This may not really be vMix specific, but I'm wondering if it's possible to pre-encode a fully produced show to a file that is in the correct codec and bitrate for the stream, and then just play the file directly to the stream without decoding it to viewable video and then re-encoding for the stream.

I have a client that is producing an entire event in advance, and I'm planning to just roll the video file in vMix, but they're already encoding it to transfer the file to me, so I could theoretically skip the transcode if they use the right settings for their encode.

Thanks for any suggestions

That's my plan at the moment, there's just a built-in inefficiency in encoding to a small size for fast file transfer, and then decoding and re-encoding at another relatively low bit rate for internet. Normally I'd have them give it to me in Pro Res and not worry about it. If they get it looking how they want in H264/5 I don't imagine there will be strong artifacts from the transcode, I just like to maximize efficiency and minimize data loss.