src/media/formats/mp2t/mp2t_stream_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/mp2t/mp2t_stream_parser.h"
   6
   7 #include "base/bind.h"
   8 #include "base/callback_helpers.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/stl_util.h"
  11 #include "media/base/audio_decoder_config.h"
  12 #include "media/base/buffers.h"
  13 #include "media/base/stream_parser_buffer.h"
  14 #include "media/base/text_track_config.h"
  15 #include "media/base/video_decoder_config.h"
  16 #include "media/formats/mp2t/es_parser.h"
  17 #include "media/formats/mp2t/es_parser_adts.h"
  18 #include "media/formats/mp2t/es_parser_h264.h"
  19 #include "media/formats/mp2t/es_parser_mpeg1audio.h"
  20 #include "media/formats/mp2t/mp2t_common.h"
  21 #include "media/formats/mp2t/ts_packet.h"
  22 #include "media/formats/mp2t/ts_section.h"
  23 #include "media/formats/mp2t/ts_section_pat.h"
  24 #include "media/formats/mp2t/ts_section_pes.h"
  25 #include "media/formats/mp2t/ts_section_pmt.h"
  26
  27 namespace media {
  28 namespace mp2t {
  29
  30 enum StreamType {
  31   // ISO-13818.1 / ITU H.222 Table 2.34 "Stream type assignments"
  32   kStreamTypeMpeg1Audio = 0x3,
  33   kStreamTypeAAC = 0xf,
  34   kStreamTypeAVC = 0x1b,
  35 };
  36
  37 class PidState {
  38  public:
  39   enum PidType {
  40     kPidPat,
  41     kPidPmt,
  42     kPidAudioPes,
  43     kPidVideoPes,
  44   };
  45
  46   PidState(int pid, PidType pid_tyoe,
  47            scoped_ptr<TsSection> section_parser);
  48
  49   // Extract the content of the TS packet and parse it.
  50   // Return true if successful.
  51   bool PushTsPacket(const TsPacket& ts_packet);
  52
  53   // Flush the PID state (possibly emitting some pending frames)
  54   // and reset its state.
  55   void Flush();
  56
  57   // Enable/disable the PID.
  58   // Disabling a PID will reset its state and ignore any further incoming TS
  59   // packets.
  60   void Enable();
  61   void Disable();
  62   bool IsEnabled() const;
  63
  64   PidType pid_type() const { return pid_type_; }
  65
  66  private:
  67   void ResetState();
  68
  69   int pid_;
  70   PidType pid_type_;
  71   scoped_ptr<TsSection> section_parser_;
  72
  73   bool enable_;
  74
  75   int continuity_counter_;
  76 };
  77
  78 PidState::PidState(int pid, PidType pid_type,
  79                    scoped_ptr<TsSection> section_parser)
  80   : pid_(pid),
  81     pid_type_(pid_type),
  82     section_parser_(section_parser.Pass()),
  83     enable_(false),
  84     continuity_counter_(-1) {
  85   DCHECK(section_parser_);
  86 }
  87
  88 bool PidState::PushTsPacket(const TsPacket& ts_packet) {
  89   DCHECK_EQ(ts_packet.pid(), pid_);
  90
  91   // The current PID is not part of the PID filter,
  92   // just discard the incoming TS packet.
  93   if (!enable_)
  94     return true;
  95
  96   int expected_continuity_counter = (continuity_counter_ + 1) % 16;
  97   if (continuity_counter_ >= 0 &&
  98       ts_packet.continuity_counter() != expected_continuity_counter) {
  99     DVLOG(1) << "TS discontinuity detected for pid: " << pid_;
 100     return false;
 101   }
 102
 103   bool status = section_parser_->Parse(
 104       ts_packet.payload_unit_start_indicator(),
 105       ts_packet.payload(),
 106       ts_packet.payload_size());
 107
 108   // At the minimum, when parsing failed, auto reset the section parser.
 109   // Components that use the StreamParser can take further action if needed.
