cast/rtcp/rtcp.cc

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/cast/rtcp/rtcp.h"

#include "base/big_endian.h"
#include "base/rand_util.h"
#include "media/cast/cast_config.h"
#include "media/cast/cast_defines.h"
#include "media/cast/cast_environment.h"
#include "media/cast/rtcp/rtcp_defines.h"
#include "media/cast/rtcp/rtcp_receiver.h"
#include "media/cast/rtcp/rtcp_sender.h"
#include "media/cast/rtcp/rtcp_utility.h"
#include "media/cast/transport/cast_transport_defines.h"

namespace media {
namespace cast {

static const int kMaxRttMs = 10000;  // 10 seconds.
static const int kMaxDelay = 2000;

class LocalRtcpRttFeedback : public RtcpRttFeedback {
 public:
  explicit LocalRtcpRttFeedback(Rtcp* rtcp) : rtcp_(rtcp) {}

  virtual void OnReceivedDelaySinceLastReport(
      uint32 receivers_ssrc, uint32 last_report,
      uint32 delay_since_last_report) OVERRIDE {
    rtcp_->OnReceivedDelaySinceLastReport(receivers_ssrc, last_report,
                                          delay_since_last_report);
  }

 private:
  Rtcp* rtcp_;
};

class LocalRtcpReceiverFeedback : public RtcpReceiverFeedback {
 public:
  LocalRtcpReceiverFeedback(Rtcp* rtcp,
                            scoped_refptr<CastEnvironment> cast_environment)
      : rtcp_(rtcp), cast_environment_(cast_environment) {}

  virtual void OnReceivedSenderReport(
      const transport::RtcpSenderInfo& remote_sender_info) OVERRIDE {
    rtcp_->OnReceivedNtp(remote_sender_info.ntp_seconds,
                         remote_sender_info.ntp_fraction);
    if (remote_sender_info.send_packet_count != 0) {
      rtcp_->OnReceivedLipSyncInfo(remote_sender_info.rtp_timestamp,
                                   remote_sender_info.ntp_seconds,
                                   remote_sender_info.ntp_fraction);
    }
  }

  virtual void OnReceiverReferenceTimeReport(
      const RtcpReceiverReferenceTimeReport& remote_time_report) OVERRIDE {
    rtcp_->OnReceivedNtp(remote_time_report.ntp_seconds,
                         remote_time_report.ntp_fraction);
  }

  virtual void OnReceivedSendReportRequest() OVERRIDE {
    rtcp_->OnReceivedSendReportRequest();
  }

  virtual void OnReceivedReceiverLog(const RtcpReceiverLogMessage& receiver_log)
      OVERRIDE {
    rtcp_->OnReceivedReceiverLog(receiver_log);
  }

 private:
  Rtcp* rtcp_;
  scoped_refptr<CastEnvironment> cast_environment_;
};

Rtcp::Rtcp(scoped_refptr<CastEnvironment> cast_environment,
           RtcpSenderFeedback* sender_feedback,
           transport::CastTransportSender* const transport_sender,
           transport::PacedPacketSender* paced_packet_sender,
           RtpReceiverStatistics* rtp_receiver_statistics, RtcpMode rtcp_mode,
           const base::TimeDelta& rtcp_interval, uint32 local_ssrc,
           uint32 remote_ssrc, const std::string& c_name,
           EventMediaType event_media_type)
    : cast_environment_(cast_environment),
      transport_sender_(transport_sender),
      rtcp_interval_(rtcp_interval),
      rtcp_mode_(rtcp_mode),
      local_ssrc_(local_ssrc),
      remote_ssrc_(remote_ssrc),
      c_name_(c_name),
      event_media_type_(event_media_type),
      rtp_receiver_statistics_(rtp_receiver_statistics),
      rtt_feedback_(new LocalRtcpRttFeedback(this)),
      receiver_feedback_(new LocalRtcpReceiverFeedback(this, cast_environment)),
      rtcp_sender_(new RtcpSender(cast_environment, paced_packet_sender,
                                  local_ssrc, c_name)),
      last_report_truncated_ntp_(0),
      local_clock_ahead_by_(ClockDriftSmoother::GetDefaultTimeConstant()),
      lip_sync_rtp_timestamp_(0),
      lip_sync_ntp_timestamp_(0),
      min_rtt_(base::TimeDelta::FromMilliseconds(kMaxRttMs)),
      number_of_rtt_in_avg_(0) {
  rtcp_receiver_.reset(new RtcpReceiver(cast_environment, sender_feedback,
                                        receiver_feedback_.get(),
                                        rtt_feedback_.get(), local_ssrc));
  rtcp_receiver_->SetRemoteSSRC(remote_ssrc);
}

