src/media/formats/webm/webm_cluster_parser.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/webm/webm_cluster_parser.h"
   6
   7 #include <vector>
   8
   9 #include "base/logging.h"
  10 #include "base/sys_byteorder.h"
  11 #include "media/base/buffers.h"
  12 #include "media/base/decrypt_config.h"
  13 #include "media/filters/webvtt_util.h"
  14 #include "media/formats/webm/webm_constants.h"
  15 #include "media/formats/webm/webm_crypto_helpers.h"
  16 #include "media/formats/webm/webm_webvtt_parser.h"
  17
  18 namespace media {
  19
  20 WebMClusterParser::WebMClusterParser(
  21     int64 timecode_scale,
  22     int audio_track_num,
  23     base::TimeDelta audio_default_duration,
  24     int video_track_num,
  25     base::TimeDelta video_default_duration,
  26     const WebMTracksParser::TextTracks& text_tracks,
  27     const std::set<int64>& ignored_tracks,
  28     const std::string& audio_encryption_key_id,
  29     const std::string& video_encryption_key_id,
  30     const LogCB& log_cb)
  31     : timecode_multiplier_(timecode_scale / 1000.0),
  32       ignored_tracks_(ignored_tracks),
  33       audio_encryption_key_id_(audio_encryption_key_id),
  34       video_encryption_key_id_(video_encryption_key_id),
  35       parser_(kWebMIdCluster, this),
  36       last_block_timecode_(-1),
  37       block_data_size_(-1),
  38       block_duration_(-1),
  39       block_add_id_(-1),
  40       block_additional_data_size_(-1),
  41       discard_padding_(-1),
  42       cluster_timecode_(-1),
  43       cluster_start_time_(kNoTimestamp()),
  44       cluster_ended_(false),
  45       audio_(audio_track_num, false, audio_default_duration, log_cb),
  46       video_(video_track_num, true, video_default_duration, log_cb),
  47       ready_buffer_upper_bound_(kNoDecodeTimestamp()),
  48       log_cb_(log_cb) {
  49   for (WebMTracksParser::TextTracks::const_iterator it = text_tracks.begin();
  50        it != text_tracks.end();
  51        ++it) {
  52     text_track_map_.insert(std::make_pair(
  53         it->first, Track(it->first, false, kNoTimestamp(), log_cb_)));
  54   }
  55 }
  56
  57 WebMClusterParser::~WebMClusterParser() {}
  58
  59 void WebMClusterParser::Reset() {
  60   last_block_timecode_ = -1;
  61   cluster_timecode_ = -1;
  62   cluster_start_time_ = kNoTimestamp();
  63   cluster_ended_ = false;
  64   parser_.Reset();
  65   audio_.Reset();
  66   video_.Reset();
  67   ResetTextTracks();
  68   ready_buffer_upper_bound_ = kNoDecodeTimestamp();
  69 }
  70
  71 int WebMClusterParser::Parse(const uint8* buf, int size) {
  72   audio_.ClearReadyBuffers();
  73   video_.ClearReadyBuffers();
  74   ClearTextTrackReadyBuffers();
  75   ready_buffer_upper_bound_ = kNoDecodeTimestamp();
  76
  77   int result = parser_.Parse(buf, size);
  78
  79   if (result < 0) {
  80     cluster_ended_ = false;
  81     return result;
  82   }
  83
  84   cluster_ended_ = parser_.IsParsingComplete();
  85   if (cluster_ended_) {
  86     // If there were no buffers in this cluster, set the cluster start time to
  87     // be the |cluster_timecode_|.
  88     if (cluster_start_time_ == kNoTimestamp()) {
  89       // If the cluster did not even have a |cluster_timecode_|, signal parse
  90       // error.
  91       if (cluster_timecode_ < 0)
  92         return -1;
  93
  94       cluster_start_time_ = base::TimeDelta::FromMicroseconds(
  95           cluster_timecode_ * timecode_multiplier_);
  96     }
  97
  98     // Reset the parser if we're done parsing so that
  99     // it is ready to accept another cluster on the next
 100     // call.
