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<li class="navelem"><a class="el" href="../../dir_3f8eec2fc361645de4b1ec14c19fffc7.html">packager</a></li><li class="navelem"><a class="el" href="../../dir_b885194e7131202a9b4650a8967e838c.html">mpd</a></li><li class="navelem"><a class="el" href="../../dir_6fe4b0529cd3ec97045d3314254a0cce.html">base</a></li> </ul>
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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 <algorithm></span></div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="preprocessor">#include <cmath></span></div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="preprocessor">#include <numeric></span></div>
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<div class="line"><a name="l00012"></a><span class="lineno"> 12</span>  </div>
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<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="preprocessor">#include "packager/base/logging.h"</span></div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span>  </div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="keyword">namespace </span><a class="code" href="../../d8/daf/namespaceshaka.html">shaka</a> {</div>
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<div class="line"><a name="l00016"></a><span class="lineno"> 16</span>  </div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span> BandwidthEstimator::BandwidthEstimator() = <span class="keywordflow">default</span>;</div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>  </div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</span> BandwidthEstimator::~BandwidthEstimator() = <span class="keywordflow">default</span>;</div>
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<div class="line"><a name="l00020"></a><span class="lineno"> 20</span>  </div>
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<div class="line"><a name="l00021"></a><span class="lineno"><a class="line" href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a53c67d33f000489d1ebb31a2bdd766a4"> 21</a></span> <span class="keywordtype">void</span> <a class="code" href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a53c67d33f000489d1ebb31a2bdd766a4">BandwidthEstimator::AddBlock</a>(uint64_t size_in_bytes, <span class="keywordtype">double</span> duration) {</div>
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<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>  <span class="keywordflow">if</span> (size_in_bytes == 0 || duration == 0) {</div>
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<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  LOG(WARNING) << <span class="stringliteral">"Ignore block with size="</span> << size_in_bytes</div>
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<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>  << <span class="stringliteral">", duration="</span> << duration;</div>
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<div class="line"><a name="l00025"></a><span class="lineno"> 25</span>  <span class="keywordflow">return</span>;</div>
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<div class="line"><a name="l00026"></a><span class="lineno"> 26</span>  }</div>
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<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>  </div>
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<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>  <span class="keyword">const</span> <span class="keywordtype">int</span> kBitsInByte = 8;</div>
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<div class="line"><a name="l00029"></a><span class="lineno"> 29</span>  <span class="keyword">const</span> uint64_t size_in_bits = size_in_bytes * kBitsInByte;</div>
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<div class="line"><a name="l00030"></a><span class="lineno"> 30</span>  total_size_in_bits_ += size_in_bits;</div>
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<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  total_duration_ += duration;</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">size_t</span> kTargetDurationThreshold = 10;</div>
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<div class="line"><a name="l00034"></a><span class="lineno"> 34</span>  <span class="keywordflow">if</span> (initial_blocks_.size() < kTargetDurationThreshold) {</div>
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<div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  initial_blocks_.push_back({size_in_bits, duration});</div>
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<div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="keywordflow">return</span>;</div>
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<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  }</div>
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<div class="line"><a name="l00038"></a><span class="lineno"> 38</span>  </div>
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<div class="line"><a name="l00039"></a><span class="lineno"> 39</span>  <span class="keywordflow">if</span> (target_block_duration_ == 0) {</div>
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<div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  <span class="comment">// Use the average duration as the target block duration. It will be used</span></div>
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<div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  <span class="comment">// to filter small blocks from bandwidth calculation.</span></div>
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<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  target_block_duration_ = GetAverageBlockDuration();</div>
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<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  <span class="keywordflow">for</span> (<span class="keyword">const</span> Block& block : initial_blocks_) {</div>
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<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  max_bitrate_ =</div>
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<div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  std::max(max_bitrate_, GetBitrate(block, target_block_duration_));</div>
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<div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  }</div>
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<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  <span class="keywordflow">return</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>  max_bitrate_ = std::max(max_bitrate_, GetBitrate({size_in_bits, duration},</div>
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<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  target_block_duration_));</div>
