src/media/mp4/track_run_iterator.cc

   1 // Copyright (c) 2012 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/mp4/track_run_iterator.h"
   6
   7 #include <algorithm>
   8
   9 #include "media/base/buffers.h"
  10 #include "media/base/stream_parser_buffer.h"
  11 #include "media/mp4/rcheck.h"
  12
  13 namespace {
  14 static const uint32 kSampleIsDifferenceSampleFlagMask = 0x10000;
  15 }
  16
  17 namespace media {
  18 namespace mp4 {
  19
  20 struct SampleInfo {
  21   int size;
  22   int duration;
  23   int cts_offset;
  24   bool is_keyframe;
  25 };
  26
  27 struct TrackRunInfo {
  28   uint32 track_id;
  29   std::vector<SampleInfo> samples;
  30   int64 timescale;
  31   int64 start_dts;
  32   int64 sample_start_offset;
  33
  34   bool is_audio;
  35   const AudioSampleEntry* audio_description;
  36   const VideoSampleEntry* video_description;
  37
  38   int64 aux_info_start_offset;  // Only valid if aux_info_total_size > 0.
  39   int aux_info_default_size;
  40   std::vector<uint8> aux_info_sizes;  // Populated if default_size == 0.
  41   int aux_info_total_size;
  42
  43   TrackRunInfo();
  44   ~TrackRunInfo();
  45 };
  46
  47 TrackRunInfo::TrackRunInfo()
  48     : track_id(0),
  49       timescale(-1),
  50       start_dts(-1),
  51       sample_start_offset(-1),
  52       is_audio(false),
  53       aux_info_start_offset(-1),
  54       aux_info_default_size(-1),
  55       aux_info_total_size(-1) {
  56 }
  57 TrackRunInfo::~TrackRunInfo() {}
  58
  59 TimeDelta TimeDeltaFromRational(int64 numer, int64 denom) {
  60   DCHECK_LT((numer > 0 ? numer : -numer),
  61             kint64max / base::Time::kMicrosecondsPerSecond);
  62   return TimeDelta::FromMicroseconds(
  63         base::Time::kMicrosecondsPerSecond * numer / denom);
  64 }
  65
  66 TrackRunIterator::TrackRunIterator(const Movie* moov,
  67                                    const LogCB& log_cb)
  68     : moov_(moov), log_cb_(log_cb), sample_offset_(0) {
  69   CHECK(moov);
  70 }
  71
  72 TrackRunIterator::~TrackRunIterator() {}
  73
  74 static void PopulateSampleInfo(const TrackExtends& trex,
  75                                const TrackFragmentHeader& tfhd,
  76                                const TrackFragmentRun& trun,
  77                                const int64 edit_list_offset,
  78                                const uint32 i,
  79                                SampleInfo* sample_info,
  80                                const SampleDependsOn sample_depends_on) {
  81   if (i < trun.sample_sizes.size()) {
  82     sample_info->size = trun.sample_sizes[i];
  83   } else if (tfhd.default_sample_size > 0) {
  84     sample_info->size = tfhd.default_sample_size;
  85   } else {
  86     sample_info->size = trex.default_sample_size;
  87   }
  88
  89   if (i < trun.sample_durations.size()) {
  90     sample_info->duration = trun.sample_durations[i];
  91   } else if (tfhd.default_sample_duration > 0) {
  92     sample_info->duration = tfhd.default_sample_duration;
  93   } else {
  94     sample_info->duration = trex.default_sample_duration;
  95   }
  96
  97   if (i < trun.sample_composition_time_offsets.size()) {
  98     sample_info->cts_offset = trun.sample_composition_time_offsets[i];
  99   } else {
 100     sample_info->cts_offset = 0;
 101   }
 102   sample_info->cts_offset += edit_list_offset;
 103
 104   uint32 flags;
 105   if (i < trun.sample_flags.size()) {
 106     flags = trun.sample_flags[i];
 107   } else if (tfhd.has_default_sample_flags) {
 108     flags = tfhd.default_sample_flags;
 109   } else {
 110     flags = trex.default_sample_flags;
 111   }
 112
 113   switch (sample_depends_on) {
 114     case kSampleDependsOnUnknown:
 115       sample_info->is_keyframe = !(flags & kSampleIsDifferenceSampleFlagMask);
 116       break;
 117
 118     case kSampleDependsOnOthers:
 119       sample_info->is_keyframe = false;
 120       break;
 121
 122     case kSampleDependsOnNoOther:
 123       sample_info->is_keyframe = true;
 124       break;
 125
 126     case kSampleDependsOnReserved:
 127       CHECK(false);
 128   }
 129 }
 130
 131 // In well-structured encrypted media, each track run will be immediately
 132 // preceded by its auxiliary information; this is the only optimal storage
 133 // pattern in terms of minimum number of bytes from a serial stream needed to
 134 // begin playback. It also allows us to optimize caching on memory-constrained
 135 // architectures, because we can cache the relatively small auxiliary
 136 // information for an entire run and then discard data from the input stream,
 137 // instead of retaining the entire 'mdat' box.
