My video project is HD-vertical (1080×1920). After exporting it as an mp4 by using the settings Computer and H.264 Better Quality at the export prompt, I see that the resolution of the exported video has downgraded without warning to 608×1080 – although the Resolution in the export prompt itself was listed as 1080×1920! I’m having to use a third-party mov-to-mp4 converter (like the online Adobe Premier converter) as a workaround to maintain 1080×1920. How do I get FCP to export mp4s in the set resolution?
FCP and macOS are up-to-date (10.6.2 and 12.3.1 respectively).
Edit: I found a suggestion that it might be a bug and to try re-selecting the desired resolution in the export prompt. Since on the prompt dropdown it was already set as 1080×1920, I changed the dropdown value to 720×1280, then back to 1080×1920, before exporting. Immediately I saw that the estimated size was significantly greater than before the switch. And it worked! Exported resolution was vertical-HD. Reported the bug to Apple.