 101     parser_.Reset();
 102
 103     last_block_timecode_ = -1;
 104     cluster_timecode_ = -1;
 105   }
 106
 107   return result;
 108 }
 109
 110 const WebMClusterParser::BufferQueue& WebMClusterParser::GetAudioBuffers() {
 111   if (ready_buffer_upper_bound_ == kNoDecodeTimestamp())
 112     UpdateReadyBuffers();
 113
 114   return audio_.ready_buffers();
 115 }
 116
 117 const WebMClusterParser::BufferQueue& WebMClusterParser::GetVideoBuffers() {
 118   if (ready_buffer_upper_bound_ == kNoDecodeTimestamp())
 119     UpdateReadyBuffers();
 120
 121   return video_.ready_buffers();
 122 }
 123
 124 const WebMClusterParser::TextBufferQueueMap&
 125 WebMClusterParser::GetTextBuffers() {
 126   if (ready_buffer_upper_bound_ == kNoDecodeTimestamp())
 127     UpdateReadyBuffers();
 128
 129   // Translate our |text_track_map_| into |text_buffers_map_|, inserting rows in
 130   // the output only for non-empty ready_buffer() queues in |text_track_map_|.
 131   text_buffers_map_.clear();
 132   for (TextTrackMap::const_iterator itr = text_track_map_.begin();
 133        itr != text_track_map_.end();
 134        ++itr) {
 135     const BufferQueue& text_buffers = itr->second.ready_buffers();
 136     if (!text_buffers.empty())
 137       text_buffers_map_.insert(std::make_pair(itr->first, text_buffers));
 138   }
 139
 140   return text_buffers_map_;
 141 }
 142
 143 WebMParserClient* WebMClusterParser::OnListStart(int id) {
 144   if (id == kWebMIdCluster) {
 145     cluster_timecode_ = -1;
 146     cluster_start_time_ = kNoTimestamp();
 147   } else if (id == kWebMIdBlockGroup) {
 148     block_data_.reset();
 149     block_data_size_ = -1;
 150     block_duration_ = -1;
 151     discard_padding_ = -1;
 152     discard_padding_set_ = false;
 153   } else if (id == kWebMIdBlockAdditions) {
 154     block_add_id_ = -1;
 155     block_additional_data_.reset();
 156     block_additional_data_size_ = -1;
 157   }
 158
 159   return this;
 160 }
 161
 162 bool WebMClusterParser::OnListEnd(int id) {
 163   if (id != kWebMIdBlockGroup)
 164     return true;
 165
 166   // Make sure the BlockGroup actually had a Block.
 167   if (block_data_size_ == -1) {
 168     MEDIA_LOG(log_cb_) << "Block missing from BlockGroup.";
 169     return false;
 170   }
 171
 172   bool result = ParseBlock(false, block_data_.get(), block_data_size_,
 173                            block_additional_data_.get(),
 174                            block_additional_data_size_, block_duration_,
 175                            discard_padding_set_ ? discard_padding_ : 0);
 176   block_data_.reset();
 177   block_data_size_ = -1;
 178   block_duration_ = -1;
 179   block_add_id_ = -1;
 180   block_additional_data_.reset();
 181   block_additional_data_size_ = -1;
 182   discard_padding_ = -1;
 183   discard_padding_set_ = false;
 184   return result;
 185 }
 186
 187 bool WebMClusterParser::OnUInt(int id, int64 val) {
 188   int64* dst;
 189   switch (id) {
 190     case kWebMIdTimecode:
 191       dst = &cluster_timecode_;
 192       break;
 193     case kWebMIdBlockDuration:
 194       dst = &block_duration_;
 195       break;
 196     case kWebMIdBlockAddID:
 197       dst = &block_add_id_;
 198       break;
 199     default:
 200       return true;
 201   }
 202   if (*dst != -1)
 203     return false;
 204   *dst = val;
 205   return true;
 206 }
 207
 208 bool WebMClusterParser::ParseBlock(bool is_simple_block, const uint8* buf,
 209                                    int size, const uint8* additional,
 210                                    int additional_size, int duration,
 211                                    int64 discard_padding) {
 212   if (size < 4)
 213     return false;
 214
 215   // Return an error if the trackNum > 127. We just aren't
 216   // going to support large track numbers right now.
