[FFmpeg-user] v360 / perspective

[Paul B Mahol]

On Wed, Dec 2, 2020 at 11:11 PM Michael Koch <astroelectronic at t-online.de>
wrote:

> Am 01.12.2020 um 19:56 schrieb Michael Koch:
> > Hello,
> >
> > there seem to be some problems in the v360 filter with "perspective"
> > output.
> > Tested with the latest Windows built, 2 days old. You can reproduce
> > this with any equirectangular input image.
> >
> > ffmpeg -i equirectangular_test.png -lavfi v360=e:perspective -y out1.png
> >
> > The output of the above command has two problems:
> > -- The center of the input image is not mapped to the center of the
> > output image. For most other projections the image center is preserved.
> > -- The output is mirror reversed (which means you cannot read text).
> >
> > Both problems can be corrected with this workaround:
> >
> > ffmpeg -i equirectangular_test.png -lavfi
> > v360=e:perspective:pitch=90:v_flip=1 -y out2.png
> >
> > Now I want to add a yaw rotation after the pitch rotation:
> >
> > ffmpeg -i equirectangular_test.png -lavfi
> > v360=e:perspective:rorder=pyr:pitch=90:yaw=20:v_flip=1 -y out3.png
> >
> > But in the output you can see that a roll rotation was done.
>
> Today I did for the very first time figure out how to compile ffmpeg.
> The above problem can be solved by changing two lines in vf_v360.c
> Sorry, I haven't yet figured out how to use git.One thing after the
> other...
>
> Old version:
> line 3136:   vec[1] = sin_theta;
> line 3137: vec[2] = cos_theta * cos_phi;
>
> New version:
> line 3136: vec[1] = cos_theta * cos_phi;
> line 3137: vec[2] = sin_theta;
>
> I'm not sure if lines 3139 to 3141 must also be changed.
>
>
Good job!
Please write a patch with correct authorship and send it to the devel list.
Fixing this for you was much more work than writing & sending patch will be.



> Michael
>
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