What's the most performant way to encode an mp4 video of frames from a webgl canvas using Javascript in a web browser?

I can capture the frames from the canvas using readPixels (https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/readPixels) but then what?

I think there are a few wasm versions of ffmpeg but they're slow.

I found this web assembly mp4 encoder but it's no longer supported and doesn't work in Chrome on my phone.

Any other suggestions?

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