src/lib/dl/ext/flac/replaygain.c

   1 /* grabbag - Convenience lib for various routines common to several tools
   2  * Copyright (C) 2002,2003,2004,2005,2006,2007  Josh Coalson
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  17  */
  18
  19 #if HAVE_CONFIG_H
  20 #  include "config.h"
  21 #endif
  22
  23 #include "share/grabbag.h"
  24 #include "share/replaygain_analysis.h"
  25 #include "flac/assert.h"
  26 #include "flac/metadata.h"
  27 #include "flac/stream_decoder.h"
  28 #include <locale.h>
  29 #include <math.h>
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33 #if defined _MSC_VER || defined __MINGW32__
  34 #include <io.h> /* for chmod() */
  35 #endif
  36 #include <sys/stat.h> /* for stat(), maybe chmod() */
  37
  38 #ifdef local_min
  39 #undef local_min
  40 #endif
  41 #define local_min(a,b) ((a)<(b)?(a):(b))
  42
  43 #ifdef local_max
  44 #undef local_max
  45 #endif
  46 #define local_max(a,b) ((a)>(b)?(a):(b))
  47
  48 static const char *reference_format_ = "%s=%2.1f dB";
  49 static const char *gain_format_ = "%s=%+2.2f dB";
  50 static const char *peak_format_ = "%s=%1.8f";
  51
  52 static double album_peak_, title_peak_;
  53
  54 const unsigned GRABBAG__REPLAYGAIN_MAX_TAG_SPACE_REQUIRED = 190;
  55 /*
  56         FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 29 + 1 + 8 +
  57         FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 10 +
  58         FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 12 +
  59         FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 10 +
  60         FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 12
  61 */
  62
  63 const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS = (const FLAC__byte * const)"REPLAYGAIN_REFERENCE_LOUDNESS";
  64 const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN = (const FLAC__byte * const)"REPLAYGAIN_TRACK_GAIN";
  65 const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK = (const FLAC__byte * const)"REPLAYGAIN_TRACK_PEAK";
  66 const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN = (const FLAC__byte * const)"REPLAYGAIN_ALBUM_GAIN";
  67 const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK = (const FLAC__byte * const)"REPLAYGAIN_ALBUM_PEAK";
  68
  69
  70 static FLAC__bool get_file_stats_(const char *filename, struct stat *stats)
  71 {
  72         FLAC__ASSERT(0 != filename);
  73         FLAC__ASSERT(0 != stats);
  74         return (0 == stat(filename, stats));
  75 }
  76
  77 static void set_file_stats_(const char *filename, struct stat *stats)
  78 {
  79         FLAC__ASSERT(0 != filename);
  80         FLAC__ASSERT(0 != stats);
  81 }
  82
  83 static FLAC__bool append_tag_(FLAC__StreamMetadata *block, const char *format, const FLAC__byte *name, float value)
  84 {
  85         char buffer[256];
  86         char *saved_locale;
  87         FLAC__StreamMetadata_VorbisComment_Entry entry;
  88
  89         FLAC__ASSERT(0 != block);
  90         FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);
  91         FLAC__ASSERT(0 != format);
  92         FLAC__ASSERT(0 != name);
  93
  94         buffer[sizeof(buffer)-1] = '\0';
  95         /*
  96          * We need to save the old locale and switch to "C" because the locale
  97          * influences the formatting of %f and we want it a certain way.
