media/formats/mp4/track_run_iterator.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/formats/mp4/track_run_iterator.h"
   6
   7 #include <algorithm>
   8 #include <iomanip>
   9
  10 #include "media/base/buffers.h"
  11 #include "media/formats/mp4/rcheck.h"
  12 #include "media/formats/mp4/sample_to_group_iterator.h"
  13
  14 namespace media {
  15 namespace mp4 {
  16
  17 struct SampleInfo {
  18   int size;
  19   int duration;
  20   int cts_offset;
  21   bool is_keyframe;
  22   uint32 cenc_group_description_index;
  23 };
  24
  25 struct TrackRunInfo {
  26   uint32 track_id;
  27   std::vector<SampleInfo> samples;
  28   int64 timescale;
  29   int64 start_dts;
  30   int64 sample_start_offset;
  31
  32   bool is_audio;
  33   const AudioSampleEntry* audio_description;
  34   const VideoSampleEntry* video_description;
  35   const SampleGroupDescription* track_sample_encryption_group;
  36
  37   int64 aux_info_start_offset;  // Only valid if aux_info_total_size > 0.
  38   int aux_info_default_size;
  39   std::vector<uint8> aux_info_sizes;  // Populated if default_size == 0.
  40   int aux_info_total_size;
  41
  42   std::vector<CencSampleEncryptionInfoEntry> fragment_sample_encryption_info;
  43
  44   TrackRunInfo();
  45   ~TrackRunInfo();
  46 };
  47
  48 TrackRunInfo::TrackRunInfo()
  49     : track_id(0),
  50       timescale(-1),
  51       start_dts(-1),
  52       sample_start_offset(-1),
  53       is_audio(false),
  54       aux_info_start_offset(-1),
  55       aux_info_default_size(-1),
  56       aux_info_total_size(-1) {
  57 }
  58 TrackRunInfo::~TrackRunInfo() {}
  59
  60 base::TimeDelta TimeDeltaFromRational(int64 numer, int64 denom) {
  61   // To avoid overflow, split the following calculation:
  62   // (numer * base::Time::kMicrosecondsPerSecond) / denom
  63   // into:
  64   //  (numer / denom) * base::Time::kMicrosecondsPerSecond +
  65   // ((numer % denom) * base::Time::kMicrosecondsPerSecond) / denom
  66   int64 a = numer / denom;
  67   DCHECK_LE((a > 0 ? a : -a), kint64max / base::Time::kMicrosecondsPerSecond);
  68   int64 timea_in_us = a * base::Time::kMicrosecondsPerSecond;
  69
  70   int64 b = numer % denom;
  71   DCHECK_LE((b > 0 ? b : -b), kint64max / base::Time::kMicrosecondsPerSecond);
  72   int64 timeb_in_us = (b * base::Time::kMicrosecondsPerSecond) / denom;
  73
  74   DCHECK((timeb_in_us < 0) || (timea_in_us <= kint64max - timeb_in_us));
  75   DCHECK((timeb_in_us > 0) || (timea_in_us >= kint64min - timeb_in_us));
  76   return base::TimeDelta::FromMicroseconds(timea_in_us + timeb_in_us);
  77 }
  78
  79 DecodeTimestamp DecodeTimestampFromRational(int64 numer, int64 denom) {
  80   return DecodeTimestamp::FromPresentationTime(
  81       TimeDeltaFromRational(numer, denom));
  82 }
  83
  84 TrackRunIterator::TrackRunIterator(const Movie* moov,
  85                                    const scoped_refptr<MediaLog>& media_log)
  86     : moov_(moov), media_log_(media_log), sample_offset_(0) {
  87   CHECK(moov);
  88 }
  89
  90 TrackRunIterator::~TrackRunIterator() {}
  91
  92 static std::string HexFlags(uint32 flags) {
  93   std::stringstream stream;
  94   stream << std::setfill('0') << std::setw(sizeof(flags)*2) << std::hex
  95          << flags;
  96   return stream.str();
  97 }
  98
  99 static bool PopulateSampleInfo(const TrackExtends& trex,
 100                                const TrackFragmentHeader& tfhd,
 101                                const TrackFragmentRun& trun,
 102                                const int64 edit_list_offset,
 103                                const uint32 i,
 104                                SampleInfo* sample_info,
 105                                const SampleDependsOn sdtp_sample_depends_on,
 106                                bool is_audio,
 107                                const scoped_refptr<MediaLog>& media_log) {
 108   if (i < trun.sample_sizes.size()) {
 109     sample_info->size = trun.sample_sizes[i];
 110   } else if (tfhd.default_sample_size > 0) {