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<div class="line"><a name="l00051"></a><span class="lineno"> 51</span> }</div>
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<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  </div>
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<div class="line"><a name="l00053"></a><span class="lineno"><a class="line" href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a9414560e16c46e7e2da3683a4dfb86cc"> 53</a></span> uint64_t <a class="code" href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a9414560e16c46e7e2da3683a4dfb86cc">BandwidthEstimator::Estimate</a>()<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  <span class="keywordflow">if</span> (total_duration_ == 0)</div>
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<div class="line"><a name="l00055"></a><span class="lineno"> 55</span>  <span class="keywordflow">return</span> 0;</div>
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<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  <span class="keywordflow">return</span> <span class="keyword">static_cast<</span>uint64_t<span class="keyword">></span>(ceil(total_size_in_bits_ / total_duration_));</div>
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<div class="line"><a name="l00057"></a><span class="lineno"> 57</span> }</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"><a class="line" href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a0df6c40f43a89d3d481392ac0298e37c"> 59</a></span> uint64_t <a class="code" href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a0df6c40f43a89d3d481392ac0298e37c">BandwidthEstimator::Max</a>()<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  <span class="keywordflow">if</span> (max_bitrate_ != 0)</div>
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<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  <span class="keywordflow">return</span> max_bitrate_;</div>
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<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  </div>
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<div class="line"><a name="l00063"></a><span class="lineno"> 63</span>  <span class="comment">// We don't have the |target_block_duration_| yet. Calculate a target</span></div>
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<div class="line"><a name="l00064"></a><span class="lineno"> 64</span>  <span class="comment">// duration from the current available blocks.</span></div>
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<div class="line"><a name="l00065"></a><span class="lineno"> 65</span>  DCHECK(target_block_duration_ == 0);</div>
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<div class="line"><a name="l00066"></a><span class="lineno"> 66</span>  <span class="keyword">const</span> <span class="keywordtype">double</span> target_block_duration = GetAverageBlockDuration();</div>
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<div class="line"><a name="l00067"></a><span class="lineno"> 67</span>  </div>
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<div class="line"><a name="l00068"></a><span class="lineno"> 68</span>  <span class="comment">// Calculate maximum bitrate with the target duration calculated above.</span></div>
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<div class="line"><a name="l00069"></a><span class="lineno"> 69</span>  uint64_t max_bitrate = 0;</div>
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<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="keywordflow">for</span> (<span class="keyword">const</span> Block& block : initial_blocks_) {</div>
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<div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  max_bitrate =</div>
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<div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  std::max(max_bitrate, GetBitrate(block, target_block_duration));</div>
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<div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  }</div>
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<div class="line"><a name="l00074"></a><span class="lineno"> 74</span>  <span class="keywordflow">return</span> max_bitrate;</div>
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<div class="line"><a name="l00075"></a><span class="lineno"> 75</span> }</div>
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<div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  </div>
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<div class="line"><a name="l00077"></a><span class="lineno"> 77</span> <span class="keywordtype">double</span> BandwidthEstimator::GetAverageBlockDuration()<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00078"></a><span class="lineno"> 78</span>  <span class="keywordflow">if</span> (initial_blocks_.empty())</div>
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<div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  <span class="keywordflow">return</span> 0.0;</div>
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<div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="keyword">const</span> <span class="keywordtype">double</span> sum =</div>
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<div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  std::accumulate(initial_blocks_.begin(), initial_blocks_.end(), 0.0,</div>
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<div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  [](<span class="keywordtype">double</span> duration, <span class="keyword">const</span> Block& block) {</div>
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<div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  return duration + block.duration;</div>
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<div class="line"><a name="l00084"></a><span class="lineno"> 84</span>  });</div>
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<div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  <span class="keywordflow">return</span> sum / initial_blocks_.size();</div>
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<div class="line"><a name="l00086"></a><span class="lineno"> 86</span> }</div>
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<div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  </div>
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<div class="line"><a name="l00088"></a><span class="lineno"> 88</span> uint64_t BandwidthEstimator::GetBitrate(<span class="keyword">const</span> Block& block,</div>
