[FFmpeg-user] multiple flat videos in a equirectangular projection - v360 filter

[Denis Połeć]

> Am 16.07.2022 um 11:46 schrieb Paul B Mahol <onemda at gmail.com>:
> 
> On Sat, Jul 16, 2022 at 11:22 AM Denis Połeć <denis.polec at gmail.com> wrote:
> 
>> Hello,
>> I wouldn't call myself a beginner, but I still need a little bit to become
>> a pro. :)
>> I have a question that might be easy to answer.
>> 
>> I am working on a script to bring multiple flat videos into a
>> equirectangular projection by using v360 filter.
>> I have the problem that the edges of the input are very jagged.
>> 
>> This did not lead to a good result when I play the equirectangular
>> projection in a 360 player. I have also already tried different
>> interpolation modes, which does not lead to a better result.
>> Does anyone have an idea how I can avoid that? Is there a better way to do
>> this task?
>> 
>> 
>> Here is an example code with the result. The video in the example has a
>> resolution of 1080p:
>> 
>> 
>> ffmpeg -i BRAIN.mp4 -lavfi "\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw='0':alpha_mask=1[fg1];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=90:alpha_mask=1[fg2];[fg2][fg1]overlay[a];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=-90:alpha_mask=1[fg3];[fg3][a]overlay[b];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=180:alpha_mask=1[fg4];[fg4][b]overlay[c];\
>> \
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=0:pitch=45:alpha_mask=1[fg5];[fg5][c]overlay[d];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=90:roll=45:alpha_mask=1[fg6];[fg6][d]overlay[e];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=-90:roll=-45:alpha_mask=1[fg7];[fg7][e]overlay[f];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=180:pitch=-45:alpha_mask=1[fg8];[fg8][f]overlay[g];\
>> \
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=0:pitch=-45:alpha_mask=1[fg9];[fg9][g]overlay[h];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=90:roll=-45:alpha_mask=1[fg10];[fg10][h]overlay[i];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=-90:roll=45:alpha_mask=1[fg11];[fg11][i]overlay[j];\
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=180:pitch=45:alpha_mask=1[fg12];[fg12][j]overlay[k];\
>> \
>> 
>> [0]v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=0:pitch=90:alpha_mask=1[fg13];[fg13][k]overlay[l];\
>> [0]drawbox=w=1:h=1:color=black,v360=input=flat:output=e:id_fov=45:w=5120:h=2560:yaw=0:pitch=-90:alpha_mask=1[fg14];[fg14][l]overlay"
>> -q:v 4  -vframes 1 -y test11.jpg
>> 
>> Your filtergraph is extremely inefficient with that many cascaded overlays
> and gives poor results. For proper stitching borders need to have small
> transition from full opacity to no opacity.
> 
> To add small transitions with opacity on borders could use blurring filters
> for example on alpha plane only.

How could I achieve that? How can I blurry just the borders? 

> Did not tried yet as I never needed to do stitching.
> 
> 
> 
>> output:
>> https://nextcloud.denispolec.de/index.php/s/8yF7rKdnB9HdJsa <
>> https://nextcloud.denispolec.de/index.php/s/8yF7rKdnB9HdJsa>
>> zoomed:
>> https://nextcloud.denispolec.de/index.php/s/fwdapyA8aGBdC2M <
>> https://nextcloud.denispolec.de/index.php/s/fwdapyA8aGBdC2M>
>> 
>> Thanks!
>> 
>> All the best,
>> denis
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