opencv/modules/videoio/src/cap_gstreamer.cpp

/*M///////////////////////////////////////////////////////////////////////////////////////
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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 "videoconvert"
#else
#define COLOR_ELEM "ffmpegcolorspace"
#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);
    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;
    GstCaps*      buffer_caps;
    IplImage*     frame;
};

/*!
 * \brief CvCapture_GStreamer::init
 * inits the class
 */
void CvCapture_GStreamer::init()
{
    pipeline = NULL;
    frame = NULL;
    buffer = NULL;
    buffer_caps = NULL;
#if GST_VERSION_MAJOR > 0
    sample = NULL;
    info = new GstMapInfo;
#endif
}

/*!
 * \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));
    }
    if(uridecodebin){
        gst_object_unref(GST_OBJECT(uridecodebin));
    }
    if(color){
        gst_object_unref(GST_OBJECT(color));
    }
    if(sink){
        gst_object_unref(GST_OBJECT(sink));
    }
    if(buffer)
        gst_buffer_unref(buffer);
    if(frame) {
        frame->imageData = 0;
        cvReleaseImage(&frame);
    }
    if(caps){
        gst_caps_unref(caps);
    }
    if(buffer_caps){
        gst_caps_unref(buffer_caps);
    }
#if GST_VERSION_MAJOR > 0
    if(sample){
        gst_sample_unref(sample);
    }
#endif

}

/*!
 * \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)
    {
        gint height, width;

        //reuse the caps ptr
        if (buffer_caps)
            gst_caps_unref(buffer_caps);

#if GST_VERSION_MAJOR == 0
        buffer_caps = gst_buffer_get_caps(buffer);
#else
        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))
        {
            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{
            return 0;
        }
    }

    // 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");
    if(gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_PLAYING) ==
            GST_STATE_CHANGE_FAILURE) {
        CV_ERROR(CV_StsError, "GStreamer: unable to start pipeline\n");
        gst_object_unref(pipeline);
        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);
        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 succesful.
 *
 * 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 stream = false;
    bool manualpipeline = false;
    char *uri = NULL;
    uridecodebin = NULL;
    GstElementFactory * testfac;

    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) {
                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);
                //close();
                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) 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);
                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);
            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);

    //we do not start recording here just yet.
    // the user probably wants to set capture properties first, so start recording whenever the first frame is requested
    __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 )
{
    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: {
        if (!buffer_caps){
            CV_WARN("GStreamer: unable to query width of frame; no frame grabbed yet");
            return 0;
        }
        GstStructure* structure = gst_caps_get_structure(buffer_caps, 0);
        gint width = 0;
        if(!gst_structure_get_int(structure, "width", &width)){
            CV_WARN("GStreamer: unable to query width of frame");
            return 0;
        }
        return width;
        break;
    }
    case CV_CAP_PROP_FRAME_HEIGHT: {
        if (!buffer_caps){
            CV_WARN("GStreamer: unable to query height of frame; no frame grabbed yet");
            return 0;
        }
        GstStructure* structure = gst_caps_get_structure(buffer_caps, 0);
        gint height = 0;
        if(!gst_structure_get_int(structure, "height", &height)){
            CV_WARN("GStreamer: unable to query height of frame");
            return 0;
        }
        return height;
        break;
    }
    case CV_CAP_PROP_FPS: {
        if (!buffer_caps){
            CV_WARN("GStreamer: unable to query framerate of stream; no frame grabbed yet");
            return 0;
        }
        GstStructure* structure = gst_caps_get_structure(buffer_caps, 0);
        gint num = 0, denom=1;
        if(!gst_structure_get_fraction(structure, "framerate", &num, &denom)){
            CV_WARN("GStreamer: unable to query framerate of stream");
            return 0;
        }
        return (double)num/(double)denom;
        break;
    }
    case CV_CAP_PROP_FOURCC:
        break;
    case CV_CAP_PROP_FRAME_COUNT:
        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_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()
{
    if (pipeline)
    {
        gst_app_src_end_of_stream(GST_APP_SRC(source));

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

        gst_element_set_state (pipeline, GST_STATE_NULL);
        handleMessage(pipeline);

        gst_object_unref (GST_OBJECT (pipeline));

        if (source)
          gst_object_unref (GST_OBJECT (source));

        if (file)
          gst_object_unref (GST_OBJECT (file));
    }
}


/*!
 * \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;

    // 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);
    if(!encodebin) {
        manualpipeline = false;
    }

    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));

        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, "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);
    g_object_set(G_OBJECT(source), "emit-signals", 1, 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");
        }
    }

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

    framerate = fps;
    num_frames = 0;

    __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 {
        assert(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_new_and_alloc (size);
    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) {
        /* something wrong, stop pushing */
        assert(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\n");
                break;
            }
        }
        gst_message_unref(msg);
    }

    gst_object_unref(GST_OBJECT(bus));

    __END__
}