if (typeof (window.MediaPlayer) == "undefined" || window.MediaPlayer == null) {

    window.MediaPlayer = function (mediaFileUrl, previewMode, targetElementID) {

        var height = isAudio(mediaFileUrl) ? 24 : 300;
        var cb = isAudio(mediaFileUrl) ? "bottom" : "over";

        jwplayer(targetElementID).setup({
            flashplayer: "../Includes/player.swf",
            file: mediaFileUrl,
            image: "../Images/video_preview.png",
            height: height,
            controlbar: cb
        });
    }

}