 217   if (!(buf[0] & 0x80)) {
 218     MEDIA_LOG(log_cb_) << "TrackNumber over 127 not supported";
 219     return false;
 220   }
 221
 222   int track_num = buf[0] & 0x7f;
 223   int timecode = buf[1] << 8 | buf[2];
 224   int flags = buf[3] & 0xff;
 225   int lacing = (flags >> 1) & 0x3;
 226
 227   if (lacing) {
 228     MEDIA_LOG(log_cb_) << "Lacing " << lacing << " is not supported yet.";
 229     return false;
 230   }
 231
 232   // Sign extend negative timecode offsets.
 233   if (timecode & 0x8000)
 234     timecode |= ~0xffff;
 235
 236   const uint8* frame_data = buf + 4;
 237   int frame_size = size - (frame_data - buf);
 238   return OnBlock(is_simple_block, track_num, timecode, duration, flags,
 239                  frame_data, frame_size, additional, additional_size,
 240                  discard_padding);
 241 }
 242
 243 bool WebMClusterParser::OnBinary(int id, const uint8* data, int size) {
 244   switch (id) {
 245     case kWebMIdSimpleBlock:
 246       return ParseBlock(true, data, size, NULL, -1, -1, 0);
 247
 248     case kWebMIdBlock:
 249       if (block_data_) {
 250         MEDIA_LOG(log_cb_) << "More than 1 Block in a BlockGroup is not "
 251                               "supported.";
 252         return false;
 253       }
 254       block_data_.reset(new uint8[size]);
 255       memcpy(block_data_.get(), data, size);
 256       block_data_size_ = size;
 257       return true;
 258
 259     case kWebMIdBlockAdditional: {
 260       uint64 block_add_id = base::HostToNet64(block_add_id_);
 261       if (block_additional_data_) {
 262         // TODO(vigneshv): Technically, more than 1 BlockAdditional is allowed
 263         // as per matroska spec. But for now we don't have a use case to
 264         // support parsing of such files. Take a look at this again when such a
 265         // case arises.
 266         MEDIA_LOG(log_cb_) << "More than 1 BlockAdditional in a BlockGroup is "
 267                               "not supported.";
 268         return false;
 269       }
 270       // First 8 bytes of side_data in DecoderBuffer is the BlockAddID
 271       // element's value in Big Endian format. This is done to mimic ffmpeg
 272       // demuxer's behavior.
 273       block_additional_data_size_ = size + sizeof(block_add_id);
 274       block_additional_data_.reset(new uint8[block_additional_data_size_]);
 275       memcpy(block_additional_data_.get(), &block_add_id,
 276              sizeof(block_add_id));
 277       memcpy(block_additional_data_.get() + 8, data, size);
 278       return true;
 279     }
 280     case kWebMIdDiscardPadding: {
 281       if (discard_padding_set_ || size <= 0 || size > 8)
 282         return false;
 283       discard_padding_set_ = true;
 284
 285       // Read in the big-endian integer.
