minimal gstreamer rtsp example: retrieve frame, save jpeg

minimal_rtsp.c

#include <stdio.h>

#include <gst/gst.h>
#include <gst/app/gstappsink.h>
#include <glib.h>
#include <libavcodec/avcodec.h>

#include "stb/stb_image.h"

void minimal_rtsp() {

	gst_init (NULL, NULL);
	gst_init_static_plugins();

	GstElement *pipeline = gst_parse_launch ("rtspsrc location=rtsp://admin:[email protected]/cam/realmonitor?"
						 "channel=1&subtype=00&authbasic=YWRtaW46a3JlZWxrYXQx !"
						 " decodebin ! videoconvert ! video/x-raw, format=RGB ! appsink name=sink",NULL);

	gst_element_set_state(pipeline, GST_STATE_PLAYING);

	GstElement *sink = gst_bin_get_by_name (GST_BIN (pipeline), "sink");
	if(!sink){
		printf("Error: GstElement sink is NULL\n");
		exit(1);
	}

	GstAppSink *appsink = GST_APP_SINK(sink);
	if(!appsink){
		printf("Error: GstAppSink appsink is NULL\n");
		exit(1);
	}

	GstSample *sample = gst_app_sink_pull_sample(appsink);
	if(!sample){
		printf("Error: GstSample sample is NULL\n");
		exit(1);
	}

	GstCaps *caps = gst_sample_get_caps(sample);
	GstStructure *capsStruct = gst_caps_get_structure(caps,0);

	int gs_width, gs_height;
	gst_structure_get_int (capsStruct, "width", &gs_width);
	gst_structure_get_int (capsStruct, "height", &gs_height);

	printf("Notice: %d %d \n", gs_width, gs_height);

	GstBuffer *buffer = gst_sample_get_buffer(sample);
	GstMapInfo map;
	gst_buffer_map(buffer, &map, GST_MAP_READ);

	stbi_write_jpg("jpg_test.jpg", gs_width, gs_height, 3, (char *) map.data, 70);

	exit(0);
}