G711格式音频编解码

/*

 * This source code is a product of Sun Microsystems, Inc. and is provided

 * for unrestricted use.  Users may copy or modify this source code without

 * charge.

 *

 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING

 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.

 *

 * Sun source code is provided with no support and without any obligation on

 * the part of Sun Microsystems, Inc. to assist in its use, correction,

 * modification or enhancement.

 *

 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE

 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE

 * OR ANY PART THEREOF.

 *

 * In no event will Sun Microsystems, Inc. be liable for any lost revenue

 * or profits or other special, indirect and consequential damages, even if

 * Sun has been advised of the possibility of such damages.

 *

 * Sun Microsystems, Inc.

 * 2550 Garcia Avenue

 * Mountain View, California  94043

 */

/*

 * g711.h

 *

 * u-law, A-law and linear PCM conversions.

 */

#ifndef G711_H

#define G711_H

/*

 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law

 *

 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.

 *

 * Linear Input CodeCompressed Code

 * ------------------------ ---------------

 * 0000000wxyza 000wxyz

 * 0000001wxyza 001wxyz

 * 000001wxyzab 010wxyz

 * 00001wxyzabc 011wxyz

 * 0001wxyzabcd 100wxyz

 * 001wxyzabcde 101wxyz

 * 01wxyzabcdef 110wxyz

 * 1wxyzabcdefg 111wxyz

 *

 * For further information see John C. Bellamy's Digital Telephony, 1982,

 * John Wiley & Sons, pps 98-111 and 472-476.

 */

/* pcm_val is 2's complement (16-bit range) */

unsigned char _af_linear2alaw (short pcm_val);

/*

 * alaw2linear() - Convert an A-law value to 16-bit linear PCM

 *

 */

short _af_alaw2linear (unsignedchar a_val);

/*

 * linear2ulaw() - Convert a linear PCM value to u-law

 *

 * In order to simplify the encoding process, the original linear magnitude

 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to

 * (33 - 8191). The result can be seen in the following encoding table:

 *

 * Biased Linear Input Code Compressed Code

 * ------------------------ ---------------

 * 00000001wxyza 000wxyz

 * 0000001wxyzab 001wxyz

 * 000001wxyzabc 010wxyz

 * 00001wxyzabcd 011wxyz

 * 0001wxyzabcde 100wxyz

 * 001wxyzabcdef 101wxyz

 * 01wxyzabcdefg 110wxyz

 * 1wxyzabcdefgh 111wxyz

 *

 * Each biased linear code has a leading 1 which identifies the segment

 * number. The value of the segment number is equal to 7 minus the number

 * of leading 0's. The quantization interval is directly available as the

 * four bits wxyz.  * The trailing bits (a - h) are ignored.

 *

 * Ordinarily the complement of the resulting code word is used for

 * transmission, and so the code word is complemented before it is returned.

 *

 * For further information see John C. Bellamy's Digital Telephony, 1982,

 * John Wiley & Sons, pps 98-111 and 472-476.

 */

/* pcm_val is 2's complement (16-bit range) */

unsigned char _af_linear2ulaw (short pcm_val);

/*

 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM

 *

 * First, a biased linear code is derived from the code word. An unbiased

 * output can then be obtained by subtracting 33 from the biased code.

 *

 * Note that this function expects to be passed the complement of the

 * original code word. This is in keeping with ISDN conventions.

 */

short _af_ulaw2linear (unsignedchar u_val);

void G711Encoder(short *pcm,unsignedchar *code,int size,int lawflag);

void G711Decoder(short *pcm,unsignedchar *code,int size,int lawflag);

#endif /* G711_H */

/*

 * This source code is a product of Sun Microsystems, Inc. and is provided

 * for unrestricted use.  Users may copy or modify this source code without

 * charge.

 *

 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING

 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.

 *

 * Sun source code is provided with no support and without any obligation on

 * the part of Sun Microsystems, Inc. to assist in its use, correction,

 * modification or enhancement.

 *

 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE

 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE

 * OR ANY PART THEREOF.

 *

 * In no event will Sun Microsystems, Inc. be liable for any lost revenue

 * or profits or other special, indirect and consequential damages, even if

 * Sun has been advised of the possibility of such damages.

 *

 * Sun Microsystems, Inc.

