HEIGHT:
        return height;
    case CV_CAP_PROP_FPS:
        return fps;
    case CV_CAP_PROP_FOURCC:
        break;
    case CV_CAP_PROP_FRAME_COUNT:
        return duration;
    case CV_CAP_PROP_FORMAT:
    case CV_CAP_PROP_MODE:
    case CV_CAP_PROP_BRIGHTNESS:
    case CV_CAP_PROP_CONTRAST:
    case CV_CAP_PROP_SATURATION:
    case CV_CAP_PROP_HUE:
    case CV_CAP_PROP_GAIN:
    case CV_CAP_PROP_CONVERT_RGB:
        break;
    case CV_CAP_GSTREAMER_QUEUE_LENGTH:
        if(!sink) {
            CV_WARN("GStreamer: there is no sink yet");
            return false;
        }
        return gst_app_sink_get_max_buffers(GST_APP_SINK(sink));
    default:
        CV_WARN("GStreamer: unhandled property");
        break;
    }

#undef FORMAT

    return false;
}

/*!
 * \brief CvCapture_GStreamer::setProperty
 * \param propId
 * \param value
 * \return success
 * Sets the desired property id with val. If the pipeline is running,
 * it is briefly stopped and started again after the property was set
 */
bool CvCapture_GStreamer::setProperty( int propId, double value )
{
    GstFormat format;
    GstSeekFlags flags;

    if(!pipeline) {
        CV_WARN("GStreamer: no pipeline");
        return false;
    }

    bool wasPlaying = this->isPipelinePlaying();
    if (wasPlaying)
        this->stopPipeline();


    switch(propId) {
    case CV_CAP_PROP_POS_MSEC:
        format = GST_FORMAT_TIME;
        flags = (GstSeekFlags) (GST_SEEK_FLAG_FLUSH|GST_SEEK_FLAG_ACCURATE);
        if(!gst_element_seek_simple(GST_ELEMENT(pipeline), format,
                                    flags, (gint64) (value * GST_MSECOND))) {
            CV_WARN("GStreamer: unable to seek");
        }
        break;
    case CV_CAP_PROP_POS_FRAMES:
        format = GST_FORMAT_DEFAULT;
        flags = (GstSeekFlags) (GST_SEEK_FLAG_FLUSH|GST_SEEK_FLAG_ACCURATE);
        if(!gst_element_seek_simple(GST_ELEMENT(pipeline), format,
                                    flags, (gint64) value)) {
            CV_WARN("GStreamer: unable to seek");
        }
        break;
    case CV_CAP_PROP_POS_AVI_RATIO:
        format = GST_FORMAT_PERCENT;
        flags = (GstSeekFlags) (GST_SEEK_FLAG_FLUSH|GST_SEEK_FLAG_ACCURATE);
        if(!gst_element_seek_simple(GST_ELEMENT(pipeline), format,
                                    flags, (gint64) (value * GST_FORMAT_PERCENT_MAX))) {
            CV_WARN("GStreamer: unable to seek");
        }
        break;
    case CV_CAP_PROP_FRAME_WIDTH:
        if(value > 0)
            setFilter("width", G_TYPE_INT, (int) value, 0);
        else
            removeFilter("width");
        break;
    case CV_CAP_PROP_FRAME_HEIGHT:
        if(value > 0)
            setFilter("height", G_TYPE_INT, (int) value, 0);
        else
            removeFilter("height");
        break;
    case CV_CAP_PROP_FPS:
        if(value > 0) {
            double num=0, denom = 1;
            toFraction(value, num,  denom);
            setFilter("framerate", GST_TYPE_FRACTION, value, denom);
        } else
            removeFilter("framerate");
        break;
    case CV_CAP_PROP_FOURCC:
    case CV_CAP_PROP_FRAME_COUNT:
    case CV_CAP_PROP_FORMAT:
    case CV_CAP_PROP_MODE:
    case CV_CAP_PROP_BRIGHTNESS:
    case CV_CAP_PROP_CONTRAST:
    case CV_CAP_PROP_SATURATION:
    case CV_CAP_PROP_HUE:
    case CV_CAP_PROP_GAIN:
    case CV_CAP_PROP_CONVERT_RGB:
        break;
    case CV_CAP_GSTREAMER_QUEUE_LENGTH:
        if(!sink)
            break;
        gst_app_sink_set_max_buffers(GST_APP_SINK(sink), (guint) value);
        break;
    default:
        CV_WARN("GStreamer: unhandled property");
    }

