Reprojecting Dual Fisheye Videos to Equirectangular (LG 360)

I still use my obsolete LG 360 Camera. When copying MP4 videos from its SD card, they come out in "Dual Fisheye" format - which looks like this: VLC and YouTube will only play "Equirectangular" videos in spherical mode. So, how to convert a dual fisheye to equirectangualr? The Simple Way ffmpeg \ -i original.mp4 \ -vf "v360=input=dfisheye:output=equirect:ih_fov=189:iv_fov=189" \ 360.mp4 However, this has some "quirks". The first part of the video filter is v360=input=dfisheye:output=equirect - that just says to use the 360 filter on an input which is dual fisheye and then output in equirectangular. The next part is :ih_fov=189:iv_fov=189 which says that the input video has a horizontal and vertical field of view of 189°. That's a weird number, right? You'd kind of expect each lens to be 180°, right? Here's what happens if :ih_fov=180:iv_fov=180 is used: The lenses overlaps a little bit. So using 180° means that certain portions are duplicated. I think the lenses technically offer…