src/media/cast/rtp_receiver/receiver_stats.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/rtp_receiver/receiver_stats.h"
   6
   7 #include "base/logging.h"
   8 #include "media/cast/rtp_receiver/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 ReceiverStats::~ReceiverStats() {}
  26
  27 void ReceiverStats::GetStatistics(uint8* fraction_lost,
  28                                   uint32* cumulative_lost,
  29                                   uint32* extended_high_sequence_number,
  30                                   uint32* jitter) {
  31   // Compute losses.
  32   if (interval_number_packets_ == 0) {
  33     *fraction_lost = 0;
  34   } else {
  35     int diff = 0;
  36     if (interval_wrap_count_ == 0) {
  37       diff = max_sequence_number_ - interval_min_sequence_number_ + 1;
  38     } else {
  39       diff = kMaxSequenceNumber * (interval_wrap_count_ - 1) +
  40         (max_sequence_number_ - interval_min_sequence_number_ +
  41             kMaxSequenceNumber + 1);
  42     }
  43
  44     if (diff < 1) {
  45       *fraction_lost = 0;
  46     } else {
  47       *fraction_lost =  static_cast<uint8>((256 * (1 -
  48           static_cast<float>(interval_number_packets_) / abs(diff))));
  49     }
  50   }
  51
  52   int expected_packets_num = max_sequence_number_ - min_sequence_number_ + 1;
  53   if (total_number_packets_ == 0) {
  54     *cumulative_lost = 0;
  55   } else if (sequence_number_cycles_ == 0) {
  56     *cumulative_lost = expected_packets_num - total_number_packets_;
  57   } else {
  58     *cumulative_lost = kMaxSequenceNumber * (sequence_number_cycles_ - 1) +
  59         (expected_packets_num - total_number_packets_ + kMaxSequenceNumber);
  60   }
  61
  62   // Extended high sequence number consists of the highest seq number and the
  63   // number of cycles (wrap).
  64   *extended_high_sequence_number = (sequence_number_cycles_ << 16) +
  65       max_sequence_number_;
  66
  67   *jitter = static_cast<uint32>(abs(jitter_.InMillisecondsRoundedUp()));
  68
  69   // Reset interval values.
  70   interval_min_sequence_number_ = 0;
  71   interval_number_packets_ = 0;
  72   interval_wrap_count_ = 0;
  73 }
  74
  75 void ReceiverStats::UpdateStatistics(const RtpCastHeader& header) {
  76   uint16 new_seq_num = header.webrtc.header.sequenceNumber;
  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.webrtc.header.timestamp);
 101   if (total_number_packets_ > 0) {
 102     // Update jitter.
 103     base::TimeDelta delta = (now - last_received_packet_time_) -
 104         ((delta_new_timestamp - last_received_timestamp_) / 90);
 105     jitter_ += (delta - jitter_) / 16;
 106   }
 107   last_received_timestamp_ = delta_new_timestamp;
 108   last_received_packet_time_ = now;
 109
 110   // Increment counters.
 111   ++total_number_packets_;
 112   ++interval_number_packets_;
 113 }
 114
 115 }  // namespace cast
 116 }  // namespace media