[FFmpeg-trac] #9872(undetermined:new): WebP vs PNG alpha

[FFmpeg]

#9872: WebP vs PNG alpha
-------------------------------------+-------------------------------------
             Reporter:  Jozef        |                    Owner:  (none)
  Chutka                             |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:  scale alpha  |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Comment (by Jozef Chutka):

 Hi Carl,

 files are different in format png vs webp, however the content/pixels it
 contains is the same. I am reporting that the scale filter produces
 different output for such setup (same pixels, different input format).

 Can you please elaborate how can I use rawvideo in my case?


 Attaching console output of the problematic command:

 {{{
 ffmpeg -filter_complex
 "color=white:200x200[b];movie=x.webp,scale=200:200,[b]overlay" -y out-
 webp-scale.png
 ffmpeg version 2022-07-31-git-1368b5a725-full_build-www.gyan.dev Copyright
 (c) 2000-2022 the FFmpeg developers
   built with gcc 12.1.0 (Rev2, 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-libsnappy --enable-zlib --enable-librist --enable-libsrt
 --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray
 --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libdavs2
 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1
 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2
 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg
 --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r
 --enable-libfreetype --enable-libfribidi --enable-liblensfun --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-libshaderc
 --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio
 --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-
 libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora
 --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-
 libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex
 --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite
 --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-
 chromaprint
   libavutil      57. 30.100 / 57. 30.100
   libavcodec     59. 40.100 / 59. 40.100
   libavformat    59. 29.100 / 59. 29.100
   libavdevice    59.  8.101 / 59.  8.101
   libavfilter     8. 46.101 /  8. 46.101
   libswscale      6.  8.101 /  6.  8.101
   libswresample   4.  8.100 /  4.  8.100
   libpostproc    56.  7.100 / 56.  7.100
 Stream mapping:
   overlay:default -> Stream #0:0 (png)
 Press [q] to stop, [?] for help
 Output #0, image2, to 'out-webp-scale.png':
   Metadata:
     encoder         : Lavf59.29.100
   Stream #0:0: Video: png, rgba(pc, gbr/unknown/unknown, progressive),
 200x200 [SAR 1:1 DAR 1:1], q=2-31, 200 kb/s, 25 fps, 25 tbn
     Metadata:
       encoder         : Lavc59.40.100 png
 [Parsed_movie_1 @ 0000023dfd060640] EOF timestamp not reliable7 bitrate=
 -0.0kbits/s speed=N/A
 [image2 @ 0000023dfd056680] The specified filename 'out-webp-scale.png'
 does not contain an image sequence pattern or a pattern is invalid.
 [image2 @ 0000023dfd056680] 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.
 [image2 @ 0000023dfd056680] Cannot write more than one file with the same
 name. Are you missing the -update option or a sequence pattern?
 av_interleaved_write_frame(): Invalid argument
 Error muxing a packet for output file #0
 frame=    2 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.60 bitrate=N/A
 speed=21.4x
 video:7kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: unknown
 Conversion failed!
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9872#comment:3>
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