[FFmpeg-user] V360 filter

[Michael Koch]

Am 11.09.2019 um 14:23 schrieb Michael Koch:
> Am 11.09.2019 um 13:13 schrieb Michael Koch:
>> Paul,
>>
>>>> I think the field of view isn't correct in the stereographic output.
>>>>
>>>> Here is a script for making really nice test images, for measuring 
>>>> field
>>>> of view:
>>> Well spotted, thanks, should be fixed.
>>
>> The field of view of the stereographic output isn't correct. Here are 
>> a few examples:
>> set in command line / measured in output image
>> 60° / 74°
>> 120° / 135°
>> 180° / 180°
>> 240° / 212°
>> 300° / 236°
>> 360° / 274°
>
> 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)

Michael