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diff --git a/libs/audiographer/src/gdither/gdither.h b/libs/audiographer/src/gdither/gdither.h
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+/*
+ *  Copyright (C) 2002 Steve Harris <steve@plugin.org.uk>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#ifndef GDITHER_H
+#define GDITHER_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "gdither_types.h"
+
+/* Create and initialise a state structure, takes a dither type, a number of
+ * channels and a bit depth as input
+ *
+ * The Dither type is one of
+ *
+ *   GDitherNone - straight nearest neighbour rounding. Theres no pressing
+ *   reason to do this at 8 or 16 bit, but you might want to at 24, for some
+ *   reason. At the lest it will save you writing int->float conversion code,
+ *   which is arder than it sounds.
+ *
+ *   GDitherRect - mathematically most accurate, lowest noise floor, but not
+ *   that good for audio. It is the fastest though.
+ *
+ *   GDitherTri - a happy medium between Rectangular and Shaped, reasonable
+ *   noise floor, not too obvious, quite fast.
+ *
+ *   GDitherShaped - should have the least audible impact, but has the highest
+ *   noise floor, fairly CPU intensive. Not advisible if your going to apply
+ *   any frequency manipulation afterwards.
+ *
+ * channels, sets the number of channels in the output data, output data will
+ * be written interleaved into the area given to gdither_run(). Set to 1
+ * if you are not working with interleaved buffers.
+ *
+ * bit depth, sets the bit width of the output sample data, it can be one of:
+ *
+ *   GDither8bit   - 8 bit unsiged
+ *   GDither16bit  - 16 bit signed
+ *   GDither32bit  - 24+bits in upper bits of a 32 bit word
+ *   GDitherFloat  - IEEE floating point (32bits)
+ *   GDitherDouble - Double precision IEEE floating point (64bits)
+ *
+ * dither_depth, set the number of bits before the signal will be truncated to,
+ * eg. 16 will produce an output stream with 16bits-worth of signal. Setting to
+ * zero or greater than the width of the output format will dither to the
+ * maximum precision allowed by the output format.
+ */
+GDither gdither_new(GDitherType type, uint32_t channels,
+
+                    GDitherSize bit_depth, int dither_depth);
+
+/* Frees memory used by gdither_new.
+ */
+void gdither_free(GDither s);
+
+/* Applies dithering to the supplied signal.
+ *
+ * channel is the channel number you are processing (0 - channles-1), length is
+ * the length of the input, in samples, x is the input samples (float), y is
+ * where the output samples will be written, it should have the approaprate
+ * type for the chosen bit depth
+ */
+void gdither_runf(GDither s, uint32_t channel, uint32_t length,
+		   float const *x, void *y);
+
+/* see gdither_runf, vut input argument is double format */
+void gdither_run(GDither s, uint32_t channel, uint32_t length,
+		   double const *x, void *y);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif