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 * g72x.c 29 * 30 * Common routines for G.721 and G.723 conversions. 31 */ 32 33#include <stdio.h> 34#include <stdlib.h> 35#include <string.h> 36 37#include "g72x.h" 38#include "g72x_priv.h" 39 40static G72x_STATE * g72x_state_new (void) ; 41static int unpack_bytes (int bits, int blocksize, const unsigned char * block, short * samples) ; 42static int pack_bytes (int bits, const short * samples, unsigned char * block) ; 43 44static 45short power2 [15] = 46{ 1, 2, 4, 8, 0x10, 0x20, 0x40, 0x80, 47 0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000 48} ; 49 50/* 51 * quan () 52 * 53 * quantizes the input val against the table of size short integers. 54 * It returns i if table [i - 1] <= val < table [i]. 55 * 56 * Using linear search for simple coding. 57 */ 58static 59int quan (int val, short *table, int size) 60{ 61 int i ; 62 63 for (i = 0 ; i < size ; i++) 64 if (val < *table++) 65 break ; 66 return i ; 67} 68 69/* 70 * fmult () 71 * 72 * returns the integer product of the 14-bit integer "an" and 73 * "floating point" representation (4-bit exponent, 6-bit mantessa) "srn". 74 */ 75static 76int fmult (int an, int srn) 77{ 78 short anmag, anexp, anmant ; 79 short wanexp, wanmant ; 80 short retval ; 81 82 anmag = (an > 0) ? an : ((-an) & 0x1FFF) ; 83 anexp = quan (anmag, power2, 15) - 6 ; 84 anmant = (anmag == 0) ? 32 : 85 (anexp >= 0) ? anmag >> anexp : anmag << -anexp ; 86 wanexp = anexp + ((srn >> 6) & 0xF) - 13 ; 87 88 /* 89 ** The original was : 90 ** wanmant = (anmant * (srn & 0x3F) + 0x30) >> 4 ; 91 ** but could see no valid reason for the + 0x30. 92 ** Removed it and it improved the SNR of the codec. 93 */ 94 95 wanmant = (anmant * (srn & 0x3F)) >> 4 ; 96 97 retval = (wanexp >= 0) ? ((wanmant << wanexp) & 0x7FFF) : (wanmant >> -wanexp) ; 98 99 return (((an ^ srn) < 0) ? -retval : retval) ; 100} 101 102static G72x_STATE * g72x_state_new (void) 103{ return calloc (1, sizeof (G72x_STATE)) ; 104} 105 106/* 107 * private_init_state () 108 * 109 * This routine initializes and/or resets the G72x_PRIVATE structure 110 * pointed to by 'state_ptr'. 111 * All the initial state values are specified in the CCITT G.721 document. 112 */ 113void private_init_state (G72x_STATE *state_ptr) 114{ 115 int cnta ; 116 117 state_ptr->yl = 34816 ; 118 state_ptr->yu = 544 ; 119 state_ptr->dms = 0 ; 120 state_ptr->dml = 0 ; 121 state_ptr->ap = 0 ; 122 for (cnta = 0 ; cnta < 2 ; cnta++) 123 { state_ptr->a [cnta] = 0 ; 124 state_ptr->pk [cnta] = 0 ; 125 state_ptr->sr [cnta] = 32 ; 126 } 127 for (cnta = 0 ; cnta < 6 ; cnta++) 128 { state_ptr->b [cnta] = 0 ; 129 state_ptr->dq [cnta] = 32 ; 130 } 131 state_ptr->td = 0 ; 132} /* private_init_state */ 133 134struct g72x_state * g72x_reader_init (int codec, int *blocksize, int *samplesperblock) 135{ G72x_STATE *pstate ; 136 137 if ((pstate = g72x_state_new ()) == NULL) 138 return