I run Utilorax, a set of free browser-based tools. The video tools are ffmpeg.wasm, which means every encode runs on the user's own machine and nothing is ever uploaded. That is the whole point of them — and it is also why they were slow.
This is what a week of trying to fix that actually taught me. The upgrade I was sure would fix it did not, and the thing that did was much less interesting and much more effective.
The starting point: one core
Every encode was pinned to a single thread:
function pinThreads(args) {
