Converted file does not play in Mac Finder and QuickTime media player

[hybridherbst]

Describe the bug
While trying to create BT.2020 H.264 files with ffmpeg.wasm I ran into a case where the conversion succeeds, but the resulting file only has a thumbnail and doesn't actually play in media players.

To Reproduce

1. Load demo file
2. Paste the conversion commands below
3. Transcode
4. Download the result and try to play it
5. Note in Mac Finder it will only display a thumbnail and not actually play. In Chrome it does play.
6. Compare with this file: https://www.wide-gamut.com/assets/video-hdr/P3-GREEN-HDR-1000nits.mp4 which will play in HDR mode in Mac Finder.

[
  "-i",
  "video.webm",
  "-vf", "format=yuv420p10le",
  "-c:v", "libx264",
  "-preset", "slow",
  "-crf", "18",
  "-color_primaries", "bt2020",
  "-colorspace", "bt2020nc",
  "-color_trc", "smpte2084",
  "video.mp4"
]

Expected behavior
Converted file plays in Mac Finder as well as in the browser

Screenshots

File does not have play button – it does play in a browser though!

File has play button and plays in Finder

Desktop (please complete the following information):

• OS: Mac OS
• Browser Chrome latest

Additional context
Workflow related to #762