 111     sample_info->size = tfhd.default_sample_size;
 112   } else {
 113     sample_info->size = trex.default_sample_size;
 114   }
 115
 116   if (i < trun.sample_durations.size()) {
 117     sample_info->duration = trun.sample_durations[i];
 118   } else if (tfhd.default_sample_duration > 0) {
 119     sample_info->duration = tfhd.default_sample_duration;
 120   } else {
 121     sample_info->duration = trex.default_sample_duration;
 122   }
 123
 124   if (i < trun.sample_composition_time_offsets.size()) {
 125     sample_info->cts_offset = trun.sample_composition_time_offsets[i];
 126   } else {
 127     sample_info->cts_offset = 0;
 128   }
 129   sample_info->cts_offset += edit_list_offset;
 130
 131   uint32 flags;
 132   if (i < trun.sample_flags.size()) {
 133     flags = trun.sample_flags[i];
 134     DVLOG(4) << __FUNCTION__ << " trun sample flags "  << HexFlags(flags);
 135   } else if (tfhd.has_default_sample_flags) {
 136     flags = tfhd.default_sample_flags;
 137     DVLOG(4) << __FUNCTION__ << " tfhd sample flags "  << HexFlags(flags);
 138   } else {
 139     flags = trex.default_sample_flags;
 140     DVLOG(4) << __FUNCTION__ << " trex sample flags "  << HexFlags(flags);
 141   }
 142
 143   SampleDependsOn sample_depends_on =
 144       static_cast<SampleDependsOn>((flags >> 24) & 0x3);
 145   if (sample_depends_on == kSampleDependsOnUnknown) {
 146     sample_depends_on = sdtp_sample_depends_on;
 147   }
 148   DVLOG(4) << __FUNCTION__ << " sample_depends_on "  << sample_depends_on;
 149   if (sample_depends_on == kSampleDependsOnReserved) {
 150     MEDIA_LOG(ERROR, media_log) << "Reserved value used in sample dependency"
 151                                    " info.";
 152     return false;
 153   }
 154
 155   // Per spec (ISO 14496-12:2012), the definition for a "sync sample" is
 156   // equivalent to the downstream code's "is keyframe" concept. But media exists
 157   // that marks non-key video frames as sync samples (http://crbug.com/507916
 158   // and http://crbug.com/310712). Hence, for video we additionally check that
 159   // the sample does not depend on others (FFmpeg does too, see mov_read_trun).
 160   // Sample dependency is not ignored for audio because encoded audio samples
 161   // can depend on other samples and still be used for random access. Generally
 162   // all audio samples are expected to be sync samples, but we  prefer to check
 163   // the flags to catch badly muxed audio (for now anyway ;P). History of
 164   // attempts to get this right discussed in http://crrev.com/1319813002
 165   bool sample_is_sync_sample = !(flags & kSampleIsNonSyncSample);
 166   bool sample_depends_on_others = sample_depends_on == kSampleDependsOnOthers;
 167   sample_info->is_keyframe = sample_is_sync_sample &&
 168                              (!sample_depends_on_others || is_audio);
 169
 170   DVLOG(4) << __FUNCTION__ << " is_kf:" << sample_info->is_keyframe
 171            << " is_sync:" << sample_is_sync_sample
 172            << " deps:" << sample_depends_on_others
 173            << " audio:" << is_audio;
 174
 175   return true;
 176 }
 177
 178 static const CencSampleEncryptionInfoEntry* GetSampleEncryptionInfoEntry(
 179     const TrackRunInfo& run_info,
 180     uint32 group_description_index) {
 181   const std::vector<CencSampleEncryptionInfoEntry>* entries = nullptr;
 182
 183   // ISO-14496-12 Section 8.9.2.3 and 8.9.4 : group description index
 184   // (1) ranges from 1 to the number of sample group entries in the track
 185   // level SampleGroupDescription Box, or (2) takes the value 0 to
 186   // indicate that this sample is a member of no group, in this case, the
 187   // sample is associated with the default values specified in
 188   // TrackEncryption Box, or (3) starts at 0x10001, i.e. the index value
 189   // 1, with the value 1 in the top 16 bits, to reference fragment-local
 190   // SampleGroupDescription Box.
 191   // Case (2) is not supported here. The caller must handle it externally
 192   // before invoking this function.
