Source File

Mask File

Result

Create mergemap

./ffmpeg -f lavfi -i nullsrc=size=2976x2976 -vf "format=gray8,geq='clip(128-128/$C*(180-$FOV/($H/2)*hypot(X-$H/2,Y-$H/2)),0,255)',v360=input=fisheye:output=e:ih_fov=$FOV:iv_fov=$FOV" -frames 1 -y ~/Desktop/mergemap.png

Create Equidirect:

ffmpeg -i ~/Desktop/weser1.png -i ~/Desktop/mergemap.png -lavfi "[0]format=rgb24,split[a][b];[a]crop=$W/2:ih:0:0,v360=input=fisheye:output=e:ih_fov=$FOV:iv_fov=$FOV[c];[b]crop=$W/2:ih:$W/2:0,v360=input=fisheye:output=e:ih_fov=$FOV:iv_fov=$FOV[d];[1]format=gbrp[e];[c][d][e]maskedmerge" -y ~/Desktop/razan.jpg

FFMPEG Version 5.1.1-static