media/cast/net/rtcp/rtcp_builder.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/cast/net/rtcp/rtcp_builder.h"
   6
   7 #include <stdint.h>
   8
   9 #include <algorithm>
  10 #include <vector>
  11
  12 #include "base/logging.h"
  13 #include "media/cast/net/rtcp/rtcp_utility.h"
  14
  15 namespace media {
  16 namespace cast {
  17 namespace {
  18
  19 // Max delta is 4095 milliseconds because we need to be able to encode it in
  20 // 12 bits.
  21 const int64 kMaxWireFormatTimeDeltaMs = INT64_C(0xfff);
  22
  23 uint16 MergeEventTypeAndTimestampForWireFormat(
  24     const CastLoggingEvent& event,
  25     const base::TimeDelta& time_delta) {
  26   int64 time_delta_ms = time_delta.InMilliseconds();
  27
  28   DCHECK_GE(time_delta_ms, 0);
  29   DCHECK_LE(time_delta_ms, kMaxWireFormatTimeDeltaMs);
  30
  31   uint16 time_delta_12_bits =
  32       static_cast<uint16>(time_delta_ms & kMaxWireFormatTimeDeltaMs);
  33
  34   uint16 event_type_4_bits = ConvertEventTypeToWireFormat(event);
  35   DCHECK(event_type_4_bits);
  36   DCHECK(~(event_type_4_bits & 0xfff0));
  37   return (event_type_4_bits << 12) | time_delta_12_bits;
  38 }
  39
  40 bool EventTimestampLessThan(const RtcpReceiverEventLogMessage& lhs,
  41                             const RtcpReceiverEventLogMessage& rhs) {
  42   return lhs.event_timestamp < rhs.event_timestamp;
  43 }
  44
  45 // A class to build a string representing the NACK list in Cast message.
  46 //
  47 // The string will look like "23:3-6 25:1,5-6", meaning packets 3 to 6 in frame
  48 // 23 are being NACK'ed (i.e. they are missing from the receiver's point of
  49 // view) and packets 1, 5 and 6 are missing in frame 25. A frame that is
  50 // completely missing will show as "26:65535".
  51 class NackStringBuilder {
  52  public:
  53   NackStringBuilder()
  54       : frame_count_(0),
  55         packet_count_(0),
  56         last_frame_id_(-1),
  57         last_packet_id_(-1),
  58         contiguous_sequence_(false) {}
  59   ~NackStringBuilder() {}
  60
  61   bool Empty() const { return frame_count_ == 0; }
  62
  63   void PushFrame(int frame_id) {
  64     DCHECK_GE(frame_id, 0);
  65     if (frame_count_ > 0) {
  66       if (frame_id == last_frame_id_) {
  67         return;
  68       }
  69       if (contiguous_sequence_) {
  70         stream_ << "-" << last_packet_id_;
  71       }
  72       stream_ << ", ";
  73     }
  74     stream_ << frame_id;
  75     last_frame_id_ = frame_id;
  76     packet_count_ = 0;
  77     contiguous_sequence_ = false;
  78     ++frame_count_;
  79   }
  80
  81   void PushPacket(int packet_id) {
  82     DCHECK_GE(last_frame_id_, 0);
  83     DCHECK_GE(packet_id, 0);
  84     if (packet_count_ == 0) {
  85       stream_ << ":" << packet_id;
  86     } else if (packet_id == last_packet_id_ + 1) {
  87       contiguous_sequence_ = true;
  88     } else {
  89       if (contiguous_sequence_) {
  90         stream_ << "-" << last_packet_id_;
  91         contiguous_sequence_ = false;
  92       }
  93       stream_ << "," << packet_id;
  94     }
  95     ++packet_count_;
  96     last_packet_id_ = packet_id;
  97   }
  98
  99   std::string GetString() {
 100     if (contiguous_sequence_) {
 101       stream_ << "-" << last_packet_id_;
 102       contiguous_sequence_ = false;
 103     }
 104     return stream_.str();
 105   }
 106
 107  private:
 108   std::ostringstream stream_;
 109   int frame_count_;
 110   int packet_count_;
 111   int last_frame_id_;
 112   int last_packet_id_;
 113   bool contiguous_sequence_;
 114 };
 115 }  // namespace
 116
 117 RtcpBuilder::RtcpBuilder(uint32 sending_ssrc)
 118     : writer_(NULL, 0),
 119       ssrc_(sending_ssrc),
 120       ptr_of_length_(NULL) {
 121 }
 122
 123 RtcpBuilder::~RtcpBuilder() {}
 124
 125 void RtcpBuilder::PatchLengthField() {
 126   if (ptr_of_length_) {
 127     // Back-patch the packet length. The client must have taken
 128     // care of proper padding to 32-bit words.
