title: Regarding rotation information when rotating a movie in Avfoundation
body: <p>I was able to rotate the movie with the following code</p>
  
  <pre><code>videoCompositionTrack.preferredTransform = CGAffineTransform(rotationAngle: CGFloat(M_PI_2))
  </code></pre>
  
  <p>I confirmed the information of the rotated video by ffmpeg. Rotate in the tag does not fluctuate as shown below, but a tag called side_data_list was generated and the value of rotation in side_data_list fluctuated, while keeping the information of rotate in tag unchanged.I want to change "tag" information.</p>
  
  <pre><code>"tags": {
                  "rotate": "90"
          },
  "side_data_list": [
                  {
  "rotation": -90
                  }
  </code></pre>
  
  <p>Are there any good advice on AVFoundation and ffmpeg?</p>