 193   DCHECK_NE(group_description_index, 0u);
 194   if (group_description_index >
 195       SampleToGroupEntry::kFragmentGroupDescriptionIndexBase) {
 196     group_description_index -=
 197         SampleToGroupEntry::kFragmentGroupDescriptionIndexBase;
 198     entries = &run_info.fragment_sample_encryption_info;
 199   } else {
 200     entries = &run_info.track_sample_encryption_group->entries;
 201   }
 202
 203   // |group_description_index| is 1-based.
 204   DCHECK_LE(group_description_index, entries->size());
 205   return (group_description_index > entries->size())
 206              ? nullptr
 207              : &(*entries)[group_description_index - 1];
 208 }
 209
 210 // In well-structured encrypted media, each track run will be immediately
 211 // preceded by its auxiliary information; this is the only optimal storage
 212 // pattern in terms of minimum number of bytes from a serial stream needed to
 213 // begin playback. It also allows us to optimize caching on memory-constrained
 214 // architectures, because we can cache the relatively small auxiliary
 215 // information for an entire run and then discard data from the input stream,
 216 // instead of retaining the entire 'mdat' box.
 217 //
 218 // We optimize for this situation (with no loss of generality) by sorting track
 219 // runs during iteration in order of their first data offset (either sample data
 220 // or auxiliary data).
 221 class CompareMinTrackRunDataOffset {
 222  public:
 223   bool operator()(const TrackRunInfo& a, const TrackRunInfo& b) {
 224     int64 a_aux = a.aux_info_total_size ? a.aux_info_start_offset : kint64max;
 225     int64 b_aux = b.aux_info_total_size ? b.aux_info_start_offset : kint64max;
 226
 227     int64 a_lesser = std::min(a_aux, a.sample_start_offset);
 228     int64 a_greater = std::max(a_aux, a.sample_start_offset);
 229     int64 b_lesser = std::min(b_aux, b.sample_start_offset);
 230     int64 b_greater = std::max(b_aux, b.sample_start_offset);
 231
 232     if (a_lesser == b_lesser) return a_greater < b_greater;
 233     return a_lesser < b_lesser;
 234   }
 235 };
 236
 237 bool TrackRunIterator::Init(const MovieFragment& moof) {
 238   runs_.clear();
 239
 240   for (size_t i = 0; i < moof.tracks.size(); i++) {
 241     const TrackFragment& traf = moof.tracks[i];
 242
 243     const Track* trak = NULL;
 244     for (size_t t = 0; t < moov_->tracks.size(); t++) {
 245       if (moov_->tracks[t].header.track_id == traf.header.track_id)
 246         trak = &moov_->tracks[t];
 247     }
 248     RCHECK(trak);
 249
 250     const TrackExtends* trex = NULL;
 251     for (size_t t = 0; t < moov_->extends.tracks.size(); t++) {
 252       if (moov_->extends.tracks[t].track_id == traf.header.track_id)
 253         trex = &moov_->extends.tracks[t];
 254     }
 255     RCHECK(trex);
 256
 257     const SampleDescription& stsd =
 258         trak->media.information.sample_table.description;
 259     if (stsd.type != kAudio && stsd.type != kVideo) {
 260       DVLOG(1) << "Skipping unhandled track type";
 261       continue;
 262     }
 263     size_t desc_idx = traf.header.sample_description_index;
 264     if (!desc_idx) desc_idx = trex->default_sample_description_index;
 265     RCHECK(desc_idx > 0);  // Descriptions are one-indexed in the file
 266     desc_idx -= 1;
 267
 268     // Process edit list to remove CTS offset introduced in the presence of
 269     // B-frames (those that contain a single edit with a nonnegative media
 270     // time). Other uses of edit lists are not supported, as they are
 271     // both uncommon and better served by higher-level protocols.
