Gstreamer库get_pos()无法调用！！！

[Chairman516]

#ifndef PLAY_H
#define PLAY_H

#define PLAY_STOP 1
#define PLAY_PAUSE 2
#define PLAY_PRE 3
#define PLAY_NEXT 4
#define PLAY_PITCH 5

void play(int cmd, void *data);
static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data);

#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gst/gst.h>
#include <glib.h>
#include "play.h"
#include "main_core.h"
#include "medialib.h"
#include "interface.h"

void play(int cmd, void *data)
{
	static char media_path[MAX_PATH_LENGTH];
	static int media_pos;
	static GMainLoop *loop;
	GstElement *pipeline;
	GstElement *source;
	GstElement *decoder;
	GstElement *sink;
	GstBus *bus;

	switch(cmd) {
	case PLAY_STOP:
		g_main_loop_quit(loop);
		break;
	case PLAY_PAUSE:
		media_pos = get_pos(loop, 0);
		g_main_loop_quit(loop);
		break;
	case PLAY_PRE:
	case PLAY_NEXT:
	case PLAY_PITCH:
		media_path[0] = '\0';
		media_pos = 0;
		g_main_loop_quit(loop);//no break;
	default:
		if (media_path[0] == '\0')
			get_pos(loop, media_pos);
		else
			strcpy(media_path, (char *)data);
		gst_init(NULL, NULL);
		loop = g_main_loop_new(NULL, FALSE);
		pipeline = gst_pipeline_new("audio-player");
		source = gst_element_factory_make("filesrc", "file-source");
		decoder = gst_element_factory_make("mad", "mad-decoder");
		sink = gst_element_factory_make("autoaudiosink", "audio-output");
		if (!pipeline || !source || !decoder || !sink) {
			g_printerr("Creating pipeline failed");
		}
		g_object_set(G_OBJECT(source), "location", media_path, NULL);
		bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
		gst_bus_add_watch(bus, bus_call, loop);
		gst_object_unref(bus);
		gst_bin_add_many(GST_BIN(pipeline), source, decoder, sink, NULL);
		gst_element_link_many(source, decoder, sink, NULL);
		gst_element_set_state(pipeline, GST_STATE_PLAYING);
		g_print("Start playing...");
		g_main_loop_run(loop);
		gst_element_set_state(pipeline, GST_STATE_NULL);
		gst_object_unref(GST_OBJECT(pipeline));
	}
}

static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data)
{
	GMainLoop *loop = (GMainLoop *)data;

	switch(GST_MESSAGE_TYPE(msg)) {
	case GST_MESSAGE_EOS:
		g_print("playing finished");
		g_main_loop_quit(loop);
		break;
	case GST_MESSAGE_TAG: {
		GstTagList *tags;
		gchar *title = "";
		gchar *artist = "";
		gst_message_parse_tag(msg, &tags);
		if (gst_tag_list_get_string(tags, GST_TAG_TITLE, &title)
				&& gst_tag_list_get_string(tags, GST_TAG_ARTIST, &artist)) {
			puts(title);
			puts(artist);
		}
		gst_tag_list_free(tags);
		break;
	}
	case GST_MESSAGE_ERROR: {
		gchar *debug;
		GError *error;
		gst_message_parse_error(msg, &error, &debug);
		g_free(debug);
		g_printerr("ERROR:%s\n", error->message);
		g_error_free(error);
		g_main_loop_quit(loop);
		break;
	}
	}
	return TRUE;
}