    if (wasPlaying)
        this->startPipeline();

    return false;
}

/*!
 * \brief cvCreateCapture_GStreamer
 * \param type
 * \param filename
 * \return
 */
CvCapture* cvCreateCapture_GStreamer(int type, const char* filename )
{
    CvCapture_GStreamer* capture = new CvCapture_GStreamer;

    if( capture->open( type, filename ))
        return capture;

    delete capture;
    return 0;
}


/*!
 * \brief The CvVideoWriter_GStreamer class
 * Use Gstreamer to write video
 */
class CvVideoWriter_GStreamer : public CvVideoWriter
{
public:
    CvVideoWriter_GStreamer() { init(); }
    virtual ~CvVideoWriter_GStreamer() { close(); }

    virtual bool open( const char* filename, int fourcc,
                       double fps, CvSize frameSize, bool isColor );
    virtual void close();
    virtual bool writeFrame( const IplImage* image );
protected:
    void init();
    const char* filenameToMimetype(const char* filename);
    GstElement* pipeline;
    GstElement* source;
    GstElement* encodebin;
    GstElement* file;

    GstBuffer* buffer;
    int input_pix_fmt;
    int num_frames;
    double framerate;
};

/*!
 * \brief CvVideoWriter_GStreamer::init
 * initialise all variables
 */
void CvVideoWriter_GStreamer::init()
{
    pipeline = NULL;
    source = NULL;
    encodebin = NULL;
    file = NULL;
    buffer = NULL;

    num_frames = 0;
    framerate = 0;
}

/*!
 * \brief CvVideoWriter_GStreamer::close
 * ends the pipeline by sending EOS and destroys the pipeline and all
 * elements afterwards
 */
void CvVideoWriter_GStreamer::close()
{
    GstStateChangeReturn status;
    if (pipeline)
    {
        handleMessage(pipeline);

        if (gst_app_src_end_of_stream(GST_APP_SRC(source)) != GST_FLOW_OK)
        {
            CV_WARN("Cannot send EOS to GStreamer pipeline\n");
            return;
        }

        //wait for EOS to trickle down the pipeline. This will let all elements finish properly
        GstBus* bus = gst_element_get_bus(pipeline);
        GstMessage *msg = gst_bus_timed_pop_filtered(bus, GST_CLOCK_TIME_NONE, (GstMessageType)(GST_MESSAGE_ERROR | GST_MESSAGE_EOS));
        if (GST_MESSAGE_TYPE(msg) == GST_MESSAGE_ERROR)
        {
            CV_WARN("Error during VideoWriter finalization\n");
            return;
        }

        if(msg != NULL)
        {
            gst_message_unref(msg);
            g_object_unref(G_OBJECT(bus));
        }

        status = gst_element_set_state (pipeline, GST_STATE_NULL);
        if (status == GST_STATE_CHANGE_ASYNC)
        {
            // wait for status update
            GstState st1;
            GstState st2;
            status = gst_element_get_state(pipeline, &st1, &st2, GST_CLOCK_TIME_NONE);
        }
        if (status == GST_STATE_CHANGE_FAILURE)
        {
            handleMessage (pipeline);
            gst_object_unref (GST_OBJECT (pipeline));
            pipeline = NULL;
            CV_WARN("Unable to stop gstreamer pipeline\n");
            return;
        }

        gst_object_unref (GST_OBJECT (pipeline));
        pipeline = NULL;
    }
}


/*!
 * \brief CvVideoWriter_GStreamer::filenameToMimetype
 * \param filename
 * \return mimetype
 * Resturns a container mime type for a given filename by looking at it's extension
 */
const char* CvVideoWriter_GStreamer::filenameToMimetype(const char *filename)
{
    //get extension
    const char *ext = strrchr(filename, '.');
    if(!ext || ext == filename) return NULL;
    ext += 1; //exclude the dot

    // return a container mime based on the given extension.
    // gstreamer's function returns too much possibilities, which is not useful to us

    //return the appropriate mime
    if (strncasecmp(ext,"avi", 3) == 0)
        return (const char*)"video/x-msvideo";

    if (strncasecmp(ext,"mkv", 3) == 0 || strncasecmp(ext,"mk3d",4) == 0  || strncasecmp(ext,"webm",4) == 0 )
        return (const char*)"video/x-matroska";

    if (strncasecmp(ext,"wmv", 3) == 0)
        return (const char*)"video/x-ms-asf";

    if (strncasecmp(ext,"mov", 3) == 0)
        return (const char*)"video/x-quicktime";

    if (strncasecmp(ext,"ogg", 3) == 0 || strncasecmp(ext,"ogv", 3) == 0)
        return (const char*)"application/ogg";

    if (strncasecmp(ext,"rm", 3) == 0)
        return (const char*)"vnd.rn-realmedia";

    if (strncasecmp(ext,"swf", 3) == 0)
        return (const char*)"application/x-shockwave-flash";

    if (strncasecmp(ext,"mp4", 3) == 0)
        return (const char*)"video/x-quicktime, variant=(string)iso";

