src/media/cast/rtcp/rtcp_sender.cc

   1 // Copyright 2013 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/cast/rtcp/rtcp_sender.h"
   6
   7 #include <algorithm>
   8 #include <vector>
   9
  10 #include "base/logging.h"
  11 #include "media/cast/cast_environment.h"
  12 #include "media/cast/rtcp/receiver_rtcp_event_subscriber.h"
  13 #include "media/cast/rtcp/rtcp_defines.h"
  14 #include "media/cast/rtcp/rtcp_utility.h"
  15 #include "media/cast/transport/cast_transport_defines.h"
  16 #include "media/cast/transport/pacing/paced_sender.h"
  17 #include "net/base/big_endian.h"
  18
  19 namespace {
  20
  21 using media::cast::kRtcpCastLogHeaderSize;
  22 using media::cast::kRtcpSenderFrameLogSize;
  23 using media::cast::kRtcpReceiverFrameLogSize;
  24 using media::cast::kRtcpReceiverEventLogSize;
  25
  26 // Converts a log event type to an integer value.
  27 int ConvertEventTypeToWireFormat(const media::cast::CastLoggingEvent& event) {
  28   switch (event) {
  29     case media::cast::kAudioAckSent:
  30       return 1;
  31     case media::cast::kAudioPlayoutDelay:
  32       return 2;
  33     case media::cast::kAudioFrameDecoded:
  34       return 3;
  35     case media::cast::kAudioPacketReceived:
  36       return 4;
  37     case media::cast::kVideoAckSent:
  38       return 5;
  39     case media::cast::kVideoFrameDecoded:
  40       return 6;
  41     case media::cast::kVideoRenderDelay:
  42       return 7;
  43     case media::cast::kVideoPacketReceived:
  44       return 8;
  45     case media::cast::kDuplicateAudioPacketReceived:
  46       return 9;
  47     case media::cast::kDuplicateVideoPacketReceived:
  48       return 10;
  49     default:
  50       return 0;  // Not an interesting event.
  51   }
  52 }
  53
  54 uint16 MergeEventTypeAndTimestampForWireFormat(
  55     const media::cast::CastLoggingEvent& event,
  56     const base::TimeDelta& time_delta) {
  57   int64 time_delta_ms = time_delta.InMilliseconds();
  58   // Max delta is 4096 milliseconds.
  59   DCHECK_GE(GG_INT64_C(0xfff), time_delta_ms);
  60
  61   uint16 event_type_and_timestamp_delta =
  62       static_cast<uint16>(time_delta_ms & 0xfff);
  63
  64   uint16 event_type = ConvertEventTypeToWireFormat(event);
  65   DCHECK(event_type);
  66   DCHECK(!(event_type & 0xfff0));
  67   return (event_type << 12) + event_type_and_timestamp_delta;
  68 }
  69
  70 bool ScanRtcpReceiverLogMessage(
  71     const media::cast::RtcpReceiverLogMessage& receiver_log_message,
  72     size_t start_size, size_t* number_of_frames,
  73     size_t* total_number_of_messages_to_send, size_t* rtcp_log_size) {
  74   if (receiver_log_message.empty()) return false;
  75
  76   size_t remaining_space = media::cast::kMaxIpPacketSize - start_size;
  77
  78   // We must have space for at least one message
  79   DCHECK_GE(remaining_space, kRtcpCastLogHeaderSize +
  80                                  kRtcpReceiverFrameLogSize +
  81                                  kRtcpReceiverEventLogSize)
  82       << "Not enough buffer space";
  83
  84   if (remaining_space < kRtcpCastLogHeaderSize + kRtcpReceiverFrameLogSize +
  85                             kRtcpReceiverEventLogSize) {
  86     return false;
  87   }
  88   // Account for the RTCP header for an application-defined packet.
