Answers.Body: <p>The problem was that different clips had different frame rates. My phone records a variable frame rate around 30 fps, the Zoom video had a fixed frame rate of 25 fps, the FB live video was variable around 30 fps and the Acapella-via-FB video was fixed 30 fps. I fixed the problem by reencoding all clips to a fixed frame rate of 30 fps with <code>ffmpeg -r 30</code>. (I also set a minimum audio bitrate of 96 kb/s, the bitrate of most of the original footage, with <code>-b:v 96k</code>. ffmpeg defaulted to an audio bitrate of 69 kb/s.)</p>
  <p>The QuickTime player refused to concatenate the frame-rate-adjusted clips, so I concatenated the clips in batches of 32 with <a href="https://trac.ffmpeg.org/wiki/Concatenate#differentcodec" rel="nofollow noreferrer">ffmpeg's concat filter</a> and then concatenated the result of that with <a href="https://trac.ffmpeg.org/wiki/Concatenate#demuxer" rel="nofollow noreferrer">ffmpeg's more efficient concat demuxer</a>. (Concatenating in one pass with ffmpeg's concat demuxer dropped the audio entirely from some scenes; I didn't take the time to figure out why.) I was able to combine frame rate adjustment and batch concatenation into one ffmpeg command, i.e. one reencoding step.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-06-23T19:08:33.853Z
Answers.LastActivityDate: 2020-06-23T19:08:33.853Z
Answers.UserDisplayName: Dave Schweisguth
Body: <p>I recorded about 20 MP4 clips: most on my Android phone with the stock camera, a couple from Facebook (downloaded from the mobile web view), and one from a Zoom session. I cropped or scaled and padded the FB and Zoom clips with ffmpeg to match the clips from my phone (vertical 1080p). I trimmed all the clips in the Mac QuickTime player, which exported .m4v. I then combined the clips into a single video with the QuickTime player, which saved .mov.</p>
  <p>The .mov video looks and sounds as it should throughout. However, when I upload the .mov video to YouTube</p>
  <p><div class="youtube-embed"><div>
                  <iframe width="640px" height="395px" src="https://www.youtube.com/embed/iGwH2qCc3ZY?start=0"></iframe>
              </div></div></p>
  <p>the result has two audio problems:</p>
  <ul>
  <li>The audio in the clips immediately before the Zoom clip and one of the FB clips is lowered in pitch. The preceding, distorted clips start at 1:08:18 and 41:01 respectively.</li>
  <li>The audio in the Zoom clip is really distorted, almost gone, partway through, at 1:11:21.</li>
  </ul>
  <p>(The clip at 6:18 doesn't seem to have been distorted by the clip from FB which follows it. The FB clip that doesn't cause the problem is from the FB Live Android app; I think the one that does is from the Acapella app, but I didn't make it so I'm not sure.)</p>
  <p>The problems are much worse in the Zoom clip and the clip that precedes it, which are the second- and third-to-last clips in the video, so I worked around the problem by posting a video including only the last 3 clips. The audio in that video is fine throughout!?!</p>
  <p><div class="youtube-embed"><div>
                  <iframe width="640px" height="395px" src="https://www.youtube.com/embed/ksW6xjb3vG8?start=0"></iframe>
              </div></div></p>
  <p><strong>How can I adjust my clips so that YouTube preserves the audio in the full-length video?</strong></p>
  <p>Side note: I found that converting the .mov video to .mp4 with a recent ffmpeg snapshot causes the exact same problems in the result, so, if we knew what to do to get a good result with ffmpeg, that might fix the problem on YouTube.</p>
  
Tags: <ffmpeg><audio><youtube><quicktime>
Title: How can I prevent YouTube from distorting the audio in my QuickTime video?
UserDisplayName: Dave Schweisguth
ThreadText: # How can I prevent YouTube from distorting the audio in my QuickTime video?
  
  (Asked by: username_0 on 2020-06-21)
  
  I recorded about 20 MP4 clips: most on my Android phone with the stock camera, a couple from Facebook (downloaded from the mobile web view), and one from a Zoom session. I cropped or scaled and padded the FB and Zoom clips with ffmpeg to match the clips from my phone (vertical 1080p). I trimmed all the clips in the Mac QuickTime player, which exported .m4v. I then combined the clips into a single video with the QuickTime player, which saved .mov.
  
  The .mov video looks and sounds as it should throughout. However, when I upload the .mov video to YouTube
  
  the result has two audio problems:
  
  * The audio in the clips immediately before the Zoom clip and one of the FB clips is lowered in pitch. The preceding, distorted clips start at 1:08:18 and 41:01 respectively.
  * The audio in the Zoom clip is really distorted, almost gone, partway through, at 1:11:21.
  
  (The clip at 6:18 doesn't seem to have been distorted by the clip from FB which follows it. The FB clip that doesn't cause the problem is from the FB Live Android app; I think the one that does is from the Acapella app, but I didn't make it so I'm not sure.)
  
  The problems are much worse in the Zoom clip and the clip that precedes it, which are the second- and third-to-last clips in the video, so I worked around the problem by posting a video including only the last 3 clips. The audio in that video is fine throughout!?!
  
  **How can I adjust my clips so that YouTube preserves the audio in the full-length video?**
  
  Side note: I found that converting the .mov video to .mp4 with a recent ffmpeg snapshot causes the exact same problems in the result, so, if we knew what to do to get a good result with ffmpeg, that might fix the problem on YouTube.
  
  **Tags:** ffmpeg, audio, youtube, quicktime
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_0 on 2020-06-23. Score: 1
  
  The problem was that different clips had different frame rates. My phone records a variable frame rate around 30 fps, the Zoom video had a fixed frame rate of 25 fps, the FB live video was variable around 30 fps and the Acapella-via-FB video was fixed 30 fps. I fixed the problem by reencoding all clips to a fixed frame rate of 30 fps with `ffmpeg -r 30`. (I also set a minimum audio bitrate of 96 kb/s, the bitrate of most of the original footage, with `-b:v 96k`. ffmpeg defaulted to an audio bitrate of 69 kb/s.)
  
  The QuickTime player refused to concatenate the frame-rate-adjusted clips, so I concatenated the clips in batches of 32 with [ffmpeg's concat filter](https://trac.ffmpeg.org/wiki/Concatenate#differentcodec) and then concatenated the result of that with [ffmpeg's more efficient concat demuxer](https://trac.ffmpeg.org/wiki/Concatenate#demuxer). (Concatenating in one pass with ffmpeg's concat demuxer dropped the audio entirely from some scenes; I didn't take the time to figure out why.) I was able to combine frame rate adjustment and batch concatenation into one ffmpeg command, i.e. one reencoding step.
  
  
  ---
  
  