 110   if (!status) {
 111     DVLOG(1) << "Parsing failed for pid = " << pid_;
 112     ResetState();
 113   }
 114
 115   return status;
 116 }
 117
 118 void PidState::Flush() {
 119   section_parser_->Flush();
 120   ResetState();
 121 }
 122
 123 void PidState::Enable() {
 124   enable_ = true;
 125 }
 126
 127 void PidState::Disable() {
 128   if (!enable_)
 129     return;
 130
 131   ResetState();
 132   enable_ = false;
 133 }
 134
 135 bool PidState::IsEnabled() const {
 136   return enable_;
 137 }
 138
 139 void PidState::ResetState() {
 140   section_parser_->Reset();
 141   continuity_counter_ = -1;
 142 }
 143
 144 Mp2tStreamParser::BufferQueueWithConfig::BufferQueueWithConfig(
 145     bool is_cfg_sent,
 146     const AudioDecoderConfig& audio_cfg,
 147     const VideoDecoderConfig& video_cfg)
 148   : is_config_sent(is_cfg_sent),
 149     audio_config(audio_cfg),
 150     video_config(video_cfg) {
 151 }
 152
 153 Mp2tStreamParser::BufferQueueWithConfig::~BufferQueueWithConfig() {
 154 }
 155
 156 Mp2tStreamParser::Mp2tStreamParser(bool sbr_in_mimetype)
 157   : sbr_in_mimetype_(sbr_in_mimetype),
 158     selected_audio_pid_(-1),
 159     selected_video_pid_(-1),
 160     is_initialized_(false),
 161     segment_started_(false) {
 162 }
 163
 164 Mp2tStreamParser::~Mp2tStreamParser() {
 165   STLDeleteValues(&pids_);
 166 }
 167
 168 void Mp2tStreamParser::Init(
 169     const InitCB& init_cb,
 170     const NewConfigCB& config_cb,
 171     const NewBuffersCB& new_buffers_cb,
 172     bool /* ignore_text_tracks */ ,
 173     const NeedKeyCB& need_key_cb,
 174     const NewMediaSegmentCB& new_segment_cb,
 175     const base::Closure& end_of_segment_cb,
 176     const LogCB& log_cb) {
 177   DCHECK(!is_initialized_);
 178   DCHECK(init_cb_.is_null());
 179   DCHECK(!init_cb.is_null());
 180   DCHECK(!config_cb.is_null());
 181   DCHECK(!new_buffers_cb.is_null());
 182   DCHECK(!need_key_cb.is_null());
 183   DCHECK(!end_of_segment_cb.is_null());
 184
 185   init_cb_ = init_cb;
 186   config_cb_ = config_cb;
 187   new_buffers_cb_ = new_buffers_cb;
 188   need_key_cb_ = need_key_cb;
 189   new_segment_cb_ = new_segment_cb;
 190   end_of_segment_cb_ = end_of_segment_cb;
 191   log_cb_ = log_cb;
 192 }
 193
 194 void Mp2tStreamParser::Flush() {
 195   DVLOG(1) << "Mp2tStreamParser::Flush";
 196
 197   // Flush the buffers and reset the pids.
 198   for (std::map<int, PidState*>::iterator it = pids_.begin();
 199        it != pids_.end(); ++it) {
 200     DVLOG(1) << "Flushing PID: " << it->first;
 201     PidState* pid_state = it->second;
 202     pid_state->Flush();
 203     delete pid_state;
 204   }
 205   pids_.clear();
 206   EmitRemainingBuffers();
 207   buffer_queue_chain_.clear();
 208
 209   // End of the segment.
 210   // Note: does not need to invoke |end_of_segment_cb_| since flushing the
 211   // stream parser already involves the end of the current segment.
 212   segment_started_ = false;
 213
 214   // Remove any bytes left in the TS buffer.
 215   // (i.e. any partial TS packet => less than 188 bytes).
 216   ts_byte_queue_.Reset();
 217
 218   // Reset the selected PIDs.
 219   selected_audio_pid_ = -1;
 220   selected_video_pid_ = -1;
 221
 222   // Reset the timestamp unroller.
 223   timestamp_unroller_.Reset();
 224 }
 225
 226 bool Mp2tStreamParser::Parse(const uint8* buf, int size) {
 227   DVLOG(1) << "Mp2tStreamParser::Parse size=" << size;
 228
 229   // Add the data to the parser state.
 230   ts_byte_queue_.Push(buf, size);
 231
 232   while (true) {
 233     const uint8* ts_buffer;
 234     int ts_buffer_size;
 235     ts_byte_queue_.Peek(&ts_buffer, &ts_buffer_size);
 236     if (ts_buffer_size < TsPacket::kPacketSize)
 237       break;
 238
 239     // Synchronization.
 240     int skipped_bytes = TsPacket::Sync(ts_buffer, ts_buffer_size);
 241     if (skipped_bytes > 0) {
 242       DVLOG(1) << "Packet not aligned on a TS syncword:"
 243                << " skipped_bytes=" << skipped_bytes;
 244       ts_byte_queue_.Pop(skipped_bytes);
 245       continue;
 246     }
 247
 248     // Parse the TS header, skipping 1 byte if the header is invalid.
