Hello, long time lurker and happy vMix operator here.

Just prior to live events, and now subsequently during tests, when I have attempted to stream to a key and URL on vMix out to Teams, I get the "failed to upload header..." error msg and error report below. It isn't happening with my FB streams and they use identical streaming quality. My research thus far (including articles on here) suggest it could either be a connectivity issue at the stream-host end, or it could be vMix not liking a stream being activated prior to a recording having started.

If anyone can help me progress to solve this issue I'd be grateful.

FFMPEG1.Exited
Last message repeated 1 times
[flv @ 05d91fc0] Failed to update header with correct duration.
[flv @ 05d91fc0] Failed to update header with correct filesize.
Error writing trailer of rtmps://emea.rtmpingest.mcr.teams.microsoft.com:1936/meeting/387191253276/csf0kxx: I/O error
frame= 24 fps=0.0 q=2.0 Lsize= 4kB time=00:00:00.97 bitrate= 35.8kbits/s speed=3.11x
video:3kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 15.194532%
[tls @ 05d98000] Writing encrypted data to socket failed
Last message repeated 1 times
[tls @ 05d98000] Failed to send close message
[libx264 @ 05d93360] frame I:1 Avg QP: 4.00 size: 2737
[libx264 @ 05d93360] frame P:23 Avg QP: 0.52 size: 12
[libx264 @ 05d93360] mb I I16..4: 100.0% 0.0% 0.0%
[libx264 @ 05d93360] mb P I16..4: 0.0% 0.0% 0.0% P16..4: 0.0% 0.0% 0.0% 0.0% 0.0% skip:100.0%
[libx264 @ 05d93360] coded y,uvDC,uvAC intra: 0.0% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 05d93360] i16 v,h,dc,p: 98% 0% 2% 0%
[libx264 @ 05d93360] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 0% 0% 100% 0% 0% 0% 0% 0% 0%
[libx264 @ 05d93360] i8c dc,h,v,p: 100% 0% 0% 0%
[libx264 @ 05d93360] kb/s:25.11
[aac @ 05d96340] Qavg: 65536.000
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