1/* 2 * This source code is a product of Sun Microsystems, Inc. and is provided 3 * for unrestricted use. Users may copy or modify this source code without 4 * charge. 5 * 6 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING 7 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR 8 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. 9 * 10 * Sun source code is provided with no support and without any obligation on 11 * the part of Sun Microsystems, Inc. to assist in its use, correction, 12 * modification or enhancement. 13 * 14 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE 15 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE 16 * OR ANY PART THEREOF. 17 * 18 * In no event will Sun Microsystems, Inc. be liable for any lost revenue 19 * or profits or other special, indirect and consequential damages, even if 20 * Sun has been advised of the possibility of such damages. 21 * 22 * Sun Microsystems, Inc. 23 * 2550 Garcia Avenue 24 * Mountain View, California 94043 25 */ 26 27/* 28 * g721.c 29 * 30 * Description: 31 * 32 * g721_encoder (), g721_decoder () 33 * 34 * These routines comprise an implementation of the CCITT G.721 ADPCM 35 * coding algorithm. Essentially, this implementation is identical to 36 * the bit level description except for a few deviations which 37 * take advantage of work station attributes, such as hardware 2's 38 * complement arithmetic and large memory. Specifically, certain time 39 * consuming operations such as multiplications are replaced 40 * with lookup tables and software 2's complement operations are 41 * replaced with hardware 2's complement. 42 * 43 * The deviation from the bit level specification (lookup tables) 44 * preserves the bit level performance specifications. 45 * 46 * As outlined in the G.721 Recommendation, the algorithm is broken 47 * down into modules. Each section of code below is preceded by 48 * the name of the module which it is implementing. 49 * 50 */ 51 52#include "g72x.h" 53#include "g72x_priv.h" 54 55static short qtab_721 [7] = { -124, 80, 178, 246, 300, 349, 400 } ; 56/* 57 * Maps G.721 code word to reconstructed scale factor normalized log 58 * magnitude values. 59 */ 60static short _dqlntab [16] = { -2048, 4, 135, 213, 273, 323, 373, 425, 61 425, 373, 323, 273, 213, 135, 4, -2048 } ; 62 63/* Maps G.721 code word to log of scale factor multiplier. */ 64static short _witab [16] = { -12, 18, 41, 64, 112, 198, 355, 1122, 65 1122, 355, 198, 112, 64, 41, 18, -12 } ; 66/* 67 * Maps G.721 code words to a set of values whose long and short 68 * term averages are computed and then compared to give an indication 69 * how stationary (steady state) the signal is. 70 */ 71static short _fitab [16] = { 0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00, 72 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0 } ; 73 74/* 75 * g721_encoder () 76 * 77 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns 78 * the resulting code. -1 is returned for unknown input coding value. 79 */ 80int 81g721_encoder ( 82 int sl, 83 G72x_STATE *state_ptr) 84{ 85 short sezi, se, sez ; /* ACCUM */ 86 short d ; /* SUBTA */ 87 short sr ; /* ADDB */ 88 short y ; /* MIX */ 89 short dqsez ; /* ADDC */ 90 short dq, i ; 91 92 /* linearize input sample to 14-bit PCM */ 93 sl >>= 2 ; /* 14-bit dynamic range */ 94 95 sezi = predictor_zero (state_ptr) ; 96 sez = sezi >> 1 ; 97 se = (sezi + predictor_pole (state_ptr)) >> 1 ; /* estimated signal */ 98 99 d = sl - se ; /* estimation difference */ 100 101 /* quantize the prediction difference */ 102 y = step_size (state_ptr) ; /* quantizer step size */ 103 i = quantize (d, y, qtab_721, 7) ; /* i = ADPCM code */ 104 105 dq = reconstruct (i & 8, _dqlntab [i], y) ; /* quantized est diff */ 106 107 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq ; /* reconst. signal */ 108 109 dqsez = sr + sez - se ; /* pole prediction diff. */ 110 111 update (4, y, arith_shift_left (_witab [i], 5), _fitab [i], dq, sr, dqsez, state_ptr) ; 112 113 return i ; 114} 115 116/* 117 * g721_decoder () 118 * 119 * Description: 120 * 121 * Decodes a 4-bit code of G.721 encoded data of i and 122 * returns the resulting linear PCM, A-law or u-law value. 123 * return -1 for unknown out_coding value. 124 */ 125int 126g721_decoder ( 127 int i, 128 G72x_STATE *state_ptr) 129{ 130 short sezi, sei, sez, se ; /* ACCUM */ 131 short y ; /* MIX */ 132 short sr ; /* ADDB */ 133 short dq ; 134 short dqsez ; 135 136 i &= 0x0f ; /* mask to get proper bits */ 137 sezi = predictor_zero (state_ptr) ; 138 sez = sezi >> 1 ; 139 sei = sezi + predictor_pole (state_ptr) ; 140 se = sei >> 1 ; /* se = estimated signal */ 141 142 y = step_size (state_ptr) ; /* dynamic quantizer step size */ 143 144 dq = reconstruct (i & 0x08, _dqlntab [i], y) ; /* quantized diff. */ 145 146 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq ; /* reconst. signal */ 147 148 dqsez = sr - se + sez ; /* pole prediction diff. */ 149 150 update (4, y, arith_shift_left (_witab [i], 5), _fitab [i], dq, sr, dqsez, state_ptr) ; 151 152 /* sr was 14-bit dynamic range */ 153 return arith_shift_left (sr, 2) ; 154} 155 156