Initial revision

CVS patchset: 1
CVS date: 2001/04/18 22:33:39

1 files changed, 37 insertions, 0 deletions

diff --git a/src/libac3/dither.h b/src/libac3/dither.h
new file mode 100644
index 000000000..abb9f518e
--- /dev/null
+++ b/src/libac3/dither.h
@@ -0,0 +1,37 @@
+/* 
+ *    dither.h
+ *
+ *	Copyright (C) Aaron Holtzman - May 1999
+ *
+ *  This file is part of ac3dec, a free Dolby AC-3 stream decoder.
+ *	
+ *  ac3dec 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, or (at your option)
+ *  any later version.
+ *   
+ *  ac3dec 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 GNU Make; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
+ *
+ */
+
+
+extern uint16_t lfsr_state;
+extern const uint16_t dither_lut[256]; 
+
+static inline uint16_t dither_gen(void)
+{
+	int16_t state;
+
+	state = dither_lut[lfsr_state >> 8] ^ (lfsr_state << 8);
+	
+	lfsr_state = (uint16_t) state;
+
+	return ((state * (int32_t) (0.707106 * 256.0))>>8);
+}