[FFmpeg-user] V360 filter

[Michael Koch]

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

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