diff --git a/sjplayer/src/sjplayer/AbstractScheduledController.d b/sjplayer/src/sjplayer/AbstractScheduledController.d
index 7a3b300..9949565 100644
--- a/sjplayer/src/sjplayer/AbstractScheduledController.d
+++ b/sjplayer/src/sjplayer/AbstractScheduledController.d
@@ -2,7 +2,9 @@
 module sjplayer.AbstractScheduledController;
 
 import std.algorithm,
+       std.array,
        std.exception,
+       std.range.primitives,
        std.typecons;
 
 import sjscript;
@@ -103,3 +105,16 @@ abstract class AbstractScheduledController : ScheduledControllerInterface {
 
   float[string] user_vars_;
 }
+
+///
+ParametersBlock[] SortParametersBlock(R)(R params)
+    if (isInputRange!R && is(ElementType!R == ParametersBlock)) {
+  auto result = params.array;
+  result.sort!"a.period.start < b.period.start";
+
+  auto before = Period(-1, 0);
+  foreach (param; result) {
+    (!param.period.IsPeriodIntersectedToPeriod(before)).enforce();
+  }
+  return result;
+}
diff --git a/sjplayer/src/sjplayer/BackgroundScheduledController.d b/sjplayer/src/sjplayer/BackgroundScheduledController.d
index 900205f..284c1fe 100644
--- a/sjplayer/src/sjplayer/BackgroundScheduledController.d
+++ b/sjplayer/src/sjplayer/BackgroundScheduledController.d
@@ -8,7 +8,8 @@ import std.algorithm,
 
 import sjscript;
 
-import sjplayer.Background,
+import sjplayer.AbstractScheduledController,
+       sjplayer.Background,
        sjplayer.ContextBuilderInterface,
        sjplayer.ScheduledController,
        sjplayer.VarStoreInterface,
@@ -45,16 +46,8 @@ struct BackgroundScheduledControllerFactory {
   ///
   void Create(R)(R params, ContextBuilderInterface builder)
       if (isInputRange!R && is(ElementType!R == ParametersBlock)) {
-    auto params_array = params.array;
-    params_array.sort!"a.period.start < b.period.start";
-
-    auto before = Period(-1, 0);
-    foreach (param; params_array) {
-      (!param.period.IsPeriodIntersectedToPeriod(before)).enforce();
-    }
-
     auto ctrl = new BackgroundScheduledController(
-        background_, varstore_, params_array);
+        background_, varstore_, SortParametersBlock(params));
     builder.AddScheduledController(ctrl);
   }