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.

Referenced by alawtolin_framein(), ast_alaw_init(), ast_dsp_process(), ast_dsp_silence_noise_with_energy(), calc_energy(), fill_rxgain(), fill_txgain(), handle_clear_alarms(), and load_module().

AST_ALAW_AMI_MASK

#define AST_ALAW_AMI_MASK   0x55

Definition at line 36 of file alaw.h.

Referenced by alaw2linear(), and linear2alaw().

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.

Referenced by ast_alaw_init().

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.

Referenced by ast_alaw_init(), ast_dsp_process(), fill_rxgain(), fill_txgain(), handle_clear_alarms(), lintoalaw_framein(), and load_module().

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.

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().

{
   int i;
   /*
    *  Set up mu-law conversion table
    */
#ifndef G711_NEW_ALGORITHM
   for (i = 0; i < 256; i++) {
      __ast_alaw[i] = alaw2linear(i);
   }
   /* set up the reverse (mu-law) conversion table */
   for (i = -32768; i < 32768; i++) {
      __ast_lin2a[((unsigned short)i) >> 3] = linear2alaw(i);
   }
#else
   for (i = 0; i < 256; i++) {
      __ast_alaw[i] = alaw2linear(i);
   }
   /* set up the reverse (a-law) conversion table */
   for (i = 0; i <= 32768; i += AST_ALAW_STEP) {
      AST_LIN2A_LOOKUP(i) = linear2alaw(i, 0 /* half-cooked */);
   }
#endif

#ifdef TEST_CODING_TABLES
   for (i = -32768; i < 32768; ++i) {
#ifndef G711_NEW_ALGORITHM
      unsigned char e1 = linear2alaw(i);
#else
      unsigned char e1 = linear2alaw(i, 1);
#endif
      short d1 = alaw2linear(e1);
      unsigned char e2 = AST_LIN2A(i);
      short d2 = alaw2linear(e2);
      short d3 = AST_ALAW(e1);

      if (e1 != e2 || d1 != d3 || d2 != d3) {
         ast_log(LOG_WARNING, "a-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n",
               i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2);
      }
   }
   ast_log(LOG_NOTICE, "a-Law coding tables test complete.\n");
#endif /* TEST_CODING_TABLES */

#ifdef TEST_TANDEM_TRANSCODING
   /* tandem transcoding test */
   for (i = -32768; i < 32768; ++i) {
      unsigned char e1 = AST_LIN2A(i);
      short d1 = AST_ALAW(e1);
      unsigned char e2 = AST_LIN2A(d1);
      short d2 = AST_ALAW(e2);
      unsigned char e3 = AST_LIN2A(d2);
      short d3 = AST_ALAW(e3);

      if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) {
         ast_log(LOG_WARNING, "a-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n",
               i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3);
      }
   }
   ast_log(LOG_NOTICE, "a-Law tandem transcoding test complete.\n");
#endif /* TEST_TANDEM_TRANSCODING */

}

Variable Documentation

__ast_alaw

short __ast_alaw[256]

help

Definition at line 150 of file alaw.c.

Referenced by ast_alaw_init().

__ast_lin2a

unsigned char __ast_lin2a[8192]

converts signed linear to alaw

Definition at line 146 of file alaw.c.

Referenced by ast_alaw_init().