[FFmpeg-user] v360 filter output eac resolution

[Paul B Mahol]

On Fri, Jul 12, 2024 at 4:04 AM Jimmie <plustone at gmail.com> wrote:

> Hi,
>
> I'm currently working on a project about Equi-Angular Cubemap (EAC).
>
> I need to sample an EAC texture but couldn't find one readily available.
> After some googling, I found that FFmpeg could be used to convert
> other 360 pictures to EAC, so I gave it a try.
>
> The input is an equirectangular texture with 3000x1500 resolution and
> the output is an EAC texture with a standard 3x2 format, as expected.
>
> What confuses me is that the EAC texture has a resolution of 3000x1688.
> To my understanding, EAC is just a special case of cubemap, which should
> consist of six square faces. Apparently, that is not the case for this
> output.
>
> Can anyone help me understand why the output EAC texture does not have
> square faces as in regular cubemaps? Thank you!
>

https://paulbourke.net/panorama/youtubeformat/


>
> Alex
>
> Command: ffmpeg -i pond.jpg -vf v360=e:eac eac.png
> The log is as below.
>
> ffmpeg version 7.0.1-essentials_build-www.gyan.dev Copyright (c)
> 2000-2024 the FFmpeg developers
>   built with gcc 13.2.0 (Rev5, 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-bzlib --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-mediafoundation --enable-libass --enable-libfreetype
> --enable-libfribidi --enable-libharfbuzz --enable-libvidstab
> --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm
> --enable-cuvid --enable-dxva2 --enable-d3d11va --enable-d3d12va
> --enable-ffnvcodec --enable-libvpl --enable-nvdec --enable-nvenc
> --enable-vaapi --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      59.  8.100 / 59.  8.100
>   libavcodec     61.  3.100 / 61.  3.100
>   libavformat    61.  1.100 / 61.  1.100
>   libavdevice    61.  1.100 / 61.  1.100
>   libavfilter    10.  1.100 / 10.  1.100
>   libswscale      8.  1.100 /  8.  1.100
>   libswresample   5.  1.100 /  5.  1.100
>   libpostproc    58.  1.100 / 58.  1.100
> Input #0, image2, from 'pond.jpg':
>   Duration: 00:00:00.04, start: 0.000000, bitrate: 154676 kb/s
>   Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc,
> bt470bg/unknown/unknown), 3000x1500 [SAR 240:240 DAR 2:1], 25 fps, 25
> tbr, 25 tbn
> Stream mapping:
>   Stream #0:0 -> #0:0 (mjpeg (native) -> png (native))
> Press [q] to stop, [?] for help
> [swscaler @ 000002ad6cac5540] deprecated pixel format used, make sure
> you did set range correctly
>     Last message repeated 3 times
> Output #0, image2, to 'eac.png':
>   Metadata:
>     encoder         : Lavf61.1.100
>   Stream #0:0: Video: png, rgb24(pc, gbr/unknown/unknown,
> progressive), 3000x1688 [SAR 1:1 DAR 375:211], q=2-31, 200 kb/s, 25
> fps, 25 tbn
>       Metadata:
>         encoder         : Lavc61.3.100 png
> [image2 @ 000002ad6cc35fc0] The specified filename 'eac.png' does not
> contain an image sequence pattern or a pattern is invalid.
> [image2 @ 000002ad6cc35fc0] Use a pattern such as %03d for an image
> sequence or use the -update option (with -frames:v 1 if needed) to
> write a single image.
> [out#0/image2 @ 000002ad6c9e0040] video:9207KiB audio:0KiB
> subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead:
> unknown
> frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.04 bitrate=N/A
> speed=0.0467x
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