  89   remaining_space -= kRtcpCastLogHeaderSize;
  90
  91   media::cast::RtcpReceiverLogMessage::const_iterator frame_it =
  92       receiver_log_message.begin();
  93   for (; frame_it != receiver_log_message.end(); ++frame_it) {
  94     (*number_of_frames)++;
  95
  96     remaining_space -= kRtcpReceiverFrameLogSize;
  97
  98     size_t messages_in_frame = frame_it->event_log_messages_.size();
  99     size_t remaining_space_in_messages =
 100         remaining_space / kRtcpReceiverEventLogSize;
 101     size_t messages_to_send =
 102         std::min(messages_in_frame, remaining_space_in_messages);
 103     if (messages_to_send > media::cast::kRtcpMaxReceiverLogMessages) {
 104       // We can't send more than 256 messages.
 105       remaining_space -=
 106           media::cast::kRtcpMaxReceiverLogMessages * kRtcpReceiverEventLogSize;
 107       *total_number_of_messages_to_send +=
 108           media::cast::kRtcpMaxReceiverLogMessages;
 109       break;
 110     }
 111     remaining_space -= messages_to_send * kRtcpReceiverEventLogSize;
 112     *total_number_of_messages_to_send += messages_to_send;
 113
 114     if (remaining_space <
 115         kRtcpReceiverFrameLogSize + kRtcpReceiverEventLogSize) {
 116       // Make sure that we have room for at least one more message.
 117       break;
 118     }
 119   }
 120   *rtcp_log_size =
 121       kRtcpCastLogHeaderSize + *number_of_frames * kRtcpReceiverFrameLogSize +
 122       *total_number_of_messages_to_send * kRtcpReceiverEventLogSize;
 123   DCHECK_GE(media::cast::kMaxIpPacketSize, start_size + *rtcp_log_size)
 124       << "Not enough buffer space";
 125
 126   VLOG(1) << "number of frames " << *number_of_frames;
 127   VLOG(1) << "total messages to send " << *total_number_of_messages_to_send;
 128   VLOG(1) << "rtcp log size " << *rtcp_log_size;
 129   return true;
 130 }
 131 }  // namespace
 132
 133 namespace media {
 134 namespace cast {
 135
 136 // TODO(mikhal): This is only used by the receiver. Consider renaming.
 137 RtcpSender::RtcpSender(scoped_refptr<CastEnvironment> cast_environment,
 138                        transport::PacedPacketSender* outgoing_transport,
 139                        uint32 sending_ssrc, const std::string& c_name)
 140     : ssrc_(sending_ssrc),
 141       c_name_(c_name),
 142       transport_(outgoing_transport),
 143       cast_environment_(cast_environment) {
 144   DCHECK_LT(c_name_.length(), kRtcpCnameSize) << "Invalid config";
 145 }
 146
 147 RtcpSender::~RtcpSender() {}
 148
 149 // static
 150 bool RtcpSender::IsReceiverEvent(const media::cast::CastLoggingEvent& event) {
 151   return ConvertEventTypeToWireFormat(event) != 0;
 152 }
 153
 154 void RtcpSender::SendRtcpFromRtpReceiver(
 155     uint32 packet_type_flags,
 156     const transport::RtcpReportBlock* report_block,
 157     const RtcpReceiverReferenceTimeReport* rrtr,
 158     const RtcpCastMessage* cast_message,
 159     ReceiverRtcpEventSubscriber* event_subscriber) {
 160   if (packet_type_flags & kRtcpSr || packet_type_flags & kRtcpDlrr ||
 161       packet_type_flags & kRtcpSenderLog) {
 162     NOTREACHED() << "Invalid argument";
 163   }
 164   if (packet_type_flags & kRtcpPli || packet_type_flags & kRtcpRpsi ||
 165       packet_type_flags & kRtcpRemb || packet_type_flags & kRtcpNack) {
 166     // Implement these for webrtc interop.
