Version 0.1.7 from FTP
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@231 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
parent
d3417cad56
commit
87255f840f
|
@ -0,0 +1,23 @@
|
|||
/*
|
||||
* Asterisk -- A telephony toolkit for Linux.
|
||||
*
|
||||
* u-Law to Signed linear conversion
|
||||
*
|
||||
* Copyright (C) 1999, Mark Spencer
|
||||
*
|
||||
* Mark Spencer <markster@linux-support.net>
|
||||
*
|
||||
* This program is free software, distributed under the terms of
|
||||
* the GNU General Public License
|
||||
*/
|
||||
|
||||
#ifndef _ASTERISK_ULAW_H
|
||||
#define _ASTERISK_ULAW_H
|
||||
|
||||
extern void ast_ulaw_init(void);
|
||||
extern unsigned char ast_lin2mu[65536];
|
||||
extern short ast_mulaw[256];
|
||||
|
||||
|
||||
|
||||
#endif
|
|
@ -0,0 +1,88 @@
|
|||
/*
|
||||
* Asterisk -- A telephony toolkit for Linux.
|
||||
*
|
||||
* u-Law to Signed linear conversion
|
||||
*
|
||||
* Copyright (C) 1999, Mark Spencer
|
||||
*
|
||||
* Mark Spencer <markster@linux-support.net>
|
||||
*
|
||||
* This program is free software, distributed under the terms of
|
||||
* the GNU General Public License
|
||||
*/
|
||||
|
||||
#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[65536];
|
||||
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);
|
||||
}
|
||||
|
||||
void ast_ulaw_init(void)
|
||||
{
|
||||
int i;
|
||||
/*
|
||||
* Set up mu-law conversion table
|
||||
*/
|
||||
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 = 0; i < 65536; i++)
|
||||
{
|
||||
ast_lin2mu[i] = linear2ulaw(i - 32768);
|
||||
}
|
||||
|
||||
}
|
||||
|
Loading…
Reference in New Issue