 129     int this_packet_length = (writer_.ptr() - ptr_of_length_ - 2);
 130     DCHECK_EQ(0, this_packet_length % 4)
 131         << "Packets must be a multiple of 32 bits long";
 132     *ptr_of_length_ = this_packet_length >> 10;
 133     *(ptr_of_length_ + 1) = (this_packet_length >> 2) & 0xFF;
 134     ptr_of_length_ = NULL;
 135   }
 136 }
 137
 138 // Set the 5-bit value in the 1st byte of the header
 139 // and the payload type. Set aside room for the length field,
 140 // and make provision for back-patching it.
 141 void RtcpBuilder::AddRtcpHeader(RtcpPacketFields payload, int format_or_count) {
 142   PatchLengthField();
 143   writer_.WriteU8(0x80 | (format_or_count & 0x1F));
 144   writer_.WriteU8(payload);
 145   ptr_of_length_ = writer_.ptr();
 146
 147   // Initialize length to "clearly illegal".
 148   writer_.WriteU16(0xDEAD);
 149 }
 150
 151 void RtcpBuilder::Start() {
 152   packet_ = new base::RefCountedData<Packet>;
 153   packet_->data.resize(kMaxIpPacketSize);
 154   writer_ = base::BigEndianWriter(
 155       reinterpret_cast<char*>(&(packet_->data[0])), kMaxIpPacketSize);
 156 }
 157
 158 PacketRef RtcpBuilder::Finish() {
 159   PatchLengthField();
 160   packet_->data.resize(kMaxIpPacketSize - writer_.remaining());
 161   writer_ = base::BigEndianWriter(NULL, 0);
 162   PacketRef ret = packet_;
 163   packet_ = NULL;
 164   return ret;
 165 }
 166
 167 PacketRef RtcpBuilder::BuildRtcpFromReceiver(
 168     const RtcpReportBlock* report_block,
 169     const RtcpReceiverReferenceTimeReport* rrtr,
 170     const RtcpCastMessage* cast_message,
 171     const ReceiverRtcpEventSubscriber::RtcpEvents* rtcp_events,
 172     base::TimeDelta target_delay) {
 173   Start();
 174
 175   if (report_block)
 176     AddRR(report_block);
 177   if (rrtr)
 178     AddRrtr(rrtr);
 179   if (cast_message)
 180     AddCast(cast_message, target_delay);
 181   if (rtcp_events)
 182     AddReceiverLog(*rtcp_events);
 183
 184   return Finish();
 185 }
 186
 187 PacketRef RtcpBuilder::BuildRtcpFromSender(const RtcpSenderInfo& sender_info) {
 188   Start();
 189   AddSR(sender_info);
 190   return Finish();
 191 }
 192
 193 void RtcpBuilder::AddRR(const RtcpReportBlock* report_block) {
 194   AddRtcpHeader(kPacketTypeReceiverReport, report_block ? 1 : 0);
 195   writer_.WriteU32(ssrc_);
 196   if (report_block) {
 197     AddReportBlocks(*report_block);  // Adds 24 bytes.
 198   }
 199 }
 200
 201 void RtcpBuilder::AddReportBlocks(const RtcpReportBlock& report_block) {
 202   writer_.WriteU32(report_block.media_ssrc);
 203   writer_.WriteU8(report_block.fraction_lost);
 204   writer_.WriteU8(report_block.cumulative_lost >> 16);
 205   writer_.WriteU8(report_block.cumulative_lost >> 8);
 206   writer_.WriteU8(report_block.cumulative_lost);
 207
 208   // Extended highest seq_no, contain the highest sequence number received.
 209   writer_.WriteU32(report_block.extended_high_sequence_number);
 210   writer_.WriteU32(report_block.jitter);
 211
 212   // Last SR timestamp; our NTP time when we received the last report.
 213   // This is the value that we read from the send report packet not when we
 214   // received it.
 215   writer_.WriteU32(report_block.last_sr);
 216
 217   // Delay since last received report, time since we received the report.