  98          */
  99         saved_locale = strdup(setlocale(LC_ALL, 0));
 100         if (0 == saved_locale)
 101                 return false;
 102         setlocale(LC_ALL, "C");
 103 #if defined _MSC_VER || defined __MINGW32__
 104         _snprintf(buffer, sizeof(buffer)-1, format, name, value);
 105 #else
 106         snprintf(buffer, sizeof(buffer)-1, format, name, value);
 107 #endif
 108         setlocale(LC_ALL, saved_locale);
 109         free(saved_locale);
 110
 111         entry.entry = (FLAC__byte *)buffer;
 112         entry.length = strlen(buffer);
 113
 114         return FLAC__metadata_object_vorbiscomment_append_comment(block, entry, /*copy=*/true);
 115 }
 116
 117 FLAC__bool grabbag__replaygain_is_valid_sample_frequency(unsigned sample_frequency)
 118 {
 119         static const unsigned valid_sample_rates[] = {
 120                 8000,
 121                 11025,
 122                 12000,
 123                 16000,
 124                 22050,
 125                 24000,
 126                 32000,
 127                 44100,
 128                 48000
 129         };
 130         static const unsigned n_valid_sample_rates = sizeof(valid_sample_rates) / sizeof(valid_sample_rates[0]);
 131
 132         unsigned i;
 133
 134         for(i = 0; i < n_valid_sample_rates; i++)
 135                 if(sample_frequency == valid_sample_rates[i])
 136                         return true;
 137         return false;
 138 }
 139
 140 FLAC__bool grabbag__replaygain_init(unsigned sample_frequency)
 141 {
 142         title_peak_ = album_peak_ = 0.0;
 143         return InitGainAnalysis((long)sample_frequency) == INIT_GAIN_ANALYSIS_OK;
 144 }
 145
 146 FLAC__bool grabbag__replaygain_analyze(const FLAC__int32 * const input[], FLAC__bool is_stereo, unsigned bps, unsigned samples)
 147 {
 148         /* using a small buffer improves data locality; we'd like it to fit easily in the dcache */
 149         static Float_t lbuffer[2048], rbuffer[2048];
 150         static const unsigned nbuffer = sizeof(lbuffer) / sizeof(lbuffer[0]);
 151         FLAC__int32 block_peak = 0, s;
 152         unsigned i, j;
 153
 154         FLAC__ASSERT(bps >= 4 && bps <= FLAC__REFERENCE_CODEC_MAX_BITS_PER_SAMPLE);
 155         FLAC__ASSERT(FLAC__MIN_BITS_PER_SAMPLE == 4);
 156         /*
 157          * We use abs() on a FLAC__int32 which is undefined for the most negative value.
 158          * If the reference codec ever handles 32bps we will have to write a special
 159          * case here.
 160          */
 161         FLAC__ASSERT(FLAC__REFERENCE_CODEC_MAX_BITS_PER_SAMPLE < 32);
 162
 163         if(bps == 16) {
 164                 if(is_stereo) {
 165                         j = 0;
 166                         while(samples > 0) {
 167                                 const unsigned n = local_min(samples, nbuffer);
 168                                 for(i = 0; i < n; i++, j++) {
 169                                         s = input[0][j];
 170                                         lbuffer[i] = (Float_t)s;
 171                                         s = abs(s);
 172                                         block_peak = local_max(block_peak, s);
 173
 174                                         s = input[1][j];
 175                                         rbuffer[i] = (Float_t)s;
 176                                         s = abs(s);
 177                                         block_peak = local_max(block_peak, s);
 178                                 }
 179                                 samples -= n;
 180                                 if(AnalyzeSamples(lbuffer, rbuffer, n, 2) != GAIN_ANALYSIS_OK)
 181                                         return false;
 182                         }
 183                 }
 184                 else {
 185                         j = 0;
 186                         while(samples > 0) {
 187                                 const unsigned n = local_min(samples, nbuffer);
 188                                 for(i = 0; i < n; i++, j++) {
 189                                         s = input[0][j];
 190                                         lbuffer[i] = (Float_t)s;
 191                                         s = abs(s);
 192                                         block_peak = local_max(block_peak, s);
 193                                 }
 194                                 samples -= n;
 195                                 if(AnalyzeSamples(lbuffer, 0, n, 1) != GAIN_ANALYSIS_OK)
 196                                         return false;
 197                         }
 198                 }
 199         }
 200         else { /* bps must be < 32 according to above assertion */
 201                 const double scale = (
 202                         (bps > 16)?
