Comment by DaleCurtis

The amount of frames necessary is going to depend on the codec and bitstream parameters. If it's H264 or H265, there's some more discussion and links here: https://github.com/w3c/webcodecs/issues/698#issuecomment-161...

The optimizeForLatency parameter may also help in some cases: https://developer.mozilla.org/en-US/docs/Web/API/VideoDecode...