 249     scoped_ptr<TsPacket> ts_packet(TsPacket::Parse(ts_buffer, ts_buffer_size));
 250     if (!ts_packet) {
 251       DVLOG(1) << "Error: invalid TS packet";
 252       ts_byte_queue_.Pop(1);
 253       continue;
 254     }
 255     DVLOG(LOG_LEVEL_TS)
 256         << "Processing PID=" << ts_packet->pid()
 257         << " start_unit=" << ts_packet->payload_unit_start_indicator();
 258
 259     // Parse the section.
 260     std::map<int, PidState*>::iterator it = pids_.find(ts_packet->pid());
 261     if (it == pids_.end() &&
 262         ts_packet->pid() == TsSection::kPidPat) {
 263       // Create the PAT state here if needed.
 264       scoped_ptr<TsSection> pat_section_parser(
 265           new TsSectionPat(
 266               base::Bind(&Mp2tStreamParser::RegisterPmt,
 267                          base::Unretained(this))));
 268       scoped_ptr<PidState> pat_pid_state(
 269           new PidState(ts_packet->pid(), PidState::kPidPat,
 270                        pat_section_parser.Pass()));
 271       pat_pid_state->Enable();
 272       it = pids_.insert(
 273           std::pair<int, PidState*>(ts_packet->pid(),
 274                                     pat_pid_state.release())).first;
 275     }
 276
 277     if (it != pids_.end()) {
 278       if (!it->second->PushTsPacket(*ts_packet))
 279         return false;
 280     } else {
 281       DVLOG(LOG_LEVEL_TS) << "Ignoring TS packet for pid: " << ts_packet->pid();
 282     }
 283
 284     // Go to the next packet.
 285     ts_byte_queue_.Pop(TsPacket::kPacketSize);
 286   }
 287
 288   RCHECK(FinishInitializationIfNeeded());
 289
 290   // Emit the A/V buffers that kept accumulating during TS parsing.
 291   return EmitRemainingBuffers();
 292 }
 293
 294 void Mp2tStreamParser::RegisterPmt(int program_number, int pmt_pid) {
 295   DVLOG(1) << "RegisterPmt:"
 296            << " program_number=" << program_number
 297            << " pmt_pid=" << pmt_pid;
 298
 299   // Only one TS program is allowed. Ignore the incoming program map table,
 300   // if there is already one registered.
 301   for (std::map<int, PidState*>::iterator it = pids_.begin();
 302        it != pids_.end(); ++it) {
 303     PidState* pid_state = it->second;
 304     if (pid_state->pid_type() == PidState::kPidPmt) {
 305       DVLOG_IF(1, pmt_pid != it->first) << "More than one program is defined";
 306       return;
 307     }
 308   }
 309
 310   // Create the PMT state here if needed.
 311   DVLOG(1) << "Create a new PMT parser";
 312   scoped_ptr<TsSection> pmt_section_parser(
 313       new TsSectionPmt(
 314           base::Bind(&Mp2tStreamParser::RegisterPes,
 315                      base::Unretained(this), pmt_pid)));
 316   scoped_ptr<PidState> pmt_pid_state(
 317       new PidState(pmt_pid, PidState::kPidPmt, pmt_section_parser.Pass()));
 318   pmt_pid_state->Enable();
 319   pids_.insert(std::pair<int, PidState*>(pmt_pid, pmt_pid_state.release()));
 320 }
 321
 322 void Mp2tStreamParser::RegisterPes(int pmt_pid,
 323                                    int pes_pid,
 324                                    int stream_type) {
 325   // TODO(damienv): check there is no mismatch if the entry already exists.
 326   DVLOG(1) << "RegisterPes:"
 327            << " pes_pid=" << pes_pid
 328            << " stream_type=" << std::hex << stream_type << std::dec;
 329   std::map<int, PidState*>::iterator it = pids_.find(pes_pid);
 330   if (it != pids_.end())
 331     return;
 332
 333   // Create a stream parser corresponding to the stream type.
