I was looking at different approaches to a in-browser Media Player for a while. It was only about a week ago that I found SourceBuffer.appendBuffer, in conjuction with FFMPEG -f segment that I thought there was something possible.
Then I finally cracked -segment_format_options which was the missing piece. I spent a whole day on that googling around, opening Upwork contracts trying to solve that problem. Could've been 1.5-2 days, I don't remember.
Point is, it wasn't just a 1-2 hackathon. There were serious technical problems that I solved.