e6b2e9a750
This patch adds 'const' tags to a number of Asterisk APIs where they are appropriate (where the API already demanded that the function argument not be modified, but the compiler was not informed of that fact). The list includes: - CLI command handlers - CLI command handler arguments - AGI command handlers - AGI command handler arguments - Dialplan application handler arguments - Speech engine API function arguments In addition, various file-scope and function-scope constant arrays got 'const' and/or 'static' qualifiers where they were missing. Review: https://reviewboard.asterisk.org/r/251/ git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@196072 65c4cc65-6c06-0410-ace0-fbb531ad65f3
247 lines
6.7 KiB
C
247 lines
6.7 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 1999 - 2005, Digium, Inc.
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*
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* Mark Spencer <markster@digium.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief u-Law to Signed linear conversion
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*
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* \author Mark Spencer <markster@digium.com>
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*/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include "asterisk/ulaw.h"
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#if 0
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/* ZEROTRAP is the military recommendation to improve the encryption
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* of u-Law traffic. It is irrelevant with modern encryption systems
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* like AES, and will simply degrade the signal quality.
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* ZEROTRAP is not implemented in AST_LIN2MU and so the coding table
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* tests will fail if you use it */
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#define ZEROTRAP /*!< turn on the trap as per the MIL-STD */
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#endif
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#define BIAS 0x84 /*!< define the add-in bias for 16 bit samples */
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#define CLIP 32635
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#ifndef G711_NEW_ALGORITHM
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unsigned char __ast_lin2mu[16384];
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short __ast_mulaw[256];
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static unsigned char linear2ulaw(short sample)
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{
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static int exp_lut[256] = {
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0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
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4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 };
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int sign, exponent, mantissa;
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unsigned char ulawbyte;
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/* Get the sample into sign-magnitude. */
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sign = (sample >> 8) & 0x80; /* set aside the sign */
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if (sign != 0)
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sample = -sample; /* get magnitude */
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if (sample > CLIP)
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sample = CLIP; /* clip the magnitude */
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/* Convert from 16 bit linear to ulaw. */
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sample = sample + BIAS;
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exponent = exp_lut[(sample >> 7) & 0xFF];
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mantissa = (sample >> (exponent + 3)) & 0x0F;
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ulawbyte = ~(sign | (exponent << 4) | mantissa);
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#ifdef ZEROTRAP
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if (ulawbyte == 0)
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ulawbyte = 0x02; /* optional CCITT trap */
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#endif
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return ulawbyte;
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}
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#else
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unsigned char __ast_lin2mu[AST_ULAW_TAB_SIZE];
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short __ast_mulaw[256];
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static unsigned char linear2ulaw(short sample, int full_coding)
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{
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static const unsigned exp_lut[256] = {
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0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
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4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 };
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unsigned sign, exponent, mantissa, mag;
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unsigned char ulawbyte;
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/* Get the sample into sign-magnitude. */
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ast_ulaw_get_sign_mag(sample, &sign, &mag);
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if (mag > CLIP)
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mag = CLIP; /* clip the magnitude */
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sign = (sample >> 8) & 0x80; /* set aside the sign */
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if (sign != 0)
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sample = -sample; /* get magnitude */
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if (sample > CLIP)
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sample = CLIP; /* clip the magnitude */
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/* Convert from 16 bit linear to ulaw. */
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mag += BIAS;
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exponent = exp_lut[(mag >> 7) & 0xFF];
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mantissa = (mag >> (exponent + 3)) & 0x0F;
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if (full_coding) {
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/* full encoding, with sign and xform */
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ulawbyte = ~(sign | (exponent << 4) | mantissa);
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#ifdef ZEROTRAP
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if (ulawbyte == 0)
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ulawbyte = 0x02; /* optional CCITT trap */
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#endif
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} else {
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/* half-cooked coding -- mantissa+exponent only (for lookup tab) */
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ulawbyte = (exponent << 4) | mantissa;
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}
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return ulawbyte;
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}
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static inline short ulaw2linear(unsigned char ulawbyte)
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{
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unsigned exponent, mantissa;
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short sample;
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static const short etab[]={0,132,396,924,1980,4092,8316,16764};
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ulawbyte = ~ulawbyte;
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exponent = (ulawbyte & 0x70) >> 4;
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mantissa = ulawbyte & 0x0f;
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sample = mantissa << (exponent + 3);
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sample += etab[exponent];
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if (ulawbyte & 0x80)
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sample = -sample;
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return sample;
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}
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#endif
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/*!
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* \brief Set up mu-law conversion table
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*/
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void ast_ulaw_init(void)
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{
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int i;
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/*
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* Set up mu-law conversion table
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*/
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#ifndef G711_NEW_ALGORITHM
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for (i = 0;i < 256;i++) {
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short mu,e,f,y;
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static const short etab[]={0,132,396,924,1980,4092,8316,16764};
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mu = 255-i;
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e = (mu & 0x70)/16;
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f = mu & 0x0f;
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y = f * (1 << (e + 3));
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y += etab[e];
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if (mu & 0x80) y = -y;
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__ast_mulaw[i] = y;
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}
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/* set up the reverse (mu-law) conversion table */
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for (i = -32768; i < 32768; i++) {
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__ast_lin2mu[((unsigned short)i) >> 2] = linear2ulaw(i);
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}
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#else
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for (i = 0; i < 256; i++) {
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__ast_mulaw[i] = ulaw2linear(i);
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}
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/* set up the reverse (mu-law) conversion table */
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for (i = 0; i <= 32768; i += AST_ULAW_STEP) {
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AST_LIN2MU_LOOKUP(i) = linear2ulaw(i, 0 /* half-cooked */);
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}
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#endif
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#ifdef TEST_CODING_TABLES
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for (i = -32768; i < 32768; ++i) {
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#ifndef G711_NEW_ALGORITHM
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unsigned char e1 = linear2ulaw(i);
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#else
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unsigned char e1 = linear2ulaw(i, 1);
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#endif
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short d1 = ulaw2linear(e1);
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unsigned char e2 = AST_LIN2MU(i);
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short d2 = ulaw2linear(e2);
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short d3 = AST_MULAW(e1);
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if (e1 != e2 || d1 != d3 || d2 != d3) {
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ast_log(LOG_WARNING, "u-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n",
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i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2);
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}
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}
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ast_log(LOG_NOTICE, "u-Law coding table test complete.\n");
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#endif /* TEST_CODING_TABLES */
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#ifdef TEST_TANDEM_TRANSCODING
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/* tandem transcoding test */
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for (i = -32768; i < 32768; ++i) {
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unsigned char e1 = AST_LIN2MU(i);
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short d1 = AST_MULAW(e1);
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unsigned char e2 = AST_LIN2MU(d1);
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short d2 = AST_MULAW(e2);
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unsigned char e3 = AST_LIN2MU(d2);
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short d3 = AST_MULAW(e3);
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if (i < 0 && e1 == 0x7f && e2 == 0xff && e3 == 0xff)
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continue; /* known and normal negative 0 case */
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if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) {
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ast_log(LOG_WARNING, "u-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n",
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i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3);
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}
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}
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ast_log(LOG_NOTICE, "u-Law tandem transcoding test complete.\n");
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#endif /* TEST_TANDEM_TRANSCODING */
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}
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