 286       discard_padding_ = static_cast<int8>(data[0]);
 287       for (int i = 1; i < size; ++i)
 288         discard_padding_ = (discard_padding_ << 8) | data[i];
 289
 290       return true;
 291     }
 292     default:
 293       return true;
 294   }
 295 }
 296
 297 bool WebMClusterParser::OnBlock(bool is_simple_block, int track_num,
 298                                 int timecode,
 299                                 int  block_duration,
 300                                 int flags,
 301                                 const uint8* data, int size,
 302                                 const uint8* additional, int additional_size,
 303                                 int64 discard_padding) {
 304   DCHECK_GE(size, 0);
 305   if (cluster_timecode_ == -1) {
 306     MEDIA_LOG(log_cb_) << "Got a block before cluster timecode.";
 307     return false;
 308   }
 309
 310   // TODO(acolwell): Should relative negative timecode offsets be rejected?  Or
 311   // only when the absolute timecode is negative?  See http://crbug.com/271794
 312   if (timecode < 0) {
 313     MEDIA_LOG(log_cb_) << "Got a block with negative timecode offset "
 314                        << timecode;
 315     return false;
 316   }
 317
 318   if (last_block_timecode_ != -1 && timecode < last_block_timecode_) {
 319     MEDIA_LOG(log_cb_)
 320         << "Got a block with a timecode before the previous block.";
 321     return false;
 322   }
 323
 324   Track* track = NULL;
 325   StreamParserBuffer::Type buffer_type = DemuxerStream::AUDIO;
 326   std::string encryption_key_id;
 327   if (track_num == audio_.track_num()) {
 328     track = &audio_;
 329     encryption_key_id = audio_encryption_key_id_;
 330   } else if (track_num == video_.track_num()) {
 331     track = &video_;
 332     encryption_key_id = video_encryption_key_id_;
 333     buffer_type = DemuxerStream::VIDEO;
 334   } else if (ignored_tracks_.find(track_num) != ignored_tracks_.end()) {
 335     return true;
 336   } else if (Track* const text_track = FindTextTrack(track_num)) {
 337     if (is_simple_block)  // BlockGroup is required for WebVTT cues
 338       return false;
 339     if (block_duration < 0)  // not specified
 340       return false;
 341     track = text_track;
 342     buffer_type = DemuxerStream::TEXT;
 343   } else {
 344     MEDIA_LOG(log_cb_) << "Unexpected track number " << track_num;
 345     return false;
 346   }
 347
 348   last_block_timecode_ = timecode;
 349
 350   base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
 351       (cluster_timecode_ + timecode) * timecode_multiplier_);
 352
 353   scoped_refptr<StreamParserBuffer> buffer;
 354   if (buffer_type != DemuxerStream::TEXT) {
 355     // The first bit of the flags is set when a SimpleBlock contains only
 356     // keyframes. If this is a Block, then inspection of the payload is
 357     // necessary to determine whether it contains a keyframe or not.
 358     // http://www.matroska.org/technical/specs/index.html
 359     bool is_keyframe =
 360         is_simple_block ? (flags & 0x80) != 0 : track->IsKeyframe(data, size);
 361
 362     // Every encrypted Block has a signal byte and IV prepended to it. Current
 363     // encrypted WebM request for comments specification is here
 364     // http://wiki.webmproject.org/encryption/webm-encryption-rfc
 365     scoped_ptr<DecryptConfig> decrypt_config;
 366     int data_offset = 0;
 367     if (!encryption_key_id.empty() &&
 368         !WebMCreateDecryptConfig(
 369              data, size,
 370              reinterpret_cast<const uint8*>(encryption_key_id.data()),
 371              encryption_key_id.size(),
 372              &decrypt_config, &data_offset)) {
 373       return false;
 374     }
 375
 376     // TODO(wolenetz/acolwell): Validate and use a common cross-parser TrackId
 377     // type with remapped bytestream track numbers and allow multiple tracks as
 378     // applicable. See https://crbug.com/341581.
 379     buffer = StreamParserBuffer::CopyFrom(
 380         data + data_offset, size - data_offset,
 381         additional, additional_size,
 382         is_keyframe, buffer_type, track_num);
 383
 384     if (decrypt_config)
 385       buffer->set_decrypt_config(decrypt_config.Pass());
 386   } else {
 387     std::string id, settings, content;
 388     WebMWebVTTParser::Parse(data, size, &id, &settings, &content);
 389
 390     std::vector<uint8> side_data;
 391     MakeSideData(id.begin(), id.end(),
 392                  settings.begin(), settings.end(),
 393                  &side_data);
 394
 395     // TODO(wolenetz/acolwell): Validate and use a common cross-parser TrackId
 396     // type with remapped bytestream track numbers and allow multiple tracks as
 397     // applicable. See https://crbug.com/341581.
