////// dbus-service
[DBus (name = "org.mpris.MediaPlayer2.Player")]
public class MprisPlayer : GLib.Object {
....
	public int64 position {
		get {
			///// запрашивает единожды и потом возвращает одно и тоже значение. Почему?
			return player.position / Constants.MILI_INV;
		}
	}
....
}
///////
public class Player : GLib.Object {
	public int64 position {
		set {
			playbin.seek_simple (fmt, Gst.SeekFlags.FLUSH, value);
		}
		get {
			int64 d = 0;
			playbin.query_position (fmt, out d);
			return d;
		}
	}
}
//////// dbus-client
[DBus (name="org.mpris.MediaPlayer2.Player")]
public interface PlayerIface : MprisIface {
	public abstract int64 position { get; }
}