Drag your *.webm video into the field
For own files please use the actually build of av1.
git clone https://aomedia.googlesource.com/aom
cmake aom
make
./aomenc --cpu-used=8 --tile-columns=4 --passes=2 --lossless=1 -o [output] [input(Y4M)]
Here you can looking for y4m files: https://media.xiph.org/video/derf/y4m/
Source Code: https://github.com/dominikhlbg/av1-ogv.js