logo

Live Production Software Forums


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

Notification

Icon
Error

Options
Go to last post Go to first unread
peixe  
#1 Posted : Tuesday, July 21, 2020 12:17:22 AM(UTC)
peixe

Rank: Newbie

Groups: Registered
Joined: 5/11/2020(UTC)
Posts: 5
Brazil
Location: Rio

Was thanked: 8 time(s) in 3 post(s)
Hi.

I understand interlaced over SRT is not supported.

Most broadcasters still are bounded to interlaced for multiple reasons and this will be a strong feature need to integrate with different workflows.

At the moment we are testing sending interlaced sgnals from a Makito encoder into vMix (1080@50i) and they show up in vmix as 540@50p which makes sense but it´s unuseable.

Is there any paln to support for incoming (and outgoing) interlaced SRT?
As said it is critical to integrate with existing workflows in the broadcast world.

Is there any workaround that would allow to convert in vMix from this 540@50p into 1080i?
DWAM  
#2 Posted : Wednesday, August 5, 2020 6:34:57 PM(UTC)
DWAM

Rank: Advanced Member

Groups: Registered
Joined: 3/20/2014(UTC)
Posts: 2,436
Man
France
Location: Bordeaux, France

Thanks: 200 times
Was thanked: 699 time(s) in 534 post(s)
Asking this question here makes no sense! vMix is not in charge of the evolution of the SRT protocol, you'd better ask your question to the SRT Alliance.

However I can give you my personal opinion : it is very unlikely to see interlaced signals supported by SRT one day. Interlacing is a thing of the past, even if broadcasters still use it.
This being said, you can still stream progressive SRT to a TV station, they just need to process it before use so that it conforms to their requirement. This can be done in realtime with a basic ffmpeg script or whatever signal processor they want to use.

For this, I'd push a 1080p50 feed to them (shot with a correct shutter speed) so that they can get a 1080i50 conversion simply by making each frame interlaced. Or you can check this:
https://en.wikipedia.org...gressive_segmented_frame
peixe  
#3 Posted : Thursday, August 6, 2020 1:43:32 AM(UTC)
peixe

Rank: Newbie

Groups: Registered
Joined: 5/11/2020(UTC)
Posts: 5
Brazil
Location: Rio

Was thanked: 8 time(s) in 3 post(s)
@DWAM
Asking this question here makes absolute sense, so let me explain further.

"it is very unlikely to see interlaced signals supported by SRT one day"
SRT does indeed support interlaced signals or, to put it more accurately, SRT doesn´t care at all about your signal flavor as it is a data transfer protocol and thus why it is agnostic to anything you send inside of it.

The problem with vMix supporting interlaced OVER SRT (note the difference) has to do with vMix handling already interlaced signals that use SRT as a means of transmission.

As I learned, this is a problem at the decoder level on vMix that is not easy to solve.

While this is a problem with the codec that vMix uses, it does present a problem unique to vMix since other receiving ends like hardware SRT receivers or even VLC player do handle interlaced video OVER SRT.

"it is very unlikely to see interlaced signals supported by SRT one day"
I can partially agree with your statement, given the fact that unless you still use a CRT display, your signal indeed will be deinterlaced at some point (probably at the TV in a way that is not controlled) so whenever possible you should go for something like 50P.

HOWEVER.
There is a ton of hardware at the source, middle and destination that cannot support 50P.
This is particularly true for most broadcasters not just because they are OLD but because the underlying infrastructure rely on other signal processing stages that cannot support 50P or even 25P sometimes (and even if they do 25P does present other issues on moving images).

It is fairly simple to integrate this interlaced workflow on a vMix workflow based on SDI as conversions to 50P and/or back to 50i can be done by the capture cards.
This solves downconverting to 50i at the delivery but I still have not found a fully working reliable workflow from hardware encoders sending 50P over SRT to vMix either (working on further testing on that).


While vMix might eventually work reliably for anyone using 50P signals over SRT, that is not always possible when your source is indeed 50i (like most existing broadcast cameras and several other hardware), or it involves undesired steps and gear to upconvert the signals.


For a broadcaster, changing all the infrastructure to 50P requires a huge investment that is not a simple change, and one I can promise, no one is going to do to be able to use vMix in the mix.

On the contrary, if there were a simple way to add interlaced support (even by converting it to 50P on arrival) on Vmix end, it will hugely improve the ability to integrate vMix with existing hardware, which is specially useful for (but not limited to) broadcasters

Unfortunately, this I am told this is not possible so I am still trying to find a workaround it since at the moment even while trying to use 50P over SRT, I have not yet been able to integrate vMix into an existing infrastructure that is heavily based on interlaced workflows.

Arguably, this might not be a problem with vMix itself, but so far it is indeed limiting it´s possible use on this kind of scenarios so I still think it would be very useful to add some level of support for it on vMix itself.

P.S.
Progressive segmented frame is a way to use PROGRESSIVE SIGNALS ON INTERLACED SYSTEMS, which is completely the other way around of this specific problem.



livepad  
#4 Posted : Sunday, August 9, 2020 7:15:17 PM(UTC)
livepad

Rank: Advanced Member

Groups: Registered
Joined: 3/31/2016(UTC)
Posts: 126
Location: london

Thanks: 2 times
Was thanked: 46 time(s) in 32 post(s)
Originally Posted by: peixe Go to Quoted Post
Hi.

I understand interlaced over SRT is not supported.

Most broadcasters still are bounded to interlaced for multiple reasons and this will be a strong feature need to integrate with different workflows.

At the moment we are testing sending interlaced sgnals from a Makito encoder into vMix (1080@50i) and they show up in vmix as 540@50p which makes sense but it´s unuseable.

Is there any paln to support for incoming (and outgoing) interlaced SRT?
As said it is critical to integrate with existing workflows in the broadcast world.

Is there any workaround that would allow to convert in vMix from this 540@50p into 1080i?



This issue mainly affects HEVC although we have also seen it on H.264

A very simple solution exists off the shelf. available today. This is a small part of a professional broadcast infrastructure workflow - the sort of workflow users of Makito encoders will be involved in.

Sienna NDI Processing Engine has a module which converts (540p50) SRT back into 1080i50 NDI (and same for 1080i5994)

This unique module detects the flags which Makito places in the bitstream to indicate upper and lower fields as they are converted into progressive frames for the 540p transit ensuring a seamless return to 1080i50 without any scaling or other deinterlacing artefacts.

Sienna NDI Processing Engine Info

Note that systems which de-interlace the 50i before encoding to create 25p or 50p tend to compromise the image somewhat, since the compression macroblocks include lines from different fields - and these will very often 'smear' the macroblock content compared to encoding macroblocks containing lines from a single field. This is the reason why the best quality systems will either use a codec with native interlaced support or in cases like HEVC they will encode pSF format, with appropriate flags in the bitstream for professional decoders to pick up to reverse the encoding.
fabfab10  
#5 Posted : Monday, September 21, 2020 6:18:00 AM(UTC)
fabfab10

Rank: Member

Groups: Registered
Joined: 2/20/2019(UTC)
Posts: 15
Italy
Location: Firenze

Was thanked: 1 time(s) in 1 post(s)
Many devices use interlaced H264 as input/output and then internally they de-interlace before encoding and re-interlace at the decoder side.
SRT being a transport protocol should be agnostic to the content it's transporting, so it's on the codec side.
VMix so far is not able to record interlaced H264, i think the problem reside in this part.
Once (and if ever) they get interlaced H264 recording it will be available on SRT as well.
H265 (HEVC) should be not very far from this as well
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.