 398     buffer = StreamParserBuffer::CopyFrom(
 399         reinterpret_cast<const uint8*>(content.data()),
 400         content.length(),
 401         &side_data[0],
 402         side_data.size(),
 403         true, buffer_type, track_num);
 404   }
 405
 406   buffer->set_timestamp(timestamp);
 407   if (cluster_start_time_ == kNoTimestamp())
 408     cluster_start_time_ = timestamp;
 409
 410   if (block_duration >= 0) {
 411     buffer->set_duration(base::TimeDelta::FromMicroseconds(
 412         block_duration * timecode_multiplier_));
 413   } else {
 414     DCHECK_NE(buffer_type, DemuxerStream::TEXT);
 415     buffer->set_duration(track->default_duration());
 416   }
 417
 418   if (discard_padding != 0) {
 419     buffer->set_discard_padding(std::make_pair(
 420         base::TimeDelta(),
 421         base::TimeDelta::FromMicroseconds(discard_padding / 1000)));
 422   }
 423
 424   return track->AddBuffer(buffer);
 425 }
 426
 427 WebMClusterParser::Track::Track(int track_num,
 428                                 bool is_video,
 429                                 base::TimeDelta default_duration,
 430                                 const LogCB& log_cb)
 431     : track_num_(track_num),
 432       is_video_(is_video),
 433       default_duration_(default_duration),
 434       estimated_next_frame_duration_(kNoTimestamp()),
 435       log_cb_(log_cb) {
 436   DCHECK(default_duration_ == kNoTimestamp() ||
 437          default_duration_ > base::TimeDelta());
 438 }
 439
 440 WebMClusterParser::Track::~Track() {}
 441
 442 DecodeTimestamp WebMClusterParser::Track::GetReadyUpperBound() {
 443   DCHECK(ready_buffers_.empty());
 444   if (last_added_buffer_missing_duration_)
 445     return last_added_buffer_missing_duration_->GetDecodeTimestamp();
 446
 447   return DecodeTimestamp::FromPresentationTime(base::TimeDelta::Max());
 448 }
 449
 450 void WebMClusterParser::Track::ExtractReadyBuffers(
 451     const DecodeTimestamp before_timestamp) {
 452   DCHECK(ready_buffers_.empty());
 453   DCHECK(DecodeTimestamp() <= before_timestamp);
 454   DCHECK(kNoDecodeTimestamp() != before_timestamp);
 455
 456   if (buffers_.empty())
 457     return;
 458
 459   if (buffers_.back()->GetDecodeTimestamp() < before_timestamp) {
 460     // All of |buffers_| are ready.
 461     ready_buffers_.swap(buffers_);
 462     DVLOG(3) << __FUNCTION__ << " : " << track_num_ << " All "
 463              << ready_buffers_.size() << " are ready: before upper bound ts "
 464              << before_timestamp.InSecondsF();
 465     return;
 466   }
 467
 468   // Not all of |buffers_| are ready yet. Move any that are ready to
 469   // |ready_buffers_|.
 470   while (true) {
 471     const scoped_refptr<StreamParserBuffer>& buffer = buffers_.front();
 472     if (buffer->GetDecodeTimestamp() >= before_timestamp)
 473       break;
 474     ready_buffers_.push_back(buffer);
 475     buffers_.pop_front();
 476     DCHECK(!buffers_.empty());
 477   }
 478
 479   DVLOG(3) << __FUNCTION__ << " : " << track_num_ << " Only "
 480            << ready_buffers_.size() << " ready, " << buffers_.size()
 481            << " at or after upper bound ts " << before_timestamp.InSecondsF();
 482 }
 483
 484 bool WebMClusterParser::Track::AddBuffer(
 485     const scoped_refptr<StreamParserBuffer>& buffer) {
 486   DVLOG(2) << "AddBuffer() : " << track_num_
 487            << " ts " << buffer->timestamp().InSecondsF()
 488            << " dur " << buffer->duration().InSecondsF()
 489            << " kf " << buffer->IsKeyframe()
 490            << " size " << buffer->data_size();
 491
 492   if (last_added_buffer_missing_duration_) {
 493     base::TimeDelta derived_duration =
 494         buffer->timestamp() - last_added_buffer_missing_duration_->timestamp();
 495     last_added_buffer_missing_duration_->set_duration(derived_duration);
 496
 497     DVLOG(2) << "AddBuffer() : applied derived duration to held-back buffer : "
 498              << " ts "
