I want to use appsink to extract the frames in the Gstbuffer in the pipeline, and then use opencv for image processing, I refer to the program in this link (Adding opencv processing to gstreamer application), but when I use imshow or cvtColor in the main function, there will be a core dump error, But in the new_sample function, I should have successfully extracted each frame in the buffer, and the map.size is also correct (BGR, width=100, height=100, map.size=30000).
opencv version:4.7.0
video/x-raw, format=(string)BGR, width=(int)100, height=(int)100, framerate=(fraction)30/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)1/1, interlace-mode=(string)progressive Erreur de segmentation (core dumped)
Gtk-Message: 17:04:05.146: Failed to load module "appmenu-gtk-module" frameSize: 30000 video/x-raw, format=(string)BGR, width=(int)100, height=(int)100, framerate=(fraction)30/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)1/1, interlace-mode=(string)progressive frameSize: 30000 Erreur de segmentation (core dumped)
#include <gst/gst.h>
#include <gst/app/app.h>
#include <gst/app/gstappsink.h>
#include <stdlib.h>
#include <opencv2/opencv.hpp>
#include <opencv2/core.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>
using namespace cv;
// TODO: use synchronized deque
std::deque<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...
Mat frame(Size(320, 240), CV_8UC3, (char*)map.data, Mat::AUTO_STEP);
int frameSize = map.size;
g_print ("frameSize: %d\n",frameSize);
// 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,width=100,height=100,format=(string)BGR ! "
"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);
namedWindow("edges",1);
while(1) {
g_main_iteration(false);
// TODO: synchronize...
if (frameQueue.size() > 0) {
// this lags pretty badly even when grabbing frames from webcam
Mat frame = frameQueue.front();
Mat edges;
cvtColor(frame, edges, cv::COLOR_BGR2GRAY);
//GaussianBlur(edges, edges, Size(7,7), 1.5, 1.5);
//Canny(edges, edges, 0, 30, 3);
//imshow("edges", edges);
//cv::waitKey(30);
frameQueue.clear();
}
}
gst_element_set_state (GST_ELEMENT (pipeline), GST_STATE_NULL);
gst_object_unref (GST_OBJECT (pipeline));
I'm a newbie and would appreciate some help, many thanks!
