diff -r 9b8e68803f6f -r 7968346b9689 src/js/widgets/polemicWidget.js
--- a/src/js/widgets/polemicWidget.js	Tue Feb 21 17:26:51 2012 +0100
+++ b/src/js/widgets/polemicWidget.js	Wed Feb 29 18:13:14 2012 +0100
@@ -51,7 +51,7 @@
     var lineSize      = this.width;        // timeline pixel width 
     var nbrframes     = lineSize/frameSize;     // frame numbers
     var numberOfTweet   = 0;            // number of tweet overide later 
-    var duration      = +this._serializer.currentMedia().meta["dc:duration"];      // timescale width 
+    var duration      = this._serializer.getDuration();      // timescale width 
     var frameLength   = lineSize / frameSize;    // frame timescale  
     var timeline;
     var colors  = new Array("","#1D973D","#C5A62D","#CE0A15","#036AAE","#585858");
@@ -171,9 +171,10 @@
           && typeof(item.meta["id-ref"]) !== "undefined"
           && item.meta["id-ref"] === view_type) {
             
-            var MyTJson = {};
-            if (typeof(item.meta['dc:source']) !== "undefined") {
-              var MyTJson = JSON.parse(item.meta['dc:source']['content']);
+            var MyTJson = {},
+                _source = IriSP.get_aliased(item.meta, ['dc:source', 'source']);
+            if (_source !== null) {
+              var MyTJson = JSON.parse(_source['content']);
             }
             
             if (item.content['polemics'] != undefined 
@@ -381,7 +382,7 @@
 IriSP.PolemicWidget.prototype.sliderUpdater = function() {
 
     var time = +this._Popcorn.currentTime();
-    var duration = +this._serializer.currentMedia().meta["dc:duration"];
+    var duration = this._serializer.getDuration();
     
     this.paperSlider.attr("width", time * (this.width / (duration / 1000)));