On Sat, Dec 5, 2020 at 12:30 PM Michael Koch <[email protected]> wrote:
> Am 05.12.2020 um 11:38 schrieb Paul B Mahol: > > On Sat, Dec 5, 2020 at 11:02 AM Michael Koch < > [email protected]> > > wrote: > > > >> Am 04.12.2020 um 18:14 schrieb Paul B Mahol: > >>> On Wed, Dec 2, 2020 at 11:11 PM Michael Koch < > >> [email protected]> > >>> 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. > >> > >> Can you please explain what's the exact meaning of "v_fov" with > >> perspective output? > >> > > What's written in documentation. It just scales differently. > > "Set perspective parameter" or "It just scales differently" are too > vague explanations. Especially since the v_fov parameter here seems to > have a completely different meaning than in other projections. One thing > is sure: It's not an angle in degrees. > Look again at the formula of projection, it explains everything. > > Michael > > _______________________________________________ > ffmpeg-user mailing list > [email protected] > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". _______________________________________________ ffmpeg-user mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
