<divclass="fragment"><divclass="line"><aname="l00001"></a><spanclass="lineno"> 1</span> <spanclass="comment">// Copyright (c) 2012 The Chromium Authors. All rights reserved.</span></div>
<divclass="line"><aname="l00002"></a><spanclass="lineno"> 2</span> <spanclass="comment">// Use of this source code is governed by a BSD-style license that can be</span></div>
<divclass="line"><aname="l00003"></a><spanclass="lineno"> 3</span> <spanclass="comment">// found in the LICENSE file.</span></div>
<divclass="line"><aname="l00015"></a><spanclass="lineno"> 15</span> <spanclass="comment">// Generates timestamps for a sequence of audio sample frames. This class should</span></div>
<divclass="line"><aname="l00016"></a><spanclass="lineno"> 16</span> <spanclass="comment">// be used any place timestamps need to be calculated for a sequence of audio</span></div>
<divclass="line"><aname="l00017"></a><spanclass="lineno"> 17</span> <spanclass="comment">// samples. It helps avoid timestamps inaccuracies caused by rounding/truncation</span></div>
<divclass="line"><aname="l00018"></a><spanclass="lineno"> 18</span> <spanclass="comment">// in repeated sample count to timestamp conversions.</span></div>
<divclass="line"><aname="l00020"></a><spanclass="lineno"> 20</span> <spanclass="comment">// The class is constructed with samples_per_second information so that it can</span></div>
<divclass="line"><aname="l00021"></a><spanclass="lineno"> 21</span> <spanclass="comment">// convert audio sample frame counts into timestamps. After the object is</span></div>
<divclass="line"><aname="l00022"></a><spanclass="lineno"> 22</span> <spanclass="comment">// constructed, SetBaseTimestamp() must be called to specify the starting</span></div>
<divclass="line"><aname="l00023"></a><spanclass="lineno"> 23</span> <spanclass="comment">// timestamp of the audio sequence. As audio samples are received, their frame</span></div>
<divclass="line"><aname="l00024"></a><spanclass="lineno"> 24</span> <spanclass="comment">// counts are added using AddFrames(). These frame counts are accumulated by</span></div>
<divclass="line"><aname="l00025"></a><spanclass="lineno"> 25</span> <spanclass="comment">// this class so GetTimestamp() can be used to determine the timestamp for the</span></div>
<divclass="line"><aname="l00026"></a><spanclass="lineno"> 26</span> <spanclass="comment">// samples that have been added. GetDuration() calculates the proper duration</span></div>
<divclass="line"><aname="l00027"></a><spanclass="lineno"> 27</span> <spanclass="comment">// values for samples added to the current timestamp. GetFramesToTarget()</span></div>
<divclass="line"><aname="l00028"></a><spanclass="lineno"> 28</span> <spanclass="comment">// determines the number of frames that need to be added/removed from the</span></div>
<divclass="line"><aname="l00029"></a><spanclass="lineno"> 29</span> <spanclass="comment">// accumulated frames to reach a target timestamp.</span></div>
<divclass="line"><aname="l00035"></a><spanclass="lineno"> 35</span> <spanclass="comment">// Sets the base timestamp to |base_timestamp| and the sets count to 0.</span></div>
<divclass="line"><aname="l00041"></a><spanclass="lineno"> 41</span> <spanclass="comment">// Adds |frame_count| to the frame counter.</span></div>
<divclass="line"><aname="l00042"></a><spanclass="lineno"> 42</span> <spanclass="comment">// Note: SetBaseTimestamp() must be called with a value other than</span></div>
<divclass="line"><aname="l00043"></a><spanclass="lineno"> 43</span> <spanclass="comment">// kNoTimestamp() before this method can be called.</span></div>
<divclass="line"><aname="l00046"></a><spanclass="lineno"> 46</span> <spanclass="comment">// Get the current timestamp. This value is computed from the base_timestamp()</span></div>
<divclass="line"><aname="l00047"></a><spanclass="lineno"> 47</span> <spanclass="comment">// and the number of sample frames that have been added so far.</span></div>
<divclass="line"><aname="l00050"></a><spanclass="lineno"> 50</span> <spanclass="comment">// Gets the duration if |frame_count| frames were added to the current</span></div>
<divclass="line"><aname="l00051"></a><spanclass="lineno"> 51</span> <spanclass="comment">// timestamp reported by GetTimestamp(). This method ensures that</span></div>
<divclass="line"><aname="l00052"></a><spanclass="lineno"> 52</span> <spanclass="comment">// (GetTimestamp() + GetFrameDuration(n)) will equal the timestamp that</span></div>
<divclass="line"><aname="l00053"></a><spanclass="lineno"> 53</span> <spanclass="comment">// GetTimestamp() will return if AddFrames(n) is called.</span></div>
<divclass="line"><aname="l00056"></a><spanclass="lineno"> 56</span> <spanclass="comment">// Returns the number of frames needed to reach the target timestamp.</span></div>
<divclass="line"><aname="l00057"></a><spanclass="lineno"> 57</span> <spanclass="comment">// Note: |target| must be >= |base_timestamp_|.</span></div>
<divclass="line"><aname="l00067"></a><spanclass="lineno"> 67</span> <spanclass="comment">// Number of frames accumulated by AddFrames() calls.</span></div>