NULL ; 139 140 private_init_state (pstate) ; 141 142 pstate->encoder = NULL ; 143 144 switch (codec) 145 { case G723_16_BITS_PER_SAMPLE : /* 2 bits per sample. */ 146 pstate->decoder = g723_16_decoder ; 147 *blocksize = G723_16_BYTES_PER_BLOCK ; 148 *samplesperblock = G723_16_SAMPLES_PER_BLOCK ; 149 pstate->codec_bits = 2 ; 150 pstate->blocksize = G723_16_BYTES_PER_BLOCK ; 151 pstate->samplesperblock = G723_16_SAMPLES_PER_BLOCK ; 152 break ; 153 154 case G723_24_BITS_PER_SAMPLE : /* 3 bits per sample. */ 155 pstate->decoder = g723_24_decoder ; 156 *blocksize = G723_24_BYTES_PER_BLOCK ; 157 *samplesperblock = G723_24_SAMPLES_PER_BLOCK ; 158 pstate->codec_bits = 3 ; 159 pstate->blocksize = G723_24_BYTES_PER_BLOCK ; 160 pstate->samplesperblock = G723_24_SAMPLES_PER_BLOCK ; 161 break ; 162 163 case G721_32_BITS_PER_SAMPLE : /* 4 bits per sample. */ 164 pstate->decoder = g721_decoder ; 165 *blocksize = G721_32_BYTES_PER_BLOCK ; 166 *samplesperblock = G721_32_SAMPLES_PER_BLOCK ; 167 pstate->codec_bits = 4 ; 168 pstate->blocksize = G721_32_BYTES_PER_BLOCK ; 169 pstate->samplesperblock = G721_32_SAMPLES_PER_BLOCK ; 170 break ; 171 172 case G721_40_BITS_PER_SAMPLE : /* 5 bits per sample. */ 173 pstate->decoder = g723_40_decoder ; 174 *blocksize = G721_40_BYTES_PER_BLOCK ; 175 *samplesperblock = G721_40_SAMPLES_PER_BLOCK ; 176 pstate->codec_bits = 5 ; 177 pstate->blocksize = G721_40_BYTES_PER_BLOCK ; 178 pstate->samplesperblock = G721_40_SAMPLES_PER_BLOCK ; 179 break ; 180 181 default : 182 free (pstate) ; 183 return NULL ; 184 } ; 185 186 return pstate ; 187} /* g72x_reader_init */ 188 189struct g72x_state * g72x_writer_init (int codec, int *blocksize, int *samplesperblock) 190{ G72x_STATE *pstate ; 191 192 if ((pstate = g72x_state_new ()) == NULL) 193 return NULL ; 194 195 private_init_state (pstate) ; 196 pstate->decoder = NULL ; 197 198 switch (codec) 199 { case G723_16_BITS_PER_SAMPLE : /* 2 bits per sample. */ 200 pstate->encoder = g723_16_encoder ; 201 *blocksize = G723_16_BYTES_PER_BLOCK ; 202 *samplesperblock = G723_16_SAMPLES_PER_BLOCK ; 203 pstate->codec_bits = 2 ; 204 pstate->blocksize = G723_16_BYTES_PER_BLOCK ; 205 pstate->samplesperblock = G723_16_SAMPLES_PER_BLOCK ; 206 break ; 207 208 case G723_24_BITS_PER_SAMPLE : /* 3 bits per sample. */ 209 pstate->encoder = g723_24_encoder ; 210 *blocksize = G723_24_BYTES_PER_BLOCK ; 211 *samplesperblock = G723_24_SAMPLES_PER_BLOCK ; 212 pstate->codec_bits = 3 ; 213 pstate->blocksize = G723_24_BYTES_PER_BLOCK ; 214 pstate->samplesperblock = G723_24_SAMPLES_PER_BLOCK ; 215 break ; 216 217 case G721_32_BITS_PER_SAMPLE : /* 4 bits per sample. */ 218 pstate->encoder = g721_encoder ; 219 *blocksize = G721_32_BYTES_PER_BLOCK ; 220 *samplesperblock = G721_32_SAMPLES_PER_BLOCK ; 221 pstate->codec_bits = 4 ; 222 pstate->blocksize = G721_32_BYTES_PER_BLOCK ; 223 pstate->samplesperblock = G721_32_SAMPLES_PER_BLOCK ; 224 