Don't think it can be done with vMix 16 since once streaming is started, you can't change or add destinations without stopping the stream.

Hi!

I think you can do it with a second encoder on external or external2 output (depending on your vmix licence) and if your pc is powerful enough.

I use Switchboard.live to schedule the Facebook Live broadcast. While I'm already streaming to Youtube
you can then publish when ready while the stream is in preview at Switchboard.
You can have up to 3 destinations with the free account along with the 3 that are available in Vmix

So you have the 1st one going to YouTube and the second one to Switchboard

Use this currently to do Press Conferences so can push our teams Presser to Facebook when they come to
the room while I was already streaming to YouTube for both teams earlier.

I can also start the stream a hour before and knowing its working and then quickly run to room after game
and click publish with out having the worry the stream not starting etc.

You can setup the live stream in Facebook, start streaming from vMix (using the url and key provided by Facebook). Your stream on FB will not be shown there until you hit its "Go Live" button. (might be a catch here if FB reacts to copyrighted content during the Preview).
https://www.facebook.com/facebookmedia/get-started/live

Yes I believe so with Switchboard live as once you publish or start broadcast to Facebook, you would need to create a new stream for new other accounts
thus have to stop and restart the stream in Vmix. I believe having multiple streams separate with cause higher CPU where when its combined it uses less cpu and memory.
Martin would be able to answer that better as I asked him about this before.

Yeap do that too, and was doing that before it was officially released using the developer account.

Ideally, I would split these tasks across 2 computers or devices; one for the YouTube Stream, and one for the stop-start Facebook Streams. This is effectively what we do with long streams; we stream continuously to our own platform, but we start and stop FB / Periscope events at key moments for shorter periods of time. The continuous stream takes an external SDI and goes into a separate encoder, while we use vMix for social streaming, all of which start and stop at the same time.

If that is not feasible for you, another option might be to use OBS on the same computer, select the vMix output as an input, and stream to YouTube using OBS, and FB through vMix (or vice versa).

I haven't tried that, but it works in my head as long as you have the bandwidth and CPU horsepower.

I can't think of anything else until we have independent control of the vMix streaming destinations which I too would like to see (but appreciate that it's not necessarily that simple).