A minimal example of building FFmpeg's libav to WebAssembly via Emscripten using Docker.

https://dev.to/alfg/ffmpeg-webassembly-2cbl

Build the WebAssembly files using Docker and copy the output to www/:

docker-compose run mp4info make
cp -a dist/. www/

Run the server:

npm install express
node server.js

Load the demo in a browser and select the tears-of-steel-10s.mp4 file:

http://localhost:8080/www

MIT