 218   writer_.WriteU32(report_block.delay_since_last_sr);
 219 }
 220
 221 void RtcpBuilder::AddRrtr(const RtcpReceiverReferenceTimeReport* rrtr) {
 222   AddRtcpHeader(kPacketTypeXr, 0);
 223   writer_.WriteU32(ssrc_);  // Add our own SSRC.
 224   writer_.WriteU8(4);       // Add block type.
 225   writer_.WriteU8(0);       // Add reserved.
 226   writer_.WriteU16(2);      // Block length.
 227
 228   // Add the media (received RTP) SSRC.
 229   writer_.WriteU32(rrtr->ntp_seconds);
 230   writer_.WriteU32(rrtr->ntp_fraction);
 231 }
 232
 233 void RtcpBuilder::AddCast(const RtcpCastMessage* cast,
 234                           base::TimeDelta target_delay) {
 235   // See RTC 4585 Section 6.4 for application specific feedback messages.
 236   AddRtcpHeader(kPacketTypePayloadSpecific, 15);
 237   writer_.WriteU32(ssrc_);              // Add our own SSRC.
 238   writer_.WriteU32(cast->media_ssrc);  // Remote SSRC.
 239   writer_.WriteU32(kCast);
 240   writer_.WriteU8(static_cast<uint8>(cast->ack_frame_id));
 241   uint8* cast_loss_field_pos = reinterpret_cast<uint8*>(writer_.ptr());
 242   writer_.WriteU8(0);  // Overwritten with number_of_loss_fields.
 243   DCHECK_LE(target_delay.InMilliseconds(),
 244             std::numeric_limits<uint16_t>::max());
 245   writer_.WriteU16(target_delay.InMilliseconds());
 246
 247   size_t number_of_loss_fields = 0;
 248   size_t max_number_of_loss_fields = std::min<size_t>(
 249       kRtcpMaxCastLossFields, writer_.remaining() / 4);
 250
 251   MissingFramesAndPacketsMap::const_iterator frame_it =
 252       cast->missing_frames_and_packets.begin();
 253
 254   NackStringBuilder nack_string_builder;
 255   for (; frame_it != cast->missing_frames_and_packets.end() &&
 256              number_of_loss_fields < max_number_of_loss_fields;
 257        ++frame_it) {
 258     nack_string_builder.PushFrame(frame_it->first);
 259     // Iterate through all frames with missing packets.
 260     if (frame_it->second.empty()) {
 261       // Special case all packets in a frame is missing.
 262       writer_.WriteU8(static_cast<uint8>(frame_it->first));
 263       writer_.WriteU16(kRtcpCastAllPacketsLost);
 264       writer_.WriteU8(0);
 265       nack_string_builder.PushPacket(kRtcpCastAllPacketsLost);
 266       ++number_of_loss_fields;
 267     } else {
 268       PacketIdSet::const_iterator packet_it = frame_it->second.begin();
 269       while (packet_it != frame_it->second.end()) {
 270         uint16 packet_id = *packet_it;
 271         // Write frame and packet id to buffer before calculating bitmask.
 272         writer_.WriteU8(static_cast<uint8>(frame_it->first));
 273         writer_.WriteU16(packet_id);
 274         nack_string_builder.PushPacket(packet_id);
 275
 276         uint8 bitmask = 0;
 277         ++packet_it;
 278         while (packet_it != frame_it->second.end()) {
 279           int shift = static_cast<uint8>(*packet_it - packet_id) - 1;
 280           if (shift >= 0 && shift <= 7) {
 281             nack_string_builder.PushPacket(*packet_it);
 282             bitmask |= (1 << shift);
 283             ++packet_it;
 284           } else {
 285             break;
 286           }
 287         }
 288         writer_.WriteU8(bitmask);
 289         ++number_of_loss_fields;
 290       }
 291     }
 292   }
 293   VLOG_IF(1, !nack_string_builder.Empty())
 294       << "SSRC: " << cast->media_ssrc
 295       << ", ACK: " << cast->ack_frame_id
 296       << ", NACK: " << nack_string_builder.GetString();
 297   DCHECK_LE(number_of_loss_fields, kRtcpMaxCastLossFields);
 298   *cast_loss_field_pos = static_cast<uint8>(number_of_loss_fields);
 299 }
 300
 301 void RtcpBuilder::AddSR(const RtcpSenderInfo& sender_info) {
 302   AddRtcpHeader(kPacketTypeSenderReport, 0);
 303   writer_.WriteU32(ssrc_);
 304   writer_.WriteU32(sender_info.ntp_seconds);
 305   writer_.WriteU32(sender_info.ntp_fraction);
 306   writer_.WriteU32(sender_info.rtp_timestamp);
 307   writer_.WriteU32(sender_info.send_packet_count);
 308   writer_.WriteU32(static_cast<uint32>(sender_info.send_octet_count));
 309 }
 310
 311 /*
 312    0                   1                   2                   3
 313    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
 314   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 315   |V=2|P|reserved |   PT=XR=207   |             length            |
 316   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 317   |                              SSRC                             |
 318   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 319   |     BT=5      |   reserved    |         block length          |
 320   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 321   |                 SSRC1 (SSRC of first receiver)               | sub-
 322   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ block
 323   |                         last RR (LRR)                         |   1
 324   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 325   |                   delay since last RR (DLRR)                  |
 326   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 327 */
 328 void RtcpBuilder::AddDlrrRb(const RtcpDlrrReportBlock& dlrr) {
 329   AddRtcpHeader(kPacketTypeXr, 0);
 330   writer_.WriteU32(ssrc_);  // Add our own SSRC.