 138 //
 139 // We optimize for this situation (with no loss of generality) by sorting track
 140 // runs during iteration in order of their first data offset (either sample data
 141 // or auxiliary data).
 142 class CompareMinTrackRunDataOffset {
 143  public:
 144   bool operator()(const TrackRunInfo& a, const TrackRunInfo& b) {
 145     int64 a_aux = a.aux_info_total_size ? a.aux_info_start_offset : kint64max;
 146     int64 b_aux = b.aux_info_total_size ? b.aux_info_start_offset : kint64max;
 147
 148     int64 a_lesser = std::min(a_aux, a.sample_start_offset);
 149     int64 a_greater = std::max(a_aux, a.sample_start_offset);
 150     int64 b_lesser = std::min(b_aux, b.sample_start_offset);
 151     int64 b_greater = std::max(b_aux, b.sample_start_offset);
 152
 153     if (a_lesser == b_lesser) return a_greater < b_greater;
 154     return a_lesser < b_lesser;
 155   }
 156 };
 157
 158 bool TrackRunIterator::Init(const MovieFragment& moof) {
 159   runs_.clear();
 160
 161   for (size_t i = 0; i < moof.tracks.size(); i++) {
 162     const TrackFragment& traf = moof.tracks[i];
 163
 164     const Track* trak = NULL;
 165     for (size_t t = 0; t < moov_->tracks.size(); t++) {
 166       if (moov_->tracks[t].header.track_id == traf.header.track_id)
 167         trak = &moov_->tracks[t];
 168     }
 169     RCHECK(trak);
 170
 171     const TrackExtends* trex = NULL;
 172     for (size_t t = 0; t < moov_->extends.tracks.size(); t++) {
 173       if (moov_->extends.tracks[t].track_id == traf.header.track_id)
 174         trex = &moov_->extends.tracks[t];
 175     }
 176     RCHECK(trex);
 177
 178     const SampleDescription& stsd =
 179         trak->media.information.sample_table.description;
 180     if (stsd.type != kAudio && stsd.type != kVideo) {
 181       DVLOG(1) << "Skipping unhandled track type";
 182       continue;
 183     }
 184     size_t desc_idx = traf.header.sample_description_index;
 185     if (!desc_idx) desc_idx = trex->default_sample_description_index;
 186     RCHECK(desc_idx > 0);  // Descriptions are one-indexed in the file
 187     desc_idx -= 1;
 188
 189     // Process edit list to remove CTS offset introduced in the presence of
 190     // B-frames (those that contain a single edit with a nonnegative media
 191     // time). Other uses of edit lists are not supported, as they are
 192     // both uncommon and better served by higher-level protocols.
 193     int64 edit_list_offset = 0;
 194     const std::vector<EditListEntry>& edits = trak->edit.list.edits;
 195     if (!edits.empty()) {
 196       if (edits.size() > 1)
 197         DVLOG(1) << "Multi-entry edit box detected; some components ignored.";
 198
 199       if (edits[0].media_time < 0) {
 200         DVLOG(1) << "Empty edit list entry ignored.";
 201       } else {
 202         edit_list_offset = -edits[0].media_time;
 203       }
 204     }
 205
 206     int64 run_start_dts = traf.decode_time.decode_time;
 207     int sample_count_sum = 0;
 208
 209     for (size_t j = 0; j < traf.runs.size(); j++) {
 210       const TrackFragmentRun& trun = traf.runs[j];
 211       TrackRunInfo tri;
 212       tri.track_id = traf.header.track_id;
 213       tri.timescale = trak->media.header.timescale;
 214       tri.start_dts = run_start_dts;
 215       tri.sample_start_offset = trun.data_offset;
 216
 217       tri.is_audio = (stsd.type == kAudio);
 218       if (tri.is_audio) {
 219         RCHECK(!stsd.audio_entries.empty());
 220         if (desc_idx > stsd.audio_entries.size())
 221           desc_idx = 0;
 222         tri.audio_description = &stsd.audio_entries[desc_idx];
 223       } else {
 224         RCHECK(!stsd.video_entries.empty());
 225         if (desc_idx > stsd.video_entries.size())
 226           desc_idx = 0;
 227         tri.video_description = &stsd.video_entries[desc_idx];
 228       }
 229
 230       // Collect information from the auxiliary_offset entry with the same index
 231       // in the 'saiz' container as the current run's index in the 'trun'
 232       // container, if it is present.