 167     NOTIMPLEMENTED();
 168   }
 169   Packet packet;
 170   packet.reserve(kMaxIpPacketSize);
 171
 172   if (packet_type_flags & kRtcpRr) {
 173     BuildRR(report_block, &packet);
 174     if (!c_name_.empty()) {
 175       BuildSdec(&packet);
 176     }
 177   }
 178   if (packet_type_flags & kRtcpBye) {
 179     BuildBye(&packet);
 180   }
 181   if (packet_type_flags & kRtcpRrtr) {
 182     DCHECK(rrtr) << "Invalid argument";
 183     BuildRrtr(rrtr, &packet);
 184   }
 185   if (packet_type_flags & kRtcpCast) {
 186     DCHECK(cast_message) << "Invalid argument";
 187     BuildCast(cast_message, &packet);
 188   }
 189   if (packet_type_flags & kRtcpReceiverLog) {
 190     DCHECK(event_subscriber) << "Invalid argument";
 191     RtcpReceiverLogMessage receiver_log;
 192     event_subscriber->GetReceiverLogMessageAndReset(&receiver_log);
 193     BuildReceiverLog(&receiver_log, &packet);
 194   }
 195   if (packet.empty()) return;  // Sanity don't send empty packets.
 196
 197   transport_->SendRtcpPacket(packet);
 198 }
 199
 200 void RtcpSender::BuildRR(const transport::RtcpReportBlock* report_block,
 201                          Packet* packet) const {
 202   size_t start_size = packet->size();
 203   DCHECK_LT(start_size + 32, kMaxIpPacketSize) << "Not enough buffer space";
 204   if (start_size + 32 > kMaxIpPacketSize) return;
 205
 206   uint16 number_of_rows = (report_block) ? 7 : 1;
 207   packet->resize(start_size + 8);
 208
 209   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 8);
 210   big_endian_writer.WriteU8(0x80 + (report_block ? 1 : 0));
 211   big_endian_writer.WriteU8(transport::kPacketTypeReceiverReport);
 212   big_endian_writer.WriteU16(number_of_rows);
 213   big_endian_writer.WriteU32(ssrc_);
 214
 215   if (report_block) {
 216     AddReportBlocks(*report_block, packet);  // Adds 24 bytes.
 217   }
 218 }
 219
 220 void RtcpSender::AddReportBlocks(const transport::RtcpReportBlock& report_block,
 221                                  Packet* packet) const {
 222   size_t start_size = packet->size();
 223   DCHECK_LT(start_size + 24, kMaxIpPacketSize) << "Not enough buffer space";
 224   if (start_size + 24 > kMaxIpPacketSize) return;
 225
 226   packet->resize(start_size + 24);
 227
 228   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 24);
 229   big_endian_writer.WriteU32(report_block.media_ssrc);
 230   big_endian_writer.WriteU8(report_block.fraction_lost);
 231   big_endian_writer.WriteU8(report_block.cumulative_lost >> 16);
 232   big_endian_writer.WriteU8(report_block.cumulative_lost >> 8);
 233   big_endian_writer.WriteU8(report_block.cumulative_lost);
 234
 235   // Extended highest seq_no, contain the highest sequence number received.
 236   big_endian_writer.WriteU32(report_block.extended_high_sequence_number);
 237   big_endian_writer.WriteU32(report_block.jitter);
 238
 239   // Last SR timestamp; our NTP time when we received the last report.
 240   // This is the value that we read from the send report packet not when we
 241   // received it.
 242   big_endian_writer.WriteU32(report_block.last_sr);
 243
 244   // Delay since last received report, time since we received the report.
 245   big_endian_writer.WriteU32(report_block.delay_since_last_sr);
 246 }
 247
 248 void RtcpSender::BuildSdec(Packet* packet) const {
 249   size_t start_size = packet->size();
 250   DCHECK_LT(start_size + 12 + c_name_.length(), kMaxIpPacketSize)
 251       << "Not enough buffer space";
 252   if (start_size + 12 > kMaxIpPacketSize) return;
 253
 254   // SDES Source Description.
 255   packet->resize(start_size + 10);
 256
 257   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 10);
 258   // We always need to add one SDES CNAME.
 259   big_endian_writer.WriteU8(0x80 + 1);
 260   big_endian_writer.WriteU8(transport::kPacketTypeSdes);
 261
 262   // Handle SDES length later on.
 263   uint32 sdes_length_position = static_cast<uint32>(start_size) + 3;
 264   big_endian_writer.WriteU16(0);
 265   big_endian_writer.WriteU32(ssrc_);  // Add our own SSRC.
