main.c

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

#define PIPELINE_STRING "gst-launch-1.0 \
	filesrc location=softboy.avi ! avidemux \
	! avdec_mpeg4 ! videorate \
	! capsfilter \
		caps=video/x-raw,framerate=10/1 \
		name=filter \
	! videoconvert ! ximagesink"

void pipeline_run(gpointer *user_data){
	GstElement *pipeline = (GstElement *)user_data;
	GstBus *bus;
	GstMessage *msg;

	gst_element_set_state (pipeline, GST_STATE_PLAYING);
	bus = gst_element_get_bus (pipeline);
	msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
			GST_MESSAGE_ERROR | GST_MESSAGE_EOS);

	if (msg != NULL)
		gst_message_unref (msg);
	gst_object_unref (bus);
	gst_element_set_state (pipeline, GST_STATE_NULL);
}

int main(int argc, char *argv[]) {
	GstTask *task;
	GRecMutex mutex;
	GstElement *pipeline;
	GstElement *filter;

	gst_init (&argc, &argv);

	pipeline = gst_parse_launch (PIPELINE_STRING, NULL);
	filter = gst_bin_get_by_name(GST_BIN(pipeline), "filter");
	(void)filter;

	task = gst_task_new((GstTaskFunction)pipeline_run, (gpointer)pipeline, NULL);

	g_rec_mutex_init (&mutex);
	gst_task_set_lock(task, &mutex);

	gst_task_start(task);

	do {
		int i;
		scanf("%d", &i);
		if (i == -1) {
			break;
		} else {
			GstCaps *caps = NULL;
			caps = gst_caps_new_simple("video/x-raw",
					"framerate", GST_TYPE_FRACTION, i, 1,
					NULL);
			g_object_set(G_OBJECT(filter), "caps", caps, NULL);
		}
	} while (1);
	
	gst_task_join(task);

	gst_object_unref (pipeline);

	return 0;
}