Rtcp::~Rtcp() {}

// static
bool Rtcp::IsRtcpPacket(const uint8* packet, size_t length) {
  DCHECK_GE(length, kMinLengthOfRtcp) << "Invalid RTCP packet";
  if (length < kMinLengthOfRtcp) return false;

  uint8 packet_type = packet[1];
  if (packet_type >= transport::kPacketTypeLow &&
      packet_type <= transport::kPacketTypeHigh) {
    return true;
  }
  return false;
}

// static
uint32 Rtcp::GetSsrcOfSender(const uint8* rtcp_buffer, size_t length) {
  DCHECK_GE(length, kMinLengthOfRtcp) << "Invalid RTCP packet";
  uint32 ssrc_of_sender;
  base::BigEndianReader big_endian_reader(
      reinterpret_cast<const char*>(rtcp_buffer), length);
  big_endian_reader.Skip(4);  // Skip header
  big_endian_reader.ReadU32(&ssrc_of_sender);
  return ssrc_of_sender;
}

base::TimeTicks Rtcp::TimeToSendNextRtcpReport() {
  if (next_time_to_send_rtcp_.is_null()) {
    UpdateNextTimeToSendRtcp();
  }
  return next_time_to_send_rtcp_;
}

void Rtcp::IncomingRtcpPacket(const uint8* rtcp_buffer, size_t length) {
  RtcpParser rtcp_parser(rtcp_buffer, length);
  if (!rtcp_parser.IsValid()) {
    // Silently ignore packet.
    DLOG(ERROR) << "Received invalid RTCP packet";
    return;
  }
  rtcp_receiver_->IncomingRtcpPacket(&rtcp_parser);
}

void Rtcp::SendRtcpFromRtpReceiver(
    const RtcpCastMessage* cast_message,
    const ReceiverRtcpEventSubscriber::RtcpEventMultiMap* rtcp_events) {
  DCHECK(cast_environment_->CurrentlyOn(CastEnvironment::MAIN));
  uint32 packet_type_flags = 0;

  base::TimeTicks now = cast_environment_->Clock()->NowTicks();
  transport::RtcpReportBlock report_block;
  RtcpReceiverReferenceTimeReport rrtr;

  // Attach our NTP to all RTCP packets; with this information a "smart" sender
  // can make decisions based on how old the RTCP message is.
  packet_type_flags |= transport::kRtcpRrtr;
  ConvertTimeTicksToNtp(now, &rrtr.ntp_seconds, &rrtr.ntp_fraction);
  SaveLastSentNtpTime(now, rrtr.ntp_seconds, rrtr.ntp_fraction);

  if (cast_message) {
    packet_type_flags |= transport::kRtcpCast;
  }
  if (rtcp_events) {
    packet_type_flags |= transport::kRtcpReceiverLog;
  }
  if (rtcp_mode_ == kRtcpCompound || now >= next_time_to_send_rtcp_) {
    packet_type_flags |= transport::kRtcpRr;

    report_block.remote_ssrc = 0;            // Not needed to set send side.
    report_block.media_ssrc = remote_ssrc_;  // SSRC of the RTP packet sender.
    if (rtp_receiver_statistics_) {
      rtp_receiver_statistics_->GetStatistics(
          &report_block.fraction_lost, &report_block.cumulative_lost,
          &report_block.extended_high_sequence_number, &report_block.jitter);
    }

    report_block.last_sr = last_report_truncated_ntp_;
    if (!time_last_report_received_.is_null()) {
      uint32 delay_seconds = 0;
      uint32 delay_fraction = 0;
      base::TimeDelta delta = now - time_last_report_received_;
      ConvertTimeToFractions(delta.InMicroseconds(), &delay_seconds,
                             &delay_fraction);
      report_block.delay_since_last_sr =
          ConvertToNtpDiff(delay_seconds, delay_fraction);
    } else {
      report_block.delay_since_last_sr = 0;
    }
    UpdateNextTimeToSendRtcp();
  }
  rtcp_sender_->SendRtcpFromRtpReceiver(packet_type_flags,
                                        &report_block,
                                        &rrtr,
                                        cast_message,
                                        rtcp_events,
                                        target_delay_ms_);
}

void Rtcp::SendRtcpFromRtpSender(base::TimeTicks current_time,
                                 uint32 current_time_as_rtp_timestamp) {
  DCHECK(transport_sender_);
  uint32 packet_type_flags = transport::kRtcpSr;
  uint32 current_ntp_seconds = 0;
  uint32 current_ntp_fractions = 0;
  ConvertTimeTicksToNtp(current_time, &current_ntp_seconds,
                        &current_ntp_fractions);
  SaveLastSentNtpTime(current_time, current_ntp_seconds,
                      current_ntp_fractions);