break ; 225 226 case G721_40_BITS_PER_SAMPLE : /* 5 bits per sample. */ 227 pstate->encoder = g723_40_encoder ; 228 *blocksize = G721_40_BYTES_PER_BLOCK ; 229 *samplesperblock = G721_40_SAMPLES_PER_BLOCK ; 230 pstate->codec_bits = 5 ; 231 pstate->blocksize = G721_40_BYTES_PER_BLOCK ; 232 pstate->samplesperblock = G721_40_SAMPLES_PER_BLOCK ; 233 break ; 234 235 default : 236 free (pstate) ; 237 return NULL ; 238 } ; 239 240 return pstate ; 241} /* g72x_writer_init */ 242 243int g72x_decode_block (G72x_STATE *pstate, const unsigned char *block, short *samples) 244{ int k, count ; 245 246 count = unpack_bytes (pstate->codec_bits, pstate->blocksize, block, samples) ; 247 248 for (k = 0 ; k < count ; k++) 249 samples [k] = pstate->decoder (samples [k], pstate) ; 250 251 return 0 ; 252} /* g72x_decode_block */ 253 254int g72x_encode_block (G72x_STATE *pstate, short *samples, unsigned char *block) 255{ int k, count ; 256 257 for (k = 0 ; k < pstate->samplesperblock ; k++) 258 samples [k] = pstate->encoder (samples [k], pstate) ; 259 260 count = pack_bytes (pstate->codec_bits, samples, block) ; 261 262 return count ; 263} /* g72x_encode_block */ 264 265/* 266 * predictor_zero () 267 * 268 * computes the estimated signal from 6-zero predictor. 269 * 270 */ 271int predictor_zero (G72x_STATE *state_ptr) 272{ 273 int i ; 274 int sezi ; 275 276 sezi = fmult (state_ptr->b [0] >> 2, state_ptr->dq [0]) ; 277 for (i = 1 ; i < 6 ; i++) /* ACCUM */ 278 sezi += fmult (state_ptr->b [i] >> 2, state_ptr->dq [i]) ; 279 return sezi ; 280} 281/* 282 * predictor_pole () 283 * 284 * computes the estimated signal from 2-pole predictor. 285 * 286 */ 287int predictor_pole (G72x_STATE *state_ptr) 288{ 289 return (fmult (state_ptr->a [1] >> 2, state_ptr->sr [1]) + 290 fmult (state_ptr->a [0] >> 2, state_ptr->sr [0])) ; 291} 292/* 293 * step_size () 294 * 295 * computes the quantization step size of the adaptive quantizer. 296 * 297 */ 298int step_size (G72x_STATE *state_ptr) 299{ 300 int y ; 301 int dif ; 302 int al ; 303 304 if (state_ptr->ap >= 256) 305 return (state_ptr->yu) ; 306 else { 307 y = state_ptr->yl >> 6 ; 308 dif = state_ptr->yu - y ; 309 al = state_ptr->ap >> 2 ; 310 if (dif > 0) 311 y += (dif * al) >> 6 ; 312 else if (dif < 0) 313 y += (dif * al + 0x3F) >> 6 ; 314 return y ; 315 } 316} 317 318/* 319 * quantize () 320 * 321 * Given a raw sample, 'd', of the difference signal and a 322 * quantization step size scale factor, 'y', this routine returns the 323 * ADPCM codeword to which that sample gets quantized. The step 324 * size scale factor division operation is done in the log base 2 domain 325 * as a subtraction. 