    //default to avi
    return (const char*)"video/x-msvideo";
}

/*!
 * \brief CvVideoWriter_GStreamer::open
 * \param filename filename to output to
 * \param fourcc desired codec fourcc
 * \param fps desired framerate
 * \param frameSize the size of the expected frames
 * \param is_color color or grayscale
 * \return success
 *
 * We support 2 modes of operation. Either the user enters a filename and a fourcc
 * code, or enters a manual pipeline description like in CvVideoCapture_Gstreamer.
 * In the latter case, we just push frames on the appsink with appropriate caps.
 * In the former case, we try to deduce the correct container from the filename,
 * and the correct encoder from the fourcc profile.
 *
 * If the file extension did was not recognize, an avi container is used
 *
 */
bool CvVideoWriter_GStreamer::open( const char * filename, int fourcc,
                                    double fps, CvSize frameSize, bool is_color )
{
    CV_FUNCNAME("CvVideoWriter_GStreamer::open");

    // check arguments
    assert (filename);
    assert (fps > 0);
    assert (frameSize.width > 0  &&  frameSize.height > 0);

    // init gstreamer
    gst_initializer::init();

    // init vars
    bool manualpipeline = true;
    int  bufsize = 0;
    GError *err = NULL;
    const char* mime = NULL;
    GstStateChangeReturn stateret;

    GstCaps* caps = NULL;
    GstCaps* videocaps = NULL;

#if FULL_GST_VERSION >= VERSION_NUM(0,10,32)
    GstCaps* containercaps = NULL;
    GstEncodingContainerProfile* containerprofile = NULL;
    GstEncodingVideoProfile* videoprofile = NULL;
#endif

    GstIterator* it = NULL;
    gboolean done = FALSE;
    GstElement *element = NULL;
    gchar* name = NULL;

#if GST_VERSION_MAJOR == 0
    GstElement* splitter = NULL;
    GstElement* combiner = NULL;
#endif

    // we first try to construct a pipeline from the given string.
    // if that fails, we assume it is an ordinary filename

    __BEGIN__;

    encodebin = gst_parse_launch(filename, &err);
    manualpipeline = (encodebin != NULL);

    if(manualpipeline)
    {
#if GST_VERSION_MAJOR == 0
        it = gst_bin_iterate_sources(GST_BIN(encodebin));
        if(gst_iterator_next(it, (gpointer *)&source) != GST_ITERATOR_OK) {
            CV_ERROR(CV_StsError, "GStreamer: cannot find appsink in manual pipeline\n");
            return false;
        }
#else
        it = gst_bin_iterate_sources (GST_BIN(encodebin));
        GValue value = G_VALUE_INIT;

        while (!done) {
          switch (gst_iterator_next (it, &value)) {
            case GST_ITERATOR_OK:
              element = GST_ELEMENT (g_value_get_object (&value));
              name = gst_element_get_name(element);
              if (name){
                if(strstr(name, "opencvsrc") != NULL || strstr(name, "appsrc") != NULL) {
                  source = GST_ELEMENT ( gst_object_ref (element) );
                  done = TRUE;
                }
                g_free(name);
              }
              g_value_unset (&value);

              break;
            case GST_ITERATOR_RESYNC:
              gst_iterator_resync (it);
              break;
            case GST_ITERATOR_ERROR:
            case GST_ITERATOR_DONE:
              done = TRUE;
              break;
          }
        }
        gst_iterator_free (it);

        if (!source){
            CV_ERROR(CV_StsError, "GStreamer: cannot find appsrc in manual pipeline\n");
            return false;
        }
#endif
        pipeline = encodebin;
    }
    else
    {
        pipeline = gst_pipeline_new (NULL);

        // we just got a filename and a fourcc code.
        // first, try to guess the container from the filename
        //encodebin = gst_element_factory_make("encodebin", NULL);

