title: Audio issues when overlaying two videos (ffmpeg)
body: <p>I'm trying to overlay a short 10 second video on top of a 2 minute video and have the 10 second video show up at the 30 second mark. Here is what I have so far</p>
  <pre><code>start = 30
  subprocess.run(
      f'ffmpeg -y \
          -i {os.path.join(path, &quot;2minutevideo.mp4&quot;)} \
          -i {os.path.join(path, &quot;popup.mov&quot;)} \
          -filter_complex \
          &quot;[0:v]setpts=PTS-STARTPTS[v0]; \
          [1:v]setpts=PTS-STARTPTS+{notify_start}/TB[v1]; \
          [v0][v1]overlay=enable=\'between(t, {notify_start}, {notify_start + get_duration(os.path.join(path, &quot;popup.mp4&quot;))})\' [out1]&quot; \
          {render_flags} -r 24 -map 1:a -map [out1] -async 1 \
          {os.path.join(source_folder, &quot;test.mp4&quot;)}')
  </code></pre>
  <p>What this does is that popup.mov shows up at 30 seconds and plays for its entire duration. However, I have two issues:</p>
  <ol>
  <li>popup.mov's audio still plays at the beginning. I've tried itsoffset, setting the pts but both seem to not work or have errors.</li>
  <li>The only audio playing is popup.mov's audio. I would like both 2minutevideo and popup.mov to play audio. Yes, I'm aware it's because -map 1:a only maps the popup's audio to the final video, but I have no idea how to have both audio play. Would I have to mix it?</li>
  </ol>
  <p>Thank you</p>