title: Problems in Audio/Video Slow motion
body: <p>I am trying do <strong>slow motion</strong> for my <strong>video</strong> file along with <strong>audio.</strong> In my case, I have to do <strong>Ramped</strong> Slow motion(Gradually slowing down and speeding up 
  like parabola not a "Linear Slow Motion". </p>
  
  <p>Ref:Linear slow motion :</p>
  
  <p><img src="https://i.stack.imgur.com/WAiJW.png" alt="enter image description here"></p>
  
  <p>Ref : Ramped Slow Motion :</p>
  
  <p><img src="https://i.stack.imgur.com/TqRm4.png" alt="enter image description here"></p>
  
  <p><strong>What have i done so far:</strong></p>
  
  <p><strong>Used AVFoundation for first three bullets</strong></p>
  
  <ol>
  <li><p>From video files, <strong>separated audio and video</strong>.</p></li>
  <li><p>Did slow motion for <strong>video using AVFoundation api (scaletimeRange)</strong>.Its really working fine. </p></li>
  <li><p>The same is <strong>not working</strong> for <strong>audio</strong>. Seems there's a bug in apple api itself (Bug ID : 14616144). The relevant question is <a href="https://stackoverflow.com/questions/17269531/scaletimerange-has-no-effect-on-audio-type-avmutablecompositiontrack">scaleTimeRange has no effect on audio type AVMutableCompositionTrack</a></p></li>
  <li><p>So i <strong>switched</strong> to <strong>Dirac</strong>. later found there is a <strong>limitation</strong> with Dirac's open source edition that it doesn't support Dynamic Time Stretching.</p></li>
  <li><p>Finally trying to do with <strong>OpenAL</strong>.</p></li>
  </ol>
  
  <p>I've taken a sample OpenAL program from Apple developer forum and executed it.</p>
  
  <p><strong>Here are my questions:</strong></p>
  
  <ol>
  <li><p>Can i <strong>store/save</strong> the processed audio in OpenAl?if its directly not possible with "OpenAl", can it be done with <strong>AVFoundation + OpenAL</strong>?</p></li>
  <li><p>Very importantly, <strong>how to do slow motion or stretch the time scale with OpenAL</strong>? If i know time stretching, i can apply logic for Ramp Slow Motion.</p></li>
  <li><p>Is there any other way?</p></li>
  </ol>