diff -r 000000000000 -r bde4ae8d615e os/mm/devsound/a3facf/inc/maudioprocessingunitobserver.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/os/mm/devsound/a3facf/inc/maudioprocessingunitobserver.h	Fri Jun 15 03:10:57 2012 +0200
@@ -0,0 +1,63 @@
+/*
+* Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).
+* All rights reserved.
+* This component and the accompanying materials are made available
+* under the terms of "Eclipse Public License v1.0"
+* which accompanies this distribution, and is available
+* at the URL "http://www.eclipse.org/legal/epl-v10.html".
+*
+* Initial Contributors:
+* Nokia Corporation - initial contribution.
+*
+* Contributors:
+*
+* Description:
+*
+*/
+
+
+
+
+/**
+ @file
+ @publishedPartner 
+ @released
+*/
+
+
+#ifndef MAUDIOPROCESSINGUNITOBSERVER_H__
+#define MAUDIOPROCESSINGUNITOBSERVER_H__
+
+#include <e32base.h>
+
+#include <a3f/a3fbase.h>
+
+class MAudioProcessingUnit;
+
+/**
+ * An interface to a set of audio processing unit callback functions.
+ * 
+ * this serves as the method of communication between the client and the audio processing unit.
+ *
+ * The class is a mixin and is intended to be inherited by the client class that is
+ * interested in observing the audio processing unit operation. The functions
+ * encapsulated by this class are called when specific events occur while
+ * processing audio.
+ * 
+ * this interface is mainly usable for advanced audio clients, that are interested in detailed
+ * operation of the processing chain. Most audio clients should be fine with only observing the audio stream.
+ * 
+ */
+class MAudioProcessingUnitObserver
+	{
+public:
+	/**
+	* Handles processing unit error event.
+	*
+	* @param aInstance A pointer to the processing unit instance.
+	* @param aError. Propagated error.
+	*/
+	virtual void ProcessingUnitError(MAudioProcessingUnit* aInstance, TInt aError)=0;
+	};
+
+#endif // MAUDIOPROCESSINGUNITOBSERVER_H__