 272     int64 edit_list_offset = 0;
 273     const std::vector<EditListEntry>& edits = trak->edit.list.edits;
 274     if (!edits.empty()) {
 275       if (edits.size() > 1)
 276         DVLOG(1) << "Multi-entry edit box detected; some components ignored.";
 277
 278       if (edits[0].media_time < 0) {
 279         DVLOG(1) << "Empty edit list entry ignored.";
 280       } else {
 281         edit_list_offset = -edits[0].media_time;
 282       }
 283     }
 284
 285     SampleToGroupIterator sample_to_group_itr(traf.sample_to_group);
 286     bool is_sample_to_group_valid = sample_to_group_itr.IsValid();
 287
 288     int64 run_start_dts = traf.decode_time.decode_time;
 289     int sample_count_sum = 0;
 290     for (size_t j = 0; j < traf.runs.size(); j++) {
 291       const TrackFragmentRun& trun = traf.runs[j];
 292       TrackRunInfo tri;
 293       tri.track_id = traf.header.track_id;
 294       tri.timescale = trak->media.header.timescale;
 295       tri.start_dts = run_start_dts;
 296       tri.sample_start_offset = trun.data_offset;
 297       tri.track_sample_encryption_group =
 298           &trak->media.information.sample_table.sample_group_description;
 299       tri.fragment_sample_encryption_info =
 300           traf.sample_group_description.entries;
 301
 302       tri.is_audio = (stsd.type == kAudio);
 303       if (tri.is_audio) {
 304         RCHECK(!stsd.audio_entries.empty());
 305         if (desc_idx > stsd.audio_entries.size())
 306           desc_idx = 0;
 307         tri.audio_description = &stsd.audio_entries[desc_idx];
 308       } else {
 309         RCHECK(!stsd.video_entries.empty());
 310         if (desc_idx > stsd.video_entries.size())
 311           desc_idx = 0;
 312         tri.video_description = &stsd.video_entries[desc_idx];
 313       }
 314
 315       // Collect information from the auxiliary_offset entry with the same index
 316       // in the 'saiz' container as the current run's index in the 'trun'
 317       // container, if it is present.
 318       if (traf.auxiliary_offset.offsets.size() > j) {
 319         // There should be an auxiliary info entry corresponding to each sample
 320         // in the auxiliary offset entry's corresponding track run.
 321         RCHECK(traf.auxiliary_size.sample_count >=
 322                sample_count_sum + trun.sample_count);
 323         tri.aux_info_start_offset = traf.auxiliary_offset.offsets[j];
 324         tri.aux_info_default_size =
 325             traf.auxiliary_size.default_sample_info_size;
 326         if (tri.aux_info_default_size == 0) {
 327           const std::vector<uint8>& sizes =
 328               traf.auxiliary_size.sample_info_sizes;
 329           tri.aux_info_sizes.insert(tri.aux_info_sizes.begin(),
 330               sizes.begin() + sample_count_sum,
 331               sizes.begin() + sample_count_sum + trun.sample_count);
 332         }
 333
 334         // If the default info size is positive, find the total size of the aux
 335         // info block from it, otherwise sum over the individual sizes of each
 336         // aux info entry in the aux_offset entry.
 337         if (tri.aux_info_default_size) {
 338           tri.aux_info_total_size =
 339               tri.aux_info_default_size * trun.sample_count;
 340         } else {
 341           tri.aux_info_total_size = 0;
 342           for (size_t k = 0; k < trun.sample_count; k++) {
 343             tri.aux_info_total_size += tri.aux_info_sizes[k];
 344           }
 345         }
 346       } else {
 347         tri.aux_info_start_offset = -1;
 348         tri.aux_info_total_size = 0;
 349       }
 350
 351       tri.samples.resize(trun.sample_count);
 352       for (size_t k = 0; k < trun.sample_count; k++) {
 353         if (!PopulateSampleInfo(*trex, traf.header, trun, edit_list_offset, k,
 354                                 &tri.samples[k], traf.sdtp.sample_depends_on(k),
 355                                 tri.is_audio, media_log_)) {
 356           return false;
 357         }
 358
 359         run_start_dts += tri.samples[k].duration;
 360
 361         if (!is_sample_to_group_valid) {
 362           // Set group description index to 0 to read encryption information
 363           // from TrackEncryption Box.
 364           tri.samples[k].cenc_group_description_index = 0;
 365           continue;
 366         }
 367
 368         uint32 index = sample_to_group_itr.group_description_index();
 369         tri.samples[k].cenc_group_description_index = index;
 370         if (index != 0)
 371           RCHECK(GetSampleEncryptionInfoEntry(tri, index));
 372         is_sample_to_group_valid = sample_to_group_itr.Advance();
 373       }
 374       runs_.push_back(tri);
 375       sample_count_sum += trun.sample_count;
 376     }
 377
 378     // We should have iterated through all samples in SampleToGroup Box.
