diff options
author | kpfleming <kpfleming@f38db490-d61c-443f-a65b-d21fe96a405b> | 2006-08-21 02:11:39 +0000 |
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committer | kpfleming <kpfleming@f38db490-d61c-443f-a65b-d21fe96a405b> | 2006-08-21 02:11:39 +0000 |
commit | 8b0c007ad990aa27d9868da49215fd1076ac77cc (patch) | |
tree | 270b9c46c1e644483d6d2a35b509f43218ba3252 /main/ulaw.c | |
parent | a42edc84034f91932a3e12d503e07f76a6eb498a (diff) |
merge new_loader_completion branch, including (at least):
- restructured build tree and makefiles to eliminate recursion problems
- support for embedded modules
- support for static builds
- simpler cross-compilation support
- simpler module/loader interface (no exported symbols)
git-svn-id: http://svn.digium.com/svn/asterisk/trunk@40722 f38db490-d61c-443f-a65b-d21fe96a405b
Diffstat (limited to 'main/ulaw.c')
-rw-r--r-- | main/ulaw.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/main/ulaw.c b/main/ulaw.c new file mode 100644 index 000000000..2735f6cce --- /dev/null +++ b/main/ulaw.c @@ -0,0 +1,106 @@ +/* + * 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" + +#define ZEROTRAP /*!< turn on the trap as per the MIL-STD */ +#define BIAS 0x84 /*!< define the add-in bias for 16 bit samples */ +#define CLIP 32635 + +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; +} + +/*! + * \brief Set up mu-law conversion table + */ +void ast_ulaw_init(void) +{ + int i; + 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); + } +} + |