I am helping an E African church with their satellite TV channel. To perform a live switch, it needs to be initiated in the studio in E Africa a fixed amount of time (pre-fade time) before the switch (opt-out) is activated in Airbox at the uplink site. Initial tests using the RTMP streaming option functionally worked but the round-trip delay time was reported to be about 1.5 minutes, due mainly to the software solution offered at the uplink site.

There appear to be three options for improvement
a) Zixi which has been requested before. Although C code is available on the seb, I belive the protocol is subject to lincense issues
b) SRT which uses ARQ to recover lost packets https://www.srtalliance.org/
c) RIST which also uses ARQ

It strikes me that options b and c above should be considered for inclusion in vMix. The link to SRT above is impressive with processing delay down to 260 mS, showing 2.7 Mbps using HEVC, using a very long GoP (60 frames, 50 frames may be OK for 1080i/25).

Another consideration is that for Broadcasting it needs to be CBR, interlaced
Thanks