Mon Sep 18 09:15:47 2006

Asterisk developer's documentation


ulaw.h File Reference

u-Law to Signed linear conversion More...

Go to the source code of this file.

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]


Detailed Description

u-Law to Signed linear conversion

Definition in file ulaw.h.


Define Documentation

#define AST_LIN2MU (  )     (__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 (  )     (__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().


Function Documentation

void ast_ulaw_init ( void   ) 

Set up mu-law conversion table.

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().

00085 {
00086    int i;
00087    for(i = 0;i < 256;i++) {
00088       short mu,e,f,y;
00089       static short etab[]={0,132,396,924,1980,4092,8316,16764};
00090 
00091       mu = 255-i;
00092       e = (mu & 0x70)/16;
00093       f = mu & 0x0f;
00094       y = f * (1 << (e + 3));
00095       y += etab[e];
00096       if (mu & 0x80) y = -y;
00097            __ast_mulaw[i] = y;
00098    }
00099    /* set up the reverse (mu-law) conversion table */
00100    for(i = -32768; i < 32768; i++) {
00101       __ast_lin2mu[((unsigned short)i) >> 2] = linear2ulaw(i);
00102    }
00103 
00104 }


Variable Documentation

unsigned char __ast_lin2mu[16384]

Definition at line 35 of file ulaw.c.

short __ast_mulaw[256]

help

Definition at line 36 of file ulaw.c.


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