When opening a file with GStreamer:

* if the filename looks like a URI, it is opened in non-blocking mode, cvQueryFrame() could skip frames or grab one frame more than once
* if the filename looks like a filename, it is opened in blocking mode. cvQueryFrame() grabs consecutive frames
* otherwise the filename is interpreted as a gstreamer pipeline as used with gst-launch. The last element of the pipeline has to have the property name=to-opencv

modules/highgui/src/cap_gstreamer.cpp

@@ -299,6 +299,8 @@ void CvCapture_GStreamer::newPad(GstElement *uridecodebin,
 
   sinkpad = gst_element_get_static_pad (color, "sink");
   
+//  printf("linking dynamic pad to colourconverter %p %p\n", uridecodebin, pad);
+
   gst_pad_link (pad, sinkpad);
 
   gst_object_unref (sinkpad);
@@ -311,52 +313,71 @@ bool CvCapture_GStreamer::open( int type, const char* filename )
 
     __BEGIN__;
 
-//	teststreamer(filename);
-
-//	return false;
-
     if(!isInited) {
 //        printf("gst_init\n");
         gst_init (NULL, NULL);
 
+//        gst_debug_set_active(TRUE);
+//        gst_debug_set_colored(TRUE);
+//        gst_debug_set_default_threshold(GST_LEVEL_WARNING);
 
         isInited = true;
     }
     bool stream = false;
+    bool manualpipeline = false;
     char *uri = NULL;
-	//const char *sourcetypes[] = {"dv1394src", "v4lsrc", "v4l2src", "filesrc"};
+    uridecodebin = NULL;
-	//printf("entered capturecreator %d\n", type);
+    if(type != CV_CAP_GSTREAMER_FILE) {
-    if  (type == CV_CAP_GSTREAMER_FILE) {	
-		if (!gst_uri_is_valid(filename)) {
-			uri=realpath(filename,NULL);
-			if (uri)
-				uri=g_filename_to_uri(uri,NULL,NULL);
-			else {
-				CV_WARN("Error opening file\n");
         close();
         return false;
     }
-			stream=false;
-		}
 
+    if(!gst_uri_is_valid(filename)) {
+//        printf("file '%s' is not uri\n", filename);
+        uri = realpath(filename, NULL);
+        stream=false;
+        if(uri) {
+//            printf("is file... ? %s\n", 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_bin_from_description(filename, FALSE, &err);
+            if(!uridecodebin) {
+                CV_WARN("GStreamer: Error opening bin\n");
+                close();
+                return false;
+            }
+            stream = true;
+//            printf("created custom bin\n");
+            manualpipeline = true;
+        }
+    }
     else {
+//        printf("file '%s' is uri\n", filename);
         stream = true;
         uri = g_strdup(filename);
-			printf("Trying to connect to stream \n");
     }
+
+    if(!uridecodebin) {
+//        printf("creating uridecodebin\n");
         uridecodebin = gst_element_factory_make ("uridecodebin", NULL);
         g_object_set(G_OBJECT(uridecodebin),"uri",uri, NULL);
+    }
     if(!uridecodebin) {
+        CV_WARN("GStreamer: Failed to create uridecodebin\n");
         close();
         return false;
     }
-	}	
+//    printf("Trying to connect to stream \n");
-	else {
-		close();
-		return false;
-	}	
     color = gst_element_factory_make("ffmpegcolorspace", NULL);
     
+    //printf("%sstreaming\n", stream ? "" : "not ");
+
 #ifdef HAVE_GSTREAMER_APP
     sink = gst_element_factory_make("appsink", NULL);
     gst_app_sink_set_max_buffers (GST_APP_SINK(sink),1);
@@ -371,33 +392,50 @@ bool CvCapture_GStreamer::open( int type, const char* filename )
                                        "green_mask", G_TYPE_INT, 65280,
                                        "blue_mask",  G_TYPE_INT, 16711680,
                                        NULL);
-    //GstCaps *caps=gst_video_format_new_caps(GST_VIDEO_FORMAT_BGR,,368,30,1,1,1);
     gst_app_sink_set_caps(GST_APP_SINK(sink), caps);
     gst_caps_unref(caps);
-	g_signal_connect(uridecodebin, "pad-added", G_CALLBACK(newPad), color);
 
     pipeline = gst_pipeline_new (NULL);
 
-	gst_bin_add_many(GST_BIN(pipeline), uridecodebin, color, sink, NULL);
+    //printf("adding stuff to pipeline\n");
-
+    if(manualpipeline) {
-	switch(type) {
+	// it is easier to link elements inside the same bin
-	case CV_CAP_GSTREAMER_V4L2: // default to 640x480, 30 fps
+        gst_bin_add_many(GST_BIN(uridecodebin), color, sink, NULL);
-		break;
+	// need the pipeline around the bin because bins don't know about timing
-	case CV_CAP_GSTREAMER_V4L:
+        gst_bin_add(GST_BIN(pipeline), uridecodebin);
-	case CV_CAP_GSTREAMER_1394:
-        break;
     }	
+    else {
+        gst_bin_add_many(GST_BIN(pipeline), uridecodebin, color, sink, NULL);
+    }
+
+    if(manualpipeline) {
+        GstElement *e = gst_bin_get_by_name(GST_BIN(uridecodebin), "to-opencv");
+        if(e) {
+	    if(!gst_element_link(e, color)) {
+		//printf("catching 'pad-added' for element 'to-opencv'\n");
+		g_signal_connect(e, "pad-added", G_CALLBACK(newPad), color);
+	    }/* else {
+		printf("linked to-opencv -> color\n");
+	    }*/
+            gst_object_unref(e);
+        } else {
+	    CV_WARN("GStreamer: no element with 'name=to-opencv'\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;
     }
 
-//	printf("linked, pausing\n");
-
     if(gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_READY) ==
        GST_STATE_CHANGE_FAILURE) {
-		CV_WARN("GStreamer: unable to set pipeline to paused\n");
+        CV_WARN("GStreamer: unable to set pipeline to ready\n");
 //        icvHandleMessage(capture);
 //        cvReleaseCapture((CvCapture **)(void *)&capture);
         gst_object_unref(pipeline);
@@ -406,7 +444,7 @@ bool CvCapture_GStreamer::open( int type, const char* filename )
 
     if(gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_PLAYING) ==
        GST_STATE_CHANGE_FAILURE) {
-		CV_WARN("GStreamer: unable to set pipeline to paused\n");
+        CV_WARN("GStreamer: unable to set pipeline to playing\n");
 //        icvHandleMessage(capture);
 //        cvReleaseCapture((CvCapture **)(void *)&capture);
         gst_object_unref(pipeline);
@@ -507,8 +545,8 @@ bool CvVideoWriter_GStreamer::open( const char * filename, int fourcc,
         caps= gst_video_format_new_caps(GST_VIDEO_FORMAT_BGR,
                                         frameSize.width,
                                         frameSize.height,
-												 fps,
+                                        (int) (fps * 1000),
-												 1,
+                                        1000,
                                         1,
                                         1);
     }