 266   big_endian_writer.WriteU8(1);       // CNAME = 1
 267   big_endian_writer.WriteU8(static_cast<uint8>(c_name_.length()));
 268
 269   size_t sdes_length = 10 + c_name_.length();
 270   packet->insert(packet->end(), c_name_.c_str(),
 271                  c_name_.c_str() + c_name_.length());
 272
 273   size_t padding = 0;
 274
 275   // We must have a zero field even if we have an even multiple of 4 bytes.
 276   if ((packet->size() % 4) == 0) {
 277     padding++;
 278     packet->push_back(0);
 279   }
 280   while ((packet->size() % 4) != 0) {
 281     padding++;
 282     packet->push_back(0);
 283   }
 284   sdes_length += padding;
 285
 286   // In 32-bit words minus one and we don't count the header.
 287   uint8 buffer_length = static_cast<uint8>((sdes_length / 4) - 1);
 288   (*packet)[sdes_length_position] = buffer_length;
 289 }
 290
 291 void RtcpSender::BuildPli(uint32 remote_ssrc, Packet* packet) const {
 292   size_t start_size = packet->size();
 293   DCHECK_LT(start_size + 12, kMaxIpPacketSize) << "Not enough buffer space";
 294   if (start_size + 12 > kMaxIpPacketSize) return;
 295
 296   packet->resize(start_size + 12);
 297
 298   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 12);
 299   uint8 FMT = 1;  // Picture loss indicator.
 300   big_endian_writer.WriteU8(0x80 + FMT);
 301   big_endian_writer.WriteU8(transport::kPacketTypePayloadSpecific);
 302   big_endian_writer.WriteU16(2);            // Used fixed length of 2.
 303   big_endian_writer.WriteU32(ssrc_);        // Add our own SSRC.
 304   big_endian_writer.WriteU32(remote_ssrc);  // Add the remote SSRC.
 305 }
 306
 307 /*
 308     0                   1                   2                   3
 309     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 310    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 311    |      PB       |0| Payload Type|    Native Rpsi bit string     |
 312    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 313    |   defined per codec          ...                | Padding (0) |
 314    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 315 */
 316 void RtcpSender::BuildRpsi(const RtcpRpsiMessage* rpsi, Packet* packet) const {
 317   size_t start_size = packet->size();
 318   DCHECK_LT(start_size + 24, kMaxIpPacketSize) << "Not enough buffer space";
 319   if (start_size + 24 > kMaxIpPacketSize) return;
 320
 321   packet->resize(start_size + 24);
 322
 323   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 24);
 324   uint8 FMT = 3;  // Reference Picture Selection Indication.
 325   big_endian_writer.WriteU8(0x80 + FMT);
 326   big_endian_writer.WriteU8(transport::kPacketTypePayloadSpecific);
 327
 328   // Calculate length.
 329   uint32 bits_required = 7;
 330   uint8 bytes_required = 1;
 331   while ((rpsi->picture_id >> bits_required) > 0) {
 332     bits_required += 7;
 333     bytes_required++;
 334   }
 335   uint8 size = 3;
 336   if (bytes_required > 6) {
 337     size = 5;
 338   } else if (bytes_required > 2) {
 339     size = 4;
 340   }
 341   big_endian_writer.WriteU8(0);
 342   big_endian_writer.WriteU8(size);
 343   big_endian_writer.WriteU32(ssrc_);
 344   big_endian_writer.WriteU32(rpsi->remote_ssrc);
 345
 346   uint8 padding_bytes = 4 - ((2 + bytes_required) % 4);
 347   if (padding_bytes == 4) {
 348     padding_bytes = 0;
 349   }
 350   // Add padding length in bits, padding can be 0, 8, 16 or 24.
 351   big_endian_writer.WriteU8(padding_bytes * 8);
 352   big_endian_writer.WriteU8(rpsi->payload_type);
 353
 354   // Add picture ID.