  transport::RtcpDlrrReportBlock dlrr;
  if (!time_last_report_received_.is_null()) {
    packet_type_flags |= transport::kRtcpDlrr;
    dlrr.last_rr = last_report_truncated_ntp_;
    uint32 delay_seconds = 0;
    uint32 delay_fraction = 0;
    base::TimeDelta delta = current_time - time_last_report_received_;
    ConvertTimeToFractions(delta.InMicroseconds(), &delay_seconds,
                           &delay_fraction);

    dlrr.delay_since_last_rr = ConvertToNtpDiff(delay_seconds, delay_fraction);
  }

  transport_sender_->SendRtcpFromRtpSender(
      packet_type_flags, current_ntp_seconds, current_ntp_fractions,
      current_time_as_rtp_timestamp, dlrr, local_ssrc_, c_name_);
  UpdateNextTimeToSendRtcp();
}

void Rtcp::OnReceivedNtp(uint32 ntp_seconds, uint32 ntp_fraction) {
  last_report_truncated_ntp_ = ConvertToNtpDiff(ntp_seconds, ntp_fraction);

  const base::TimeTicks now = cast_environment_->Clock()->NowTicks();
  time_last_report_received_ = now;

  // TODO(miu): This clock offset calculation does not account for packet
  // transit time over the network.  End2EndTest.EvilNetwork confirms that this
  // contributes a very significant source of error here.  Fix this along with
  // the RTT clean-up.
  const base::TimeDelta measured_offset =
      now - ConvertNtpToTimeTicks(ntp_seconds, ntp_fraction);
  local_clock_ahead_by_.Update(now, measured_offset);
  if (measured_offset < local_clock_ahead_by_.Current()) {
    // Logically, the minimum offset between the clocks has to be the correct
    // one.  For example, the time it took to transmit the current report may
    // have been lower than usual, and so some of the error introduced by the
    // transmission time can be eliminated.
    local_clock_ahead_by_.Reset(now, measured_offset);
  }
  VLOG(1) << "Local clock is ahead of the remote clock by: "
          << "measured=" << measured_offset.InMicroseconds() << " usec, "
          << "filtered=" << local_clock_ahead_by_.Current().InMicroseconds()
          << " usec.";
}

void Rtcp::OnReceivedLipSyncInfo(uint32 rtp_timestamp, uint32 ntp_seconds,
                                 uint32 ntp_fraction) {
  if (ntp_seconds == 0) {
    NOTREACHED();
    return;
  }
  lip_sync_rtp_timestamp_ = rtp_timestamp;
  lip_sync_ntp_timestamp_ =
      (static_cast<uint64>(ntp_seconds) << 32) | ntp_fraction;
}

bool Rtcp::GetLatestLipSyncTimes(uint32* rtp_timestamp,
                                 base::TimeTicks* reference_time) const {
  if (!lip_sync_ntp_timestamp_)
    return false;

  const base::TimeTicks local_reference_time =
      ConvertNtpToTimeTicks(static_cast<uint32>(lip_sync_ntp_timestamp_ >> 32),
                            static_cast<uint32>(lip_sync_ntp_timestamp_)) +
      local_clock_ahead_by_.Current();

  // Sanity-check: Getting regular lip sync updates?
  DCHECK((cast_environment_->Clock()->NowTicks() - local_reference_time) <
             base::TimeDelta::FromMinutes(1));

  *rtp_timestamp = lip_sync_rtp_timestamp_;
  *reference_time = local_reference_time;
  return true;
}

void Rtcp::OnReceivedSendReportRequest() {
  base::TimeTicks now = cast_environment_->Clock()->NowTicks();

  // Trigger a new RTCP report at next timer.
  next_time_to_send_rtcp_ = now;
}

void Rtcp::SetCastReceiverEventHistorySize(size_t size) {
  rtcp_receiver_->SetCastReceiverEventHistorySize(size);
}

void Rtcp::SetTargetDelay(base::TimeDelta target_delay) {
  DCHECK(target_delay.InMilliseconds() < kMaxDelay);
  target_delay_ms_ = static_cast<uint16>(target_delay.InMilliseconds());
}

void Rtcp::OnReceivedDelaySinceLastReport(uint32 receivers_ssrc,
                                          uint32 last_report,
                                          uint32 delay_since_last_report) {
  RtcpSendTimeMap::iterator it = last_reports_sent_map_.find(last_report);
  if (it == last_reports_sent_map_.end()) {
    return;  // Feedback on another report.
  }

  base::TimeDelta sender_delay =
      cast_environment_->Clock()->NowTicks() - it->second;
  UpdateRtt(sender_delay, ConvertFromNtpDiff(delay_since_last_report));
}

void Rtcp::SaveLastSentNtpTime(const base::TimeTicks& now,
                               uint32 last_ntp_seconds,
                               uint32 last_ntp_fraction) {
  // Make sure |now| is always greater than the last element in
  // |last_reports_sent_queue_|.
  if (!last_reports_sent_queue_.empty())
    DCHECK(now >= last_reports_sent_queue_.back().second);

  uint32 last_report = ConvertToNtpDiff(last_ntp_seconds, last_ntp_fraction);
  last_reports_sent_map_[last_report] = now;
  last_reports_sent_queue_.push(std::make_pair(last_report, now));

  base::TimeTicks timeout = now - base::TimeDelta::FromMilliseconds(kMaxRttMs);

