gstreamer正确的结束办法

原来的方案：

gboolean callback_bus_call (GstBus * bus, GstMessage * msg, gpointer data)
{
    ......
    gst_element_set_state(pipeline, GST_STATE_NULL);
    g_main_loop_quit(loop);
 
    return true;
}
 
int main_thread()
{
    ......
    GstBus* bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
    guint bus_watch_id = gst_bus_add_watch(bus, callback_bus_call, pTask);
    gst_object_unref(bus);
 
    ......
 
    g_main_loop_run (loop);
}      

试图在callbak_bus_call()中得到出错和结束消息，然后再退出．结果发现要么无法退出，要么直接崩溃．

　　以下是正确办法：

int main_thread()
{
......
    //阻塞，直到收到指定的消息
    GstBus* bus = gst_element_get_bus(pipeline);
    GstMessage* msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE, (GstMessageType)(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);
    gst_object_unref(pipeline);
......
}