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diff --git a/arts/modules/synth/synth_delay_impl.cpp b/arts/modules/synth/synth_delay_impl.cpp
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+++ b/arts/modules/synth/synth_delay_impl.cpp
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+/*
+
+    Copyright (C) 2000 Jeff Tranter
+                       tranter@pobox.com
+                       Stefan Westerfeld
+                       stefan@space.twc.de
+                       Jens Hahn
+                       Jens.Hahn@t-online.de
+                  2001 Matthias Kretz
+                       kretz@kde.org
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+  
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+   
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA 02110-1301, USA.
+
+    */
+
+#include "artsmodulessynth.h"
+#include "stdsynthmodule.h"
+
+#include <math.h>
+
+using namespace Arts;
+
+// This delays the input signal for an amount of time. The time
+// specification must be between 0 and 1 for a delay between 0 seconds
+// and 1 second.
+//
+// This kind of delay may not be used in feedback structures. This is
+// because it's a variable delay. You can modify it's length while it
+// is running, and even set it down to zero. But since in a feedback
+// structure the own output is needed to calculate the next samples, a
+// delay whose value could drop to zero during synthesis could lead to
+// a stall situation.
+//
+// Use CDELAYs in that setup, perhaps combine a small constant delay
+// (of 0.001 seconds) with a flexible delay.
+//
+// You can also combine a CDELAY and a DELAY to achieve a variable
+// length delay with a minimum value in a feedback loop. Just make
+// sure that you have a CDELAY involved.
+
+class Synth_DELAY_impl : virtual public Synth_DELAY_skel,
+							virtual public StdSynthModule
+{
+protected:
+	unsigned long _buffersize;
+	unsigned long _bitmask;
+	float * _buffer;
+	float _maxdelay;
+	unsigned int _writepos;
+ 
+public:
+	Synth_DELAY_impl() : _buffersize( 0 ), _bitmask( 0 ), _buffer( 0 ), _maxdelay( 0 ), _writepos( 0 )
+	{
+		maxdelay( 1 ); // take a one second buffer if nothing else is specified
+	}
+
+	~Synth_DELAY_impl()
+	{
+		delete[] _buffer;
+	}
+
+	void streamInit()
+	{
+		// initialize buffer to all zeroes
+		for ( unsigned long i = 0; i < _buffersize; i++ )
+			_buffer[i] = 0.0;
+	}
+
+	void calculateBlock(unsigned long samples)
+	{
+		for( unsigned long i = 0; i <samples; i++ )
+		{
+			double int_pos;
+			double error = modf( time[i] * samplingRateFloat, &int_pos );
+			unsigned long readpos1 = ( _writepos - (unsigned long)(int_pos) ) & _bitmask;
+			unsigned long readpos2 = ( readpos1 - 1 ) & _bitmask; // Shouldn't this be +1? (mkretz)
+			// No, it's right this way:
+			// ( 1 - error ) needs to be multiplied with the second
+			// sample; error with the first
+			_buffer[_writepos] = invalue[i];
+			outvalue[i] = _buffer[readpos1] * ( 1 - error ) + _buffer[readpos2] * error;
+			_writepos++;
+			_writepos &= _bitmask;
+		}
+	}
+
+	float maxdelay() { return _maxdelay; }
+
+	void maxdelay(float newmaxdelay)
+	{
+		if( newmaxdelay <= 0 )
+			return;
+		_maxdelay = newmaxdelay;
+		double n = ceil( log( double(_maxdelay * samplingRateFloat) ) / log( 2. ) );
+		unsigned long newbuffersize = (unsigned long)( pow( 2, n ) );
+		unsigned long newbitmask = newbuffersize - 1;
+		if( newbuffersize != _buffersize )
+		{
+			float *newbuffer = new float[newbuffersize];
+			if( newbuffersize > _buffersize ) {
+				for( unsigned long i = 0; i < _buffersize; i++ ) {
+					newbuffer[i] = _buffer[_writepos];
+					_writepos++;
+					_writepos &= newbitmask;
+				}
+				for( unsigned long i = _buffersize; i < newbuffersize; i++ )
+					newbuffer[i] = 0;
+			} else {
+				_writepos -= newbuffersize;
+				_writepos &= newbitmask;
+				for( unsigned long i = 0; i < newbuffersize; i++ ) {
+					newbuffer[i] = _buffer[_writepos];
+					_writepos++;
+					_writepos &= newbitmask;
+				}
+			}
+			_buffer = newbuffer;
+			_buffersize = newbuffersize;
+			_bitmask = newbitmask;
+		}
+		maxdelay_changed( _maxdelay );
+	}         
+};
+
+REGISTER_IMPLEMENTATION(Synth_DELAY_impl);