How to share to a 1920x1080 TV?

[Saturn2888]

I have a 3440x1440 21:9 monitor I'd like to share on a 1920x1080 TV. I'm looking for a 60 frames per second solution with little to no lag so the people watching me play in the room are able to react to what I'm seeing while I'm seeing it that allows me to play in 21:9 whilst sharing the display on the TV. I can think of two ways I'd like to do this, the first one required:
1. Scaled vertically with the extra 21:9-16:9 on the sides cut off
2. Scaled horizontally w/ letterboxing

So far, there are only 2 solutions I've seen and both do only the second sharing method: Chromecast desktop sharing and Steam broadcasting. Neither of these do exactly what I want. Steam's broadcast lag is 5-10 seconds, and I'm unable to find framerate info on the Chromecast nor any info on how to scale just the center of the desktop.

[Haldi]

Mhmm, thats a cpmplicated task!
I know that h264 is able to crop (tested via Handbrake) so if you have the correct settings you should be able to grab the screen, re-encode to 1920x1080 and send.

I'm not sure how good VLC works with directX 11 Screen grabbing and stuff but you should be able to stream as http via VLC and re-encode to your needs.
Else MSI Afterburner supports live H264 recording, but no idea how you would stream that file.
But i'm not the Pro for Videostreaming here

[Delphium]

Failing that the best solution would be a hardware video scaler which would be expensive(~$2000) but will display in real time, or you could look at Open Broadcaster Software (free) to capture the screen or portion of screen and push out as an RTMP feed which can be made to be of low latency, ~1-2 seconds.