Fix compatibility with gstreamer < 1.18

Makefile

@@ -20,7 +20,7 @@ CFLAGS += -DWFB_OSD_VERSION='"$(VERSION)-$(shell /bin/bash -c '_tmp=$(COMMIT); e
 ifeq ($(mode), gst)
     CFLAGS += -Wall -pthread -std=gnu99 -D__GST_OPENGL__ -fPIC $(shell pkg-config --cflags glib-2.0) $(shell pkg-config --cflags gstreamer-1.0)
     LDFLAGS += $(shell pkg-config --libs glib-2.0) $(shell pkg-config --libs gstreamer-1.0) $(shell pkg-config --libs gstreamer-video-1.0) -lgstapp-1.0 -lpthread -lrt -lm
-    OBJS = main.o osdrender.o osdmavlink.o graphengine.o UAVObj.o m2dlib.o math3d.o osdconfig.o osdvar.o fonts.o font_outlined8x14.o font_outlined8x8.o appsrc.o
+    OBJS = main.o osdrender.o osdmavlink.o graphengine.o UAVObj.o m2dlib.o math3d.o osdconfig.o osdvar.o fonts.o font_outlined8x14.o font_outlined8x8.o appsrc.o gst-compat.o
 else
     CFLAGS += -Wall -pthread -std=gnu99 -D__BCM_OPENVG__ -I$(SYSROOT)/opt/vc/include/ -I$(SYSROOT)/opt/vc/include/interface/vcos/pthreads -I$(SYSROOT)/opt/vc/include/interface/vmcs_host/linux
     LDFLAGS += -L$(SYSROOT)/opt/vc/lib/ -lbrcmGLESv2 -lbrcmEGL -lopenmaxil -lbcm_host -lvcos -lvchiq_arm -lpthread -lrt -lm

appsrc.c

@@ -33,6 +33,10 @@
 
 #include "graphengine.h"
 
+// For gstreamer < 1.18
+GstClockTime gst_element_get_current_running_time (GstElement * element);
+
+
 static gboolean
 on_message (GstBus * bus, GstMessage * message, gpointer user_data)
 {

gst-compat.c

@@ -0,0 +1,76 @@
+#include <gst/gst.h>
+#include <gst/gstelement.h>
+
+/**
+ * gst_element_get_current_clock_time:
+ * @element: a #GstElement.
+ *
+ * Returns the current clock time of the element, as in, the time of the
+ * element's clock, or GST_CLOCK_TIME_NONE if there is no clock.
+ *
+ * Returns: the clock time of the element, or GST_CLOCK_TIME_NONE if there is
+ * no clock.
+ *
+ * Since: 1.18
+ */
+GstClockTime
+gst_element_get_current_clock_time (GstElement * element)
+{
+  GstClock *clock = NULL;
+  GstClockTime ret;
+
+  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_CLOCK_TIME_NONE);
+
+  clock = gst_element_get_clock (element);
+
+  if (!clock) {
+    GST_DEBUG_OBJECT (element, "Element has no clock");
+    return GST_CLOCK_TIME_NONE;
+  }
+
+  ret = gst_clock_get_time (clock);
+  gst_object_unref (clock);
+
+  return ret;
+}
+
+/**
+ * gst_element_get_current_running_time:
+ * @element: a #GstElement.
+ *
+ * Returns the running time of the element. The running time is the
+ * element's clock time minus its base time. Will return GST_CLOCK_TIME_NONE
+ * if the element has no clock, or if its base time has not been set.
+ *
+ * Returns: the running time of the element, or GST_CLOCK_TIME_NONE if the
+ * element has no clock or its base time has not been set.
+ *
+ * Since: 1.18
+ */
+GstClockTime
+gst_element_get_current_running_time (GstElement * element)
+{
+  GstClockTime base_time, clock_time;
+
+  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_CLOCK_TIME_NONE);
+
+  base_time = gst_element_get_base_time (element);
+
+  if (!GST_CLOCK_TIME_IS_VALID (base_time)) {
+    GST_DEBUG_OBJECT (element, "Could not determine base time");
+    return GST_CLOCK_TIME_NONE;
+  }
+
+  clock_time = gst_element_get_current_clock_time (element);
+
+  if (!GST_CLOCK_TIME_IS_VALID (clock_time)) {
+    return GST_CLOCK_TIME_NONE;
+  }
+
+  if (clock_time < base_time) {
+    GST_DEBUG_OBJECT (element, "Got negative current running time");
+    return GST_CLOCK_TIME_NONE;
+  }
+
+  return clock_time - base_time;
+}