src/third_party/libjingle/source/talk/base/bandwidthsmoother.cc

   1 /*
   2  * libjingle
   3  * Copyright 2011, Google Inc.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are met:
   7  *
   8  *  1. Redistributions of source code must retain the above copyright notice,
   9  *     this list of conditions and the following disclaimer.
  10  *  2. Redistributions in binary form must reproduce the above copyright notice,
  11  *     this list of conditions and the following disclaimer in the documentation
  12  *     and/or other materials provided with the distribution.
  13  *  3. The name of the author may not be used to endorse or promote products
  14  *     derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
  19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #include "talk/base/bandwidthsmoother.h"
  29
  30 #include <limits.h>
  31
  32 namespace talk_base {
  33
  34 BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess,
  35                                      uint32 time_between_increase,
  36                                      double percent_increase,
  37                                      size_t samples_count_to_average,
  38                                      double min_sample_count_percent)
  39     : time_between_increase_(time_between_increase),
  40       percent_increase_(talk_base::_max(1.0, percent_increase)),
  41       time_at_last_change_(0),
  42       bandwidth_estimation_(initial_bandwidth_guess),
  43       accumulator_(samples_count_to_average),
  44       min_sample_count_percent_(
  45           talk_base::_min(1.0,
  46                           talk_base::_max(0.0, min_sample_count_percent))) {
  47 }
  48
  49 // Samples a new bandwidth measurement
  50 // returns true if the bandwidth estimation changed
  51 bool BandwidthSmoother::Sample(uint32 sample_time, int bandwidth) {
  52   if (bandwidth < 0) {
  53     return false;
  54   }
  55
  56   accumulator_.AddSample(bandwidth);
  57
  58   if (accumulator_.count() < static_cast<size_t>(
  59           accumulator_.max_count() * min_sample_count_percent_)) {
  60     // We have not collected enough samples yet.
  61     return false;
  62   }
  63
  64   // Replace bandwidth with the mean of sampled bandwidths.
  65   const int mean_bandwidth = accumulator_.ComputeMean();
  66
  67   if (mean_bandwidth < bandwidth_estimation_) {
  68     time_at_last_change_ = sample_time;
  69     bandwidth_estimation_ = mean_bandwidth;
  70     return true;
  71   }
  72
  73   const int old_bandwidth_estimation = bandwidth_estimation_;
  74   const double increase_threshold_d = percent_increase_ * bandwidth_estimation_;
  75   if (increase_threshold_d > INT_MAX) {
  76     // If bandwidth goes any higher we would overflow.
  77     return false;
  78   }
  79
  80   const int increase_threshold = static_cast<int>(increase_threshold_d);
  81   if (mean_bandwidth < increase_threshold) {
  82     time_at_last_change_ = sample_time;
  83     // The value of bandwidth_estimation remains the same if we don't exceed
  84     // percent_increase_ * bandwidth_estimation_ for at least
  85     // time_between_increase_ time.
  86   } else if (sample_time >= time_at_last_change_ + time_between_increase_) {
  87     time_at_last_change_ = sample_time;
  88     if (increase_threshold == 0) {
  89       // Bandwidth_estimation_ must be zero. Assume a jump from zero to a
  90       // positive bandwidth means we have regained connectivity.
  91       bandwidth_estimation_ = mean_bandwidth;
  92     } else {
  93       bandwidth_estimation_ = increase_threshold;
  94     }
  95   }
  96   // Else don't make a change.
  97
  98   return old_bandwidth_estimation != bandwidth_estimation_;
  99 }
 100
 101 }  // namespace talk_base