<div dir="ltr"><div><div><div>Hello, </div>I used the basic tutorial 8 in order to get a frame in memory buffer from v4l2src using appsink, without success. </div>The code compiles, but I get a segmentation fault and the pipeline doesn't even start.. </div><div>Any help would be much appreciated. </div><div>Cheers, </div><div>Panos </div>PS: My code is the following: <div><div> #include <gst/gst.h> /* Set V4L2 device to grab from. */ char * v4l2dev = "/dev/video0"; /* Structure to contain all our information, so we can pass it to callbacks */ typedef struct _CustomData { GstElement *pipeline; GstElement *source; GstElement *filter; GstElement *sink; } CustomData; /* The appsink has received a buffer */ static void new_sample (GstElement *sink, CustomData *data) { g_printerr ("In the callback function.\n"); GstSample *sample; /* Retrieve the buffer */ g_signal_emit_by_name (sink, "pull-sample", &sample); if (sample) { /* The only thing we do in this example is print a * to indicate a received buffer */ g_print ("*"); gst_sample_unref (sample); } } int main(int argc, char *argv[]) { CustomData data; GstCaps *cap; GstCaps *app_cap; GstBus *bus; GstMessage *msg; GstStateChangeReturn ret; gboolean terminate = FALSE; /* Initialize GStreamer */ gst_init (&argc, &argv); g_printerr ("Init done.\n"); /* Create caps */ cap = gst_caps_new_simple ("video/x-raw", "format", G_TYPE_STRING, "YUY2", "width", G_TYPE_INT, 640, "height", G_TYPE_INT, 480, "framerate", GST_TYPE_FRACTION, 30, 1, NULL); app_cap = cap; g_printerr ("Caps created.\n"); /* Create the elements */ data.source = gst_element_factory_make ("v4l2src", "source"); data.filter = gst_element_factory_make ("capsfilter","filter"); data.sink = gst_element_factory_make ("appsink", "sink"); g_printerr ("Elements created.\n"); /* Create the empty pipeline */ data.pipeline = gst_pipeline_new ("test-pipeline"); if (!data.pipeline || !data.source || !data.filter || !data.sink) { g_printerr ("Not all elements could be created.\n"); return -1; } g_printerr ("Pipeline created.\n"); /* Configure appsink */ g_object_set (data.sink, "emit-signals", TRUE, "caps", app_cap, NULL); g_signal_connect (data.sink, "new-sample", G_CALLBACK (new_sample), &data); gst_caps_unref (app_cap); g_printerr ("Appsink configured.\n"); /* Build the pipeline. */ gst_bin_add_many (GST_BIN (data.pipeline), data.source, data.filter, data.sink, NULL); if (!gst_element_link_many (data.source, data.filter, data.sink, NULL)) { g_printerr ("Elements could not be linked.\n"); gst_object_unref (data.pipeline); return -1; } g_printerr ("Pipeline builded.\n"); /* Modify the elements' properties */ g_object_set (data.source, "device", v4l2dev, NULL); g_object_set (data.filter,"caps",cap,NULL); g_printerr ("Elements' properties set.\n"); /* Start playing */ ret = gst_element_set_state (data.pipeline, GST_STATE_PLAYING); if (ret == GST_STATE_CHANGE_FAILURE) { g_printerr ("Unable to set the pipeline to the playing state.\n"); gst_object_unref (data.pipeline); return -1; } g_printerr ("Pipeline in playing mode.\n"); /* Listen to the bus */ bus = gst_element_get_bus (data.pipeline); do { msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE, GST_MESSAGE_STATE_CHANGED | GST_MESSAGE_ERROR | GST_MESSAGE_EOS); /* Parse message */ if (msg != NULL) { GError *err; gchar *debug_info; switch (GST_MESSAGE_TYPE (msg)) { case GST_MESSAGE_ERROR: gst_message_parse_error (msg, &err, &debug_info); g_printerr ("Error received from element %s: %s\n", GST_OBJECT_NAME (msg->src), err->message); g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none"); g_clear_error (&err); g_free (debug_info); terminate = TRUE; break; case GST_MESSAGE_EOS: g_print ("End-Of-Stream reached.\n"); terminate = TRUE; break; case GST_MESSAGE_STATE_CHANGED: /* We are only interested in state-changed messages from the pipeline */ if (GST_MESSAGE_SRC (msg) == GST_OBJECT (data.pipeline)) { GstState old_state, new_state, pending_state; gst_message_parse_state_changed (msg, &old_state, &new_state, &pending_state); g_print ("Pipeline state changed from %s to %s:\n", gst_element_state_get_name (old_state), gst_element_state_get_name (new_state)); } break; default: /* We should not reach here */ g_printerr ("Unexpected message received.\n"); break; } gst_message_unref (msg); } } while (!terminate); /* Free resources */ gst_caps_unref (cap); gst_object_unref (bus); gst_element_set_state (data.pipeline, GST_STATE_NULL); gst_object_unref (data.pipeline); return 0; } </div></div></div>