I came across a doc by google that they no longer accept 360 vr resolution in between 4k and 8k. just to be sure about the resolution to encode the 4k video res for youtube, is it 3840 x 1920? I mean it should be 2:1 right? That will make this 360 res lower than the normal 4k of 3840 x 2160.
https://support.google.com/youtube/answer/6375112?sjid=7272702231138100274-EU
YT still accepts 4k, or 8k, just nothing in between.
I managed to download a 360 clip from youtube that I upload before, I could only download the HD res version not the 4k. The resolution is 1920 x 1080 meaning Youtube encoded my 360 video (which was 2:1 aspect ratio) into 16:9 which makes me assume the 4k that Youtube is hosting for 360vr is 3840x2160(16:9)
So, (for Youtube uploading only) would it be more appropriate to produce the 360 video at 3840x2160(with the pan/crop setting stretching the 2:1 to 16:9?
Worth a try.
Going to try this, I tried the google spacial metadata injector on a 16-9 video and it does the 360 metadata job.
Here's a 3840 x 2160(16-9) 360-video injected with the 360 metadata. It needs some 360vr player like vlc though.