 355   for (int i = bytes_required - 1; i > 0; i--) {
 356     big_endian_writer.WriteU8(0x80 |
 357                               static_cast<uint8>(rpsi->picture_id >> (i * 7)));
 358   }
 359   // Add last byte of picture ID.
 360   big_endian_writer.WriteU8(static_cast<uint8>(rpsi->picture_id & 0x7f));
 361
 362   // Add padding.
 363   for (int j = 0; j < padding_bytes; ++j) {
 364     big_endian_writer.WriteU8(0);
 365   }
 366 }
 367
 368 void RtcpSender::BuildRemb(const RtcpRembMessage* remb, Packet* packet) const {
 369   size_t start_size = packet->size();
 370   size_t remb_size = 20 + 4 * remb->remb_ssrcs.size();
 371   DCHECK_LT(start_size + remb_size, kMaxIpPacketSize)
 372       << "Not enough buffer space";
 373   if (start_size + remb_size > kMaxIpPacketSize) return;
 374
 375   packet->resize(start_size + remb_size);
 376
 377   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), remb_size);
 378
 379   // Add application layer feedback.
 380   uint8 FMT = 15;
 381   big_endian_writer.WriteU8(0x80 + FMT);
 382   big_endian_writer.WriteU8(transport::kPacketTypePayloadSpecific);
 383   big_endian_writer.WriteU8(0);
 384   big_endian_writer.WriteU8(static_cast<uint8>(remb->remb_ssrcs.size() + 4));
 385   big_endian_writer.WriteU32(ssrc_);  // Add our own SSRC.
 386   big_endian_writer.WriteU32(0);      // Remote SSRC must be 0.
 387   big_endian_writer.WriteU32(kRemb);
 388   big_endian_writer.WriteU8(static_cast<uint8>(remb->remb_ssrcs.size()));
 389
 390   // 6 bit exponent and a 18 bit mantissa.
 391   uint8 bitrate_exponent;
 392   uint32 bitrate_mantissa;
 393   BitrateToRembExponentBitrate(remb->remb_bitrate, &bitrate_exponent,
 394                                &bitrate_mantissa);
 395
 396   big_endian_writer.WriteU8(static_cast<uint8>(
 397       (bitrate_exponent << 2) + ((bitrate_mantissa >> 16) & 0x03)));
 398   big_endian_writer.WriteU8(static_cast<uint8>(bitrate_mantissa >> 8));
 399   big_endian_writer.WriteU8(static_cast<uint8>(bitrate_mantissa));
 400
 401   std::list<uint32>::const_iterator it = remb->remb_ssrcs.begin();
 402   for (; it != remb->remb_ssrcs.end(); ++it) {
 403     big_endian_writer.WriteU32(*it);
 404   }
 405   base::TimeTicks now = cast_environment_->Clock()->NowTicks();
 406   cast_environment_->Logging()->InsertGenericEvent(now, kRembBitrate,
 407                                                    remb->remb_bitrate);
 408 }
 409
 410 void RtcpSender::BuildNack(const RtcpNackMessage* nack, Packet* packet) const {
 411   size_t start_size = packet->size();
 412   DCHECK_LT(start_size + 16, kMaxIpPacketSize) << "Not enough buffer space";
 413   if (start_size + 16 > kMaxIpPacketSize) return;
 414
 415   packet->resize(start_size + 16);
 416
 417   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 16);
 418
 419   uint8 FMT = 1;
 420   big_endian_writer.WriteU8(0x80 + FMT);
 421   big_endian_writer.WriteU8(transport::kPacketTypeGenericRtpFeedback);
 422   big_endian_writer.WriteU8(0);
 423   size_t nack_size_pos = start_size + 3;
 424   big_endian_writer.WriteU8(3);
 425   big_endian_writer.WriteU32(ssrc_);              // Add our own SSRC.
 426   big_endian_writer.WriteU32(nack->remote_ssrc);  // Add the remote SSRC.
 427
 428   // Build NACK bitmasks and write them to the Rtcp message.
 429   // The nack list should be sorted and not contain duplicates.
