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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;<span class="comment">// Copyright (c) 2012 The Chromium Authors. All rights reserved.</span></div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;<span class="comment">// Use of this source code is governed by a BSD-style license that can be</span></div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>&#160;<span class="comment">// found in the LICENSE file.</span></div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>&#160;</div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span>&#160;<span class="preprocessor">#ifndef MEDIA_BASE_AUDIO_TIMESTAMP_HELPER_H_</span></div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;<span class="preprocessor"></span><span class="preprocessor">#define MEDIA_BASE_AUDIO_TIMESTAMP_HELPER_H_</span></div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span>&#160;<span class="preprocessor"></span></div>
<div class="line"><a name="l00008"></a><span class="lineno"> 8</span>&#160;<span class="preprocessor">#include &lt;stdint.h&gt;</span></div>
<div class="line"><a name="l00009"></a><span class="lineno"> 9</span>&#160;</div>
<div class="line"><a name="l00010"></a><span class="lineno"> 10</span>&#160;<span class="preprocessor">#include &quot;packager/base/macros.h&quot;</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="keyword">namespace </span>shaka {</div>
<div class="line"><a name="l00013"></a><span class="lineno"> 13</span>&#160;<span class="keyword">namespace </span>media {</div>
<div class="line"><a name="l00014"></a><span class="lineno"> 14</span>&#160;</div>
<div class="line"><a name="l00015"></a><span class="lineno"> 15</span>&#160;<span class="comment">// Generates timestamps for a sequence of audio sample frames. This class should</span></div>
<div class="line"><a name="l00016"></a><span class="lineno"> 16</span>&#160;<span class="comment">// be used any place timestamps need to be calculated for a sequence of audio</span></div>
<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>&#160;<span class="comment">// samples. It helps avoid timestamps inaccuracies caused by rounding/truncation</span></div>
<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>&#160;<span class="comment">// in repeated sample count to timestamp conversions.</span></div>
<div class="line"><a name="l00019"></a><span class="lineno"> 19</span>&#160;<span class="comment">//</span></div>
<div class="line"><a name="l00020"></a><span class="lineno"> 20</span>&#160;<span class="comment">// The class is constructed with samples_per_second information so that it can</span></div>
<div class="line"><a name="l00021"></a><span class="lineno"> 21</span>&#160;<span class="comment">// convert audio sample frame counts into timestamps. After the object is</span></div>
<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>&#160;<span class="comment">// constructed, SetBaseTimestamp() must be called to specify the starting</span></div>
<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>&#160;<span class="comment">// timestamp of the audio sequence. As audio samples are received, their frame</span></div>
<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>&#160;<span class="comment">// counts are added using AddFrames(). These frame counts are accumulated by</span></div>
<div class="line"><a name="l00025"></a><span class="lineno"> 25</span>&#160;<span class="comment">// this class so GetTimestamp() can be used to determine the timestamp for the</span></div>
<div class="line"><a name="l00026"></a><span class="lineno"> 26</span>&#160;<span class="comment">// samples that have been added. GetDuration() calculates the proper duration</span></div>
<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>&#160;<span class="comment">// values for samples added to the current timestamp. GetFramesToTarget()</span></div>
<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>&#160;<span class="comment">// determines the number of frames that need to be added/removed from the</span></div>
<div class="line"><a name="l00029"></a><span class="lineno"> 29</span>&#160;<span class="comment">// accumulated frames to reach a target timestamp.</span></div>
<div class="line"><a name="l00030"></a><span class="lineno"><a class="line" href="../../d0/d4d/classshaka_1_1media_1_1AudioTimestampHelper.html"> 30</a></span>&#160;<span class="keyword">class </span><a class="code" href="../../d0/d4d/classshaka_1_1media_1_1AudioTimestampHelper.html">AudioTimestampHelper</a> {</div>
<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>&#160; <span class="keyword">public</span>:</div>
<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>&#160; <span class="keyword">explicit</span> <a class="code" href="../../d0/d4d/classshaka_1_1media_1_1AudioTimestampHelper.html">AudioTimestampHelper</a>(uint32_t timescale,</div>
<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>&#160; uint32_t samples_per_second);</div>
<div class="line"><a name="l00034"></a><span class="lineno"> 34</span>&#160;</div>
<div class="line"><a name="l00035"></a><span class="lineno"> 35</span>&#160; <span class="comment">// Sets the base timestamp to |base_timestamp| and the sets count to 0.</span></div>
<div class="line"><a name="l00036"></a><span class="lineno"> 36</span>&#160; <span class="keywordtype">void</span> SetBaseTimestamp(int64_t base_timestamp);</div>
