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.