title: ffmpeg-Error "Buffer queue overflow, dropping." when merging two videos with delay
body: <p>I want to merge two videos (as example the iphone video from <a href="https://peach.blender.org/trailer-page/" rel="nofollow">https://peach.blender.org/trailer-page/</a>). The videos are placed on an background image with the overlay filter and the second video starts 3 seconds later.</p>
  
  <p>And I need that the audio is mixed. </p>
  
  <p>Here is my code:</p>
  
  <pre><code>ffmpeg \
      -loop 1 -i background.png  \
      -itsoffset 0  -i trailer_iphone.m4v \
      -itsoffset 3  -i trailer_iphone.m4v \
      \
      -y \
      -t 36 \
      -filter_complex "
          [2:a] adelay=3000 [2delayed];
          [1:a][2delayed] amerge=inputs=2 [audio];
          [0][1:v] overlay=10:10:enable='between(t,0,33)' [lv1];
          [lv1][2:v] overlay=10:300:enable='between(t,0,36)' [video]
      " \
      \
      -threads 0 \
      -map "[video]" -map "[audio]" \
      -vcodec libx264 -acodec aac \
      merged-video.mp4
  </code></pre>
  
  <p>I get the error message: </p>
  
  <pre><code>[Parsed_overlay_3 @ 0x7fe892502ac0] [framesync @ 0x7fe892502b88] Buffer queue overflow, dropping.
  </code></pre>
  
  <p>And the merged video has many dropped frames.</p>
  
  <p>I know that are some other posting with this error message. But the suggested solutions doesn't work for me.</p>
  
  <p>How can I fix the problem?</p>