Am 24.10.2020 um 11:03 schrieb Michael Koch:
Am 23.10.2020 um 18:46 schrieb Michael Koch:
Am 23.10.2020 um 17:19 schrieb Michael Koch:
Hello,
It seems there is a problem in the v360 filter. This command line
doesn't rotate the correct point to the image center. The default
rotation order should be yaw pitch roll, which means after the
rotation the point with azimut 180° and height +45° should be in the
center. It is nearby, but not in the center. Tested with latest
Windows build, 2 days old.
ffmpeg -i equirectangular_test.png -vf v360=e:e:yaw=-90:pitch=45 -y
out.png
If the rotation is only yaw or only pitch or only roll, then it's
working fine. But all rotations around two or more axes fail.
I'm not sure, but the problem might be in the function
multiply_quaternion() in vf_v360.c
Please compare the signs with this Wikipedia article:
https://en.wikipedia.org/wiki/Quaternion#Hamilton_product
After a deeper look into the quaternion multiplication, it seems to be
correct. The terms are only written in a different order in the
Wikipedia article.
But it's a fact that the v360 rotations are broken, as can be shown by
this simple test:
You can use any equirectangular input image.
First make a combined rotation yaw=90 and pitch=45 in the default
rotation order (ypr),
then rotate back pitch = -45,
then rotate back yaw = -90.
The output image should be the same as the input image. But it isn't.
ffmpeg -i input.png -vf
v360=e:e:yaw=90:pitch=45,v360=e:e:pitch=-45,v360=e:e:yaw=-90 -y out.png
Michael
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