         }
     }
 
-    private var _input: AKNode?
-    public var input: AKNode? {
+    private var _input: AKNode
+    public var input: AKNode {
         get {
             return _input
         }

    /// - parameter input: Node to analyze
    public init(_ input: AKNode, bufferSize: UInt32 = 4_096, handler: @escaping Handler) {
        self.bufferSize = bufferSize
        self.input = input
        self.handler = handler
    }


        if isStarted {
            stop()
        }
    }
}
