This demo extracts all frames from an MP4 file and renders them to a canvas as fast as requestAnimationFrame will allow. It uses mp4box.js to parse and demux the file. This is based on https://w3c.github.io/webcodecs/samples/mp4-decode/.
If the videos above 360p aren't loading, enable the CORS-anywhere demo server here: https://cors-anywhere.herokuapp.com/.