 430   size_t number_of_nack_fields = 0;
 431   size_t max_number_of_nack_fields = std::min<size_t>(
 432       kRtcpMaxNackFields, (kMaxIpPacketSize - packet->size()) / 4);
 433
 434   std::list<uint16>::const_iterator it = nack->nack_list.begin();
 435   while (it != nack->nack_list.end() &&
 436          number_of_nack_fields < max_number_of_nack_fields) {
 437     uint16 nack_sequence_number = *it;
 438     uint16 bitmask = 0;
 439     ++it;
 440     while (it != nack->nack_list.end()) {
 441       int shift = static_cast<uint16>(*it - nack_sequence_number) - 1;
 442       if (shift >= 0 && shift <= 15) {
 443         bitmask |= (1 << shift);
 444         ++it;
 445       } else {
 446         break;
 447       }
 448     }
 449     // Write the sequence number and the bitmask to the packet.
 450     start_size = packet->size();
 451     DCHECK_LT(start_size + 4, kMaxIpPacketSize) << "Not enough buffer space";
 452     if (start_size + 4 > kMaxIpPacketSize) return;
 453
 454     packet->resize(start_size + 4);
 455     net::BigEndianWriter big_endian_nack_writer(&((*packet)[start_size]), 4);
 456     big_endian_nack_writer.WriteU16(nack_sequence_number);
 457     big_endian_nack_writer.WriteU16(bitmask);
 458     number_of_nack_fields++;
 459   }
 460   DCHECK_GE(kRtcpMaxNackFields, number_of_nack_fields);
 461   (*packet)[nack_size_pos] = static_cast<uint8>(2 + number_of_nack_fields);
 462 }
 463
 464 void RtcpSender::BuildBye(Packet* packet) const {
 465   size_t start_size = packet->size();
 466   DCHECK_LT(start_size + 8, kMaxIpPacketSize) << "Not enough buffer space";
 467   if (start_size + 8 > kMaxIpPacketSize) return;
 468
 469   packet->resize(start_size + 8);
 470
 471   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 8);
 472   big_endian_writer.WriteU8(0x80 + 1);
 473   big_endian_writer.WriteU8(transport::kPacketTypeBye);
 474   big_endian_writer.WriteU16(1);      // Length.
 475   big_endian_writer.WriteU32(ssrc_);  // Add our own SSRC.
 476 }
 477
 478 void RtcpSender::BuildRrtr(const RtcpReceiverReferenceTimeReport* rrtr,
 479                            Packet* packet) const {
 480   size_t start_size = packet->size();
 481   DCHECK_LT(start_size + 20, kMaxIpPacketSize) << "Not enough buffer space";
 482   if (start_size + 20 > kMaxIpPacketSize) return;
 483
 484   packet->resize(start_size + 20);
 485
 486   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 20);
 487
 488   big_endian_writer.WriteU8(0x80);
 489   big_endian_writer.WriteU8(transport::kPacketTypeXr);
 490   big_endian_writer.WriteU16(4);      // Length.
 491   big_endian_writer.WriteU32(ssrc_);  // Add our own SSRC.
 492   big_endian_writer.WriteU8(4);       // Add block type.
 493   big_endian_writer.WriteU8(0);       // Add reserved.
 494   big_endian_writer.WriteU16(2);      // Block length.
 495
 496   // Add the media (received RTP) SSRC.
 497   big_endian_writer.WriteU32(rrtr->ntp_seconds);
 498   big_endian_writer.WriteU32(rrtr->ntp_fraction);
 499 }
 500
 501 void RtcpSender::BuildCast(const RtcpCastMessage* cast, Packet* packet) const {
 502   size_t start_size = packet->size();
 503   DCHECK_LT(start_size + 20, kMaxIpPacketSize) << "Not enough buffer space";
 504   if (start_size + 20 > kMaxIpPacketSize) return;
 505
 506   packet->resize(start_size + 20);
 507
 508   net::BigEndianWriter big_endian_writer(&((*packet)[start_size]), 20);
 509   uint8 FMT = 15;  // Application layer feedback.