 331   writer_.WriteU8(5);  // Add block type.
 332   writer_.WriteU8(0);  // Add reserved.
 333   writer_.WriteU16(3);  // Block length.
 334   writer_.WriteU32(ssrc_);  // Add the media (received RTP) SSRC.
 335   writer_.WriteU32(dlrr.last_rr);
 336   writer_.WriteU32(dlrr.delay_since_last_rr);
 337 }
 338
 339 void RtcpBuilder::AddReceiverLog(
 340     const ReceiverRtcpEventSubscriber::RtcpEvents& rtcp_events) {
 341   size_t total_number_of_messages_to_send = 0;
 342   RtcpReceiverLogMessage receiver_log_message;
 343
 344   if (!GetRtcpReceiverLogMessage(rtcp_events,
 345                                  &receiver_log_message,
 346                                  &total_number_of_messages_to_send)) {
 347     return;
 348   }
 349
 350   AddRtcpHeader(kPacketTypeApplicationDefined, kReceiverLogSubtype);
 351   writer_.WriteU32(ssrc_);  // Add our own SSRC.
 352   writer_.WriteU32(kCast);
 353
 354   while (!receiver_log_message.empty() &&
 355          total_number_of_messages_to_send > 0) {
 356     RtcpReceiverFrameLogMessage& frame_log_messages(
 357         receiver_log_message.front());
 358
 359     // Add our frame header.
 360     writer_.WriteU32(frame_log_messages.rtp_timestamp_);
 361     size_t messages_in_frame = frame_log_messages.event_log_messages_.size();
 362     if (messages_in_frame > total_number_of_messages_to_send) {
 363       // We are running out of space.
 364       messages_in_frame = total_number_of_messages_to_send;
 365     }
 366     // Keep track of how many messages we have left to send.
 367     total_number_of_messages_to_send -= messages_in_frame;
 368
 369     // On the wire format is number of messages - 1.
 370     writer_.WriteU8(static_cast<uint8>(messages_in_frame - 1));
 371
 372     base::TimeTicks event_timestamp_base =
 373         frame_log_messages.event_log_messages_.front().event_timestamp;
 374     uint32 base_timestamp_ms =
 375         (event_timestamp_base - base::TimeTicks()).InMilliseconds();
 376     writer_.WriteU8(static_cast<uint8>(base_timestamp_ms >> 16));
 377     writer_.WriteU8(static_cast<uint8>(base_timestamp_ms >> 8));
 378     writer_.WriteU8(static_cast<uint8>(base_timestamp_ms));
 379
 380     while (!frame_log_messages.event_log_messages_.empty() &&
 381            messages_in_frame > 0) {
 382       const RtcpReceiverEventLogMessage& event_message =
 383           frame_log_messages.event_log_messages_.front();
 384       uint16 event_type_and_timestamp_delta =
 385           MergeEventTypeAndTimestampForWireFormat(
 386               event_message.type,
 387               event_message.event_timestamp - event_timestamp_base);
 388       switch (event_message.type) {
 389         case FRAME_ACK_SENT:
 390         case FRAME_PLAYOUT:
 391         case FRAME_DECODED:
 392           writer_.WriteU16(
 393               static_cast<uint16>(event_message.delay_delta.InMilliseconds()));
 394           writer_.WriteU16(event_type_and_timestamp_delta);
 395           break;
 396         case PACKET_RECEIVED:
 397           writer_.WriteU16(event_message.packet_id);
 398           writer_.WriteU16(event_type_and_timestamp_delta);
 399           break;
 400         default:
 401           NOTREACHED();
 402       }
 403       messages_in_frame--;
 404       frame_log_messages.event_log_messages_.pop_front();
 405     }
 406     if (frame_log_messages.event_log_messages_.empty()) {
 407       // We sent all messages on this frame; pop the frame header.
