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