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-rw-r--r--trunk/main/ulaw.c246
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diff --git a/trunk/main/ulaw.c b/trunk/main/ulaw.c
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+/*
+ * 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
+ *
+ * \author Mark Spencer <markster@digium.com>
+ */
+
+#include "asterisk.h"
+
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
+
+#include "asterisk/ulaw.h"
+
+#if 0
+/* ZEROTRAP is the military recommendation to improve the encryption
+ * of u-Law traffic. It is irrelevant with modern encryption systems
+ * like AES, and will simply degrade the signal quality.
+ * ZEROTRAP is not implemented in AST_LIN2MU and so the coding table
+ * tests will fail if you use it */
+#define ZEROTRAP /*!< turn on the trap as per the MIL-STD */
+#endif
+
+#define BIAS 0x84 /*!< define the add-in bias for 16 bit samples */
+#define CLIP 32635
+
+#ifndef G711_NEW_ALGORITHM
+
+unsigned char __ast_lin2mu[16384];
+short __ast_mulaw[256];
+
+static unsigned char linear2ulaw(short sample)
+{
+ static int exp_lut[256] = {
+ 0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
+ 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
+ 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+ 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 };
+ int sign, exponent, mantissa;
+ unsigned char ulawbyte;
+
+ /* Get the sample into sign-magnitude. */
+ sign = (sample >> 8) & 0x80; /* set aside the sign */
+ if (sign != 0)
+ sample = -sample; /* get magnitude */
+ if (sample > CLIP)
+ sample = CLIP; /* clip the magnitude */
+
+ /* Convert from 16 bit linear to ulaw. */
+ sample = sample + BIAS;
+ exponent = exp_lut[(sample >> 7) & 0xFF];
+ mantissa = (sample >> (exponent + 3)) & 0x0F;
+ ulawbyte = ~(sign | (exponent << 4) | mantissa);
+
+#ifdef ZEROTRAP
+ if (ulawbyte == 0)
+ ulawbyte = 0x02; /* optional CCITT trap */
+#endif
+
+ return ulawbyte;
+}
+
+#else
+
+unsigned char __ast_lin2mu[AST_ULAW_TAB_SIZE];
+short __ast_mulaw[256];
+
+static unsigned char linear2ulaw(short sample, int full_coding)
+{
+ static const unsigned exp_lut[256] = {
+ 0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
+ 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
+ 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+ 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+ 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 };
+ unsigned sign, exponent, mantissa, mag;
+ unsigned char ulawbyte;
+
+ /* Get the sample into sign-magnitude. */
+ ast_ulaw_get_sign_mag(sample, &sign, &mag);
+ if (mag > CLIP)
+ mag = CLIP; /* clip the magnitude */
+
+ sign = (sample >> 8) & 0x80; /* set aside the sign */
+ if (sign != 0)
+ sample = -sample; /* get magnitude */
+ if (sample > CLIP)
+ sample = CLIP; /* clip the magnitude */
+
+ /* Convert from 16 bit linear to ulaw. */
+ mag += BIAS;
+ exponent = exp_lut[(mag >> 7) & 0xFF];
+ mantissa = (mag >> (exponent + 3)) & 0x0F;
+
+ if (full_coding) {
+ /* full encoding, with sign and xform */
+ ulawbyte = ~(sign | (exponent << 4) | mantissa);
+#ifdef ZEROTRAP
+ if (ulawbyte == 0)
+ ulawbyte = 0x02; /* optional CCITT trap */
+#endif
+ } else {
+ /* half-cooked coding -- mantissa+exponent only (for lookup tab) */
+ ulawbyte = (exponent << 4) | mantissa;
+ }
+
+ return ulawbyte;
+}
+
+static inline short ulaw2linear(unsigned char ulawbyte)
+{
+ unsigned exponent, mantissa;
+ short sample;
+ static const short etab[]={0,132,396,924,1980,4092,8316,16764};
+
+ ulawbyte = ~ulawbyte;
+ exponent = (ulawbyte & 0x70) >> 4;
+ mantissa = ulawbyte & 0x0f;
+ sample = mantissa << (exponent + 3);
+ sample += etab[exponent];
+ if (ulawbyte & 0x80)
+ sample = -sample;
+ return sample;
+}
+#endif
+
+/*!
+ * \brief Set up mu-law conversion table
+ */
+void ast_ulaw_init(void)
+{
+ int i;
+
+ /*
+ * Set up mu-law conversion table
+ */
+#ifndef G711_NEW_ALGORITHM
+ for (i = 0;i < 256;i++) {
+ short mu,e,f,y;
+ static short etab[]={0,132,396,924,1980,4092,8316,16764};
+
+ mu = 255-i;
+ e = (mu & 0x70)/16;
+ f = mu & 0x0f;
+ y = f * (1 << (e + 3));
+ y += etab[e];
+ if (mu & 0x80) y = -y;
+ __ast_mulaw[i] = y;
+ }
+ /* set up the reverse (mu-law) conversion table */
+ for (i = -32768; i < 32768; i++) {
+ __ast_lin2mu[((unsigned short)i) >> 2] = linear2ulaw(i);
+ }
+#else
+
+ for (i = 0; i < 256; i++) {
+ __ast_mulaw[i] = ulaw2linear(i);
+ }
+ /* set up the reverse (mu-law) conversion table */
+ for (i = 0; i <= 32768; i += AST_ULAW_STEP) {
+ AST_LIN2MU_LOOKUP(i) = linear2ulaw(i, 0 /* half-cooked */);
+ }
+#endif
+
+#ifdef TEST_CODING_TABLES
+ for (i = -32768; i < 32768; ++i) {
+#ifndef G711_NEW_ALGORITHM
+ unsigned char e1 = linear2ulaw(i);
+#else
+ unsigned char e1 = linear2ulaw(i, 1);
+#endif
+ short d1 = ulaw2linear(e1);
+ unsigned char e2 = AST_LIN2MU(i);
+ short d2 = ulaw2linear(e2);
+ short d3 = AST_MULAW(e1);
+
+ if (e1 != e2 || d1 != d3 || d2 != d3) {
+ ast_log(LOG_WARNING, "u-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n",
+ i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2);
+ }
+ }
+ ast_log(LOG_NOTICE, "u-Law coding table test complete.\n");
+#endif /* TEST_CODING_TABLES */
+
+#ifdef TEST_TANDEM_TRANSCODING
+ /* tandem transcoding test */
+ for (i = -32768; i < 32768; ++i) {
+ unsigned char e1 = AST_LIN2MU(i);
+ short d1 = AST_MULAW(e1);
+ unsigned char e2 = AST_LIN2MU(d1);
+ short d2 = AST_MULAW(e2);
+ unsigned char e3 = AST_LIN2MU(d2);
+ short d3 = AST_MULAW(e3);
+
+ if (i < 0 && e1 == 0x7f && e2 == 0xff && e3 == 0xff)
+ continue; /* known and normal negative 0 case */
+
+ if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) {
+ ast_log(LOG_WARNING, "u-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n",
+ i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3);
+ }
+ }
+ ast_log(LOG_NOTICE, "u-Law tandem transcoding test complete.\n");
+#endif /* TEST_TANDEM_TRANSCODING */
+}
+
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