[FFmpeg-user] V360 filter

[Paul B Mahol]

On 9/12/19, Michael Koch <astroelectronic at t-online.de> wrote:
> Paul,
>
>>
>>>> Make this correction:
>>>>
>>>> new_fov = 180 * tan(fov/4)
>>>>
>>>> where fov the the field of view you get from the command line, and
>>>> fov_new is the value that you use for the filter.
>>>> You must exclude values too close to 360°, because 360° stereographic
>>>> projection is impossible.
>>>>
>>> P.S. of course fov must be converted to radians before using tan():
>>>
>>> new_fov = 180 * tan(fov * pi / 720)
>> Thanks, that cleared some stuff.
>> Should be fixed.
>
> Converting from equirectangular to stereographic is working fine now.
> Field of view is correct.
> But in the other direction from stereographic to equirectangular the
> output is wrong.
> The output doesn't contain any no-data areas. I mean those areas that
> aren't visible in the stereographic input. These areas should be filled
> with black (or better a user-defined color).

That is not doable by design.

> Also, the default output size should be width/height=2, but it is quadratic.

output size for what?

> I tested with these command lines:
>
> ffmpeg -i equirectangular_test.png -lavfi
> "v360=input=e:output=sg:h_fov=300:v_fov=300" -y sg.png
> ffmpeg -i sg.png -lavfi "v360=input=sg:output=e:h_fov=300:v_fov=300" -y
> e.png
>
> Michael
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