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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>&#160;<span class="comment">// Copyright 2014 Google Inc. All rights reserved.</span></div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;<span class="comment">//</span></div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>&#160;<span class="comment">// Use of this source code is governed by a BSD-style</span></div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>&#160;<span class="comment">// license that can be found in the LICENSE file or at</span></div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span>&#160;<span class="comment">// https://developers.google.com/open-source/licenses/bsd</span></div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;</div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span>&#160;<span class="preprocessor">#include &quot;packager/mpd/base/bandwidth_estimator.h&quot;</span></div>
<div class="line"><a name="l00008"></a><span class="lineno"> 8</span>&#160;</div>
<div class="line"><a name="l00009"></a><span class="lineno"> 9</span>&#160;<span class="preprocessor">#include &lt;cmath&gt;</span></div>
<div class="line"><a name="l00010"></a><span class="lineno"> 10</span>&#160;<span class="preprocessor">#include &lt;cstdlib&gt;</span></div>
<div class="line"><a name="l00011"></a><span class="lineno"> 11</span>&#160;</div>
<div class="line"><a name="l00012"></a><span class="lineno"> 12</span>&#160;<span class="preprocessor">#include &quot;packager/base/logging.h&quot;</span></div>
<div class="line"><a name="l00013"></a><span class="lineno"> 13</span>&#160;</div>
<div class="line"><a name="l00014"></a><span class="lineno"> 14</span>&#160;<span class="keyword">const</span> <span class="keywordtype">int</span> BandwidthEstimator::kUseAllBlocks = 0;</div>
<div class="line"><a name="l00015"></a><span class="lineno"> 15</span>&#160;</div>
<div class="line"><a name="l00016"></a><span class="lineno"><a class="line" href="../../d2/d6f/classBandwidthEstimator.html#aaae9573785ee9d62e0927f806537ea97"> 16</a></span>&#160;<a class="code" href="../../d2/d6f/classBandwidthEstimator.html#aaae9573785ee9d62e0927f806537ea97">BandwidthEstimator::BandwidthEstimator</a>(<span class="keywordtype">int</span> num_blocks)</div>
<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>&#160; : num_blocks_for_estimation_(num_blocks),</div>
<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>&#160; harmonic_mean_denominator_(0.0),</div>
<div class="line"><a name="l00019"></a><span class="lineno"> 19</span>&#160; num_blocks_added_(0) {}</div>
<div class="line"><a name="l00020"></a><span class="lineno"> 20</span>&#160;BandwidthEstimator::~BandwidthEstimator() {}</div>
<div class="line"><a name="l00021"></a><span class="lineno"> 21</span>&#160;</div>
<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>&#160;<span class="keywordtype">void</span> BandwidthEstimator::AddBlock(uint64_t size, <span class="keywordtype">double</span> duration) {</div>
<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>&#160; DCHECK_GT(duration, 0.0);</div>
<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>&#160; DCHECK_GT(size, 0u);</div>
<div class="line"><a name="l00025"></a><span class="lineno"> 25</span>&#160;</div>
<div class="line"><a name="l00026"></a><span class="lineno"> 26</span>&#160; <span class="keywordflow">if</span> (num_blocks_for_estimation_ &lt; 0 &amp;&amp;</div>
<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>&#160; static_cast&lt;int&gt;(history_.size()) &gt;= -1 * num_blocks_for_estimation_) {</div>
<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>&#160; <span class="comment">// Short circuiting the case where |num_blocks_for_estimation_| number of</span></div>
<div class="line"><a name="l00029"></a><span class="lineno"> 29</span>&#160; <span class="comment">// blocks have been added already.</span></div>
<div class="line"><a name="l00030"></a><span class="lineno"> 30</span>&#160; <span class="keywordflow">return</span>;</div>
<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>&#160; }</div>
<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>&#160;</div>
<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>&#160; <span class="keyword">const</span> <span class="keywordtype">int</span> kBitsInByte = 8;</div>
<div class="line"><a name="l00034"></a><span class="lineno"> 34</span>&#160; <span class="keyword">const</span> <span class="keywordtype">double</span> bits_per_second_reciprocal = duration / (kBitsInByte * size);</div>
<div class="line"><a name="l00035"></a><span class="lineno"> 35</span>&#160; harmonic_mean_denominator_ += bits_per_second_reciprocal;</div>
<div class="line"><a name="l00036"></a><span class="lineno"> 36</span>&#160; <span class="keywordflow">if</span> (num_blocks_for_estimation_ == kUseAllBlocks) {</div>
<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>&#160; DCHECK_EQ(history_.size(), 0u);</div>
<div class="line"><a name="l00038"></a><span class="lineno"> 38</span>&#160; ++num_blocks_added_;</div>
<div class="line"><a name="l00039"></a><span class="lineno"> 39</span>&#160; <span class="keywordflow">return</span>;</div>
<div class="line"><a name="l00040"></a><span class="lineno"> 40</span>&#160; }</div>
<div class="line"><a name="l00041"></a><span class="lineno"> 41</span>&#160;</div>
<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>&#160; history_.push_back(bits_per_second_reciprocal);</div>
<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>&#160; <span class="keywordflow">if</span> (num_blocks_for_estimation_ &gt; 0 &amp;&amp;</div>
<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>&#160; static_cast&lt;int&gt;(history_.size()) &gt; num_blocks_for_estimation_) {</div>
<div class="line"><a name="l00045"></a><span class="lineno"> 45</span>&#160; harmonic_mean_denominator_ -= history_.front();</div>
<div class="line"><a name="l00046"></a><span class="lineno"> 46</span>&#160; history_.pop_front();</div>
<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>&#160; }</div>
<div class="line"><a name="l00048"></a><span class="lineno"> 48</span>&#160;</div>
<div class="line"><a name="l00049"></a><span class="lineno"> 49</span>&#160; DCHECK_NE(num_blocks_for_estimation_, kUseAllBlocks);</div>
<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>&#160; DCHECK_LE(static_cast&lt;int&gt;(history_.size()), abs(num_blocks_for_estimation_));</div>
<div class="line"><a name="l00051"></a><span class="lineno"> 51</span>&#160; DCHECK_EQ(num_blocks_added_, 0u);</div>
<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>&#160; <span class="keywordflow">return</span>;</div>
<div class="line"><a name="l00053"></a><span class="lineno"> 53</span>&#160;}</div>
<div class="line"><a name="l00054"></a><span class="lineno"> 54</span>&#160;</div>
<div class="line"><a name="l00055"></a><span class="lineno"> 55</span>&#160;uint64_t BandwidthEstimator::Estimate()<span class="keyword"> const </span>{</div>
<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>&#160; <span class="keywordflow">if</span> (harmonic_mean_denominator_ == 0.0)</div>
<div class="line"><a name="l00057"></a><span class="lineno"> 57</span>&#160; <span class="keywordflow">return</span> 0;</div>
<div class="line"><a name="l00058"></a><span class="lineno"> 58</span>&#160;</div>
<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>&#160; <span class="keyword">const</span> uint64_t num_blocks = num_blocks_for_estimation_ == kUseAllBlocks</div>
<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>&#160; ? num_blocks_added_</div>
<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>&#160; : history_.size();</div>
<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>&#160; <span class="keywordflow">return</span> <span class="keyword">static_cast&lt;</span>uint64_t<span class="keyword">&gt;</span>(ceil(num_blocks / harmonic_mean_denominator_));</div>
<div class="line"><a name="l00063"></a><span class="lineno"> 63</span>&#160;}</div>
<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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