 203                                 (double)1. / (double)(1u << (bps - 16)) :
 204                                 (double)(1u << (16 - bps))
 205                 );
 206
 207                 if(is_stereo) {
 208                         j = 0;
 209                         while(samples > 0) {
 210                                 const unsigned n = local_min(samples, nbuffer);
 211                                 for(i = 0; i < n; i++, j++) {
 212                                         s = input[0][j];
 213                                         lbuffer[i] = (Float_t)(scale * (double)s);
 214                                         s = abs(s);
 215                                         block_peak = local_max(block_peak, s);
 216
 217                                         s = input[1][j];
 218                                         rbuffer[i] = (Float_t)(scale * (double)s);
 219                                         s = abs(s);
 220                                         block_peak = local_max(block_peak, s);
 221                                 }
 222                                 samples -= n;
 223                                 if(AnalyzeSamples(lbuffer, rbuffer, n, 2) != GAIN_ANALYSIS_OK)
 224                                         return false;
 225                         }
 226                 }
 227                 else {
 228                         j = 0;
 229                         while(samples > 0) {
 230                                 const unsigned n = local_min(samples, nbuffer);
 231                                 for(i = 0; i < n; i++, j++) {
 232                                         s = input[0][j];
 233                                         lbuffer[i] = (Float_t)(scale * (double)s);
 234                                         s = abs(s);
 235                                         block_peak = local_max(block_peak, s);
 236                                 }
 237                                 samples -= n;
 238                                 if(AnalyzeSamples(lbuffer, 0, n, 1) != GAIN_ANALYSIS_OK)
 239                                         return false;
 240                         }
 241                 }
 242         }
 243
 244         {
 245                 const double peak_scale = (double)(1u << (bps - 1));
 246                 double peak = (double)block_peak / peak_scale;
 247                 if(peak > title_peak_)
 248                         title_peak_ = peak;
 249                 if(peak > album_peak_)
 250                         album_peak_ = peak;
 251         }
 252
 253         return true;
 254 }
 255
 256 void grabbag__replaygain_get_album(float *gain, float *peak)
 257 {
 258         *gain = (float)GetAlbumGain();
 259         *peak = (float)album_peak_;
 260         album_peak_ = 0.0;
 261 }
 262
 263 void grabbag__replaygain_get_title(float *gain, float *peak)
 264 {
 265         *gain = (float)GetTitleGain();
 266         *peak = (float)title_peak_;
 267         title_peak_ = 0.0;
 268 }
 269
 270
 271 typedef struct {
 272         unsigned channels;
 273         unsigned bits_per_sample;
 274         unsigned sample_rate;
 275         FLAC__bool error;
 276 } DecoderInstance;
 277
 278 static FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data)
 279 {
 280         DecoderInstance *instance = (DecoderInstance*)client_data;
 281         const unsigned bits_per_sample = frame->header.bits_per_sample;
 282         const unsigned channels = frame->header.channels;
 283         const unsigned sample_rate = frame->header.sample_rate;
 284         const unsigned samples = frame->header.blocksize;
 285
 286         (void)decoder;
 287
 288         if(
 289                 !instance->error &&
 290                 (channels == 2 || channels == 1) &&
 291                 bits_per_sample == instance->bits_per_sample &&
 292                 channels == instance->channels &&
 293                 sample_rate == instance->sample_rate
 294         ) {
 295                 instance->error = !grabbag__replaygain_analyze(buffer, channels==2, bits_per_sample, samples);
 296         }
 297         else {
 298                 instance->error = true;
 299         }
 300
 301         if(!instance->error)
 302                 return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
 303         else
 304                 return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;
 305 }
 306
 307 static void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)
 308 {
 309         DecoderInstance *instance = (DecoderInstance*)client_data;
 310
 311         (void)decoder;
 312
 313         if(metadata->type == FLAC__METADATA_TYPE_STREAMINFO) {
 314                 instance->bits_per_sample = metadata->data.stream_info.bits_per_sample;
 315                 instance->channels = metadata->data.stream_info.channels;
 316                 instance->sample_rate = metadata->data.stream_info.sample_rate;
 317
 318                 if(instance->channels != 1 && instance->channels != 2) {