 * 2550 Garcia Avenue

 * Mountain View, California  94043

 */

#include "g711.h"

#define SUPERCEDED

/*

 * g711.c

 *

 * u-law, A-law and linear PCM conversions.

 */

#define SIGN_BIT (0x80)/* Sign bit for a A-law byte. */

#define QUANT_MASK (0xf)/* Quantization field mask. */

#define NSEGS (8)/* Number of A-law segments. */

#define SEG_SHIFT (4)/* Left shift for segment number. */

#define SEG_MASK (0x70)/* Segment field mask. */

/* copy from CCITT G.711 specifications */

unsigned char _u2a[128] = {/* u- to A-law conversions */

1,1,2,2,3,3,4,4,

5,5,6,6,7,7,8,8,

9,10,11,12,13,14,15,16,

17,18,19,20,21,22,23,24,

25,27,29,31,33,34,35,36,

37,38,39,40,41,42,43,44,

46,48,49,50,51,52,53,54,

55,56,57,58,59,60,61,62,

64,65,66,67,68,69,70,71,

72,73,74,75,76,77,78,79,

81,82,83,84,85,86,87,88,

89,90,91,92,93,94,95,96,

97,98,99,100,101,102,103,104,

105,106,107,108,109,110,111,112,

113,114,115,116,117,118,119,120,

121,122,123,124,125,126,127,128};

unsigned char _a2u[128] = {/* A- to u-law conversions */

1,3,5,7,9,11,13,15,

16,17,18,19,20,21,22,23,

24,25,26,27,28,29,30,31,

32,32,33,33,34,34,35,35,

36,37,38,39,40,41,42,43,

44,45,46,47,48,48,49,49,

50,51,52,53,54,55,56,57,

58,59,60,61,62,63,64,64,

65,66,67,68,69,70,71,72,

73,74,75,76,77,78,79,79,

80,81,82,83,84,85,86,87,

88,89,90,91,92,93,94,95,

96,97,98,99,100,101,102,103,

104,105,106,107,108,109,110,111,

112,113,114,115,116,117,118,119,

120,121,122,123,124,125,126,127};

/* see libst.h */

#ifdef SUPERCEDED

static short seg_end[8] = {0xFF,0x1FF,0x3FF,0x7FF,

    0xFFF,0x1FFF,0x3FFF,0x7FFF};

static short

search(short val,short *table,short size)

{

shorti;

    

for (i =0; i < size; i++) {

if (val <= *table++)

return (i);

}

return (size);

}

/*

 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law

 *

 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.

 *

 * Linear Input CodeCompressed Code

 * ------------------------ ---------------

 * 0000000wxyza 000wxyz

 * 0000001wxyza 001wxyz

 * 000001wxyzab 010wxyz

 * 00001wxyzabc 011wxyz

 * 0001wxyzabcd 100wxyz

 * 001wxyzabcde 101wxyz

 * 01wxyzabcdef 110wxyz

 * 1wxyzabcdefg 111wxyz

 *

 * For further information see John C. Bellamy's Digital Telephony, 1982,

 * John Wiley & Sons, pps 98-111 and 472-476.

 */

unsigned char

_af_linear2alaw(short pcm_val)

/* 2's complement (16-bit range) */

{

shortmask;

shortseg;

unsignedcharaval;

    

if (pcm_val >=0) {

mask = 0xD5;/* sign (7th) bit = 1 */

} else {

mask = 0x55;/* sign bit = 0 */

pcm_val = -pcm_val-1;/* - 8;*/

if(pcm_val<0)pcm_val =32767;

}

    

/* Convert the scaled magnitude to segment number. */

seg = search(pcm_val,seg_end,8);

    

/* Combine the sign, segment, and quantization bits. */

    

if (seg >=8)/* out of range, return maximum value. */

return (0x7F ^ mask);

else {

aval = seg << SEG_SHIFT;

if (seg <2)

aval |= (pcm_val >>4) &QUANT_MASK;

else

aval |= (pcm_val >> (seg +3)) &QUANT_MASK;

return (aval ^ mask);

}

}

/*

 * alaw2linear() - Convert an A-law value to 16-bit linear PCM

 *

 */

short

_af_alaw2linear( unsignedchar a_val)

{

shortt;

shortseg;

    

a_val ^= 0x55;