326 */ 327int quantize ( 328 int d, /* Raw difference signal sample */ 329 int y, /* Step size multiplier */ 330 short *table, /* quantization table */ 331 int size) /* table size of short integers */ 332{ 333 short dqm ; /* Magnitude of 'd' */ 334 short expon ; /* Integer part of base 2 log of 'd' */ 335 short mant ; /* Fractional part of base 2 log */ 336 short dl ; /* Log of magnitude of 'd' */ 337 short dln ; /* Step size scale factor normalized log */ 338 int i ; 339 340 /* 341 * LOG 342 * 343 * Compute base 2 log of 'd', and store in 'dl'. 344 */ 345 dqm = abs (d) ; 346 expon = quan (dqm >> 1, power2, 15) ; 347 mant = ((dqm << 7) >> expon) & 0x7F ; /* Fractional portion. */ 348 dl = (expon << 7) + mant ; 349 350 /* 351 * SUBTB 352 * 353 * "Divide" by step size multiplier. 354 */ 355 dln = dl - (y >> 2) ; 356 357 /* 358 * QUAN 359 * 360 * Obtain codword i for 'd'. 361 */ 362 i = quan (dln, table, size) ; 363 if (d < 0) /* take 1's complement of i */ 364 return ((size << 1) + 1 - i) ; 365 else if (i == 0) /* take 1's complement of 0 */ 366 return ((size << 1) + 1) ; /* new in 1988 */ 367 368 return i ; 369} 370/* 371 * reconstruct () 372 * 373 * Returns reconstructed difference signal 'dq' obtained from 374 * codeword 'i' and quantization step size scale factor 'y'. 375 * Multiplication is performed in log base 2 domain as addition. 376 */ 377int 378reconstruct ( 379 int sign, /* 0 for non-negative value */ 380 int dqln, /* G.72x codeword */ 381 int y) /* Step size multiplier */ 382{ 383 short dql ; /* Log of 'dq' magnitude */ 384 short dex ; /* Integer part of log */ 385 short dqt ; 386 short dq ; /* Reconstructed difference signal sample */ 387 388 dql = dqln + (y >> 2) ; /* ADDA */ 389 390 if (dql < 0) 391 return ((sign) ? -0x8000 : 0) ; 392 else /* ANTILOG */ 393 { dex = (dql >> 7) & 15 ; 394 dqt = 128 + (dql & 127) ; 395 dq = (dqt << 7) >> (14 - dex) ; 396 return ((sign) ? (dq - 0x8000) : dq) ; 397 } 398} 399 400 401/* 402 * update () 403 * 404 * updates the state variables for each output code 405 */ 406void 407update ( 408 int code_size, /* distinguish 723_40 with others */ 409 int y, /* quantizer step size */ 410 int wi, /* scale factor multiplier */ 411 int fi, /* for long/short term energies */ 412 int dq, /* quantized prediction difference */ 413 int sr, /* reconstructed signal */ 414 int dqsez, /* difference from 2-pole predictor */ 415 G72x_STATE *state_ptr) /* coder state pointer */ 416{ 417 int cnt ; 418 short mag, expon ; /* Adaptive predictor, FLOAT A */ 419 short a2p = 0 ; /* LIMC */ 420 short a1ul ; /* UPA1 */ 421 short pks1 ; /* UPA2 */ 422 short fa1 ; 423 char tr ; /* tone/transition detector */ 424 short ylint, thr2, dqthr ; 425 short ylfrac, thr1 ; 426 short pk0 ; 427 428 pk0 = (dqsez < 0) ? 1 : 0 ; /* needed in updating predictor poles */ 429 430 mag = dq & 0x7FFF ; /* prediction difference magnitude */ 431 /* TRANS */ 432 ylint = state_ptr->yl >> 15 ; /* exponent part of yl */ 433 ylfrac = (state_ptr->yl >> 10) & 0x1F ; /* fractional part of yl */ 434 thr1 = (32 + ylfrac) << ylint ; /* threshold */ 435 thr2 = (ylint > 9) ? 