media/cast/net/rtp/receiver_stats.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/rtp/receiver_stats.h"
   6
   7 #include "base/logging.h"
   8 #include "media/cast/net/rtp/rtp_receiver_defines.h"
   9
  10 namespace media {
  11 namespace cast {
  12
  13 static const uint32 kMaxSequenceNumber = 65536;
  14
  15 ReceiverStats::ReceiverStats(base::TickClock* clock)
  16     : clock_(clock),
  17       min_sequence_number_(0),
  18       max_sequence_number_(0),
  19       total_number_packets_(0),
  20       sequence_number_cycles_(0),
  21       interval_min_sequence_number_(0),
  22       interval_number_packets_(0),
  23       interval_wrap_count_(0) {}
  24
  25 RtpReceiverStatistics ReceiverStats::GetStatistics() {
  26   RtpReceiverStatistics ret;
  27   // Compute losses.
  28   if (interval_number_packets_ == 0) {
  29     ret.fraction_lost = 0;
  30   } else {
  31     int diff = 0;
  32     if (interval_wrap_count_ == 0) {
  33       diff = max_sequence_number_ - interval_min_sequence_number_ + 1;
  34     } else {
  35       diff = kMaxSequenceNumber * (interval_wrap_count_ - 1) +
  36              (max_sequence_number_ - interval_min_sequence_number_ +
  37               kMaxSequenceNumber + 1);
  38     }
  39
  40     if (diff < 1) {
  41       ret.fraction_lost = 0;
  42     } else {
  43       float tmp_ratio =
  44           (1 - static_cast<float>(interval_number_packets_) / abs(diff));
  45       ret.fraction_lost = static_cast<uint8>(256 * tmp_ratio);
  46     }
  47   }
  48
  49   int expected_packets_num = max_sequence_number_ - min_sequence_number_ + 1;
  50   if (total_number_packets_ == 0) {
  51     ret.cumulative_lost = 0;
  52   } else if (sequence_number_cycles_ == 0) {
  53     ret.cumulative_lost = expected_packets_num - total_number_packets_;
  54   } else {
  55     ret.cumulative_lost =
  56         kMaxSequenceNumber * (sequence_number_cycles_ - 1) +
  57         (expected_packets_num - total_number_packets_ + kMaxSequenceNumber);
  58   }
  59
  60   // Extended high sequence number consists of the highest seq number and the
  61   // number of cycles (wrap).
  62   ret.extended_high_sequence_number =
  63       (sequence_number_cycles_ << 16) + max_sequence_number_;
  64
  65   ret.jitter = static_cast<uint32>(std::abs(jitter_.InMillisecondsRoundedUp()));
  66
  67   // Reset interval values.
  68   interval_min_sequence_number_ = 0;
  69   interval_number_packets_ = 0;
  70   interval_wrap_count_ = 0;
  71
  72   return ret;
  73 }
  74
  75 void ReceiverStats::UpdateStatistics(const RtpCastHeader& header) {
  76   const uint16 new_seq_num = header.sequence_number;
  77
  78   if (interval_number_packets_ == 0) {
  79     // First packet in the interval.
  80     interval_min_sequence_number_ = new_seq_num;
  81   }
  82   if (total_number_packets_ == 0) {
  83     // First incoming packet.
  84     min_sequence_number_ = new_seq_num;
  85     max_sequence_number_ = new_seq_num;
  86   }
  87
  88   if (IsNewerSequenceNumber(new_seq_num, max_sequence_number_)) {
  89     // Check wrap.
  90     if (new_seq_num < max_sequence_number_) {
  91       ++sequence_number_cycles_;
  92       ++interval_wrap_count_;
  93     }
  94     max_sequence_number_ = new_seq_num;
  95   }
  96
  97   // Compute Jitter.
  98   base::TimeTicks now = clock_->NowTicks();
  99   base::TimeDelta delta_new_timestamp =
 100       base::TimeDelta::FromMilliseconds(header.rtp_timestamp);
 101   if (total_number_packets_ > 0) {
 102     // Update jitter.
 103     base::TimeDelta delta =
 104         (now - last_received_packet_time_) -
 105         ((delta_new_timestamp - last_received_timestamp_) / 90);
 106     jitter_ += (delta - jitter_) / 16;
 107   }
 108   last_received_timestamp_ = delta_new_timestamp;
 109   last_received_packet_time_ = now;
 110
 111   // Increment counters.
 112   ++total_number_packets_;
 113   ++interval_number_packets_;
 114 }
 115
 116 }  // namespace cast
 117 }  // namespace media