 379     RCHECK(!sample_to_group_itr.IsValid());
 380   }
 381
 382   std::sort(runs_.begin(), runs_.end(), CompareMinTrackRunDataOffset());
 383   run_itr_ = runs_.begin();
 384   ResetRun();
 385   return true;
 386 }
 387
 388 void TrackRunIterator::AdvanceRun() {
 389   ++run_itr_;
 390   ResetRun();
 391 }
 392
 393 void TrackRunIterator::ResetRun() {
 394   if (!IsRunValid()) return;
 395   sample_dts_ = run_itr_->start_dts;
 396   sample_offset_ = run_itr_->sample_start_offset;
 397   sample_itr_ = run_itr_->samples.begin();
 398   cenc_info_.clear();
 399 }
 400
 401 void TrackRunIterator::AdvanceSample() {
 402   DCHECK(IsSampleValid());
 403   sample_dts_ += sample_itr_->duration;
 404   sample_offset_ += sample_itr_->size;
 405   ++sample_itr_;
 406 }
 407
 408 // This implementation only indicates a need for caching if CENC auxiliary
 409 // info is available in the stream.
 410 bool TrackRunIterator::AuxInfoNeedsToBeCached() {
 411   DCHECK(IsRunValid());
 412   return aux_info_size() > 0 && cenc_info_.size() == 0;
 413 }
 414
 415 // This implementation currently only caches CENC auxiliary info.
 416 bool TrackRunIterator::CacheAuxInfo(const uint8* buf, int buf_size) {
 417   RCHECK(AuxInfoNeedsToBeCached() && buf_size >= aux_info_size());
 418
 419   cenc_info_.resize(run_itr_->samples.size());
 420   int64 pos = 0;
 421   for (size_t i = 0; i < run_itr_->samples.size(); i++) {
 422     int info_size = run_itr_->aux_info_default_size;
 423     if (!info_size)
 424       info_size = run_itr_->aux_info_sizes[i];
 425
 426     if (IsSampleEncrypted(i)) {
 427       BufferReader reader(buf + pos, info_size);
 428       RCHECK(cenc_info_[i].Parse(GetIvSize(i), &reader));
 429     }
 430     pos += info_size;
 431   }
 432
 433   return true;
 434 }
 435
 436 bool TrackRunIterator::IsRunValid() const {
 437   return run_itr_ != runs_.end();
 438 }
 439
 440 bool TrackRunIterator::IsSampleValid() const {
 441   return IsRunValid() && (sample_itr_ != run_itr_->samples.end());
 442 }
 443
 444 // Because tracks are in sorted order and auxiliary information is cached when
 445 // returning samples, it is guaranteed that no data will be required before the
 446 // lesser of the minimum data offset of this track and the next in sequence.
 447 // (The stronger condition - that no data is required before the minimum data
 448 // offset of this track alone - is not guaranteed, because the BMFF spec does
 449 // not have any inter-run ordering restrictions.)
 450 int64 TrackRunIterator::GetMaxClearOffset() {
 451   int64 offset = kint64max;
 452
 453   if (IsSampleValid()) {
 454     offset = std::min(offset, sample_offset_);
 455     if (AuxInfoNeedsToBeCached())
 456       offset = std::min(offset, aux_info_offset());
 457   }
 458   if (run_itr_ != runs_.end()) {
 459     std::vector<TrackRunInfo>::const_iterator next_run = run_itr_ + 1;
 460     if (next_run != runs_.end()) {
 461       offset = std::min(offset, next_run->sample_start_offset);
 462       if (next_run->aux_info_total_size)
 463         offset = std::min(offset, next_run->aux_info_start_offset);
 464     }
 465   }
 466   if (offset == kint64max) return 0;
 467   return offset;
 468 }
 469
 470 uint32 TrackRunIterator::track_id() const {
 471   DCHECK(IsRunValid());
 472   return run_itr_->track_id;
 473 }
 474
 475 bool TrackRunIterator::is_encrypted() const {
 476   DCHECK(IsSampleValid());
 477   return IsSampleEncrypted(sample_itr_ - run_itr_->samples.begin());
 478 }
 479
 480 int64 TrackRunIterator::aux_info_offset() const {
 481   return run_itr_->aux_info_start_offset;
 482 }
 483
 484 int TrackRunIterator::aux_info_size() const {
 485   return run_itr_->aux_info_total_size;
 486 }
 487
 488 bool TrackRunIterator::is_audio() const {
 489   DCHECK(IsRunValid());
 490   return run_itr_->is_audio;
 491 }
 492
 493 const AudioSampleEntry& TrackRunIterator::audio_description() const {
 494   DCHECK(is_audio());