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<div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  <span class="keywordtype">double</span> target_block_duration)<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  <span class="keywordflow">if</span> (block.duration < 0.5 * target_block_duration) {</div>
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<div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  <span class="comment">// https://tools.ietf.org/html/rfc8216#section-4.1</span></div>
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<div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  <span class="comment">// The peak segment bit rate of a Media Playlist is the largest bit rate of</span></div>
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<div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  <span class="comment">// any continuous set of segments whose total duration is between 0.5</span></div>
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<div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  <span class="comment">// and 1.5 times the target duration.</span></div>
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<div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  <span class="comment">// Only the short segments are excluded here as our media playlist generator</span></div>
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<div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  <span class="comment">// sets the target duration in the playlist to the largest segment duration.</span></div>
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<div class="line"><a name="l00097"></a><span class="lineno"> 97</span>  <span class="comment">// So although the segment duration could be 1.5 times the user provided</span></div>
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<div class="line"><a name="l00098"></a><span class="lineno"> 98</span>  <span class="comment">// segment duration, it will never be larger than the actual target</span></div>
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<div class="line"><a name="l00099"></a><span class="lineno"> 99</span>  <span class="comment">// duration.</span></div>
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<div class="line"><a name="l00100"></a><span class="lineno"> 100</span>  <span class="comment">//</span></div>
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<div class="line"><a name="l00101"></a><span class="lineno"> 101</span>  <span class="comment">// We also apply the same exclusion to the bandwidth computation for DASH as</span></div>
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<div class="line"><a name="l00102"></a><span class="lineno"> 102</span>  <span class="comment">// the bitrate for the short segment is not a good signal for peak</span></div>
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<div class="line"><a name="l00103"></a><span class="lineno"> 103</span>  <span class="comment">// bandwidth.</span></div>
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<div class="line"><a name="l00104"></a><span class="lineno"> 104</span>  <span class="comment">// See https://github.com/google/shaka-packager/issues/498 for details.</span></div>
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<div class="line"><a name="l00105"></a><span class="lineno"> 105</span>  VLOG(1) << <span class="stringliteral">"Exclude short segment (duration "</span> << block.duration</div>
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<div class="line"><a name="l00106"></a><span class="lineno"> 106</span>  << <span class="stringliteral">", target_duration "</span> << target_block_duration</div>
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<div class="line"><a name="l00107"></a><span class="lineno"> 107</span>  << <span class="stringliteral">") in peak bandwidth computation."</span>;</div>
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<div class="line"><a name="l00108"></a><span class="lineno"> 108</span>  <span class="keywordflow">return</span> 0.0;</div>
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<div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  }</div>
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<div class="line"><a name="l00110"></a><span class="lineno"> 110</span>  <span class="keywordflow">return</span> <span class="keyword">static_cast<</span>uint64_t<span class="keyword">></span>(ceil(block.size_in_bits / block.duration));</div>
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<div class="line"><a name="l00111"></a><span class="lineno"> 111</span> }</div>
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<div class="line"><a name="l00112"></a><span class="lineno"> 112</span>  </div>
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<div class="line"><a name="l00113"></a><span class="lineno"> 113</span> } <span class="comment">// namespace shaka</span></div>
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<div class="ttc" id="aclassshaka_1_1BandwidthEstimator_html_a0df6c40f43a89d3d481392ac0298e37c"><div class="ttname"><a href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a0df6c40f43a89d3d481392ac0298e37c">shaka::BandwidthEstimator::Max</a></div><div class="ttdeci">uint64_t Max() const</div><div class="ttdef"><b>Definition:</b> <a href="../../d6/d86/bandwidth__estimator_8cc_source.html#l00059">bandwidth_estimator.cc:59</a></div></div>
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<div class="ttc" id="aclassshaka_1_1BandwidthEstimator_html_a53c67d33f000489d1ebb31a2bdd766a4"><div class="ttname"><a href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a53c67d33f000489d1ebb31a2bdd766a4">shaka::BandwidthEstimator::AddBlock</a></div><div class="ttdeci">void AddBlock(uint64_t size_in_bytes, double duration)</div><div class="ttdef"><b>Definition:</b> <a href="../../d6/d86/bandwidth__estimator_8cc_source.html#l00021">bandwidth_estimator.cc:21</a></div></div>
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<div class="ttc" id="aclassshaka_1_1BandwidthEstimator_html_a9414560e16c46e7e2da3683a4dfb86cc"><div class="ttname"><a href="../../da/d2c/classshaka_1_1BandwidthEstimator.html#a9414560e16c46e7e2da3683a4dfb86cc">shaka::BandwidthEstimator::Estimate</a></div><div class="ttdeci">uint64_t Estimate() const</div><div class="ttdef"><b>Definition:</b> <a href="../../d6/d86/bandwidth__estimator_8cc_source.html#l00053">bandwidth_estimator.cc:53</a></div></div>
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<div class="ttc" id="anamespaceshaka_html"><div class="ttname"><a href="../../d8/daf/namespaceshaka.html">shaka</a></div><div class="ttdoc">All the methods that are virtual are virtual for mocking.</div><div class="ttdef"><b>Definition:</b> <a href="../../d4/d15/gflags__hex__bytes_8cc_source.html#l00011">gflags_hex_bytes.cc:11</a></div></div>
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