1 files changed, 87 insertions, 0 deletions
diff --git a/trunk/include/asterisk/ulaw.h b/trunk/include/asterisk/ulaw.h
new file mode 100644
index 000000000..0f3eae58b
--- /dev/null
+++ b/trunk/include/asterisk/ulaw.h
@@ -0,0 +1,87 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 1999 - 2005, Digium, Inc.
+ *
+ * Mark Spencer <markster@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! \file
+ * \brief u-Law to Signed linear conversion
+ */
+
+#ifndef _ASTERISK_ULAW_H
+#define _ASTERISK_ULAW_H
+
+
+/*!
+ * To init the ulaw to slinear conversion stuff, this needs to be run.
+ */
+void ast_ulaw_init(void);
+
+#define AST_ULAW_BIT_LOSS  3
+#define AST_ULAW_STEP      (1 << AST_ULAW_BIT_LOSS)
+#define AST_ULAW_TAB_SIZE  (32768 / AST_ULAW_STEP + 1)
+#define AST_ULAW_SIGN_BIT  0x80
+
+/*! \brief converts signed linear to mulaw */
+#ifndef G711_NEW_ALGORITHM
+extern unsigned char __ast_lin2mu[16384];
+#else
+extern unsigned char __ast_lin2mu[AST_ULAW_TAB_SIZE];
+#endif
+
+/*! help */
+extern short __ast_mulaw[256];
+
+#ifndef G711_NEW_ALGORITHM
+
+#define AST_LIN2MU(a) (__ast_lin2mu[((unsigned short)(a)) >> 2])
+
+#else
+
+#define AST_LIN2MU_LOOKUP(mag)											\
+	__ast_lin2mu[((mag) + AST_ULAW_STEP / 2) >> AST_ULAW_BIT_LOSS]
+
+
+/*! \brief convert signed linear sample to sign-magnitude pair for u-Law */
+static inline void ast_ulaw_get_sign_mag(short sample, unsigned *sign, unsigned *mag)
+{
+       /* It may look illogical to retrive the sign this way in both cases,
+        * but this helps gcc eliminate the branch below and produces
+        * faster code */
+       *sign = ((unsigned short)sample >> 8) & AST_ULAW_SIGN_BIT;
+#if defined(G711_REDUCED_BRANCHING)
+       {
+               unsigned dual_mag = (-sample << 16) | (unsigned short)sample;
+               *mag = (dual_mag >> (*sign >> 3)) & 0xffffU;
+       }
+#else
+       if (sample < 0)
+               *mag = -sample;
+       else
+               *mag = sample;
+#endif /* G711_REDUCED_BRANCHING */
+}
+
+static inline unsigned char AST_LIN2MU(short sample)
+{
+       unsigned mag, sign;
+       ast_ulaw_get_sign_mag(sample, &sign, &mag);
+       return ~(sign | AST_LIN2MU_LOOKUP(mag));
+}
+#endif
+
+#define AST_MULAW(a) (__ast_mulaw[(a)])
+
+#endif /* _ASTERISK_ULAW_H */