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Diffstat (limited to 'trunk/main/alaw.c')
| -rw-r--r-- | trunk/main/alaw.c | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/trunk/main/alaw.c b/trunk/main/alaw.c new file mode 100644 index 000000000..8d3595206 --- /dev/null +++ b/trunk/main/alaw.c @@ -0,0 +1,210 @@ +/* + * 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 a-Law to Signed linear conversion + * + * \author Mark Spencer <markster@digium.com> + */ + +#include "asterisk.h" + +ASTERISK_FILE_VERSION(__FILE__, "$Revision$") + +#include "asterisk/alaw.h" + +#ifndef G711_NEW_ALGORITHM +#define AMI_MASK 0x55 + +static inline unsigned char linear2alaw(short int linear) +{ + int mask; + int seg; + int pcm_val; + static int seg_end[8] = + { + 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF + }; + + pcm_val = linear; + if (pcm_val >= 0) { + /* Sign (7th) bit = 1 */ + mask = AMI_MASK | 0x80; + } else { + /* Sign bit = 0 */ + mask = AMI_MASK; + pcm_val = -pcm_val; + } + + /* Convert the scaled magnitude to segment number. */ + for (seg = 0; seg < 8; seg++) { + if (pcm_val <= seg_end[seg]) + break; + } + /* Combine the sign, segment, and quantization bits. */ + return ((seg << 4) | ((pcm_val >> ((seg) ? (seg + 3) : 4)) & 0x0F)) ^ mask; +} +#else +static unsigned char linear2alaw(short sample, int full_coding) +{ + static const unsigned exp_lut[128] = { + 1,1,2,2,3,3,3,3, + 4,4,4,4,4,4,4,4, + 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, + 7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7, + 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 alawbyte; + + ast_alaw_get_sign_mag(sample, &sign, &mag); + if (mag > 32767) + mag = 32767; /* clip the magnitude for -32768 */ + + exponent = exp_lut[(mag >> 8) & 0x7f]; + mantissa = (mag >> (exponent + 3)) & 0x0f; + if (mag < 0x100) + exponent = 0; + + if (full_coding) { + /* full encoding, with sign and xform */ + alawbyte = (unsigned char)(sign | (exponent << 4) | mantissa); + alawbyte ^= AST_ALAW_AMI_MASK; + } else { + /* half-cooked coding -- mantissa+exponent only (for lookup tab) */ + alawbyte = (exponent << 4) | mantissa; + } + return alawbyte; +} +#endif + +#ifndef G711_NEW_ALGORITHM +static inline short int alaw2linear (unsigned char alaw) +{ + int i; + int seg; + + alaw ^= AMI_MASK; + i = ((alaw & 0x0F) << 4) + 8 /* rounding error */; + seg = (((int) alaw & 0x70) >> 4); + if (seg) + i = (i + 0x100) << (seg - 1); + return (short int) ((alaw & 0x80) ? i : -i); +} +#else +static inline short alaw2linear(unsigned char alawbyte) +{ + unsigned exponent, mantissa; + short sample; + + alawbyte ^= AST_ALAW_AMI_MASK; + exponent = (alawbyte & 0x70) >> 4; + mantissa = alawbyte & 0x0f; + sample = (mantissa << 4) + 8 /* rounding error */; + if (exponent) + sample = (sample + 0x100) << (exponent - 1); + if (!(alawbyte & 0x80)) + sample = -sample; + return sample; +} +#endif + + + +#ifndef G711_NEW_ALGORITHM +unsigned char __ast_lin2a[8192]; +#else +unsigned char __ast_lin2a[AST_ALAW_TAB_SIZE]; +#endif +short __ast_alaw[256]; + +void ast_alaw_init(void) +{ + int i; + /* + * Set up mu-law conversion table + */ +#ifndef G711_NEW_ALGORITHM + for (i = 0; i < 256; i++) { + __ast_alaw[i] = alaw2linear(i); + } + /* set up the reverse (mu-law) conversion table */ + for (i = -32768; i < 32768; i++) { + __ast_lin2a[((unsigned short)i) >> 3] = linear2alaw(i); + } +#else + for (i = 0; i < 256; i++) { + __ast_alaw[i] = alaw2linear(i); + } + /* set up the reverse (a-law) conversion table */ + for (i = 0; i <= 32768; i += AST_ALAW_STEP) { + AST_LIN2A_LOOKUP(i) = linear2alaw(i, 0 /* half-cooked */); + } +#endif + +#ifdef TEST_CODING_TABLES + for (i = -32768; i < 32768; ++i) { +#ifndef G711_NEW_ALGORITHM + unsigned char e1 = linear2alaw(i); +#else + unsigned char e1 = linear2alaw(i, 1); +#endif + short d1 = alaw2linear(e1); + unsigned char e2 = AST_LIN2A(i); + short d2 = alaw2linear(e2); + short d3 = AST_ALAW(e1); + + if (e1 != e2 || d1 != d3 || d2 != d3) { + ast_log(LOG_WARNING, "a-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, "a-Law coding tables test complete.\n"); +#endif /* TEST_CODING_TABLES */ + +#ifdef TEST_TANDEM_TRANSCODING + /* tandem transcoding test */ + for (i = -32768; i < 32768; ++i) { + unsigned char e1 = AST_LIN2A(i); + short d1 = AST_ALAW(e1); + unsigned char e2 = AST_LIN2A(d1); + short d2 = AST_ALAW(e2); + unsigned char e3 = AST_LIN2A(d2); + short d3 = AST_ALAW(e3); + + if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) { + ast_log(LOG_WARNING, "a-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, "a-Law tandem transcoding test complete.\n"); +#endif /* TEST_TANDEM_TRANSCODING */ + +} + |