 233       if (traf.auxiliary_offset.offsets.size() > j) {
 234         // There should be an auxiliary info entry corresponding to each sample
 235         // in the auxiliary offset entry's corresponding track run.
 236         RCHECK(traf.auxiliary_size.sample_count >=
 237                sample_count_sum + trun.sample_count);
 238         tri.aux_info_start_offset = traf.auxiliary_offset.offsets[j];
 239         tri.aux_info_default_size =
 240             traf.auxiliary_size.default_sample_info_size;
 241         if (tri.aux_info_default_size == 0) {
 242           const std::vector<uint8>& sizes =
 243               traf.auxiliary_size.sample_info_sizes;
 244           tri.aux_info_sizes.insert(tri.aux_info_sizes.begin(),
 245               sizes.begin() + sample_count_sum,
 246               sizes.begin() + sample_count_sum + trun.sample_count);
 247         }
 248
 249         // If the default info size is positive, find the total size of the aux
 250         // info block from it, otherwise sum over the individual sizes of each
 251         // aux info entry in the aux_offset entry.
 252         if (tri.aux_info_default_size) {
 253           tri.aux_info_total_size =
 254               tri.aux_info_default_size * trun.sample_count;
 255         } else {
 256           tri.aux_info_total_size = 0;
 257           for (size_t k = 0; k < trun.sample_count; k++) {
 258             tri.aux_info_total_size += tri.aux_info_sizes[k];
 259           }
 260         }
 261       } else {
 262         tri.aux_info_start_offset = -1;
 263         tri.aux_info_total_size = 0;
 264       }
 265
 266       tri.samples.resize(trun.sample_count);
 267       for (size_t k = 0; k < trun.sample_count; k++) {
 268         PopulateSampleInfo(*trex, traf.header, trun, edit_list_offset,
 269                            k, &tri.samples[k], traf.sdtp.sample_depends_on(k));
 270         run_start_dts += tri.samples[k].duration;
 271       }
 272       runs_.push_back(tri);
 273       sample_count_sum += trun.sample_count;
 274     }
 275   }
 276
 277   std::sort(runs_.begin(), runs_.end(), CompareMinTrackRunDataOffset());
 278   run_itr_ = runs_.begin();
 279   ResetRun();
 280   return true;
 281 }
 282
 283 void TrackRunIterator::AdvanceRun() {
 284   ++run_itr_;
 285   ResetRun();
 286 }
 287
 288 void TrackRunIterator::ResetRun() {
 289   if (!IsRunValid()) return;
 290   sample_dts_ = run_itr_->start_dts;
 291   sample_offset_ = run_itr_->sample_start_offset;
 292   sample_itr_ = run_itr_->samples.begin();
 293   cenc_info_.clear();
 294 }
 295
 296 void TrackRunIterator::AdvanceSample() {
 297   DCHECK(IsSampleValid());
 298   sample_dts_ += sample_itr_->duration;
 299   sample_offset_ += sample_itr_->size;
 300   ++sample_itr_;
 301 }
 302
 303 // This implementation only indicates a need for caching if CENC auxiliary
 304 // info is available in the stream.
 305 bool TrackRunIterator::AuxInfoNeedsToBeCached() {
 306   DCHECK(IsRunValid());
 307   return is_encrypted() && aux_info_size() > 0 && cenc_info_.size() == 0;
 308 }
 309
 310 // This implementation currently only caches CENC auxiliary info.
 311 bool TrackRunIterator::CacheAuxInfo(const uint8* buf, int buf_size) {
 312   RCHECK(AuxInfoNeedsToBeCached() && buf_size >= aux_info_size());
 313
 314   cenc_info_.resize(run_itr_->samples.size());
 315   int64 pos = 0;
 316   for (size_t i = 0; i < run_itr_->samples.size(); i++) {
 317     int info_size = run_itr_->aux_info_default_size;
 318     if (!info_size)
 319       info_size = run_itr_->aux_info_sizes[i];
 320
 321     BufferReader reader(buf + pos, info_size);
 322     RCHECK(cenc_info_[i].Parse(track_encryption().default_iv_size, &reader));
 323     pos += info_size;
 324   }
 325
 326   return true;
 327 }
 328
 329 bool TrackRunIterator::IsRunValid() const {
 330   return run_itr_ != runs_.end();
 331 }
 332
 333 bool TrackRunIterator::IsSampleValid() const {
 334   return IsRunValid() && (sample_itr_ != run_itr_->samples.end());
 335 }
 336
 337 // Because tracks are in sorted order and auxiliary information is cached when
 338 // returning samples, it is guaranteed that no data will be required before the
 339 // lesser of the minimum data offset of this track and the next in sequence.
 340 // (The stronger condition - that no data is required before the minimum data
 341 // offset of this track alone - is not guaranteed, because the BMFF spec does
 342 // not have any inter-run ordering restrictions.)
