Nr 2 Flummi, wenn du mir die Ehre erweist :3

s/item.tpl.html

@@ -62,12 +62,12 @@
   <script src="./s/video.min.js"></script>
   <script src="./s/videojs.persistvolume.js"></script>
   <script>
-    (function() {
-      var vid1 = videojs('my-video_html5_api');
-      vid1.persistvolume({
-        namespace: "f0ck"
-      });
-    })();
+    (function() {                                               
+        var vid1 = videojs( document.querySelector("video") );
+        vid1.persistvolume({                                  
+            namespace: "f0ck"                                   
+        });                                                   
+    })();                                                   
   </script>
   <script>
   $(document).ready(() => {