[FFmpeg-user] Problem in v360?

[Michael Koch]

Am 25.10.2020 um 09:05 schrieb Michael Koch:
> Am 25.10.2020 um 03:02 schrieb Edward Park:
>> Hi,
>>
>>> 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.
>>
>> It seems to me it assumes a 45° vertical fov and 90° horizontal fov 
>> on both input and output, does that affect the behavior at all? (Or 
>> am I not understanding right)
>
> If the input and output images are specified as "equirectangular" 
> (V360=e:e:...) then the field of view is always 360° x 180°. There are 
> options for for input and output field of view, but these aren't used 
> in the case of equirectangular images. Something seems to be wrong 
> with the quaternions that were added October 7th.
> This is difficult stuff. A wild guess that might be worth testing:
> Swap the order of quaternion multiplication, 2nd and 3rd argument of 
> multiply_quaternion()

In this FFmpeg version from October 1th the v360 rotations are working 
correctly:

C:\Users\astro\Desktop>c:\ffmpeg\ffmpeg -i equirectangular_test.png -vf 
v360=e:e:yaw=90:pitch=45,v360=e:e:pitch=-45,v360=e:e:yaw=-90 -y out.png
ffmpeg version 4.3.1-2020-10-01-essentials_build-www.gyan.dev Copyright 
(c) 2000-2020 the FFmpeg developers
   built with gcc 10.2.0 (Rev3, Built by MSYS2 project)
   configuration: --enable-gpl --enable-version3 --enable-static 
--disable-w32threads --disable-autodetect --enable-fontconfig 
--enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp 
--enable-lzma --enable-zlib --enable-libsrt --enable-libssh 
--enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp 
--enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom 
--enable-libopenjpeg --enable-libvpx --enable-libass 
--enable-libfreetype --enable-libfribidi --enable-libvidstab 
--enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm 
--enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc 
--enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme 
--enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame 
--enable-libtheora --enable-libvo-amrwbenc --enable-libgsm 
--enable-libopencore-amrnb --enable-libopus --enable-libspeex 
--enable-libvorbis --enable-librubberband
   libavutil      56. 51.100 / 56. 51.100
   libavcodec     58. 91.100 / 58. 91.100
   libavformat    58. 45.100 / 58. 45.100
   libavdevice    58. 10.100 / 58. 10.100
   libavfilter     7. 85.100 /  7. 85.100
   libswscale      5.  7.100 /  5.  7.100
   libswresample   3.  7.100 /  3.  7.100
   libpostproc    55.  7.100 / 55.  7.100
Input #0, png_pipe, from 'equirectangular_test.png':
   Duration: N/A, bitrate: N/A
     Stream #0:0: Video: png, rgb24(pc), 2400x1200, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
   Stream #0:0 -> #0:0 (png (native) -> png (native))
Press [q] to stop, [?] for help
Output #0, image2, to 'out.png':
   Metadata:
     encoder         : Lavf58.45.100
     Stream #0:0: Video: png, rgb24, 2400x1200, q=2-31, 200 kb/s, 25 
fps, 25 tbn, 25 tbc
     Metadata:
       encoder         : Lavc58.91.100 png
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.04 bitrate=N/A 
speed=0.0459x
video:1851kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB 
muxing overhead: unknown