 499              << last_added_buffer_missing_duration_->timestamp().InSecondsF()
 500              << " dur "
 501              << last_added_buffer_missing_duration_->duration().InSecondsF()
 502              << " kf " << last_added_buffer_missing_duration_->IsKeyframe()
 503              << " size " << last_added_buffer_missing_duration_->data_size();
 504     scoped_refptr<StreamParserBuffer> updated_buffer =
 505         last_added_buffer_missing_duration_;
 506     last_added_buffer_missing_duration_ = NULL;
 507     if (!QueueBuffer(updated_buffer))
 508       return false;
 509   }
 510
 511   if (buffer->duration() == kNoTimestamp()) {
 512     last_added_buffer_missing_duration_ = buffer;
 513     DVLOG(2) << "AddBuffer() : holding back buffer that is missing duration";
 514     return true;
 515   }
 516
 517   return QueueBuffer(buffer);
 518 }
 519
 520 void WebMClusterParser::Track::ApplyDurationEstimateIfNeeded() {
 521   if (!last_added_buffer_missing_duration_)
 522     return;
 523
 524   last_added_buffer_missing_duration_->set_duration(GetDurationEstimate());
 525
 526   DVLOG(2) << "ApplyDurationEstimateIfNeeded() : new dur : "
 527            << " ts "
 528            << last_added_buffer_missing_duration_->timestamp().InSecondsF()
 529            << " dur "
 530            << last_added_buffer_missing_duration_->duration().InSecondsF()
 531            << " kf " << last_added_buffer_missing_duration_->IsKeyframe()
 532            << " size " << last_added_buffer_missing_duration_->data_size();
 533
 534   // Don't use the applied duration as a future estimation (don't use
 535   // QueueBuffer() here.)
 536   buffers_.push_back(last_added_buffer_missing_duration_);
 537   last_added_buffer_missing_duration_ = NULL;
 538 }
 539
 540 void WebMClusterParser::Track::ClearReadyBuffers() {
 541   // Note that |buffers_| are kept and |estimated_next_frame_duration_| is not
 542   // reset here.
 543   ready_buffers_.clear();
 544 }
 545
 546 void WebMClusterParser::Track::Reset() {
 547   ClearReadyBuffers();
 548   buffers_.clear();
 549   last_added_buffer_missing_duration_ = NULL;
 550 }
 551
 552 bool WebMClusterParser::Track::IsKeyframe(const uint8* data, int size) const {
 553   // For now, assume that all blocks are keyframes for datatypes other than
 554   // video. This is a valid assumption for Vorbis, WebVTT, & Opus.
 555   if (!is_video_)
 556     return true;
 557
 558   // Make sure the block is big enough for the minimal keyframe header size.
 559   if (size < 7)
 560     return false;
 561
 562   // The LSb of the first byte must be a 0 for a keyframe.
 563   // http://tools.ietf.org/html/rfc6386 Section 19.1
 564   if ((data[0] & 0x01) != 0)
 565     return false;
 566
 567   // Verify VP8 keyframe startcode.
 568   // http://tools.ietf.org/html/rfc6386 Section 19.1
 569   if (data[3] != 0x9d || data[4] != 0x01 || data[5] != 0x2a)
 570     return false;
 571
 572   return true;
 573 }
 574
 575 bool WebMClusterParser::Track::QueueBuffer(
 576     const scoped_refptr<StreamParserBuffer>& buffer) {
 577   DCHECK(!last_added_buffer_missing_duration_);
 578
 579   // WebMClusterParser::OnBlock() gives MEDIA_LOG and parse error on decreasing
 580   // block timecode detection within a cluster. Therefore, we should not see
 581   // those here.
 582   DecodeTimestamp previous_buffers_timestamp = buffers_.empty() ?
 583       DecodeTimestamp() : buffers_.back()->GetDecodeTimestamp();
 584   CHECK(previous_buffers_timestamp <= buffer->GetDecodeTimestamp());
 585
 586   base::TimeDelta duration = buffer->duration();
 587   if (duration < base::TimeDelta() || duration == kNoTimestamp()) {
 588     MEDIA_LOG(log_cb_) << "Invalid buffer duration: " << duration.InSecondsF();
 589     return false;
 590   }
 591
 592   // The estimated frame duration is the minimum non-zero duration since the
 593   // last initialization segment.  The minimum is used to ensure frame durations
 594   // aren't overestimated.
