I am not exactly sure what you are trying to do or need, but there is this
interesting 360 video filter that can be integrated into FFmpeg/libavfilter
(manual patching):
https://github.com/facebook/transform360
It does more that just equirectangular and cubemap. It also does 2D
flat_fixed extraction and stereoscopic, but it does not take fisheye input
layouts. In any case, it might be a starting point for you.

On Tue, Apr 23, 2019 at 9:44 AM Federico Allegretti <allegfede@???>
wrote:

> hello everybody, i'm starting a project that will use a stupid simple vr
> head set (google cardboard vr like) to render some images on "eyes" and i
> think could be a frei0r plug in or plug in chain to get a 16:9 image and
> split in two, deform it and render on the correct screen position, so lens
> and brain could reconscruct the corrent "fake" stereo image.
>
> Is already there? If not, could you address me to some
> docs/papers/articles to write a frei0r plugin to handle those
> transformations by myself (i'll try at least)?
>
> Thanks,
>
> Federico
> --
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>
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