 334   bool is_audio = false;
 335   scoped_ptr<EsParser> es_parser;
 336   if (stream_type == kStreamTypeAVC) {
 337     es_parser.reset(
 338         new EsParserH264(
 339             base::Bind(&Mp2tStreamParser::OnVideoConfigChanged,
 340                        base::Unretained(this),
 341                        pes_pid),
 342             base::Bind(&Mp2tStreamParser::OnEmitVideoBuffer,
 343                        base::Unretained(this),
 344                        pes_pid)));
 345   } else if (stream_type == kStreamTypeAAC) {
 346     es_parser.reset(
 347         new EsParserAdts(
 348             base::Bind(&Mp2tStreamParser::OnAudioConfigChanged,
 349                        base::Unretained(this),
 350                        pes_pid),
 351             base::Bind(&Mp2tStreamParser::OnEmitAudioBuffer,
 352                        base::Unretained(this),
 353                        pes_pid),
 354             sbr_in_mimetype_));
 355     is_audio = true;
 356   } else if (stream_type == kStreamTypeMpeg1Audio) {
 357     es_parser.reset(
 358         new EsParserMpeg1Audio(
 359             base::Bind(&Mp2tStreamParser::OnAudioConfigChanged,
 360                        base::Unretained(this),
 361                        pes_pid),
 362             base::Bind(&Mp2tStreamParser::OnEmitAudioBuffer,
 363                        base::Unretained(this),
 364                        pes_pid),
 365             log_cb_));
 366     is_audio = true;
 367   } else {
 368     return;
 369   }
 370
 371   // Create the PES state here.
 372   DVLOG(1) << "Create a new PES state";
 373   scoped_ptr<TsSection> pes_section_parser(
 374       new TsSectionPes(es_parser.Pass(), &timestamp_unroller_));
 375   PidState::PidType pid_type =
 376       is_audio ? PidState::kPidAudioPes : PidState::kPidVideoPes;
 377   scoped_ptr<PidState> pes_pid_state(
 378       new PidState(pes_pid, pid_type, pes_section_parser.Pass()));
 379   pids_.insert(std::pair<int, PidState*>(pes_pid, pes_pid_state.release()));
 380
 381   // A new PES pid has been added, the PID filter might change.
 382   UpdatePidFilter();
 383 }
 384
 385 void Mp2tStreamParser::UpdatePidFilter() {
 386   // Applies the HLS rule to select the default audio/video PIDs:
 387   // select the audio/video streams with the lowest PID.
 388   // TODO(damienv): this can be changed when the StreamParser interface
 389   // supports multiple audio/video streams.
 390   PidMap::iterator lowest_audio_pid = pids_.end();
 391   PidMap::iterator lowest_video_pid = pids_.end();
 392   for (PidMap::iterator it = pids_.begin(); it != pids_.end(); ++it) {
 393     int pid = it->first;
 394     PidState* pid_state = it->second;
 395     if (pid_state->pid_type() == PidState::kPidAudioPes &&
 396         (lowest_audio_pid == pids_.end() || pid < lowest_audio_pid->first))
 397       lowest_audio_pid = it;
 398     if (pid_state->pid_type() == PidState::kPidVideoPes &&
 399         (lowest_video_pid == pids_.end() || pid < lowest_video_pid->first))
 400       lowest_video_pid = it;
 401   }
 402
 403   // Enable both the lowest audio and video PIDs.
 404   if (lowest_audio_pid != pids_.end()) {
 405     DVLOG(1) << "Enable audio pid: " << lowest_audio_pid->first;
 406     lowest_audio_pid->second->Enable();
 407     selected_audio_pid_ = lowest_audio_pid->first;
 408   }
 409   if (lowest_video_pid != pids_.end()) {
 410     DVLOG(1) << "Enable video pid: " << lowest_video_pid->first;
 411     lowest_video_pid->second->Enable();
 412     selected_video_pid_ = lowest_video_pid->first;
 413   }
 414
 415   // Disable all the other audio and video PIDs.
 416   for (PidMap::iterator it = pids_.begin(); it != pids_.end(); ++it) {
 417     PidState* pid_state = it->second;
 418     if (it != lowest_audio_pid && it != lowest_video_pid &&
 419         (pid_state->pid_type() == PidState::kPidAudioPes ||
 420          pid_state->pid_type() == PidState::kPidVideoPes))
 421       pid_state->Disable();
 422   }
 423 }
 424
 425 void Mp2tStreamParser::OnVideoConfigChanged(
 426     int pes_pid,
 427     const VideoDecoderConfig& video_decoder_config) {
 428   DVLOG(1) << "OnVideoConfigChanged for pid=" << pes_pid;
 429   DCHECK_EQ(pes_pid, selected_video_pid_);
 430   DCHECK(video_decoder_config.IsValidConfig());
 431
 432   if (!buffer_queue_chain_.empty() &&
 433       !buffer_queue_chain_.back().video_config.IsValidConfig()) {
 434     // No video has been received so far, can reuse the existing video queue.