        //proxy old non existing fourcc ids. These were used in previous opencv versions,
        //but do not even exist in gstreamer any more
        if (fourcc == CV_FOURCC('M','P','1','V')) fourcc = CV_FOURCC('M', 'P', 'G' ,'1');
        if (fourcc == CV_FOURCC('M','P','2','V')) fourcc = CV_FOURCC('M', 'P', 'G' ,'2');
        if (fourcc == CV_FOURCC('D','R','A','C')) fourcc = CV_FOURCC('d', 'r', 'a' ,'c');


        //create encoder caps from fourcc

        videocaps = gst_riff_create_video_caps(fourcc, NULL, NULL, NULL, NULL, NULL);
        if (!videocaps){
            CV_ERROR( CV_StsUnsupportedFormat, "Gstreamer Opencv backend does not support this codec.");
        }

        //create container caps from file extension
        mime = filenameToMimetype(filename);
        if (!mime) {
            CV_ERROR( CV_StsUnsupportedFormat, "Gstreamer Opencv backend does not support this file type.");
        }

#if FULL_GST_VERSION >= VERSION_NUM(0,10,32)
        containercaps = gst_caps_from_string(mime);

        //create encodebin profile
        containerprofile = gst_encoding_container_profile_new("container", "container", containercaps, NULL);
        videoprofile = gst_encoding_video_profile_new(videocaps, NULL, NULL, 1);
        gst_encoding_container_profile_add_profile(containerprofile, (GstEncodingProfile *) videoprofile);
#endif

        //create pipeline elements
        encodebin = gst_element_factory_make("encodebin", NULL);

#if FULL_GST_VERSION >= VERSION_NUM(0,10,32)
        g_object_set(G_OBJECT(encodebin), "profile", containerprofile, NULL);
#endif
        source = gst_element_factory_make("appsrc", NULL);
        file = gst_element_factory_make("filesink", NULL);
        g_object_set(G_OBJECT(file), "location", filename, NULL);
    }

    if (is_color)
    {
        input_pix_fmt = GST_VIDEO_FORMAT_BGR;
        bufsize = frameSize.width * frameSize.height * 3;

#if GST_VERSION_MAJOR == 0
        caps = gst_video_format_new_caps(GST_VIDEO_FORMAT_BGR,
                                         frameSize.width,
                                         frameSize.height,
                                         int(fps), 1,
                                         1, 1);
#else
        caps = gst_caps_new_simple("video/x-raw",
                                   "format", G_TYPE_STRING, "BGR",
                                   "width", G_TYPE_INT, frameSize.width,
                                   "height", G_TYPE_INT, frameSize.height,
                                   "framerate", GST_TYPE_FRACTION, int(fps), 1,
                                   NULL);
        caps = gst_caps_fixate(caps);

#endif

    }
    else
    {
#if FULL_GST_VERSION >= VERSION_NUM(0,10,29)
        input_pix_fmt = GST_VIDEO_FORMAT_GRAY8;
        bufsize = frameSize.width * frameSize.height;

#if GST_VERSION_MAJOR == 0
        caps = gst_video_format_new_caps(GST_VIDEO_FORMAT_GRAY8,
                                         frameSize.width,
                                         frameSize.height,
                                         int(fps), 1,
                                         1, 1);
#else
        caps = gst_caps_new_simple("video/x-raw",
                                   "format", G_TYPE_STRING, "GRAY8",
                                   "width", G_TYPE_INT, frameSize.width,
                                   "height", G_TYPE_INT, frameSize.height,
                                   "framerate", GST_TYPE_FRACTION, int(fps), 1,
                                   NULL);
        caps = gst_caps_fixate(caps);
#endif
#else
        CV_Assert(!"Gstreamer 0.10.29 or newer is required for grayscale input");
#endif
    }

    gst_app_src_set_caps(GST_APP_SRC(source), caps);
    gst_app_src_set_stream_type(GST_APP_SRC(source), GST_APP_STREAM_TYPE_STREAM);
    gst_app_src_set_size (GST_APP_SRC(source), -1);

    g_object_set(G_OBJECT(source), "format", GST_FORMAT_TIME, NULL);
    g_object_set(G_OBJECT(source), "block", 1, NULL);
    g_object_set(G_OBJECT(source), "is-live", 0, NULL);


    if(!manualpipeline)
    {
        g_object_set(G_OBJECT(file), "buffer-size", bufsize, NULL);
        gst_bin_add_many(GST_BIN(pipeline), source, encodebin, file, NULL);
        if(!gst_element_link_many(source, encodebin, file, NULL)) {
            CV_ERROR(CV_StsError, "GStreamer: cannot link elements\n");
        }
    }