 343 int64 TrackRunIterator::GetMaxClearOffset() {
 344   int64 offset = kint64max;
 345
 346   if (IsSampleValid()) {
 347     offset = std::min(offset, sample_offset_);
 348     if (AuxInfoNeedsToBeCached())
 349       offset = std::min(offset, aux_info_offset());
 350   }
 351   if (run_itr_ != runs_.end()) {
 352     std::vector<TrackRunInfo>::const_iterator next_run = run_itr_ + 1;
 353     if (next_run != runs_.end()) {
 354       offset = std::min(offset, next_run->sample_start_offset);
 355       if (next_run->aux_info_total_size)
 356         offset = std::min(offset, next_run->aux_info_start_offset);
 357     }
 358   }
 359   if (offset == kint64max) return 0;
 360   return offset;
 361 }
 362
 363 uint32 TrackRunIterator::track_id() const {
 364   DCHECK(IsRunValid());
 365   return run_itr_->track_id;
 366 }
 367
 368 bool TrackRunIterator::is_encrypted() const {
 369   DCHECK(IsRunValid());
 370   return track_encryption().is_encrypted;
 371 }
 372
 373 int64 TrackRunIterator::aux_info_offset() const {
 374   return run_itr_->aux_info_start_offset;
 375 }
 376
 377 int TrackRunIterator::aux_info_size() const {
 378   return run_itr_->aux_info_total_size;
 379 }
 380
 381 bool TrackRunIterator::is_audio() const {
 382   DCHECK(IsRunValid());
 383   return run_itr_->is_audio;
 384 }
 385
 386 const AudioSampleEntry& TrackRunIterator::audio_description() const {
 387   DCHECK(is_audio());
 388   DCHECK(run_itr_->audio_description);
 389   return *run_itr_->audio_description;
 390 }
 391
 392 const VideoSampleEntry& TrackRunIterator::video_description() const {
 393   DCHECK(!is_audio());
 394   DCHECK(run_itr_->video_description);
 395   return *run_itr_->video_description;
 396 }
 397
 398 int64 TrackRunIterator::sample_offset() const {
 399   DCHECK(IsSampleValid());
 400   return sample_offset_;
 401 }
 402
 403 int TrackRunIterator::sample_size() const {
 404   DCHECK(IsSampleValid());
 405   return sample_itr_->size;
 406 }
 407
 408 TimeDelta TrackRunIterator::dts() const {
 409   DCHECK(IsSampleValid());
 410   return TimeDeltaFromRational(sample_dts_, run_itr_->timescale);
 411 }
 412
 413 TimeDelta TrackRunIterator::cts() const {
 414   DCHECK(IsSampleValid());
 415   return TimeDeltaFromRational(sample_dts_ + sample_itr_->cts_offset,
 416                                run_itr_->timescale);
 417 }
 418
 419 TimeDelta TrackRunIterator::duration() const {
 420   DCHECK(IsSampleValid());
 421   return TimeDeltaFromRational(sample_itr_->duration, run_itr_->timescale);
 422 }
 423
 424 bool TrackRunIterator::is_keyframe() const {
 425   DCHECK(IsSampleValid());
 426   return sample_itr_->is_keyframe;
 427 }
 428
 429 const TrackEncryption& TrackRunIterator::track_encryption() const {
 430   if (is_audio())
 431     return audio_description().sinf.info.track_encryption;
 432   return video_description().sinf.info.track_encryption;
 433 }
 434
 435 scoped_ptr<DecryptConfig> TrackRunIterator::GetDecryptConfig() {
 436   size_t sample_idx = sample_itr_ - run_itr_->samples.begin();
 437   DCHECK(sample_idx < cenc_info_.size());
 438   const FrameCENCInfo& cenc_info = cenc_info_[sample_idx];
 439   DCHECK(is_encrypted() && !AuxInfoNeedsToBeCached());
 440
 441   if (!cenc_info.subsamples.empty() &&
 442       (cenc_info.GetTotalSizeOfSubsamples() !=
 443        static_cast<size_t>(sample_size()))) {
 444     MEDIA_LOG(log_cb_) << "Incorrect CENC subsample size.";
 445     return scoped_ptr<DecryptConfig>();
 446   }
 447
 448   const std::vector<uint8>& kid = track_encryption().default_kid;
 449   return scoped_ptr<DecryptConfig>(new DecryptConfig(
 450       std::string(reinterpret_cast<const char*>(&kid[0]), kid.size()),
 451       std::string(reinterpret_cast<const char*>(cenc_info.iv),
 452                   arraysize(cenc_info.iv)),
 453       0,  // No offset to start of media data in MP4 using CENC.
 454       cenc_info.subsamples));
 455 }
 456
 457 }  // namespace mp4
 458 }  // namespace media