248 lines
6.7 KiB
C
248 lines
6.7 KiB
C
/*
|
|
* 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"
|
|
#include "asterisk/logger.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 const 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 */
|
|
}
|
|
|