<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>&#160;</div>
<div class="line"><a name="l00038"></a><span class="lineno"> 38</span>&#160; int64_t base_timestamp() <span class="keyword">const</span>;</div>
<div class="line"><a name="l00039"></a><span class="lineno"> 39</span>&#160; int64_t frame_count()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> frame_count_; }</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; <span class="comment">// Adds |frame_count| to the frame counter.</span></div>
<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>&#160; <span class="comment">// Note: SetBaseTimestamp() must be called with a value other than</span></div>
<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>&#160; <span class="comment">// kNoTimestamp() before this method can be called.</span></div>
<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>&#160; <span class="keywordtype">void</span> AddFrames(int64_t frame_count);</div>
<div class="line"><a name="l00045"></a><span class="lineno"> 45</span>&#160;</div>
<div class="line"><a name="l00046"></a><span class="lineno"> 46</span>&#160; <span class="comment">// Get the current timestamp. This value is computed from the base_timestamp()</span></div>
<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>&#160; <span class="comment">// and the number of sample frames that have been added so far.</span></div>
<div class="line"><a name="l00048"></a><span class="lineno"> 48</span>&#160; int64_t GetTimestamp() <span class="keyword">const</span>;</div>
<div class="line"><a name="l00049"></a><span class="lineno"> 49</span>&#160;</div>
<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>&#160; <span class="comment">// Gets the duration if |frame_count| frames were added to the current</span></div>
<div class="line"><a name="l00051"></a><span class="lineno"> 51</span>&#160; <span class="comment">// timestamp reported by GetTimestamp(). This method ensures that</span></div>
<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>&#160; <span class="comment">// (GetTimestamp() + GetFrameDuration(n)) will equal the timestamp that</span></div>
<div class="line"><a name="l00053"></a><span class="lineno"> 53</span>&#160; <span class="comment">// GetTimestamp() will return if AddFrames(n) is called.</span></div>
<div class="line"><a name="l00054"></a><span class="lineno"> 54</span>&#160; int64_t GetFrameDuration(int64_t frame_count) <span class="keyword">const</span>;</div>
<div class="line"><a name="l00055"></a><span class="lineno"> 55</span>&#160;</div>
<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>&#160; <span class="comment">// Returns the number of frames needed to reach the target timestamp.</span></div>
<div class="line"><a name="l00057"></a><span class="lineno"> 57</span>&#160; <span class="comment">// Note: |target| must be &gt;= |base_timestamp_|.</span></div>
<div class="line"><a name="l00058"></a><span class="lineno"> 58</span>&#160; int64_t GetFramesToTarget(int64_t target) <span class="keyword">const</span>;</div>
<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>&#160;</div>
<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>&#160; <span class="keyword">private</span>:</div>
<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>&#160; int64_t ComputeTimestamp(int64_t frame_count) <span class="keyword">const</span>;</div>
<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>&#160;</div>
<div class="line"><a name="l00063"></a><span class="lineno"> 63</span>&#160; <span class="keywordtype">double</span> ticks_per_frame_;</div>
<div class="line"><a name="l00064"></a><span class="lineno"> 64</span>&#160;</div>
<div class="line"><a name="l00065"></a><span class="lineno"> 65</span>&#160; int64_t base_timestamp_;</div>
<div class="line"><a name="l00066"></a><span class="lineno"> 66</span>&#160;</div>
<div class="line"><a name="l00067"></a><span class="lineno"> 67</span>&#160; <span class="comment">// Number of frames accumulated by AddFrames() calls.</span></div>
<div class="line"><a name="l00068"></a><span class="lineno"> 68</span>&#160; int64_t frame_count_;</div>
<div class="line"><a name="l00069"></a><span class="lineno"> 69</span>&#160;</div>
<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>&#160; DISALLOW_IMPLICIT_CONSTRUCTORS(<a class="code" href="../../d0/d4d/classshaka_1_1media_1_1AudioTimestampHelper.html">AudioTimestampHelper</a>);</div>
<div class="line"><a name="l00071"></a><span class="lineno"> 71</span>&#160;};</div>
<div class="line"><a name="l00072"></a><span class="lineno"> 72</span>&#160;</div>
<div class="line"><a name="l00073"></a><span class="lineno"> 73</span>&#160;} <span class="comment">// namespace media</span></div>
<div class="line"><a name="l00074"></a><span class="lineno"> 74</span>&#160;} <span class="comment">// namespace shaka</span></div>
<div class="line"><a name="l00075"></a><span class="lineno"> 75</span>&#160;</div>
<div class="line"><a name="l00076"></a><span class="lineno"> 76</span>&#160;<span class="preprocessor">#endif</span></div>
<div class="ttc" id="classshaka_1_1media_1_1AudioTimestampHelper_html"><div class="ttname"><a href="../../d0/d4d/classshaka_1_1media_1_1AudioTimestampHelper.html">shaka::media::AudioTimestampHelper</a></div><div class="ttdef"><b>Definition:</b> <a href="../../dd/d9a/audio__timestamp__helper_8h_source.html#l00030">audio_timestamp_helper.h:30</a></div></div>
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