Alexandre Lision | 7c6f4a6 | 2013-09-05 13:27:01 -0400 | [diff] [blame] | 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 | |
| 55 | static 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 | */ |
| 60 | static 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. */ |
| 64 | static 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 | */ |
| 71 | static 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 | */ |
| 80 | int |
| 81 | g721_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, _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 | */ |
| 125 | int |
| 126 | g721_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, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr); |
| 151 | |
| 152 | /* sr was 14-bit dynamic range */ |
| 153 | return (sr << 2); |
| 154 | } |
| 155 | |