 319                         instance->error = true;
 320                         return;
 321                 }
 322
 323                 if(!grabbag__replaygain_is_valid_sample_frequency(instance->sample_rate)) {
 324                         instance->error = true;
 325                         return;
 326                 }
 327         }
 328 }
 329
 330 static void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
 331 {
 332         DecoderInstance *instance = (DecoderInstance*)client_data;
 333
 334         (void)decoder, (void)status;
 335
 336         instance->error = true;
 337 }
 338
 339 const char *grabbag__replaygain_analyze_file(const char *filename, float *title_gain, float *title_peak)
 340 {
 341         DecoderInstance instance;
 342         FLAC__StreamDecoder *decoder = FLAC__stream_decoder_new();
 343
 344         if(0 == decoder)
 345                 return "memory allocation error";
 346
 347         instance.error = false;
 348
 349         /* It does these three by default but lets be explicit: */
 350         FLAC__stream_decoder_set_md5_checking(decoder, false);
 351         FLAC__stream_decoder_set_metadata_ignore_all(decoder);
 352         FLAC__stream_decoder_set_metadata_respond(decoder, FLAC__METADATA_TYPE_STREAMINFO);
 353
 354         if(FLAC__stream_decoder_init_file(decoder, filename, write_callback_, metadata_callback_, error_callback_, &instance) != FLAC__STREAM_DECODER_INIT_STATUS_OK) {
 355                 FLAC__stream_decoder_delete(decoder);
 356                 return "initializing decoder";
 357         }
 358
 359         if(!FLAC__stream_decoder_process_until_end_of_stream(decoder) || instance.error) {
 360                 FLAC__stream_decoder_delete(decoder);
 361                 return "decoding file";
 362         }
 363
 364         FLAC__stream_decoder_delete(decoder);
 365
 366         grabbag__replaygain_get_title(title_gain, title_peak);
 367
 368         return 0;
 369 }
 370
 371 const char *grabbag__replaygain_store_to_vorbiscomment(FLAC__StreamMetadata *block, float album_gain, float album_peak, float title_gain, float title_peak)
 372 {
 373         const char *error;
 374
 375         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_reference(block)))
 376                 return error;
 377
 378         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_title(block, title_gain, title_peak)))
 379                 return error;
 380
 381         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_album(block, album_gain, album_peak)))
 382                 return error;
 383
 384         return 0;
 385 }
 386
 387 const char *grabbag__replaygain_store_to_vorbiscomment_reference(FLAC__StreamMetadata *block)
 388 {
 389         FLAC__ASSERT(0 != block);
 390         FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);
 391
 392         if(FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS) < 0)
 393                 return "memory allocation error";
 394
 395         if(!append_tag_(block, reference_format_, GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS, ReplayGainReferenceLoudness))
 396                 return "memory allocation error";
 397
 398         return 0;
 399 }
 400
 401 const char *grabbag__replaygain_store_to_vorbiscomment_album(FLAC__StreamMetadata *block, float album_gain, float album_peak)
 402 {
 403         FLAC__ASSERT(0 != block);
 404         FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);
 405
 406         if(
 407                 FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN) < 0 ||
 408                 FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK) < 0
 409         )
 410                 return "memory allocation error";
 411
 412         if(
 413                 !append_tag_(block, gain_format_, GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN, album_gain) ||
 414                 !append_tag_(block, peak_format_, GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK, album_peak)
 415         )
 416                 return "memory allocation error";
 417
 418         return 0;
 419 }
 420
 421 const char *grabbag__replaygain_store_to_vorbiscomment_title(FLAC__StreamMetadata *block, float title_gain, float title_peak)
 422 {
 423         FLAC__ASSERT(0 != block);
 424         FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);
 425
 426         if(
 427                 FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN) < 0 ||
 428                 FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK) < 0
 429         )
 430                 return "memory allocation error";
 431
 432         if(
 433                 !append_tag_(block, gain_format_, GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN, title_gain) ||
 434                 !append_tag_(block, peak_format_, GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK, title_peak)
 435         )
 436                 return "memory allocation error";
 437
 438         return 0;