#if GST_VERSION_MAJOR == 0
    // HACK: remove streamsplitter and streamcombiner from
    // encodebin pipeline to prevent early EOF event handling
    // We always fetch BGR or gray-scale frames, so combiner->spliter
    // endge in graph is useless.
    it = gst_bin_iterate_recurse (GST_BIN(encodebin));
    while (!done) {
      switch (gst_iterator_next (it, (void**)&element)) {
        case GST_ITERATOR_OK:
          name = gst_element_get_name(element);
          if (strstr(name, "streamsplitter"))
            splitter = element;
          else if (strstr(name, "streamcombiner"))
            combiner = element;
          break;
        case GST_ITERATOR_RESYNC:
          gst_iterator_resync (it);
          break;
        case GST_ITERATOR_ERROR:
          done = true;
          break;
        case GST_ITERATOR_DONE:
          done = true;
          break;
      }
    }

    gst_iterator_free (it);

    if (splitter && combiner)
    {
        gst_element_unlink(splitter, combiner);

        GstPad* src  = gst_element_get_pad(combiner, "src");
        GstPad* sink = gst_element_get_pad(combiner, "encodingsink");

        GstPad* srcPeer = gst_pad_get_peer(src);
        GstPad* sinkPeer = gst_pad_get_peer(sink);

        gst_pad_unlink(sinkPeer, sink);
        gst_pad_unlink(src, srcPeer);

        gst_pad_link(sinkPeer, srcPeer);

        src = gst_element_get_pad(splitter, "encodingsrc");
        sink = gst_element_get_pad(splitter, "sink");

        srcPeer = gst_pad_get_peer(src);
        sinkPeer = gst_pad_get_peer(sink);

        gst_pad_unlink(sinkPeer, sink);
        gst_pad_unlink(src, srcPeer);

        gst_pad_link(sinkPeer, srcPeer);
    }
#endif

    stateret = gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_PLAYING);
    if(stateret  == GST_STATE_CHANGE_FAILURE) {
        handleMessage(pipeline);
        CV_ERROR(CV_StsError, "GStreamer: cannot put pipeline to play\n");
    }

    framerate = fps;
    num_frames = 0;

    handleMessage(pipeline);

    __END__;

    return true;
}


/*!
 * \brief CvVideoWriter_GStreamer::writeFrame
 * \param image
 * \return
 * Pushes the given frame on the pipeline.
 * The timestamp for the buffer is generated from the framerate set in open
 * and ensures a smooth video
 */
bool CvVideoWriter_GStreamer::writeFrame( const IplImage * image )
{
    CV_FUNCNAME("CvVideoWriter_GStreamer::writerFrame");

    GstClockTime duration, timestamp;
    GstFlowReturn ret;
    int size;

    __BEGIN__;

    handleMessage(pipeline);

    if (input_pix_fmt == GST_VIDEO_FORMAT_BGR) {
        if (image->nChannels != 3 || image->depth != IPL_DEPTH_8U) {
            CV_ERROR(CV_StsUnsupportedFormat, "cvWriteFrame() needs images with depth = IPL_DEPTH_8U and nChannels = 3.");
        }
    }
#if FULL_GST_VERSION >= VERSION_NUM(0,10,29)
    else if (input_pix_fmt == GST_VIDEO_FORMAT_GRAY8) {
        if (image->nChannels != 1 || image->depth != IPL_DEPTH_8U) {
            CV_ERROR(CV_StsUnsupportedFormat, "cvWriteFrame() needs images with depth = IPL_DEPTH_8U and nChannels = 1.");
        }
    }
#endif
    else {
        CV_ERROR(CV_StsUnsupportedFormat, "cvWriteFrame() needs BGR or grayscale images\n");
        return false;
    }

    size = image->imageSize;
    duration = ((double)1/framerate) * GST_SECOND;
    timestamp = num_frames * duration;

