The GtkRadiant sources as originally released under the GPL license.

tools/quake2/qdata_heretic2/adpcm.h

@@ -0,0 +1,49 @@
+/*
+Copyright (C) 1999-2006 Id Software, Inc. and contributors.
+For a list of contributors, see the accompanying CONTRIBUTORS file.
+
+This file is part of GtkRadiant.
+
+GtkRadiant 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.
+
+GtkRadiant 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 GtkRadiant; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+/*
+** adpcm.h - include file for adpcm coder.
+**
+** Version 1.0, 7-Jul-92.
+** 
+** Modded 10/3/98
+** John Scott
+*/
+
+typedef struct adpcm_state_s
+{
+    short	in_valprev;			// Previous output value
+    short	in_index;	 		// Index into stepsize table
+    short	out_valprev; 		// Previous output value
+    short	out_index;			// Index into stepsize table
+	int		count;				// Number of sample counts
+}	adpcm_state_t;
+
+typedef struct adpcm_s
+{
+	adpcm_state_t	state;
+	char			adpcm[0x10000];			
+}	adpcm_t;
+
+void adpcm_coder(short [], adpcm_t *);
+void adpcm_decoder(adpcm_t *, short []);
+
+// end