Asterisk - The Open Source Telephony Project GIT-master-2de1a68
Macros | Functions | Variables
alaw.h File Reference

A-Law to Signed linear conversion. More...

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Macros

#define AST_ALAW(a)   (__ast_alaw[(int)(a)])
 
#define AST_ALAW_AMI_MASK   0x55
 
#define AST_ALAW_BIT_LOSS   4
 
#define AST_ALAW_SIGN_BIT   0x80
 
#define AST_ALAW_STEP   (1 << AST_ALAW_BIT_LOSS)
 
#define AST_ALAW_TAB_SIZE   (32768 / AST_ALAW_STEP + 1)
 
#define AST_LIN2A(a)   (__ast_lin2a[((unsigned short)(a)) >> 3])
 

Functions

void ast_alaw_init (void)
 To init the alaw to slinear conversion stuff, this needs to be run. More...
 

Variables

short __ast_alaw [256]
 
unsigned char __ast_lin2a [8192]
 converts signed linear to alaw More...
 

Detailed Description

A-Law to Signed linear conversion.

Definition in file alaw.h.

Macro Definition Documentation

◆ AST_ALAW

#define AST_ALAW (   a)    (__ast_alaw[(int)(a)])

Definition at line 84 of file alaw.h.

◆ AST_ALAW_AMI_MASK

#define AST_ALAW_AMI_MASK   0x55

Definition at line 36 of file alaw.h.

◆ AST_ALAW_BIT_LOSS

#define AST_ALAW_BIT_LOSS   4

Definition at line 32 of file alaw.h.

◆ AST_ALAW_SIGN_BIT

#define AST_ALAW_SIGN_BIT   0x80

Definition at line 35 of file alaw.h.

◆ AST_ALAW_STEP

#define AST_ALAW_STEP   (1 << AST_ALAW_BIT_LOSS)

Definition at line 33 of file alaw.h.

◆ AST_ALAW_TAB_SIZE

#define AST_ALAW_TAB_SIZE   (32768 / AST_ALAW_STEP + 1)

Definition at line 34 of file alaw.h.

◆ AST_LIN2A

#define AST_LIN2A (   a)    (__ast_lin2a[((unsigned short)(a)) >> 3])

Definition at line 50 of file alaw.h.

Function Documentation

◆ ast_alaw_init()

void ast_alaw_init ( void  )

To init the alaw to slinear conversion stuff, this needs to be run.

Definition at line 152 of file alaw.c.

153{
154 int i;
155 /*
156 * Set up mu-law conversion table
157 */
158#ifndef G711_NEW_ALGORITHM
159 for (i = 0; i < 256; i++) {
160 __ast_alaw[i] = alaw2linear(i);
161 }
162 /* set up the reverse (mu-law) conversion table */
163 for (i = -32768; i < 32768; i++) {
164 __ast_lin2a[((unsigned short)i) >> 3] = linear2alaw(i);
165 }
166#else
167 for (i = 0; i < 256; i++) {
168 __ast_alaw[i] = alaw2linear(i);
169 }
170 /* set up the reverse (a-law) conversion table */
171 for (i = 0; i <= 32768; i += AST_ALAW_STEP) {
172 AST_LIN2A_LOOKUP(i) = linear2alaw(i, 0 /* half-cooked */);
173 }
174#endif
175
176#ifdef TEST_CODING_TABLES
177 for (i = -32768; i < 32768; ++i) {
178#ifndef G711_NEW_ALGORITHM
179 unsigned char e1 = linear2alaw(i);
180#else
181 unsigned char e1 = linear2alaw(i, 1);
182#endif
183 short d1 = alaw2linear(e1);
184 unsigned char e2 = AST_LIN2A(i);
185 short d2 = alaw2linear(e2);
186 short d3 = AST_ALAW(e1);
187
188 if (e1 != e2 || d1 != d3 || d2 != d3) {
189 ast_log(LOG_WARNING, "a-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n",
190 i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2);
191 }
192 }
193 ast_log(LOG_NOTICE, "a-Law coding tables test complete.\n");
194#endif /* TEST_CODING_TABLES */
195
196#ifdef TEST_TANDEM_TRANSCODING
197 /* tandem transcoding test */
198 for (i = -32768; i < 32768; ++i) {
199 unsigned char e1 = AST_LIN2A(i);
200 short d1 = AST_ALAW(e1);
201 unsigned char e2 = AST_LIN2A(d1);
202 short d2 = AST_ALAW(e2);
203 unsigned char e3 = AST_LIN2A(d2);
204 short d3 = AST_ALAW(e3);
205
206 if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) {
207 ast_log(LOG_WARNING, "a-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n",
208 i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3);
209 }
210 }
211 ast_log(LOG_NOTICE, "a-Law tandem transcoding test complete.\n");
212#endif /* TEST_TANDEM_TRANSCODING */
213
214}
static unsigned char linear2alaw(short int linear)
Definition: alaw.c:38
unsigned char __ast_lin2a[8192]
converts signed linear to alaw
Definition: alaw.c:146
static short int alaw2linear(unsigned char alaw)
Definition: alaw.c:112
short __ast_alaw[256]
Definition: alaw.c:150
#define AST_ALAW_STEP
Definition: alaw.h:33
#define AST_LIN2A(a)
Definition: alaw.h:50
#define AST_ALAW(a)
Definition: alaw.h:84
#define ast_log
Definition: astobj2.c:42
#define LOG_NOTICE
#define LOG_WARNING

References __ast_alaw, __ast_lin2a, alaw2linear(), AST_ALAW, AST_ALAW_STEP, AST_LIN2A, ast_log, linear2alaw(), LOG_NOTICE, and LOG_WARNING.

Referenced by asterisk_daemon().

Variable Documentation

◆ __ast_alaw

short __ast_alaw[256]
extern

help

Definition at line 150 of file alaw.c.

Referenced by ast_alaw_init().

◆ __ast_lin2a

unsigned char __ast_lin2a[8192]
extern

converts signed linear to alaw

Definition at line 146 of file alaw.c.

Referenced by ast_alaw_init().