 510   big_endian_writer.WriteU8(0x80 + FMT);
 511   big_endian_writer.WriteU8(transport::kPacketTypePayloadSpecific);
 512   big_endian_writer.WriteU8(0);
 513   size_t cast_size_pos = start_size + 3;  // Save length position.
 514   big_endian_writer.WriteU8(4);
 515   big_endian_writer.WriteU32(ssrc_);              // Add our own SSRC.
 516   big_endian_writer.WriteU32(cast->media_ssrc_);  // Remote SSRC.
 517   big_endian_writer.WriteU32(kCast);
 518   big_endian_writer.WriteU8(static_cast<uint8>(cast->ack_frame_id_));
 519   size_t cast_loss_field_pos = start_size + 17;  // Save loss field position.
 520   big_endian_writer.WriteU8(0);  // Overwritten with number_of_loss_fields.
 521   big_endian_writer.WriteU8(0);  // Reserved.
 522   big_endian_writer.WriteU8(0);  // Reserved.
 523
 524   size_t number_of_loss_fields = 0;
 525   size_t max_number_of_loss_fields = std::min<size_t>(
 526       kRtcpMaxCastLossFields, (kMaxIpPacketSize - packet->size()) / 4);
 527
 528   MissingFramesAndPacketsMap::const_iterator frame_it =
 529       cast->missing_frames_and_packets_.begin();
 530
 531   for (; frame_it != cast->missing_frames_and_packets_.end() &&
 532              number_of_loss_fields < max_number_of_loss_fields;
 533        ++frame_it) {
 534     // Iterate through all frames with missing packets.
 535     if (frame_it->second.empty()) {
 536       // Special case all packets in a frame is missing.
 537       start_size = packet->size();
 538       packet->resize(start_size + 4);
 539       net::BigEndianWriter big_endian_nack_writer(&((*packet)[start_size]), 4);
 540       big_endian_nack_writer.WriteU8(static_cast<uint8>(frame_it->first));
 541       big_endian_nack_writer.WriteU16(kRtcpCastAllPacketsLost);
 542       big_endian_nack_writer.WriteU8(0);
 543       ++number_of_loss_fields;
 544     } else {
 545       PacketIdSet::const_iterator packet_it = frame_it->second.begin();
 546       while (packet_it != frame_it->second.end()) {
 547         uint16 packet_id = *packet_it;
 548
 549         start_size = packet->size();
 550         packet->resize(start_size + 4);
 551         net::BigEndianWriter big_endian_nack_writer(&((*packet)[start_size]),
 552                                                     4);
 553
 554         // Write frame and packet id to buffer before calculating bitmask.
 555         big_endian_nack_writer.WriteU8(static_cast<uint8>(frame_it->first));
 556         big_endian_nack_writer.WriteU16(packet_id);
 557
 558         uint8 bitmask = 0;
 559         ++packet_it;
 560         while (packet_it != frame_it->second.end()) {
 561           int shift = static_cast<uint8>(*packet_it - packet_id) - 1;
 562           if (shift >= 0 && shift <= 7) {
 563             bitmask |= (1 << shift);
 564             ++packet_it;
 565           } else {
 566             break;
 567           }
 568         }
 569         big_endian_nack_writer.WriteU8(bitmask);
 570         ++number_of_loss_fields;
 571       }
 572     }
 573   }
 574   DCHECK_LE(number_of_loss_fields, kRtcpMaxCastLossFields);
 575   (*packet)[cast_size_pos] = static_cast<uint8>(4 + number_of_loss_fields);
 576   (*packet)[cast_loss_field_pos] = static_cast<uint8>(number_of_loss_fields);
 577 }
 578
 579 void RtcpSender::BuildReceiverLog(RtcpReceiverLogMessage* receiver_log_message,
 580                                   Packet* packet) const {
 581   DCHECK(receiver_log_message);
 582   const size_t packet_start_size = packet->size();
 583   size_t number_of_frames = 0;
 584   size_t total_number_of_messages_to_send = 0;
 585   size_t rtcp_log_size = 0;
 586
 587   if (!ScanRtcpReceiverLogMessage(
 588            *receiver_log_message, packet_start_size, &number_of_frames,
 589            &total_number_of_messages_to_send, &rtcp_log_size)) {
 590     return;
 591   }
 592   packet->resize(packet_start_size + rtcp_log_size);
 593
 594   net::BigEndianWriter big_endian_writer(&((*packet)[packet_start_size]),
 595                                          rtcp_log_size);
 596   big_endian_writer.WriteU8(0x80 + kReceiverLogSubtype);
 597   big_endian_writer.WriteU8(transport::kPacketTypeApplicationDefined);
 598   big_endian_writer.WriteU16(static_cast<uint16>(
 599       2 + 2 * number_of_frames + total_number_of_messages_to_send));
 600   big_endian_writer.WriteU32(ssrc_);  // Add our own SSRC.
