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git-svn-id: http://svn.digium.com/svn/asterisk/trunk@105840 f38db490-d61c-443f-a65b-d21fe96a405b
213 lines
5 KiB
C
213 lines
5 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 a-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/alaw.h"
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#ifndef G711_NEW_ALGORITHM
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#define AMI_MASK 0x55
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static inline unsigned char linear2alaw(short int linear)
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{
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int mask;
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int seg;
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int pcm_val;
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static int seg_end[8] =
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{
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0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF
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};
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pcm_val = linear;
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if (pcm_val >= 0) {
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/* Sign (7th) bit = 1 */
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mask = AMI_MASK | 0x80;
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} else {
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/* Sign bit = 0 */
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mask = AMI_MASK;
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pcm_val = -pcm_val;
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}
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/* Convert the scaled magnitude to segment number. */
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for (seg = 0; seg < 8; seg++) {
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if (pcm_val <= seg_end[seg]) {
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break;
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}
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}
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/* Combine the sign, segment, and quantization bits. */
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return ((seg << 4) | ((pcm_val >> ((seg) ? (seg + 3) : 4)) & 0x0F)) ^ mask;
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}
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#else
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static unsigned char linear2alaw(short sample, int full_coding)
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{
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static const unsigned exp_lut[128] = {
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1,1,2,2,3,3,3,3,
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4,4,4,4,4,4,4,4,
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5,5,5,5,5,5,5,5,
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5,5,5,5,5,5,5,5,
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6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7 };
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unsigned sign, exponent, mantissa, mag;
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unsigned char alawbyte;
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ast_alaw_get_sign_mag(sample, &sign, &mag);
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if (mag > 32767)
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mag = 32767; /* clip the magnitude for -32768 */
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exponent = exp_lut[(mag >> 8) & 0x7f];
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mantissa = (mag >> (exponent + 3)) & 0x0f;
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if (mag < 0x100)
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exponent = 0;
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if (full_coding) {
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/* full encoding, with sign and xform */
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alawbyte = (unsigned char)(sign | (exponent << 4) | mantissa);
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alawbyte ^= AST_ALAW_AMI_MASK;
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} else {
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/* half-cooked coding -- mantissa+exponent only (for lookup tab) */
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alawbyte = (exponent << 4) | mantissa;
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}
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return alawbyte;
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}
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#endif
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#ifndef G711_NEW_ALGORITHM
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static inline short int alaw2linear (unsigned char alaw)
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{
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int i;
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int seg;
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alaw ^= AMI_MASK;
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i = ((alaw & 0x0F) << 4) + 8 /* rounding error */;
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seg = (((int) alaw & 0x70) >> 4);
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if (seg) {
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i = (i + 0x100) << (seg - 1);
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}
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return (short int) ((alaw & 0x80) ? i : -i);
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}
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#else
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static inline short alaw2linear(unsigned char alawbyte)
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{
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unsigned exponent, mantissa;
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short sample;
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alawbyte ^= AST_ALAW_AMI_MASK;
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exponent = (alawbyte & 0x70) >> 4;
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mantissa = alawbyte & 0x0f;
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sample = (mantissa << 4) + 8 /* rounding error */;
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if (exponent)
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sample = (sample + 0x100) << (exponent - 1);
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if (!(alawbyte & 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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#ifndef G711_NEW_ALGORITHM
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unsigned char __ast_lin2a[8192];
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#else
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unsigned char __ast_lin2a[AST_ALAW_TAB_SIZE];
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#endif
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short __ast_alaw[256];
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void ast_alaw_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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__ast_alaw[i] = alaw2linear(i);
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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_lin2a[((unsigned short)i) >> 3] = linear2alaw(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_alaw[i] = alaw2linear(i);
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}
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/* set up the reverse (a-law) conversion table */
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for (i = 0; i <= 32768; i += AST_ALAW_STEP) {
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AST_LIN2A_LOOKUP(i) = linear2alaw(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 = linear2alaw(i);
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#else
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unsigned char e1 = linear2alaw(i, 1);
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#endif
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short d1 = alaw2linear(e1);
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unsigned char e2 = AST_LIN2A(i);
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short d2 = alaw2linear(e2);
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short d3 = AST_ALAW(e1);
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if (e1 != e2 || d1 != d3 || d2 != d3) {
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ast_log(LOG_WARNING, "a-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, "a-Law coding tables 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_LIN2A(i);
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short d1 = AST_ALAW(e1);
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unsigned char e2 = AST_LIN2A(d1);
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short d2 = AST_ALAW(e2);
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unsigned char e3 = AST_LIN2A(d2);
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short d3 = AST_ALAW(e3);
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if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) {
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ast_log(LOG_WARNING, "a-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, "a-Law tandem transcoding test complete.\n");
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#endif /* TEST_TANDEM_TRANSCODING */
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}
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