I have no idea why vMix can't support 1080i over SRT. SRT is supposed to be a data agnostic transport, and doesn't care whether the signal being passed is interlaced or not. I presume the issue is actually the way the h.264 encoder used within vMix is either incapable or Martin has chosen not to implement interlaced encoding. This may be because RTMP was the preferd transport for web streaming, and all computers are effectively progressive devices, the requirement for interlacing was forgotten.

As 1080i is the PREDOMINANT HD broadcast format here in the UK, I find it bizarre that vMix fails to support it over SRT (or RTMP for that matter) again suggesting its the way the encoder is configured.

I also use Harmonic Electra encoders, and the only way I can get the feed up to the bird in the sky, is by using HD-SDI on Decklink cards directly to the Encoders (actually going via a couple of Blackmagic Universal Videohubs).

It may be possible, and I will do some experiments and report back, that you could use FFMPEG. I have a private build of FFMPEG (Non-Free) that supports NDI, Decklink, and NVenc. It could pick up your 1080i signal using NDI, encode it using hardware (i.e the hardware encoders on an NVIDIA card), and send it out using SRT (which is available in FFMPEG). Unfortunately the FFMEG version is locked, as it was built during the brief period FFMPEG supported NDI, before the BIG argument that saw it removed.

The other option is to petition Martin to support interlacing in his encoders - especially as 1080i25 is the format HD broadcasters like, as it used a fraction of the broadcast bandwidth a 1080p50 signal uses, but retains the 50/60 fps temporal fluidity.

Keith

Dear Vmix community,

I totally agree 1080i50 is THE distribution standard at this time for europe broadcast world!
Why double up horizontal resolution on the small budget feeds (and reducing effective bandwith/pixel) instead of running the SRT Feed native!?

Concerning Interlaced SRT feeds coming from professional haivision encoders or teradek cube encoders (supporting SRT in 1080i50!)(showing up in vmix as 1920x540p50) there IS a FFMPEG option to properly "reformat" it to 1920x1080i50)

the option is called
mode=merge of the tinterlace-filter, see here

https://ffmpeg.org/ffmpeg-filters.html#tinterlace

It would be soooooooo great to properly handle 1080i50 to a 1920x540p50 SRT stream and the decode it back proper again or at least decode-reformat a SRT stream coming in with that resolution back to standard 1080i50.
that saves bandwith, bad upscaling deinterlacing etc on transmitter side and really helps those people working in a complete 1080i50 format - broadcast world.

Looking so much forward maybe using this tinterlace option here!

Thanks!