#include "asterisk.h"
#include "asterisk/alaw.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 109 of file alaw.c.
References AMI_MASK.
Referenced by ast_alaw_init().
00110 { 00111 int i; 00112 int seg; 00113 00114 alaw ^= AMI_MASK; 00115 i = ((alaw & 0x0F) << 4) + 8 /* rounding error */; 00116 seg = (((int) alaw & 0x70) >> 4); 00117 if (seg) { 00118 i = (i + 0x100) << (seg - 1); 00119 } 00120 return (short int) ((alaw & 0x80) ? i : -i); 00121 }
void ast_alaw_init | ( | void | ) |
To init the alaw to slinear conversion stuff, this needs to be run.
Definition at line 149 of file alaw.c.
References alaw2linear(), AST_ALAW, AST_ALAW_STEP, AST_LIN2A, ast_log(), linear2alaw(), LOG_NOTICE, and LOG_WARNING.
Referenced by main().
00150 { 00151 int i; 00152 /* 00153 * Set up mu-law conversion table 00154 */ 00155 #ifndef G711_NEW_ALGORITHM 00156 for (i = 0; i < 256; i++) { 00157 __ast_alaw[i] = alaw2linear(i); 00158 } 00159 /* set up the reverse (mu-law) conversion table */ 00160 for (i = -32768; i < 32768; i++) { 00161 __ast_lin2a[((unsigned short)i) >> 3] = linear2alaw(i); 00162 } 00163 #else 00164 for (i = 0; i < 256; i++) { 00165 __ast_alaw[i] = alaw2linear(i); 00166 } 00167 /* set up the reverse (a-law) conversion table */ 00168 for (i = 0; i <= 32768; i += AST_ALAW_STEP) { 00169 AST_LIN2A_LOOKUP(i) = linear2alaw(i, 0 /* half-cooked */); 00170 } 00171 #endif 00172 00173 #ifdef TEST_CODING_TABLES 00174 for (i = -32768; i < 32768; ++i) { 00175 #ifndef G711_NEW_ALGORITHM 00176 unsigned char e1 = linear2alaw(i); 00177 #else 00178 unsigned char e1 = linear2alaw(i, 1); 00179 #endif 00180 short d1 = alaw2linear(e1); 00181 unsigned char e2 = AST_LIN2A(i); 00182 short d2 = alaw2linear(e2); 00183 short d3 = AST_ALAW(e1); 00184 00185 if (e1 != e2 || d1 != d3 || d2 != d3) { 00186 ast_log(LOG_WARNING, "a-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n", 00187 i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2); 00188 } 00189 } 00190 ast_log(LOG_NOTICE, "a-Law coding tables test complete.\n"); 00191 #endif /* TEST_CODING_TABLES */ 00192 00193 #ifdef TEST_TANDEM_TRANSCODING 00194 /* tandem transcoding test */ 00195 for (i = -32768; i < 32768; ++i) { 00196 unsigned char e1 = AST_LIN2A(i); 00197 short d1 = AST_ALAW(e1); 00198 unsigned char e2 = AST_LIN2A(d1); 00199 short d2 = AST_ALAW(e2); 00200 unsigned char e3 = AST_LIN2A(d2); 00201 short d3 = AST_ALAW(e3); 00202 00203 if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) { 00204 ast_log(LOG_WARNING, "a-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n", 00205 i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3); 00206 } 00207 } 00208 ast_log(LOG_NOTICE, "a-Law tandem transcoding test complete.\n"); 00209 #endif /* TEST_TANDEM_TRANSCODING */ 00210 00211 }
static unsigned char linear2alaw | ( | short int | linear | ) | [inline, static] |
Definition at line 35 of file alaw.c.
References AMI_MASK.
Referenced by ast_alaw_init().
00036 { 00037 int mask; 00038 int seg; 00039 int pcm_val; 00040 static int seg_end[8] = 00041 { 00042 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF 00043 }; 00044 00045 pcm_val = linear; 00046 if (pcm_val >= 0) { 00047 /* Sign (7th) bit = 1 */ 00048 mask = AMI_MASK | 0x80; 00049 } else { 00050 /* Sign bit = 0 */ 00051 mask = AMI_MASK; 00052 pcm_val = -pcm_val; 00053 } 00054 00055 /* Convert the scaled magnitude to segment number. */ 00056 for (seg = 0; seg < 8; seg++) { 00057 if (pcm_val <= seg_end[seg]) { 00058 break; 00059 } 00060 } 00061 /* Combine the sign, segment, and quantization bits. */ 00062 return ((seg << 4) | ((pcm_val >> ((seg) ? (seg + 3) : 4)) & 0x0F)) ^ mask; 00063 }
short __ast_alaw[256] |
unsigned char __ast_lin2a[8192] |