#include <stdio.h>
#include <gst/gst.h>

// compile with:
// gcc jitter.c -o jitter -I/usr/include/gstreamer-1.0 -I/usr/include/glib-2.0 -I/usr/lib/aarch64-linux-gnu/glib-2.0/include -lgstreamer-1.0 -lgobject-2.0

static double time_last = 0;

static void pts_analysis_cb (GstElement * identity, GstBuffer * buffer, gpointer user_data)
{
	GstClockTime pts = GST_BUFFER_PTS(buffer);
	double time = pts / 1000000.0;
	double time_step = time - time_last;
	fprintf(stderr, "%04.1f ms\n", time_step);
	time_last = time;
}

void main (void)
{
	gst_init(NULL, NULL);

	GstElement * pipeline = gst_parse_launch_full(
		"nvarguscamerasrc sensor-id=0 do-timestamp=true "
		"! video/x-raw(memory:NVMM),width=4032,height=3040,framerate=30/1,format=NV12 "
		"! identity name=identity "
		"! fakesink "
		, NULL, GST_PARSE_FLAG_FATAL_ERRORS, NULL
	);

	GstElement * identity = GST_ELEMENT(gst_bin_get_by_name(GST_BIN(pipeline), "identity"));
	g_signal_connect_data(identity, "handoff", G_CALLBACK(pts_analysis_cb), NULL, NULL, 0);
	gst_element_set_state (pipeline, GST_STATE_PLAYING);
	while (1);
}