 435     DCHECK(buffer_queue_chain_.back().video_queue.empty());
 436     buffer_queue_chain_.back().video_config = video_decoder_config;
 437   } else {
 438     // Create a new entry in |buffer_queue_chain_| with the updated configs.
 439     BufferQueueWithConfig buffer_queue_with_config(
 440         false,
 441         buffer_queue_chain_.empty()
 442         ? AudioDecoderConfig() : buffer_queue_chain_.back().audio_config,
 443         video_decoder_config);
 444     buffer_queue_chain_.push_back(buffer_queue_with_config);
 445   }
 446
 447   // Replace any non valid config with the 1st valid entry.
 448   // This might happen if there was no available config before.
 449   for (std::list<BufferQueueWithConfig>::iterator it =
 450        buffer_queue_chain_.begin(); it != buffer_queue_chain_.end(); ++it) {
 451     if (it->video_config.IsValidConfig())
 452       break;
 453     it->video_config = video_decoder_config;
 454   }
 455 }
 456
 457 void Mp2tStreamParser::OnAudioConfigChanged(
 458     int pes_pid,
 459     const AudioDecoderConfig& audio_decoder_config) {
 460   DVLOG(1) << "OnAudioConfigChanged for pid=" << pes_pid;
 461   DCHECK_EQ(pes_pid, selected_audio_pid_);
 462   DCHECK(audio_decoder_config.IsValidConfig());
 463
 464   if (!buffer_queue_chain_.empty() &&
 465       !buffer_queue_chain_.back().audio_config.IsValidConfig()) {
 466     // No audio has been received so far, can reuse the existing audio queue.
 467     DCHECK(buffer_queue_chain_.back().audio_queue.empty());
 468     buffer_queue_chain_.back().audio_config = audio_decoder_config;
 469   } else {
 470     // Create a new entry in |buffer_queue_chain_| with the updated configs.
 471     BufferQueueWithConfig buffer_queue_with_config(
 472         false,
 473         audio_decoder_config,
 474         buffer_queue_chain_.empty()
 475         ? VideoDecoderConfig() : buffer_queue_chain_.back().video_config);
 476     buffer_queue_chain_.push_back(buffer_queue_with_config);
 477   }
 478
 479   // Replace any non valid config with the 1st valid entry.
 480   // This might happen if there was no available config before.
 481   for (std::list<BufferQueueWithConfig>::iterator it =
 482        buffer_queue_chain_.begin(); it != buffer_queue_chain_.end(); ++it) {
 483     if (it->audio_config.IsValidConfig())
 484       break;
 485     it->audio_config = audio_decoder_config;
 486   }
 487 }
 488
 489 bool Mp2tStreamParser::FinishInitializationIfNeeded() {
 490   // Nothing to be done if already initialized.
 491   if (is_initialized_)
 492     return true;
 493
 494   // Wait for more data to come to finish initialization.
 495   if (buffer_queue_chain_.empty())
 496     return true;
 497
 498   // Wait for more data to come if one of the config is not available.
 499   BufferQueueWithConfig& queue_with_config = buffer_queue_chain_.front();
 500   if (selected_audio_pid_ > 0 &&
 501       !queue_with_config.audio_config.IsValidConfig())
 502     return true;
 503   if (selected_video_pid_ > 0 &&
 504       !queue_with_config.video_config.IsValidConfig())
 505     return true;
 506
 507   // Pass the config before invoking the initialization callback.
 508   RCHECK(config_cb_.Run(queue_with_config.audio_config,
 509                         queue_with_config.video_config,
 510                         TextTrackConfigMap()));
 511   queue_with_config.is_config_sent = true;
 512
 513   // For Mpeg2 TS, the duration is not known.
 514   DVLOG(1) << "Mpeg2TS stream parser initialization done";
 515   base::ResetAndReturn(&init_cb_)
 516       .Run(true, InitParameters(kInfiniteDuration()));
 517   is_initialized_ = true;
 518
 519   return true;
 520 }
 521
 522 void Mp2tStreamParser::OnEmitAudioBuffer(
 523     int pes_pid,
 524     scoped_refptr<StreamParserBuffer> stream_parser_buffer) {
 525   DCHECK_EQ(pes_pid, selected_audio_pid_);
 526
 527   DVLOG(LOG_LEVEL_ES)
 528       << "OnEmitAudioBuffer: "
 529       << " size="
 530       << stream_parser_buffer->data_size()
 531       << " dts="
 532       << stream_parser_buffer->GetDecodeTimestamp().InMilliseconds()
 533       << " pts="
 534       << stream_parser_buffer->timestamp().InMilliseconds()
 535       << " dur="
 536       << stream_parser_buffer->duration().InMilliseconds();
 537
 538   // Ignore the incoming buffer if it is not associated with any config.
