ulaw.h File Reference

u-Law to Signed linear conversion More...

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Defines
#define	AST_LIN2MU(a)   (__ast_lin2mu[((unsigned short)(a)) >> 2])
#define	AST_MULAW(a)   (__ast_mulaw[(a)])
Functions
void	ast_ulaw_init (void)
	Set up mu-law conversion table.
Variables
unsigned char	__ast_lin2mu [16384]
short	__ast_mulaw [256]

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Detailed Description

u-Law to Signed linear conversion

Definition in file ulaw.h.

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Define Documentation

#define AST_LIN2MU

(

a

)

(__ast_lin2mu[((unsigned short)(a)) >> 2])

Definition at line 40 of file ulaw.h.

Referenced by fill_rxgain(), fill_txgain(), i4l_write(), lintoulaw_framein(), load_module(), and make_tone_burst().

#define AST_MULAW

(

a

)

(__ast_mulaw[(a)])

Definition at line 41 of file ulaw.h.

Referenced by ast_dsp_process(), fill_rxgain(), fill_txgain(), i4l_read(), load_module(), tdd_feed(), and ulawtolin_framein().

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Function Documentation

void ast_ulaw_init

(

void

)

Set up mu-law conversion table.

Init the ulaw conversion stuff

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

Definition at line 84 of file ulaw.c.

References linear2ulaw().

Referenced by main().

{
   int i;
   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 = -32768; i < 32768; i++) {
      __ast_lin2mu[((unsigned short)i) >> 2] = linear2ulaw(i);
   }

}

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Variable Documentation

unsigned char __ast_lin2mu[16384]

converts signed linear to mulaw

Definition at line 35 of file ulaw.c.

short __ast_mulaw[256]

help

Definition at line 36 of file ulaw.c.