  // Cleanup old statistics older than |timeout|.
  while (!last_reports_sent_queue_.empty()) {
    RtcpSendTimePair oldest_report = last_reports_sent_queue_.front();
    if (oldest_report.second < timeout) {
      last_reports_sent_map_.erase(oldest_report.first);
      last_reports_sent_queue_.pop();
    } else {
      break;
    }
  }
}

void Rtcp::UpdateRtt(const base::TimeDelta& sender_delay,
                     const base::TimeDelta& receiver_delay) {
  base::TimeDelta rtt = sender_delay - receiver_delay;
  // TODO(miu): Find out why this must be >= 1 ms, and remove the fudge if it's
  // bogus.
  rtt = std::max(rtt, base::TimeDelta::FromMilliseconds(1));
  rtt_ = rtt;
  min_rtt_ = std::min(min_rtt_, rtt);
  max_rtt_ = std::max(max_rtt_, rtt);

  // TODO(miu): Replace "average for all time" with an EWMA, or suitable
  // "average over recent past" mechanism.
  if (number_of_rtt_in_avg_ != 0) {
    const double ac = static_cast<double>(number_of_rtt_in_avg_);
    avg_rtt_ms_ = ((ac / (ac + 1.0)) * avg_rtt_ms_) +
                  ((1.0 / (ac + 1.0)) * rtt.InMillisecondsF());
  } else {
    avg_rtt_ms_ = rtt.InMillisecondsF();
  }
  number_of_rtt_in_avg_++;
}

bool Rtcp::Rtt(base::TimeDelta* rtt, base::TimeDelta* avg_rtt,
               base::TimeDelta* min_rtt, base::TimeDelta* max_rtt) const {
  DCHECK(rtt) << "Invalid argument";
  DCHECK(avg_rtt) << "Invalid argument";
  DCHECK(min_rtt) << "Invalid argument";
  DCHECK(max_rtt) << "Invalid argument";

  if (number_of_rtt_in_avg_ == 0) return false;

  *rtt = rtt_;
  *avg_rtt = base::TimeDelta::FromMillisecondsD(avg_rtt_ms_);
  *min_rtt = min_rtt_;
  *max_rtt = max_rtt_;
  return true;
}

void Rtcp::UpdateNextTimeToSendRtcp() {
  int random = base::RandInt(0, 999);
  base::TimeDelta time_to_next =
      (rtcp_interval_ / 2) + (rtcp_interval_ * random / 1000);

  base::TimeTicks now = cast_environment_->Clock()->NowTicks();
  next_time_to_send_rtcp_ = now + time_to_next;
}

void Rtcp::OnReceivedReceiverLog(const RtcpReceiverLogMessage& receiver_log) {
  // Add received log messages into our log system.
  RtcpReceiverLogMessage::const_iterator it = receiver_log.begin();
  for (; it != receiver_log.end(); ++it) {
    uint32 rtp_timestamp = it->rtp_timestamp_;

    RtcpReceiverEventLogMessages::const_iterator event_it =
        it->event_log_messages_.begin();
    for (; event_it != it->event_log_messages_.end(); ++event_it) {
      switch (event_it->type) {
        case PACKET_RECEIVED:
          cast_environment_->Logging()->InsertPacketEvent(
              event_it->event_timestamp, event_it->type,
              event_media_type_, rtp_timestamp,
              kFrameIdUnknown, event_it->packet_id, 0, 0);
          break;
        case FRAME_ACK_SENT:
        case FRAME_DECODED:
          cast_environment_->Logging()->InsertFrameEvent(
              event_it->event_timestamp, event_it->type, event_media_type_,
              rtp_timestamp, kFrameIdUnknown);
          break;
        case FRAME_PLAYOUT:
          cast_environment_->Logging()->InsertFrameEventWithDelay(
              event_it->event_timestamp, event_it->type, event_media_type_,
              rtp_timestamp, kFrameIdUnknown, event_it->delay_delta);
          break;
        default:
          VLOG(2) << "Received log message via RTCP that we did not expect: "
                  << static_cast<int>(event_it->type);
          break;
      }
    }
  }
}

}  // namespace cast
}  // namespace media