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       float tmp_ratio =
  48           (1 - static_cast<float>(interval_number_packets_) / abs(diff));
  49       *fraction_lost = static_cast<uint8>(256 * tmp_ratio);
  50     }
  51   }
  52
  53   int expected_packets_num = max_sequence_number_ - min_sequence_number_ + 1;
  54   if (total_number_packets_ == 0) {
  55     *cumulative_lost = 0;
  56   } else if (sequence_number_cycles_ == 0) {
  57     *cumulative_lost = expected_packets_num - total_number_packets_;
  58   } else {
  59     *cumulative_lost =
  60         kMaxSequenceNumber * (sequence_number_cycles_ - 1) +
  61         (expected_packets_num - total_number_packets_ + kMaxSequenceNumber);
  62   }
  63
  64   // Extended high sequence number consists of the highest seq number and the
  65   // number of cycles (wrap).
  66   *extended_high_sequence_number =
  67       (sequence_number_cycles_ << 16) + max_sequence_number_;
  68
  69   *jitter = static_cast<uint32>(std::abs(jitter_.InMillisecondsRoundedUp()));
  70
  71   // Reset interval values.
  72   interval_min_sequence_number_ = 0;
  73   interval_number_packets_ = 0;
  74   interval_wrap_count_ = 0;
  75 }
  76
  77 void ReceiverStats::UpdateStatistics(const RtpCastHeader& header) {
  78   const uint16 new_seq_num = header.sequence_number;
  79
  80   if (interval_number_packets_ == 0) {
  81     // First packet in the interval.
  82     interval_min_sequence_number_ = new_seq_num;
  83   }
  84   if (total_number_packets_ == 0) {
  85     // First incoming packet.
  86     min_sequence_number_ = new_seq_num;
  87     max_sequence_number_ = new_seq_num;
  88   }
  89
  90   if (IsNewerSequenceNumber(new_seq_num, max_sequence_number_)) {
  91     // Check wrap.
  92     if (new_seq_num < max_sequence_number_) {
  93       ++sequence_number_cycles_;
  94       ++interval_wrap_count_;
  95     }
  96     max_sequence_number_ = new_seq_num;
  97   }
  98
  99   // Compute Jitter.
 100   base::TimeTicks now = clock_->NowTicks();
 101   base::TimeDelta delta_new_timestamp =
 102       base::TimeDelta::FromMilliseconds(header.rtp_timestamp);
 103   if (total_number_packets_ > 0) {
 104     // Update jitter.
 105     base::TimeDelta delta =
 106         (now - last_received_packet_time_) -
 107         ((delta_new_timestamp - last_received_timestamp_) / 90);
 108     jitter_ += (delta - jitter_) / 16;
 109   }
 110   last_received_timestamp_ = delta_new_timestamp;
 111   last_received_packet_time_ = now;
 112
 113   // Increment counters.
 114   ++total_number_packets_;
 115   ++interval_number_packets_;
 116 }
 117
 118 }  // namespace cast
 119 }  // namespace media