Firefox Video Preloading

ffmpeg invocation:

ffmpeg -i original.mp4 -s 1280x720 -t 5 -b:v 0 -an -c:v libvpx-vp9 -crf 20 -keyint_min 25 -pass 1 -f null NUL &&
ffmpeg -i original.mp4 -s 1280x720 -t 5 -b:v 0 -an -c:v libvpx-vp9 -crf 20 -keyint_min 25 -pass 2 vp9-keyframes.webm

Please scroll down to load the video.