We've already implemented this as part of a web-based AV1 analyzer tool. You provide the URL to both the image and the decoder, which is very convenient because

We've already implemented this as part of a web-based AV1 analyzer tool. You provide the URL to both the image and the decoder, which is very convenient because the decoder is constantly changing [1]. Wikipedia also does this to enable video playback on Edge and Safari [2]. The idea to do this within the format itself is quite old. The very early versions of what became Vorbis had a very similar concept, with programmable passes. Matroska once had a field for a link to download the VfW decoder dll (the horror!). It's never really caught on, due to reasons already listed by sibling comments. [1] https://arewecompressedyet.com/analyzer/?maxFrames=4&decoder=https://arewecompressedyet.com/runs/mvref-seed-after@2017-05-17T22:29:27.499Z/js/decoder.js&decoderName=mvref-seed-after%402017-05-17T22%3A29%3A27.499Z&file=https://arewecompressedyet.com/runs/mvref-seed-after@2017-05-17T22:29:27.499Z/objective-1-fast/Netflix_SquareAndTimelapse_1920x1080_60fps_8bit_420_60f.y4m-55.ivf https://arewecompressedyet.com/analyzer/?maxFrames=4&decoder... [2] https://github.com/brion/ogv.js/ https://github.com/brion/ogv.js/