 495   DCHECK(run_itr_->audio_description);
 496   return *run_itr_->audio_description;
 497 }
 498
 499 const VideoSampleEntry& TrackRunIterator::video_description() const {
 500   DCHECK(!is_audio());
 501   DCHECK(run_itr_->video_description);
 502   return *run_itr_->video_description;
 503 }
 504
 505 int64 TrackRunIterator::sample_offset() const {
 506   DCHECK(IsSampleValid());
 507   return sample_offset_;
 508 }
 509
 510 int TrackRunIterator::sample_size() const {
 511   DCHECK(IsSampleValid());
 512   return sample_itr_->size;
 513 }
 514
 515 DecodeTimestamp TrackRunIterator::dts() const {
 516   DCHECK(IsSampleValid());
 517   return DecodeTimestampFromRational(sample_dts_, run_itr_->timescale);
 518 }
 519
 520 base::TimeDelta TrackRunIterator::cts() const {
 521   DCHECK(IsSampleValid());
 522   return TimeDeltaFromRational(sample_dts_ + sample_itr_->cts_offset,
 523                                run_itr_->timescale);
 524 }
 525
 526 base::TimeDelta TrackRunIterator::duration() const {
 527   DCHECK(IsSampleValid());
 528   return TimeDeltaFromRational(sample_itr_->duration, run_itr_->timescale);
 529 }
 530
 531 bool TrackRunIterator::is_keyframe() const {
 532   DCHECK(IsSampleValid());
 533   return sample_itr_->is_keyframe;
 534 }
 535
 536 const TrackEncryption& TrackRunIterator::track_encryption() const {
 537   if (is_audio())
 538     return audio_description().sinf.info.track_encryption;
 539   return video_description().sinf.info.track_encryption;
 540 }
 541
 542 scoped_ptr<DecryptConfig> TrackRunIterator::GetDecryptConfig() {
 543   DCHECK(is_encrypted());
 544
 545   if (cenc_info_.empty()) {
 546     DCHECK_EQ(0, aux_info_size());
 547     MEDIA_LOG(ERROR, media_log_) << "Aux Info is not available.";
 548     return scoped_ptr<DecryptConfig>();
 549   }
 550
 551   size_t sample_idx = sample_itr_ - run_itr_->samples.begin();
 552   DCHECK_LT(sample_idx, cenc_info_.size());
 553   const FrameCENCInfo& cenc_info = cenc_info_[sample_idx];
 554
 555   size_t total_size = 0;
 556   if (!cenc_info.subsamples.empty() &&
 557       (!cenc_info.GetTotalSizeOfSubsamples(&total_size) ||
 558        total_size != static_cast<size_t>(sample_size()))) {
 559     MEDIA_LOG(ERROR, media_log_) << "Incorrect CENC subsample size.";
 560     return scoped_ptr<DecryptConfig>();
 561   }
 562
 563   const std::vector<uint8>& kid = GetKeyId(sample_idx);
 564   return scoped_ptr<DecryptConfig>(new DecryptConfig(
 565       std::string(reinterpret_cast<const char*>(&kid[0]), kid.size()),
 566       std::string(reinterpret_cast<const char*>(cenc_info.iv),
 567                   arraysize(cenc_info.iv)),
 568       cenc_info.subsamples));
 569 }
 570
 571 uint32 TrackRunIterator::GetGroupDescriptionIndex(uint32 sample_index) const {
 572   DCHECK(IsRunValid());
 573   DCHECK_LT(sample_index, run_itr_->samples.size());
 574   return run_itr_->samples[sample_index].cenc_group_description_index;
 575 }
 576
 577 bool TrackRunIterator::IsSampleEncrypted(size_t sample_index) const {
 578   uint32 index = GetGroupDescriptionIndex(sample_index);
 579   return (index == 0)
 580              ? track_encryption().is_encrypted
 581              : GetSampleEncryptionInfoEntry(*run_itr_, index)->is_encrypted;
 582 }
 583
 584 const std::vector<uint8>& TrackRunIterator::GetKeyId(
 585     size_t sample_index) const {
 586   uint32 index = GetGroupDescriptionIndex(sample_index);
 587   return (index == 0) ? track_encryption().default_kid
 588                       : GetSampleEncryptionInfoEntry(*run_itr_, index)->key_id;
 589 }
 590
 591 uint8 TrackRunIterator::GetIvSize(size_t sample_index) const {
 592   uint32 index = GetGroupDescriptionIndex(sample_index);
 593   return (index == 0) ? track_encryption().default_iv_size
 594                       : GetSampleEncryptionInfoEntry(*run_itr_, index)->iv_size;
 595 }
 596
 597 }  // namespace mp4
 598 }  // namespace media