 408       receiver_log_message.pop_front();
 409     }
 410   }
 411   DCHECK_EQ(total_number_of_messages_to_send, 0u);
 412 }
 413
 414 bool RtcpBuilder::GetRtcpReceiverLogMessage(
 415     const ReceiverRtcpEventSubscriber::RtcpEvents& rtcp_events,
 416     RtcpReceiverLogMessage* receiver_log_message,
 417     size_t* total_number_of_messages_to_send) {
 418   size_t number_of_frames = 0;
 419   size_t remaining_space = writer_.remaining();
 420   if (remaining_space < kRtcpCastLogHeaderSize + kRtcpReceiverFrameLogSize +
 421                             kRtcpReceiverEventLogSize) {
 422     return false;
 423   }
 424
 425   // We use this to do event timestamp sorting and truncating for events of
 426   // a single frame.
 427   std::vector<RtcpReceiverEventLogMessage> sorted_log_messages;
 428
 429   // Account for the RTCP header for an application-defined packet.
 430   remaining_space -= kRtcpCastLogHeaderSize;
 431
 432   ReceiverRtcpEventSubscriber::RtcpEvents::const_reverse_iterator rit =
 433       rtcp_events.rbegin();
 434
 435   while (rit != rtcp_events.rend() &&
 436          remaining_space >=
 437              kRtcpReceiverFrameLogSize + kRtcpReceiverEventLogSize) {
 438     const RtpTimestamp rtp_timestamp = rit->first;
 439     RtcpReceiverFrameLogMessage frame_log(rtp_timestamp);
 440     remaining_space -= kRtcpReceiverFrameLogSize;
 441     ++number_of_frames;
 442
 443     // Get all events of a single frame.
 444     sorted_log_messages.clear();
 445     do {
 446       RtcpReceiverEventLogMessage event_log_message;
 447       event_log_message.type = rit->second.type;
 448       event_log_message.event_timestamp = rit->second.timestamp;
 449       event_log_message.delay_delta = rit->second.delay_delta;
 450       event_log_message.packet_id = rit->second.packet_id;
 451       sorted_log_messages.push_back(event_log_message);
 452       ++rit;
 453     } while (rit != rtcp_events.rend() && rit->first == rtp_timestamp);
 454
 455     std::sort(sorted_log_messages.begin(),
 456               sorted_log_messages.end(),
 457               &EventTimestampLessThan);
 458
 459     // From |sorted_log_messages|, only take events that are no greater than
 460     // |kMaxWireFormatTimeDeltaMs| seconds away from the latest event. Events
 461     // older than that cannot be encoded over the wire.
 462     std::vector<RtcpReceiverEventLogMessage>::reverse_iterator sorted_rit =
 463         sorted_log_messages.rbegin();
 464     base::TimeTicks first_event_timestamp = sorted_rit->event_timestamp;
 465     size_t events_in_frame = 0;
 466     while (sorted_rit != sorted_log_messages.rend() &&
 467            events_in_frame < kRtcpMaxReceiverLogMessages &&
 468            remaining_space >= kRtcpReceiverEventLogSize) {
 469       base::TimeDelta delta(first_event_timestamp -
 470                             sorted_rit->event_timestamp);
 471       if (delta.InMilliseconds() > kMaxWireFormatTimeDeltaMs)
 472         break;
 473       frame_log.event_log_messages_.push_front(*sorted_rit);
 474       ++events_in_frame;
 475       ++*total_number_of_messages_to_send;
 476       remaining_space -= kRtcpReceiverEventLogSize;
 477       ++sorted_rit;
 478     }
 479
 480     receiver_log_message->push_front(frame_log);
 481   }
 482
 483   VLOG(3) << "number of frames: " << number_of_frames;
 484   VLOG(3) << "total messages to send: " << *total_number_of_messages_to_send;
 485   return number_of_frames > 0;
 486 }
 487
 488 }  // namespace cast
 489 }  // namespace media