 601   big_endian_writer.WriteU32(kCast);
 602
 603   while (!receiver_log_message->empty() &&
 604          total_number_of_messages_to_send > 0) {
 605     RtcpReceiverFrameLogMessage& frame_log_messages(
 606         receiver_log_message->front());
 607
 608     // Add our frame header.
 609     big_endian_writer.WriteU32(frame_log_messages.rtp_timestamp_);
 610     size_t messages_in_frame = frame_log_messages.event_log_messages_.size();
 611     if (messages_in_frame > total_number_of_messages_to_send) {
 612       // We are running out of space.
 613       messages_in_frame = total_number_of_messages_to_send;
 614     }
 615     // Keep track of how many messages we have left to send.
 616     total_number_of_messages_to_send -= messages_in_frame;
 617
 618     // On the wire format is number of messages - 1.
 619     big_endian_writer.WriteU8(static_cast<uint8>(messages_in_frame - 1));
 620
 621     base::TimeTicks event_timestamp_base =
 622         frame_log_messages.event_log_messages_.front().event_timestamp;
 623     uint32 base_timestamp_ms =
 624         (event_timestamp_base - base::TimeTicks()).InMilliseconds();
 625     big_endian_writer.WriteU8(static_cast<uint8>(base_timestamp_ms >> 16));
 626     big_endian_writer.WriteU8(static_cast<uint8>(base_timestamp_ms >> 8));
 627     big_endian_writer.WriteU8(static_cast<uint8>(base_timestamp_ms));
 628
 629     while (!frame_log_messages.event_log_messages_.empty() &&
 630            messages_in_frame > 0) {
 631       const RtcpReceiverEventLogMessage& event_message =
 632           frame_log_messages.event_log_messages_.front();
 633       uint16 event_type_and_timestamp_delta =
 634           MergeEventTypeAndTimestampForWireFormat(
 635               event_message.type,
 636               event_message.event_timestamp - event_timestamp_base);
 637       switch (event_message.type) {
 638         case kAudioAckSent:
 639         case kVideoAckSent:
 640         case kAudioPlayoutDelay:
 641         case kAudioFrameDecoded:
 642         case kVideoFrameDecoded:
 643         case kVideoRenderDelay:
 644           big_endian_writer.WriteU16(
 645               static_cast<uint16>(event_message.delay_delta.InMilliseconds()));
 646           big_endian_writer.WriteU16(event_type_and_timestamp_delta);
 647           break;
 648         case kAudioPacketReceived:
 649         case kVideoPacketReceived:
 650         case kDuplicateAudioPacketReceived:
 651         case kDuplicateVideoPacketReceived:
 652           big_endian_writer.WriteU16(event_message.packet_id);
 653           big_endian_writer.WriteU16(event_type_and_timestamp_delta);
 654           break;
 655         default:
 656           NOTREACHED();
 657       }
 658       messages_in_frame--;
 659       frame_log_messages.event_log_messages_.pop_front();
 660     }
 661     if (frame_log_messages.event_log_messages_.empty()) {
 662       // We sent all messages on this frame; pop the frame header.
 663       receiver_log_message->pop_front();
 664     }
 665   }
 666   DCHECK_EQ(total_number_of_messages_to_send, 0);
 667 }
 668
 669 }  // namespace cast
 670 }  // namespace media