D:\>ffmpeg -f lavfi -i "[email protected]:size=1280x720:duration=10,format=yuva420p" -c:v libvpx-vp9 -pix_fmt yuva420p transparent_black.webm
ffmpeg version 8.0-full_build-http://www.gyan.devCopyright (c) 2000-2025 the FFmpeg developers
built with gcc 15.2.0 (Rev8, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-lcms2 --enable-libxml2 --enable-gmp --enable-bzlib --enable-
lz
ma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-libdvdnav --enable-libdvdread --enable-sdl2 --enable-libaribb24 --enable-libaribcaption --enable-libdav1d --enable-libdavs2 --enable-libopenjpeg --enable-libquirc --enable-libuavs3d --enable-libxevd --enable-libzvbi --enable-liboapv --enable-libqrencode --enable-librav1e --enable-libsvtav1 --enable-libvvenc --enable-libwe
bp
--enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxeve --enable-libxvid --enable-libaom --enable-libjxl --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libharfbuzz --enable-liblensfun --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-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-openal --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libcodec2 --enable-libilbc --enable-libgsm --enable-liblc3 --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint --enable-whisper
libavutil 60. 8.100 / 60. 8.100
libavcodec 62. 11.100 / 62. 11.100
libavformat 62. 3.100 / 62. 3.100
libavdevice 62. 1.100 / 62. 1.100
libavfilter 11. 4.100 / 11. 4.100
libswscale 9. 1.100 / 9. 1.100
libswresample 6. 1.100 / 6. 1.100
Input #0, lavfi, from '[email protected]:size=1280x720:duration=10,format=yuva420p':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Video: wrapped_avframe, yuva420p, 1280x720 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 25 tbn
Stream mapping:
Stream
#0:0 -> #
0:0 (wrapped_avframe (native) -> vp9 (libvpx-vp9))
Press [q] to stop, [?] for help
[libvpx-vp9 @ 000001fa36e401c0] v1.15.2-100-g40561f514
[libvpx-vp9 @ 000001fa36e401c0] Neither bitrate nor constrained quality specified, using default CRF of 32
Output #0, webm, to 'transparent_black.webm':
Metadata:
encoder : Lavf62.3.100
Stream #0:0: Video: vp9, yuva420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 25 fps, 1k tbn
Metadata:
encoder : Lavc62.11.100 libvpx-vp9
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
[out#0/webm @ 000001fa36dcc580] video:10KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: 154.070962%
frame= 250 fps= 49 q=32.0 Lsize= 27KiB time=00:00:10.00 bitrate= 21.8kbits/s speed=1.95x elapsed=0:00:05.11
D:\>ffprobe -v error -select_streams v:0 -show_entries stream=pix_fmt transparent_black.webm
[STREAM]
pix_fmt=yuv420p
[/STREAM]