 439 }
 440
 441 static const char *store_to_file_pre_(const char *filename, FLAC__Metadata_Chain **chain, FLAC__StreamMetadata **block)
 442 {
 443         FLAC__Metadata_Iterator *iterator;
 444         const char *error;
 445         FLAC__bool found_vc_block = false;
 446
 447         if(0 == (*chain = FLAC__metadata_chain_new()))
 448                 return "memory allocation error";
 449
 450         if(!FLAC__metadata_chain_read(*chain, filename)) {
 451                 error = FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(*chain)];
 452                 FLAC__metadata_chain_delete(*chain);
 453                 return error;
 454         }
 455
 456         if(0 == (iterator = FLAC__metadata_iterator_new())) {
 457                 FLAC__metadata_chain_delete(*chain);
 458                 return "memory allocation error";
 459         }
 460
 461         FLAC__metadata_iterator_init(iterator, *chain);
 462
 463         do {
 464                 *block = FLAC__metadata_iterator_get_block(iterator);
 465                 if((*block)->type == FLAC__METADATA_TYPE_VORBIS_COMMENT)
 466                         found_vc_block = true;
 467         } while(!found_vc_block && FLAC__metadata_iterator_next(iterator));
 468
 469         if(!found_vc_block) {
 470                 /* create a new block */
 471                 *block = FLAC__metadata_object_new(FLAC__METADATA_TYPE_VORBIS_COMMENT);
 472                 if(0 == *block) {
 473                         FLAC__metadata_chain_delete(*chain);
 474                         FLAC__metadata_iterator_delete(iterator);
 475                         return "memory allocation error";
 476                 }
 477                 while(FLAC__metadata_iterator_next(iterator))
 478                         ;
 479                 if(!FLAC__metadata_iterator_insert_block_after(iterator, *block)) {
 480                         error = FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(*chain)];
 481                         FLAC__metadata_chain_delete(*chain);
 482                         FLAC__metadata_iterator_delete(iterator);
 483                         return error;
 484                 }
 485                 /* iterator is left pointing to new block */
 486                 FLAC__ASSERT(FLAC__metadata_iterator_get_block(iterator) == *block);
 487         }
 488
 489         FLAC__metadata_iterator_delete(iterator);
 490
 491         FLAC__ASSERT(0 != *block);
 492         FLAC__ASSERT((*block)->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);
 493
 494         return 0;
 495 }
 496
 497 static const char *store_to_file_post_(const char *filename, FLAC__Metadata_Chain *chain, FLAC__bool preserve_modtime)
 498 {
 499         struct stat stats;
 500         const FLAC__bool have_stats = get_file_stats_(filename, &stats);
 501
 502         (void)grabbag__file_change_stats(filename, /*read_only=*/false);
 503
 504         FLAC__metadata_chain_sort_padding(chain);
 505         if(!FLAC__metadata_chain_write(chain, /*use_padding=*/true, preserve_modtime)) {
 506                 FLAC__metadata_chain_delete(chain);
 507                 return FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)];
 508         }
 509
 510         FLAC__metadata_chain_delete(chain);
 511
 512         if(have_stats)
 513                 set_file_stats_(filename, &stats);
 514
 515         return 0;
 516 }
 517
 518 const char *grabbag__replaygain_store_to_file(const char *filename, float album_gain, float album_peak, float title_gain, float title_peak, FLAC__bool preserve_modtime)
 519 {
 520         FLAC__Metadata_Chain *chain;
 521         FLAC__StreamMetadata *block;
 522         const char *error;
 523
 524         if(0 != (error = store_to_file_pre_(filename, &chain, &block)))
 525                 return error;
 526
 527         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment(block, album_gain, album_peak, title_gain, title_peak))) {
 528                 FLAC__metadata_chain_delete(chain);
 529                 return error;
 530         }
 531
 532         if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))
 533                 return error;
 534
 535         return 0;
 536 }
 537
 538 const char *grabbag__replaygain_store_to_file_reference(const char *filename, FLAC__bool preserve_modtime)
 539 {
 540         FLAC__Metadata_Chain *chain;
 541         FLAC__StreamMetadata *block;
 542         const char *error;
 543
 544         if(0 != (error = store_to_file_pre_(filename, &chain, &block)))
 545                 return error;
 546
 547         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_reference(block))) {
 548                 FLAC__metadata_chain_delete(chain);
 549                 return error;
 550         }
 551
 552         if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))
 553                 return error;
 554
 555         return 0;
 556 }
 557
 558 const char *grabbag__replaygain_store_to_file_album(const char *filename, float album_gain, float album_peak, FLAC__bool preserve_modtime)