31 << 10 : thr1 ; /* limit thr2 to 31 << 10 */ 436 dqthr = (thr2 + (thr2 >> 1)) >> 1 ; /* dqthr = 0.75 * thr2 */ 437 if (state_ptr->td == 0) /* signal supposed voice */ 438 tr = 0 ; 439 else if (mag <= dqthr) /* supposed data, but small mag */ 440 tr = 0 ; /* treated as voice */ 441 else /* signal is data (modem) */ 442 tr = 1 ; 443 444 /* 445 * Quantizer scale factor adaptation. 446 */ 447 448 /* FUNCTW & FILTD & DELAY */ 449 /* update non-steady state step size multiplier */ 450 state_ptr->yu = y + ((wi - y) >> 5) ; 451 452 /* LIMB */ 453 if (state_ptr->yu < 544) /* 544 <= yu <= 5120 */ 454 state_ptr->yu = 544 ; 455 else if (state_ptr->yu > 5120) 456 state_ptr->yu = 5120 ; 457 458 /* FILTE & DELAY */ 459 /* update steady state step size multiplier */ 460 state_ptr->yl += state_ptr->yu + ((-state_ptr->yl) >> 6) ; 461 462 /* 463 * Adaptive predictor coefficients. 464 */ 465 if (tr == 1) { /* reset a's and b's for modem signal */ 466 state_ptr->a [0] = 0 ; 467 state_ptr->a [1] = 0 ; 468 state_ptr->b [0] = 0 ; 469 state_ptr->b [1] = 0 ; 470 state_ptr->b [2] = 0 ; 471 state_ptr->b [3] = 0 ; 472 state_ptr->b [4] = 0 ; 473 state_ptr->b [5] = 0 ; 474 } 475 else /* update a's and b's */ 476 { pks1 = pk0 ^ state_ptr->pk [0] ; /* UPA2 */ 477 478 /* update predictor pole a [1] */ 479 a2p = state_ptr->a [1] - (state_ptr->a [1] >> 7) ; 480 if (dqsez != 0) 481 { fa1 = (pks1) ? state_ptr->a [0] : -state_ptr->a [0] ; 482 if (fa1 < -8191) /* a2p = function of fa1 */ 483 a2p -= 0x100 ; 484 else if (fa1 > 8191) 485 a2p += 0xFF ; 486 else 487 a2p += fa1 >> 5 ; 488 489 if (pk0 ^ state_ptr->pk [1]) 490 { /* LIMC */ 491 if (a2p <= -12160) 492 a2p = -12288 ; 493 else if (a2p >= 12416) 494 a2p = 12288 ; 495 else 496 a2p -= 0x80 ; 497 } 498 else if (a2p <= -12416) 499 a2p = -12288 ; 500 else if (a2p >= 12160) 501 a2p = 12288 ; 502 else 503 a2p += 0x80 ; 504 } 505 506 /* TRIGB & DELAY */ 507 state_ptr->a [1] = a2p ; 508 509 /* UPA1 */ 510 /* update predictor pole a [0] */ 511 state_ptr->a [0] -= state_ptr->a [0] >> 8 ; 512 if (dqsez != 0) 513 { if (pks1 == 0) 514 state_ptr->a [0] += 192 ; 515 else 516 state_ptr->a [0] -= 192 ; 517 } ; 518 519 /* LIMD */ 520 a1ul = 15360 - a2p ; 521 if (state_ptr->a [0] < -a1ul) 522 state_ptr->a [0] = -a1ul ; 523 else if (state_ptr->a [0] > a1ul) 524 state_ptr->a [0] = a1ul ; 525 526 /* UPB : update predictor zeros b [6] */ 527 for (cnt = 0 ; cnt < 6 ; cnt++) 528 { if (code_size == 5) /* for 40Kbps G.723 */ 529 state_ptr->b [cnt] -= state_ptr->b [cnt] >> 9 ; 530 else /* for G.721 and 24Kbps G.723 */ 531 state_ptr->b [cnt] -= state_ptr->b [cnt] >> 8 ; 532 if (dq & 0x7FFF) /* XOR */ 533 { if ((dq ^ state_ptr->dq [cnt]) >= 0) 534 state_ptr->b [cnt] += 128 ; 535 else 536 state_ptr->b [cnt] -= 128 ; 537 } 538 } 539 } 540 541 for (cnt = 5 ; cnt > 0 ; cnt--) 542 state_ptr->dq [cnt] = state_ptr->dq [cnt - 1] ; 543 /* FLOAT A : convert dq [0] to 4-bit exp, 6-bit mantissa f.p. */ 544 if (mag == 0) 545 state_ptr->dq [0] = (dq >= 0) ? 