[FFmpeg-user] v360 / perspective

Michael Koch astroelectronic at t-online.de
Fri Dec 4 19:58:23 EET 2020

Am 04.12.2020 um 18:14 schrieb 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.

lol, fixing this problem was done in 10 minutes. Since 3 days I'm trying 
to figure out how git works. Git is the pure horror! I think I have the 
patch file now, but now the next problem is that the subscription to the 
ffmpeg-devel list doesn't work.


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