 559 {
 560         FLAC__Metadata_Chain *chain;
 561         FLAC__StreamMetadata *block;
 562         const char *error;
 563
 564         if(0 != (error = store_to_file_pre_(filename, &chain, &block)))
 565                 return error;
 566
 567         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_album(block, album_gain, album_peak))) {
 568                 FLAC__metadata_chain_delete(chain);
 569                 return error;
 570         }
 571
 572         if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))
 573                 return error;
 574
 575         return 0;
 576 }
 577
 578 const char *grabbag__replaygain_store_to_file_title(const char *filename, float title_gain, float title_peak, FLAC__bool preserve_modtime)
 579 {
 580         FLAC__Metadata_Chain *chain;
 581         FLAC__StreamMetadata *block;
 582         const char *error;
 583
 584         if(0 != (error = store_to_file_pre_(filename, &chain, &block)))
 585                 return error;
 586
 587         if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_title(block, title_gain, title_peak))) {
 588                 FLAC__metadata_chain_delete(chain);
 589                 return error;
 590         }
 591
 592         if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))
 593                 return error;
 594
 595         return 0;
 596 }
 597
 598 static FLAC__bool parse_double_(const FLAC__StreamMetadata_VorbisComment_Entry *entry, double *val)
 599 {
 600         char s[32], *end;
 601         const char *p, *q;
 602         double v;
 603
 604         FLAC__ASSERT(0 != entry);
 605         FLAC__ASSERT(0 != val);
 606
 607         p = (const char *)entry->entry;
 608         q = strchr(p, '=');
 609         if(0 == q)
 610                 return false;
 611         q++;
 612         memset(s, 0, sizeof(s)-1);
 613         strncpy(s, q, local_min(sizeof(s)-1, entry->length - (q-p)));
 614
 615         v = strtod(s, &end);
 616         if(end == s)
 617                 return false;
 618
 619         *val = v;
 620         return true;
 621 }
 622
 623 FLAC__bool grabbag__replaygain_load_from_vorbiscomment(const FLAC__StreamMetadata *block, FLAC__bool album_mode, FLAC__bool strict, double *reference, double *gain, double *peak)
 624 {
 625         int reference_offset, gain_offset, peak_offset;
 626
 627         FLAC__ASSERT(0 != block);
 628         FLAC__ASSERT(0 != reference);
 629         FLAC__ASSERT(0 != gain);
 630         FLAC__ASSERT(0 != peak);
 631         FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);
 632
 633         /* Default to current level until overridden by a detected tag; this
 634          * will always be true until we change replaygain_analysis.c
 635          */
 636         *reference = ReplayGainReferenceLoudness;
 637
 638         if(0 <= (reference_offset = FLAC__metadata_object_vorbiscomment_find_entry_from(block, /*offset=*/0, (const char *)GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS)))
 639                 (void)parse_double_(block->data.vorbis_comment.comments + reference_offset, reference);
 640
 641         if(0 > (gain_offset = FLAC__metadata_object_vorbiscomment_find_entry_from(block, /*offset=*/0, (const char *)(album_mode? GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN : GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN))))
 642                 return !strict && grabbag__replaygain_load_from_vorbiscomment(block, !album_mode, /*strict=*/true, reference, gain, peak);
 643         if(0 > (peak_offset = FLAC__metadata_object_vorbiscomment_find_entry_from(block, /*offset=*/0, (const char *)(album_mode? GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK : GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK))))
 644                 return !strict && grabbag__replaygain_load_from_vorbiscomment(block, !album_mode, /*strict=*/true, reference, gain, peak);
 645
 646         if(!parse_double_(block->data.vorbis_comment.comments + gain_offset, gain))
 647                 return !strict && grabbag__replaygain_load_from_vorbiscomment(block, !album_mode, /*strict=*/true, reference, gain, peak);
 648         if(!parse_double_(block->data.vorbis_comment.comments + peak_offset, peak))
 649                 return !strict && grabbag__replaygain_load_from_vorbiscomment(block, !album_mode, /*strict=*/true, reference, gain, peak);
 650
 651         return true;
 652 }
 653
 654 double grabbag__replaygain_compute_scale_factor(double peak, double gain, double preamp, FLAC__bool prevent_clipping)
 655 {
 656         double scale;
 657         FLAC__ASSERT(peak >= 0.0);
 658         gain += preamp;
 659         scale = (float) pow(10.0, gain * 0.05);
 660         if(prevent_clipping && peak > 0.0) {
 661                 const double max_scale = (float)(1.0 / peak);
 662                 if(scale > max_scale)
 663                         scale = max_scale;
 664         }
 665         return scale;
 666 }