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[swftools.git] / lib / lame / tools.h

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+/*
+ *    LAME tools library include file
+ *    Simple context free functions
+ *      - no references to gfc, to gfp, or to any other function not defined
+ *        in this module
+ * 
+ *    Copyright (c) 2000 Frank Klemm
+ *    Copyright (c) 2001 John Dahlstrom
+ *
+ * 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; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/* $Id: tools.h,v 1.1 2002/04/28 17:30:30 kramm Exp $ */
+
+#ifndef LAME_TOOLS_H
+#define LAME_TOOLS_H
+
+#include "machine.h"
+
+
+
+/***********************************************************************
+*  Function Prototype Declarations
+***********************************************************************/
+
+static inline void qinterp_cf_42( const FLOAT y[4], FLOAT c[3] );
+static inline void qinterp_cf_3( const FLOAT y[3], FLOAT c[3] );
+static inline FLOAT qinterp_eval( const FLOAT c[3], FLOAT x, 
+                                  FLOAT xtrans, FLOAT xratio );
+
+
+
+/***********************************************************************
+*  Macros and Static Inline Function Definitions
+***********************************************************************/
+
+/* qinterp_cf_42 - Given 4 points, find the coefficients for a quadratic
+                   that connects the 2 center points.  -jd
+  in: y    coordinate values, paired with constant x coordinates, -1, 0, 1, 2
+ out: c    coefficients ordered for quadratic, (c[2] * x*x + c[1] * x + c[0])
+design note:
+  Utilize the inverse of two constant 3x3 matrices to compute two quadratics,
+  one from the points at (-1,0,1), and the other from the points at (0,1,2).
+  The mean of the two yields a quadratic between the points at 0 and 1.
+*/
+static inline void
+qinterp_cf_42( const FLOAT y[4], FLOAT c[3] )
+{
+  c[2] = ( y[0] - y[1] - y[2] + y[3]) * 0.25; /* ([1 -1 -1 1] .* Y) * 0.25 */
+  c[1] = y[2] - y[1] - c[2];    /* ([-1 -3 5 -1] .* Y) * 0.25 */
+  c[0] = y[1];
+}
+
+/* qinterp_cf_3 - Given 3 points, find the coefficients for a quadratic
+                  that connects the 3 points.  -jd
+  in: y    coordinate values, paired with constant x coordinates, 0, 1, 2
+ out: c    coefficients ordered for quadratic, (c[2] * x*x + c[1] * x + c[0])
+*/
+static inline void
+qinterp_cf_3( const FLOAT y[3], FLOAT c[3] )
+{
+  c[2] = ( y[0] + y[2]) * 0.5 - y[1]; /* ([1 -2 1] .* Y) * 0.5 */
+  c[1] = y[1] - y[0] - c[2];    /* ([-3 4 -1] .* Y) * 0.5 */
+  c[0] = y[0];
+}
+
+
+
+/* qinterp_eval - Evaluate a quadratic at a point, given polynomial 
+                  coefficients, and an x coordinate with translation and scale
+                  ratio values.  This function evaluates the quadratic at the
+                  transformed x coordinate ((x - xtrans) * xratio)).  -jd
+ in: c       quadratic coefficients, for (c[2] * x * x + c[1] * x + c[0])
+     x
+     xtrans
+     xratio
+returns: y coordinate (the quadratic evaluated)
+*/
+static inline FLOAT
+qinterp_eval( const FLOAT c[3], FLOAT x, FLOAT xtrans, FLOAT xratio )
+{
+  x = (x - xtrans) * xratio;
+  return( (c[2] * x + c[1]) * x + c[0] );
+}
+
+
+
+#endif /* LAME_TOOLS_H */