#include "asterisk.h"
#include "asterisk/alaw.h"
#include "asterisk/logger.h"
Go to the source code of this file.
Defines | |
#define | AMI_MASK 0x55 |
Functions | |
static short int | alaw2linear (unsigned char alaw) |
void | ast_alaw_init (void) |
To init the alaw to slinear conversion stuff, this needs to be run. | |
static unsigned char | linear2alaw (short int linear) |
Variables | |
short | __ast_alaw [256] |
unsigned char | __ast_lin2a [8192] |
converts signed linear to alaw |
Definition in file alaw.c.
#define AMI_MASK 0x55 |
static short int alaw2linear | ( | unsigned char | alaw | ) | [inline, static] |
Definition at line 114 of file alaw.c.
References AMI_MASK.
Referenced by ast_alaw_init().
00115 { 00116 int i; 00117 int seg; 00118 00119 alaw ^= AMI_MASK; 00120 i = ((alaw & 0x0F) << 4) + 8 /* rounding error */; 00121 seg = (((int) alaw & 0x70) >> 4); 00122 if (seg) { 00123 i = (i + 0x100) << (seg - 1); 00124 } 00125 return (short int) ((alaw & 0x80) ? i : -i); 00126 }
void ast_alaw_init | ( | void | ) |
To init the alaw to slinear conversion stuff, this needs to be run.
Definition at line 154 of file alaw.c.
References alaw2linear(), AST_ALAW, AST_ALAW_STEP, AST_LIN2A, ast_log(), linear2alaw(), LOG_NOTICE, and LOG_WARNING.
Referenced by main().
00155 { 00156 int i; 00157 /* 00158 * Set up mu-law conversion table 00159 */ 00160 #ifndef G711_NEW_ALGORITHM 00161 for (i = 0; i < 256; i++) { 00162 __ast_alaw[i] = alaw2linear(i); 00163 } 00164 /* set up the reverse (mu-law) conversion table */ 00165 for (i = -32768; i < 32768; i++) { 00166 __ast_lin2a[((unsigned short)i) >> 3] = linear2alaw(i); 00167 } 00168 #else 00169 for (i = 0; i < 256; i++) { 00170 __ast_alaw[i] = alaw2linear(i); 00171 } 00172 /* set up the reverse (a-law) conversion table */ 00173 for (i = 0; i <= 32768; i += AST_ALAW_STEP) { 00174 AST_LIN2A_LOOKUP(i) = linear2alaw(i, 0 /* half-cooked */); 00175 } 00176 #endif 00177 00178 #ifdef TEST_CODING_TABLES 00179 for (i = -32768; i < 32768; ++i) { 00180 #ifndef G711_NEW_ALGORITHM 00181 unsigned char e1 = linear2alaw(i); 00182 #else 00183 unsigned char e1 = linear2alaw(i, 1); 00184 #endif 00185 short d1 = alaw2linear(e1); 00186 unsigned char e2 = AST_LIN2A(i); 00187 short d2 = alaw2linear(e2); 00188 short d3 = AST_ALAW(e1); 00189 00190 if (e1 != e2 || d1 != d3 || d2 != d3) { 00191 ast_log(LOG_WARNING, "a-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n", 00192 i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2); 00193 } 00194 } 00195 ast_log(LOG_NOTICE, "a-Law coding tables test complete.\n"); 00196 #endif /* TEST_CODING_TABLES */ 00197 00198 #ifdef TEST_TANDEM_TRANSCODING 00199 /* tandem transcoding test */ 00200 for (i = -32768; i < 32768; ++i) { 00201 unsigned char e1 = AST_LIN2A(i); 00202 short d1 = AST_ALAW(e1); 00203 unsigned char e2 = AST_LIN2A(d1); 00204 short d2 = AST_ALAW(e2); 00205 unsigned char e3 = AST_LIN2A(d2); 00206 short d3 = AST_ALAW(e3); 00207 00208 if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) { 00209 ast_log(LOG_WARNING, "a-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n", 00210 i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3); 00211 } 00212 } 00213 ast_log(LOG_NOTICE, "a-Law tandem transcoding test complete.\n"); 00214 #endif /* TEST_TANDEM_TRANSCODING */ 00215 00216 }
static unsigned char linear2alaw | ( | short int | linear | ) | [inline, static] |
Definition at line 40 of file alaw.c.
References AMI_MASK.
Referenced by ast_alaw_init().
00041 { 00042 int mask; 00043 int seg; 00044 int pcm_val; 00045 static int seg_end[8] = 00046 { 00047 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF 00048 }; 00049 00050 pcm_val = linear; 00051 if (pcm_val >= 0) { 00052 /* Sign (7th) bit = 1 */ 00053 mask = AMI_MASK | 0x80; 00054 } else { 00055 /* Sign bit = 0 */ 00056 mask = AMI_MASK; 00057 pcm_val = -pcm_val; 00058 } 00059 00060 /* Convert the scaled magnitude to segment number. */ 00061 for (seg = 0; seg < 8; seg++) { 00062 if (pcm_val <= seg_end[seg]) { 00063 break; 00064 } 00065 } 00066 /* Combine the sign, segment, and quantization bits. */ 00067 return ((seg << 4) | ((pcm_val >> ((seg) ? (seg + 3) : 4)) & 0x0F)) ^ mask; 00068 }
short __ast_alaw[256] |
unsigned char __ast_lin2a[8192] |