 539   if (buffer_queue_chain_.empty()) {
 540     NOTREACHED() << "Cannot provide buffers before configs";
 541     return;
 542   }
 543
 544   buffer_queue_chain_.back().audio_queue.push_back(stream_parser_buffer);
 545 }
 546
 547 void Mp2tStreamParser::OnEmitVideoBuffer(
 548     int pes_pid,
 549     scoped_refptr<StreamParserBuffer> stream_parser_buffer) {
 550   DCHECK_EQ(pes_pid, selected_video_pid_);
 551
 552   DVLOG(LOG_LEVEL_ES)
 553       << "OnEmitVideoBuffer"
 554       << " size="
 555       << stream_parser_buffer->data_size()
 556       << " dts="
 557       << stream_parser_buffer->GetDecodeTimestamp().InMilliseconds()
 558       << " pts="
 559       << stream_parser_buffer->timestamp().InMilliseconds()
 560       << " dur="
 561       << stream_parser_buffer->duration().InMilliseconds()
 562       << " IsKeyframe="
 563       << stream_parser_buffer->IsKeyframe();
 564
 565   // Ignore the incoming buffer if it is not associated with any config.
 566   if (buffer_queue_chain_.empty()) {
 567     NOTREACHED() << "Cannot provide buffers before configs";
 568     return;
 569   }
 570
 571   buffer_queue_chain_.back().video_queue.push_back(stream_parser_buffer);
 572 }
 573
 574 bool Mp2tStreamParser::EmitRemainingBuffers() {
 575   DVLOG(LOG_LEVEL_ES) << "Mp2tStreamParser::EmitRemainingBuffers";
 576
 577   // No buffer should be sent until fully initialized.
 578   if (!is_initialized_)
 579     return true;
 580
 581   if (buffer_queue_chain_.empty())
 582     return true;
 583
 584   // Keep track of the last audio and video config sent.
 585   AudioDecoderConfig last_audio_config =
 586       buffer_queue_chain_.back().audio_config;
 587   VideoDecoderConfig last_video_config =
 588       buffer_queue_chain_.back().video_config;
 589
 590   // Do not have all the configs, need more data.
 591   if (selected_audio_pid_ >= 0 && !last_audio_config.IsValidConfig())
 592     return true;
 593   if (selected_video_pid_ >= 0 && !last_video_config.IsValidConfig())
 594     return true;
 595
 596   // Buffer emission.
 597   while (!buffer_queue_chain_.empty()) {
 598     // Start a segment if needed.
 599     if (!segment_started_) {
 600       DVLOG(1) << "Starting a new segment";
 601       segment_started_ = true;
 602       new_segment_cb_.Run();
 603     }
 604
 605     // Update the audio and video config if needed.
 606     BufferQueueWithConfig& queue_with_config = buffer_queue_chain_.front();
 607     if (!queue_with_config.is_config_sent) {
 608       if (!config_cb_.Run(queue_with_config.audio_config,
 609                           queue_with_config.video_config,
 610                           TextTrackConfigMap()))
 611         return false;
 612       queue_with_config.is_config_sent = true;
 613     }
 614
 615     // Add buffers.
 616     TextBufferQueueMap empty_text_map;
 617     if (!queue_with_config.audio_queue.empty() ||
 618         !queue_with_config.video_queue.empty()) {
 619       if (!new_buffers_cb_.Run(queue_with_config.audio_queue,
 620                                queue_with_config.video_queue,
 621                                empty_text_map)) {
 622         return false;
 623       }
 624     }
 625
 626     buffer_queue_chain_.pop_front();
 627   }
 628
 629   // Push an empty queue with the last audio/video config
 630   // so that buffers with the same config can be added later on.
 631   BufferQueueWithConfig queue_with_config(
 632       true, last_audio_config, last_video_config);
 633   buffer_queue_chain_.push_back(queue_with_config);
 634
 635   return true;
 636 }
 637
 638 }  // namespace mp2t
 639 }  // namespace media