   var mediaDataSource = JSON.parse(xhr.response);
                    flv_load_mds(mediaDataSource);
                }
                xhr.send();
            } else {
                var i;
                var mediaDataSource = {
                    type: 'flv'
                };
                for (i = 0; i < checkBoxFields.length; i++) {
                    var field = checkBoxFields[i];
                    /** @type {HTMLInputElement} */
                    var checkbox = document.getElementById(field