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      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
    117