 595   if (duration > base::TimeDelta()) {
 596     if (estimated_next_frame_duration_ == kNoTimestamp()) {
 597       estimated_next_frame_duration_ = duration;
 598     } else {
 599       estimated_next_frame_duration_ =
 600           std::min(duration, estimated_next_frame_duration_);
 601     }
 602   }
 603
 604   buffers_.push_back(buffer);
 605   return true;
 606 }
 607
 608 base::TimeDelta WebMClusterParser::Track::GetDurationEstimate() {
 609   base::TimeDelta duration = estimated_next_frame_duration_;
 610   if (duration != kNoTimestamp()) {
 611     DVLOG(3) << __FUNCTION__ << " : using estimated duration";
 612   } else {
 613     DVLOG(3) << __FUNCTION__ << " : using hardcoded default duration";
 614     if (is_video_) {
 615       duration = base::TimeDelta::FromMilliseconds(
 616           kDefaultVideoBufferDurationInMs);
 617     } else {
 618       duration = base::TimeDelta::FromMilliseconds(
 619           kDefaultAudioBufferDurationInMs);
 620     }
 621   }
 622
 623   DCHECK(duration > base::TimeDelta());
 624   DCHECK(duration != kNoTimestamp());
 625   return duration;
 626 }
 627
 628 void WebMClusterParser::ClearTextTrackReadyBuffers() {
 629   text_buffers_map_.clear();
 630   for (TextTrackMap::iterator it = text_track_map_.begin();
 631        it != text_track_map_.end();
 632        ++it) {
 633     it->second.ClearReadyBuffers();
 634   }
 635 }
 636
 637 void WebMClusterParser::ResetTextTracks() {
 638   ClearTextTrackReadyBuffers();
 639   for (TextTrackMap::iterator it = text_track_map_.begin();
 640        it != text_track_map_.end();
 641        ++it) {
 642     it->second.Reset();
 643   }
 644 }
 645
 646 void WebMClusterParser::UpdateReadyBuffers() {
 647   DCHECK(ready_buffer_upper_bound_ == kNoDecodeTimestamp());
 648   DCHECK(text_buffers_map_.empty());
 649
 650   if (cluster_ended_) {
 651     audio_.ApplyDurationEstimateIfNeeded();
 652     video_.ApplyDurationEstimateIfNeeded();
 653     // Per OnBlock(), all text buffers should already have valid durations, so
 654     // there is no need to call ApplyDurationEstimateIfNeeded() on text tracks
 655     // here.
 656     ready_buffer_upper_bound_ =
 657         DecodeTimestamp::FromPresentationTime(base::TimeDelta::Max());
 658     DCHECK(ready_buffer_upper_bound_ == audio_.GetReadyUpperBound());
 659     DCHECK(ready_buffer_upper_bound_ == video_.GetReadyUpperBound());
 660   } else {
 661     ready_buffer_upper_bound_ = std::min(audio_.GetReadyUpperBound(),
 662                                          video_.GetReadyUpperBound());
 663     DCHECK(DecodeTimestamp() <= ready_buffer_upper_bound_);
 664     DCHECK(kNoDecodeTimestamp() != ready_buffer_upper_bound_);
 665   }
 666
 667   // Prepare each track's ready buffers for retrieval.
 668   audio_.ExtractReadyBuffers(ready_buffer_upper_bound_);
 669   video_.ExtractReadyBuffers(ready_buffer_upper_bound_);
 670   for (TextTrackMap::iterator itr = text_track_map_.begin();
 671        itr != text_track_map_.end();
 672        ++itr) {
 673     itr->second.ExtractReadyBuffers(ready_buffer_upper_bound_);
 674   }
 675 }
 676
 677 WebMClusterParser::Track*
 678 WebMClusterParser::FindTextTrack(int track_num) {
 679   const TextTrackMap::iterator it = text_track_map_.find(track_num);
 680
 681   if (it == text_track_map_.end())
 682     return NULL;
 683
 684   return &it->second;
 685 }
 686
 687 }  // namespace media