    

t = (a_val & QUANT_MASK) <<4;

seg = ((unsigned)a_val &SEG_MASK) >>SEG_SHIFT;

switch (seg) {

        case0:

            t += 8;

            break;

        case1:

            t += 0x108;

            break;

        default:

            t += 0x108;

            t <<= seg - 1;

}

return ((a_val &SIGN_BIT) ? t : -t);

}

#define BIAS (0x84)/* Bias for linear code. */

/*

 * linear2ulaw() - Convert a linear PCM value to u-law

 *

 * In order to simplify the encoding process, the original linear magnitude

 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to

 * (33 - 8191). The result can be seen in the following encoding table:

 *

 * Biased Linear Input Code Compressed Code

 * ------------------------ ---------------

 * 00000001wxyza 000wxyz

 * 0000001wxyzab 001wxyz

 * 000001wxyzabc 010wxyz

 * 00001wxyzabcd 011wxyz

 * 0001wxyzabcde 100wxyz

 * 001wxyzabcdef 101wxyz

 * 01wxyzabcdefg 110wxyz

 * 1wxyzabcdefgh 111wxyz

 *

 * Each biased linear code has a leading 1 which identifies the segment

 * number. The value of the segment number is equal to 7 minus the number

 * of leading 0's. The quantization interval is directly available as the

 * four bits wxyz.  * The trailing bits (a - h) are ignored.

 *

 * Ordinarily the complement of the resulting code word is used for

 * transmission, and so the code word is complemented before it is returned.

 *

 * For further information see John C. Bellamy's Digital Telephony, 1982,

 * John Wiley & Sons, pps 98-111 and 472-476.

 */

/* 2's complement (16-bit range) */

unsigned char _af_linear2ulaw (short pcm_val)

{

shortmask;

shortseg;

unsignedcharuval;

    

/* Get the sign and the magnitude of the value. */

if (pcm_val <0) {

pcm_val = BIAS - pcm_val;

mask = 0x7F;

} else {

pcm_val += BIAS;

mask = 0xFF;

}

    

/* Convert the scaled magnitude to segment number. */

seg = search(pcm_val,seg_end,8);

    

/*

* Combine the sign, segment, quantization bits;

* and complement the code word.

*/

if (seg >=8)/* out of range, return maximum value. */

return (0x7F ^ mask);

else {

uval = (seg << 4) | ((pcm_val >> (seg +3)) &0xF);

return (uval ^ mask);

}

    

}

/*

 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM

 *

 * First, a biased linear code is derived from the code word. An unbiased

 * output can then be obtained by subtracting 33 from the biased code.

 *

 * Note that this function expects to be passed the complement of the

 * original code word. This is in keeping with ISDN conventions.

 */

short _af_ulaw2linear (unsignedchar u_val)

{

shortt;

    

/* Complement to obtain normal u-law value. */

u_val = ~u_val;

    

/*

* Extract and bias the quantization bits. Then

* shift up by the segment number and subtract out the bias.

*/

t = ((u_val & QUANT_MASK) <<3) +BIAS;

t <<= ((unsigned)u_val &SEG_MASK) >>SEG_SHIFT;

    

return ((u_val &SIGN_BIT) ? (BIAS - t) : (t -BIAS));

}

#endif

/* A-law to u-law conversion */

unsigned char

alaw2ulaw(unsignedchar aval)

{

aval &= 0xff;

return ((aval &0x80) ? (0xFF ^_a2u[aval ^ 0xD5]) :

            (0x7F ^_a2u[aval ^0x55]));

}

/* u-law to A-law conversion */

unsigned char

ulaw2alaw(unsignedchar uval)

{

uval &= 0xff;

return ((uval &0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] -1)) :

            (0x55 ^ (_u2a[0x7F ^ uval] -1)));

}

//lawflag :0-A,1-U

void G711Encoder(short *pcm,unsignedchar *code,int size,int lawflag)

{

int i;

    

if(lawflag==0){

for(i=0;i<size;i++){

code[i]=_af_linear2alaw(pcm[i]);

}

}

else{

for(i=0;i<size;i++){

code[i]=_af_linear2ulaw(pcm[i]);

}

}

}

void G711Decoder(short *pcm,unsignedchar *code,int size,int lawflag)

{

int i;

    

if(lawflag==0){

for(i=0;i<size;i++){

pcm[i]=_af_alaw2linear(code[i]);

}

}

else{

for(i=0;i<size;i++){

pcm[i]=_af_ulaw2linear(code[i]);

}

}

}