0x20 : 0xFC20 ; 546 else 547 { expon = quan (mag, power2, 15) ; 548 state_ptr->dq [0] = (dq >= 0) ? 549 (expon << 6) + ((mag << 6) >> expon) : 550 (expon << 6) + ((mag << 6) >> expon) - 0x400 ; 551 } 552 553 state_ptr->sr [1] = state_ptr->sr [0] ; 554 /* FLOAT B : convert sr to 4-bit exp., 6-bit mantissa f.p. */ 555 if (sr == 0) 556 state_ptr->sr [0] = 0x20 ; 557 else if (sr > 0) 558 { expon = quan (sr, power2, 15) ; 559 state_ptr->sr [0] = (expon << 6) + ((sr << 6) >> expon) ; 560 } 561 else if (sr > -32768) 562 { mag = -sr ; 563 expon = quan (mag, power2, 15) ; 564 state_ptr->sr [0] = (expon << 6) + ((mag << 6) >> expon) - 0x400 ; 565 } 566 else 567 state_ptr->sr [0] = (short) 0xFC20 ; 568 569 /* DELAY A */ 570 state_ptr->pk [1] = state_ptr->pk [0] ; 571 state_ptr->pk [0] = pk0 ; 572 573 /* TONE */ 574 if (tr == 1) /* this sample has been treated as data */ 575 state_ptr->td = 0 ; /* next one will be treated as voice */ 576 else if (a2p < -11776) /* small sample-to-sample correlation */ 577 state_ptr->td = 1 ; /* signal may be data */ 578 else /* signal is voice */ 579 state_ptr->td = 0 ; 580 581 /* 582 * Adaptation speed control. 583 */ 584 state_ptr->dms += (fi - state_ptr->dms) >> 5 ; /* FILTA */ 585 state_ptr->dml += (((fi << 2) - state_ptr->dml) >> 7) ; /* FILTB */ 586 587 if (tr == 1) 588 state_ptr->ap = 256 ; 589 else if (y < 1536) /* SUBTC */ 590 state_ptr->ap += (0x200 - state_ptr->ap) >> 4 ; 591 else if (state_ptr->td == 1) 592 state_ptr->ap += (0x200 - state_ptr->ap) >> 4 ; 593 else if (abs ((state_ptr->dms << 2) - state_ptr->dml) >= (state_ptr->dml >> 3)) 594 state_ptr->ap += (0x200 - state_ptr->ap) >> 4 ; 595 else 596 state_ptr->ap += (-state_ptr->ap) >> 4 ; 597 598 return ; 599} /* update */ 600 601/*------------------------------------------------------------------------------ 602*/ 603 604static int 605unpack_bytes (int bits, int blocksize, const unsigned char * block, short * samples) 606{ unsigned int in_buffer = 0 ; 607 unsigned char in_byte ; 608 int k, in_bits = 0, bindex = 0 ; 609 610 for (k = 0 ; bindex <= blocksize && k < G72x_BLOCK_SIZE ; k++) 611 { if (in_bits < bits) 612 { in_byte = block [bindex++] ; 613 614 in_buffer |= (in_byte << in_bits) ; 615 in_bits += 8 ; 616 } 617 samples [k] = in_buffer & ((1 << bits) - 1) ; 618 in_buffer >>= bits ; 619 in_bits -= bits ; 620 } ; 621 622 return k ; 623} /* unpack_bytes */ 624 625static int 626pack_bytes (int bits, const short * samples, unsigned char * block) 627{ 628 unsigned int out_buffer = 0 ; 629 int k, bindex = 0, out_bits = 0 ; 630 unsigned char out_byte ; 631 632 for (k = 0 ; k < G72x_BLOCK_SIZE ; k++) 633 { out_buffer |= (samples [k] << out_bits) ; 634 out_bits += bits ; 635 if (out_bits >= 8) 636 { out_byte = out_buffer & 0xFF ; 637 out_bits -= 8 ; 638 out_buffer >>= 8 ; 639 block [bindex++] = out_byte ; 640 } 641 } ; 642 643 return bindex ; 644} /* pack_bytes */ 645 646