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<div class="title">bandwidth_estimator.cc</div> </div>
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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">// Copyright 2014 Google Inc. All rights reserved.</span></div>
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<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">//</span></div>
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<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">// Use of this source code is governed by a BSD-style</span></div>
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<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment">// license that can be found in the LICENSE file or at</span></div>
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<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment">// https://developers.google.com/open-source/licenses/bsd</span></div>
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<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> </div>
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<div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="preprocessor">#include "packager/mpd/base/bandwidth_estimator.h"</span></div>
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<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> </div>
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<div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="preprocessor">#include <cmath></span></div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="preprocessor">#include <cstdlib></span></div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> </div>
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<div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="preprocessor">#include "packager/base/logging.h"</span></div>
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<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> </div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="keyword">const</span> <span class="keywordtype">int</span> BandwidthEstimator::kUseAllBlocks = 0;</div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> </div>
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<div class="line"><a name="l00016"></a><span class="lineno"><a class="line" href="../../d2/d6f/classBandwidthEstimator.html#aaae9573785ee9d62e0927f806537ea97"> 16</a></span> <a class="code" href="../../d2/d6f/classBandwidthEstimator.html#aaae9573785ee9d62e0927f806537ea97">BandwidthEstimator::BandwidthEstimator</a>(<span class="keywordtype">int</span> num_blocks)</div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>  : num_blocks_for_estimation_(num_blocks),</div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>  harmonic_mean_denominator_(0.0),</div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</span>  num_blocks_added_(0) {}</div>
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<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> BandwidthEstimator::~BandwidthEstimator() {}</div>
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<div class="line"><a name="l00021"></a><span class="lineno"> 21</span> </div>
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<div class="line"><a name="l00022"></a><span class="lineno"> 22</span> <span class="keywordtype">void</span> BandwidthEstimator::AddBlock(uint64_t size, <span class="keywordtype">double</span> duration) {</div>
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<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  DCHECK_GT(duration, 0.0);</div>
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<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>  DCHECK_GT(size, 0u);</div>
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<div class="line"><a name="l00025"></a><span class="lineno"> 25</span> </div>
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<div class="line"><a name="l00026"></a><span class="lineno"> 26</span>  <span class="keywordflow">if</span> (num_blocks_for_estimation_ < 0 &&</div>
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<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>  static_cast<int>(history_.size()) >= -1 * num_blocks_for_estimation_) {</div>
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<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>  <span class="comment">// Short circuiting the case where |num_blocks_for_estimation_| number of</span></div>
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<div class="line"><a name="l00029"></a><span class="lineno"> 29</span>  <span class="comment">// blocks have been added already.</span></div>
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<div class="line"><a name="l00030"></a><span class="lineno"> 30</span>  <span class="keywordflow">return</span>;</div>
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<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  }</div>
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<div class="line"><a name="l00032"></a><span class="lineno"> 32</span> </div>
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<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>  <span class="keyword">const</span> <span class="keywordtype">int</span> kBitsInByte = 8;</div>
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<div class="line"><a name="l00034"></a><span class="lineno"> 34</span>  <span class="keyword">const</span> <span class="keywordtype">double</span> bits_per_second_reciprocal = duration / (kBitsInByte * size);</div>
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<div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  harmonic_mean_denominator_ += bits_per_second_reciprocal;</div>
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<div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="keywordflow">if</span> (num_blocks_for_estimation_ == kUseAllBlocks) {</div>
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<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  DCHECK_EQ(history_.size(), 0u);</div>
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<div class="line"><a name="l00038"></a><span class="lineno"> 38</span>  ++num_blocks_added_;</div>
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<div class="line"><a name="l00039"></a><span class="lineno"> 39</span>  <span class="keywordflow">return</span>;</div>
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<div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  }</div>
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<div class="line"><a name="l00041"></a><span class="lineno"> 41</span> </div>
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<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  history_.push_back(bits_per_second_reciprocal);</div>
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<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  <span class="keywordflow">if</span> (num_blocks_for_estimation_ > 0 &&</div>
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<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  static_cast<int>(history_.size()) > num_blocks_for_estimation_) {</div>
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<div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  harmonic_mean_denominator_ -= history_.front();</div>
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<div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  history_.pop_front();</div>
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<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  }</div>
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<div class="line"><a name="l00048"></a><span class="lineno"> 48</span> </div>
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<div class="line"><a name="l00049"></a><span class="lineno"> 49</span>  DCHECK_NE(num_blocks_for_estimation_, kUseAllBlocks);</div>
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<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  DCHECK_LE(static_cast<int>(history_.size()), abs(num_blocks_for_estimation_));</div>
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<div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  DCHECK_EQ(num_blocks_added_, 0u);</div>
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<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  <span class="keywordflow">return</span>;</div>
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<div class="line"><a name="l00053"></a><span class="lineno"> 53</span> }</div>
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<div class="line"><a name="l00054"></a><span class="lineno"> 54</span> </div>
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<div class="line"><a name="l00055"></a><span class="lineno"> 55</span> uint64_t BandwidthEstimator::Estimate()<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  <span class="keywordflow">if</span> (harmonic_mean_denominator_ == 0.0)</div>
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<div class="line"><a name="l00057"></a><span class="lineno"> 57</span>  <span class="keywordflow">return</span> 0;</div>
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<div class="line"><a name="l00058"></a><span class="lineno"> 58</span> </div>
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<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  <span class="keyword">const</span> uint64_t num_blocks = num_blocks_for_estimation_ == kUseAllBlocks</div>
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<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  ? num_blocks_added_</div>
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<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  : history_.size();</div>
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<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  <span class="keywordflow">return</span> <span class="keyword">static_cast<</span>uint64_t<span class="keyword">></span>(ceil(num_blocks / harmonic_mean_denominator_));</div>
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<div class="line"><a name="l00063"></a><span class="lineno"> 63</span> }</div>
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<div class="ttc" id="classBandwidthEstimator_html_aaae9573785ee9d62e0927f806537ea97"><div class="ttname"><a href="../../d2/d6f/classBandwidthEstimator.html#aaae9573785ee9d62e0927f806537ea97">BandwidthEstimator::BandwidthEstimator</a></div><div class="ttdeci">BandwidthEstimator(int num_blocks)</div><div class="ttdef"><b>Definition:</b> <a href="../../d6/d86/bandwidth__estimator_8cc_source.html#l00016">bandwidth_estimator.cc:16</a></div></div>
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