Some videos can't be previewed in Safari and Firefox because the pixel format of the source video is kept for the mp4 conversion but is not supported by those web browsers.
The solution is to add
-pix_fmt yuv420p
to the command line as described in https://doc.nuxeo.com/nxdoc/alternative-command-parameters-for-prores-codec-users/
- is related to
-
ELEMENTS-895 Video player does not work in Safari (Web UI)
- Resolved
-
NXP-26982 Video player does not work in Safari (JSF)
- Resolved