OK to your credit your original request was to get this all working in a single html file. That is not possible with the easy paths documented on ffmpeg.
By default, the build relies on web workers which need to load their code from somewhere (and usually it has to be the same origin as the code making the request)
Through much mastery of JS build systems that I would not wish on my enemies, I bet you could get it working on localhost, but you’ll have a much better time of it if you set up vite or something for a local build. You can still easily do a “serverless” deploy with GitHub pages or similar but you do need an http server correctly configured for asset requests.
By default, the build relies on web workers which need to load their code from somewhere (and usually it has to be the same origin as the code making the request)
Through much mastery of JS build systems that I would not wish on my enemies, I bet you could get it working on localhost, but you’ll have a much better time of it if you set up vite or something for a local build. You can still easily do a “serverless” deploy with GitHub pages or similar but you do need an http server correctly configured for asset requests.