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<div class="title">audio_timestamp_helper.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 (c) 2012 The Chromium Authors. All rights reserved.</span></div>
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<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">// Use of this source code is governed by a BSD-style license that can be</span></div>
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<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">// found in the LICENSE file.</span></div>
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<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> </div>
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<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="preprocessor">#include "packager/media/base/audio_timestamp_helper.h"</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/base/logging.h"</span></div>
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<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="preprocessor">#include "packager/media/base/timestamp.h"</span></div>
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<div class="line"><a name="l00009"></a><span class="lineno"> 9</span> </div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="keyword">namespace </span>shaka {</div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="keyword">namespace </span>media {</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> AudioTimestampHelper::AudioTimestampHelper(uint32_t timescale,</div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span>  uint32_t samples_per_second)</div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span>  : base_timestamp_(kNoTimestamp), frame_count_(0) {</div>
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<div class="line"><a name="l00016"></a><span class="lineno"> 16</span>  DCHECK_GT(samples_per_second, 0u);</div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>  <span class="keywordtype">double</span> fps = samples_per_second;</div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>  ticks_per_frame_ = timescale / fps;</div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</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"> 21</span> <span class="keywordtype">void</span> AudioTimestampHelper::SetBaseTimestamp(int64_t base_timestamp) {</div>
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<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>  base_timestamp_ = base_timestamp;</div>
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<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  frame_count_ = 0;</div>
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<div class="line"><a name="l00024"></a><span class="lineno"> 24</span> }</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> int64_t AudioTimestampHelper::base_timestamp()<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>  <span class="keywordflow">return</span> base_timestamp_;</div>
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<div class="line"><a name="l00028"></a><span class="lineno"> 28</span> }</div>
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<div class="line"><a name="l00029"></a><span class="lineno"> 29</span> </div>
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<div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="keywordtype">void</span> AudioTimestampHelper::AddFrames(int64_t frame_count) {</div>
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<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  DCHECK_GE(frame_count, 0);</div>
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<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>  DCHECK(base_timestamp_ != kNoTimestamp);</div>
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<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>  frame_count_ += frame_count;</div>
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<div class="line"><a name="l00034"></a><span class="lineno"> 34</span> }</div>
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<div class="line"><a name="l00035"></a><span class="lineno"> 35</span> </div>
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<div class="line"><a name="l00036"></a><span class="lineno"> 36</span> int64_t AudioTimestampHelper::GetTimestamp()<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  <span class="keywordflow">return</span> ComputeTimestamp(frame_count_);</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> </div>
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<div class="line"><a name="l00040"></a><span class="lineno"> 40</span> int64_t AudioTimestampHelper::GetFrameDuration(int64_t frame_count)<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  DCHECK_GE(frame_count, 0);</div>
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<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  int64_t end_timestamp = ComputeTimestamp(frame_count_ + frame_count);</div>
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<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  <span class="keywordflow">return</span> end_timestamp - GetTimestamp();</div>
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<div class="line"><a name="l00044"></a><span class="lineno"> 44</span> }</div>
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<div class="line"><a name="l00045"></a><span class="lineno"> 45</span> </div>
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<div class="line"><a name="l00046"></a><span class="lineno"> 46</span> int64_t AudioTimestampHelper::GetFramesToTarget(int64_t target)<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  DCHECK(base_timestamp_ != kNoTimestamp);</div>
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<div class="line"><a name="l00048"></a><span class="lineno"> 48</span>  DCHECK(target >= base_timestamp_);</div>
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<div class="line"><a name="l00049"></a><span class="lineno"> 49</span> </div>
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<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  int64_t delta_in_ticks = (target - GetTimestamp());</div>
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<div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  <span class="keywordflow">if</span> (delta_in_ticks == 0)</div>
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<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  <span class="keywordflow">return</span> 0;</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>  <span class="comment">// Compute a timestamp relative to |base_timestamp_| since timestamps</span></div>
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<div class="line"><a name="l00055"></a><span class="lineno"> 55</span>  <span class="comment">// created from |frame_count_| are computed relative to this base.</span></div>
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<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  <span class="comment">// This ensures that the time to frame computation here is the proper inverse</span></div>
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<div class="line"><a name="l00057"></a><span class="lineno"> 57</span>  <span class="comment">// of the frame to time computation in ComputeTimestamp().</span></div>
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<div class="line"><a name="l00058"></a><span class="lineno"> 58</span>  int64_t delta_from_base = target - base_timestamp_;</div>
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<div class="line"><a name="l00059"></a><span class="lineno"> 59</span> </div>
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<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  <span class="comment">// Compute frame count for the time delta. This computation rounds to</span></div>
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<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  <span class="comment">// the nearest whole number of frames.</span></div>
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<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  <span class="keywordtype">double</span> threshold = ticks_per_frame_ / 2;</div>
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<div class="line"><a name="l00063"></a><span class="lineno"> 63</span>  int64_t target_frame_count = (delta_from_base + threshold) / ticks_per_frame_;</div>
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<div class="line"><a name="l00064"></a><span class="lineno"> 64</span>  <span class="keywordflow">return</span> target_frame_count - frame_count_;</div>
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<div class="line"><a name="l00065"></a><span class="lineno"> 65</span> }</div>
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<div class="line"><a name="l00066"></a><span class="lineno"> 66</span> </div>
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<div class="line"><a name="l00067"></a><span class="lineno"> 67</span> int64_t AudioTimestampHelper::ComputeTimestamp(int64_t frame_count)<span class="keyword"> const </span>{</div>
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<div class="line"><a name="l00068"></a><span class="lineno"> 68</span>  DCHECK_GE(frame_count, 0);</div>
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<div class="line"><a name="l00069"></a><span class="lineno"> 69</span>  DCHECK(base_timestamp_ != kNoTimestamp);</div>
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<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="keywordtype">double</span> frames_ticks = ticks_per_frame_ * frame_count;</div>
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<div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  <span class="keywordflow">return</span> base_timestamp_ + frames_ticks;</div>
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<div class="line"><a name="l00072"></a><span class="lineno"> 72</span> }</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="comment">// namespace media</span></div>
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<div class="line"><a name="l00075"></a><span class="lineno"> 75</span> } <span class="comment">// namespace shaka</span></div>
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