javascript创建media播放列表，如何设置每个歌曲的标题?

如下列代码：
   <object id="player" height="190" width="100%" classid="CLSID:6BF52A52-394A-11d3-B153-00C04F79FAA6">....        function setPlayer() {
            var player = document.getElementById("player");
            if (player.settings.mediaAccessRights != "full") {
                player.settings.requestMediaAccessRights("full");
            }
            try {
                var playlist = player.playlistCollection.newPlaylist("试听预警文件");
                var cm = player.newMedia("http://localhost:804/天堂.mp3");
                if (cm.isReadOnlyItem("title") == false)
                 {
                     cm.setItemInfo("title", "标题—天堂");
                }
                playlist.appendItem(cm);
                player.currentPlaylist = playlist;
                player.controls.play();
            }
            catch (ex) {
                alert(ex);
            }
        }
用 cm.isReadOnlyItem 检测，title是只读的无法重新设置标题。
是否有别的方法？