v1

try_1.cpp

@@ -0,0 +1,148 @@
+/*
+ * Based on this example
+ * https://stackoverflow.com/a/26402282/3312367
+ */
+#include <gst/gst.h>
+#include <gst/app/gstappsink.h>
+//#include <stdlib.h>
+#include <cstdlib>
+#include <deque>
+
+#include "opencv2/opencv.hpp"
+//using namespace cv;
+
+// TODO: use synchronized deque
+std::deque<cv::Mat> frameQueue;
+
+GstFlowReturn new_preroll(GstAppSink *appsink, gpointer data) {
+    g_print ("Got preroll!\n");
+    return GST_FLOW_OK;
+}
+
+GstFlowReturn new_sample(GstAppSink *appsink, gpointer data) {
+    static int framecount = 0;
+    framecount++;
+
+    GstSample *sample = gst_app_sink_pull_sample(appsink);
+    GstCaps *caps = gst_sample_get_caps(sample);
+    GstBuffer *buffer = gst_sample_get_buffer(sample);
+    const GstStructure *info = gst_sample_get_info(sample);
+
+    // ---- Read frame and convert to opencv format ---------------
+
+    GstMapInfo map;
+    gst_buffer_map (buffer, &map, GST_MAP_READ);
+
+    // convert gstreamer data to OpenCV Mat, you could actually
+    // resolve height / width from caps...
+    cv::Mat frame(cv::Size(320, 240), CV_8UC3, (char*)map.data, cv::Mat::AUTO_STEP);
+    int frameSize = map.size;
+
+    // TODO: synchronize this....
+    frameQueue.push_back(frame);
+
+    gst_buffer_unmap(buffer, &map);
+
+    // ------------------------------------------------------------
+
+    // print dot every 30 frames
+    if (framecount%30 == 0) {
+        g_print (".");
+    }
+
+    // show caps on first frame
+    if (framecount == 1) {
+        g_print ("%s\n", gst_caps_to_string(caps));
+    }
+
+    gst_sample_unref (sample);
+    return GST_FLOW_OK;
+}
+
+static gboolean my_bus_callback (GstBus *bus, GstMessage *message, gpointer data) {
+    g_print ("Got %s message\n", GST_MESSAGE_TYPE_NAME (message));
+    switch (GST_MESSAGE_TYPE (message)) {
+        case GST_MESSAGE_ERROR: {
+            GError *err;
+            gchar *debug;
+
+            gst_message_parse_error (message, &err, &debug);
+            g_print ("Error: %s\n", err->message);
+            g_error_free (err);
+            g_free (debug);
+            break;
+        }
+        case GST_MESSAGE_EOS:
+            /* end-of-stream */
+            break;
+        default:
+            /* unhandled message */
+            break;
+    }
+    /* we want to be notified again the next time there is a message
+     * on the bus, so returning TRUE (FALSE means we want to stop watching
+     * for messages on the bus and our callback should not be called again)
+     */
+    return TRUE;
+}
+
+int main (int argc, char *argv[]) {
+    GError *error = NULL;
+
+    gst_init (&argc, &argv);
+
+    gchar *descr = g_strdup(
+            "videotestsrc  pattern=ball ! "
+            "video/x-raw,format=RGB ! "
+            "videoconvert ! "
+            "appsink name=sink sync=true"
+    );
+    GstElement *pipeline = gst_parse_launch (descr, &error);
+
+    if (error != NULL) {
+        g_print ("could not construct pipeline: %s\n", error->message);
+        g_error_free (error);
+        exit (-1);
+    }
+
+    /* get sink */
+    GstElement *sink = gst_bin_get_by_name (GST_BIN (pipeline), "sink");
+
+    gst_app_sink_set_emit_signals((GstAppSink*)sink, true);
+    gst_app_sink_set_drop((GstAppSink*)sink, true);
+    gst_app_sink_set_max_buffers((GstAppSink*)sink, 1);
+    GstAppSinkCallbacks callbacks = { NULL, new_preroll, new_sample };
+    gst_app_sink_set_callbacks (GST_APP_SINK(sink), &callbacks, NULL, NULL);
+
+    GstBus *bus;
+    guint bus_watch_id;
+    bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
+    bus_watch_id = gst_bus_add_watch (bus, my_bus_callback, NULL);
+    gst_object_unref (bus);
+
+    gst_element_set_state (GST_ELEMENT (pipeline), GST_STATE_PLAYING);
+
+    cv::namedWindow("edges", 1);
+    bool is_terminated = false;
+    while (!is_terminated) {
+        // g_main_iteration(false);
+        g_main_context_iteration(NULL, false);
+        // TODO: synchronize...
+        if (frameQueue.size() > 0) {
+            // this lags pretty badly even when grabbing frames from webcam
+            cv::Mat frame = frameQueue.front();
+            cv::Mat edges;
+            cvtColor(frame, edges, cv::COLOR_BGR2BGRA);
+//            GaussianBlur(edges, edges, Size(7,7), 1.5, 1.5);
+//            Canny(edges, edges, 0, 30, 3);
+            cv::imshow("edges", edges);
+            cv::waitKey(30);
+            frameQueue.clear();
+        }
+    }
+
+    gst_element_set_state (GST_ELEMENT (pipeline), GST_STATE_NULL);
+    gst_object_unref (GST_OBJECT (pipeline));
+
+    return 0;
+}