Live Production Software Forums

Welcome Guest! To enable all features please Login or Register.



Go to last post Go to first unread
#1 Posted : Sunday, September 5, 2021 12:45:23 AM(UTC)

Rank: Newbie

Groups: Registered
Joined: 5/26/2021(UTC)
Posts: 4
Location: Lahoe

Using Harmonic Electra 8000 Encoder - I want to convert my SRT stream to 1080i 25fps in order to get it correctly in my encoder - any ideas how to convert my SRT Stream to 1080i?
#2 Posted : Friday, September 10, 2021 12:31:26 PM(UTC)

Rank: Advanced Member

Groups: Registered
Joined: 6/16/2015(UTC)
Posts: 192
United Kingdom
Location: Milton Keynes, UK

Thanks: 10 times
Was thanked: 53 time(s) in 27 post(s)
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.

#3 Posted : Friday, September 10, 2021 6:30:07 PM(UTC)

Rank: Administration

Groups: Administrators
Joined: 1/13/2010(UTC)
Posts: 4,789
Location: Gold Coast, Australia

Was thanked: 3410 time(s) in 1303 post(s)
vMix SRT support was designed to be solely hardware accelerated.

Interlaced support with NVENC/NVDEC and other hardware encoder/decoders is problematic at best.
Early during the development phase we had to make the decision to drop interlaced support as it just made things very buggy and problematic and
impossible to overcome in many cases.

The future is progressive and SRT is a part of that. If you need interlaced support, then it is fine to use
other hardware encoders/decoders instead of vMix, interfacing with vMix using standard SDI/HDMI capture cards.

To be clear: vMix will never be supporting interlaced with SRT for the reasons outlined above.


thanks 3 users thanked admin for this useful post.
eduardocfs on 9/10/2021(UTC), ask on 9/11/2021(UTC), mjgraves on 9/18/2021(UTC)
Users browsing this topic
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.