    //gst_app_src_push_buffer takes ownership of the buffer, so we need to supply it a copy
#if GST_VERSION_MAJOR == 0
    buffer = gst_buffer_try_new_and_alloc (size);
    if (!buffer)
    {
        CV_ERROR(CV_StsBadSize, "Cannot create GStreamer buffer");
    }

    memcpy(GST_BUFFER_DATA (buffer), (guint8*)image->imageData, size);
    GST_BUFFER_DURATION(buffer) = duration;
    GST_BUFFER_TIMESTAMP(buffer) = timestamp;
#else
    buffer = gst_buffer_new_allocate (NULL, size, NULL);
    GstMapInfo info;
    gst_buffer_map(buffer, &info, (GstMapFlags)GST_MAP_READ);
    memcpy(info.data, (guint8*)image->imageData, size);
    gst_buffer_unmap(buffer, &info);
    GST_BUFFER_DURATION(buffer) = duration;
    GST_BUFFER_PTS(buffer) = timestamp;
    GST_BUFFER_DTS(buffer) = timestamp;
#endif
    //set the current number in the frame
    GST_BUFFER_OFFSET(buffer) =  num_frames;

    ret = gst_app_src_push_buffer(GST_APP_SRC(source), buffer);
    if (ret != GST_FLOW_OK) {
        CV_WARN("Error pushing buffer to GStreamer pipeline");
        return false;
    }

    //GST_DEBUG_BIN_TO_DOT_FILE(GST_BIN(pipeline), GST_DEBUG_GRAPH_SHOW_ALL, "pipeline");

    ++num_frames;

    __END__;

    return true;
}

/*!
 * \brief cvCreateVideoWriter_GStreamer
 * \param filename
 * \param fourcc
 * \param fps
 * \param frameSize
 * \param isColor
 * \return
 * Constructor
 */
CvVideoWriter* cvCreateVideoWriter_GStreamer(const char* filename, int fourcc, double fps,
                                             CvSize frameSize, int isColor )
{
    CvVideoWriter_GStreamer* wrt = new CvVideoWriter_GStreamer;
    if( wrt->open(filename, fourcc, fps,frameSize, isColor))
        return wrt;

    delete wrt;
    return 0;
}

// utility functions

/*!
 * \brief toFraction
 * \param decimal
 * \param numerator
 * \param denominator
 * Split a floating point value into numerator and denominator
 */
void toFraction(double decimal, double &numerator, double &denominator)
{
    double dummy;
    double whole;
    decimal = modf (decimal, &whole);
    for (denominator = 1; denominator<=100; denominator++){
        if (modf(denominator * decimal, &dummy) < 0.001f)
            break;
    }
    numerator = denominator * decimal;
}


/*!
 * \brief handleMessage
 * Handles gstreamer bus messages. Mainly for debugging purposes and ensuring clean shutdown on error
 */
void handleMessage(GstElement * pipeline)
{
    CV_FUNCNAME("handlemessage");

    GError *err = NULL;
    gchar *debug = NULL;
    GstBus* bus = NULL;
    GstStreamStatusType tp;
    GstElement * elem = NULL;
    GstMessage* msg  = NULL;

    __BEGIN__;
    bus = gst_element_get_bus(pipeline);

    while(gst_bus_have_pending(bus)) {
        msg = gst_bus_pop(bus);

        //printf("Got %s message\n", GST_MESSAGE_TYPE_NAME(msg));

        if(gst_is_missing_plugin_message(msg))
        {
            CV_ERROR(CV_StsError, "GStreamer: your gstreamer installation is missing a required plugin\n");
        }
        else
        {
            switch (GST_MESSAGE_TYPE (msg)) {
            case GST_MESSAGE_STATE_CHANGED:
                GstState oldstate, newstate, pendstate;
                gst_message_parse_state_changed(msg, &oldstate, &newstate, &pendstate);
                //fprintf(stderr, "state changed from %s to %s (pending: %s)\n", gst_element_state_get_name(oldstate),
                //                gst_element_state_get_name(newstate), gst_element_state_get_name(pendstate));
                break;
            case GST_MESSAGE_ERROR:
                gst_message_parse_error(msg, &err, &debug);
                fprintf(stderr, "GStreamer Plugin: Embedded video playback halted; module %s reported: %s\n",
                                gst_element_get_name(GST_MESSAGE_SRC (msg)), err->message);

                g_error_free(err);
                g_free(debug);

                gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_NULL);
                break;
            case GST_MESSAGE_EOS:
                //fprintf(stderr, "reached the end of the stream.");
                break;
            case GST_MESSAGE_STREAM_STATUS:
                gst_message_parse_stream_status(msg,&tp,&elem);
                //fprintf(stderr, "stream status: elem %s, %i\n", GST_ELEMENT_NAME(elem), tp);
                break;
            default:
                //fprintf(stderr, "unhandled message %s\n",GST_MESSAGE_TYPE_NAME(msg));
                break;
            }
        }
        gst_message_unref(msg);
    }

    gst_object_unref(GST_OBJECT(bus));

    __END__
}