NDI questions

[jeremie.g...@free.fr]

Hi !

First, I'd like to thank QLab team to have added NDI capability in QLab 5.

For an ongoing creation, I'm using 2 Birddog Play to send video and audio to 2 TV.

I have 2 questions : 

- I've seen that in QLab 5.3, it will be possible to choose an audio output that isn't the NDI output in a video cue using NDI : would there be a way to route an audio cue to an NDI output ? (for now, I have to create a video cue instead of an audio one but it isn't very convenient).

- I have a strange behavior in the TVs (in QLab 5.2.4) : when I start a video cue in a state where nothing is running, the TVs displays a message as if the signal has changed... Is there a way to have a continuous NDI flow that starts with the workspace and never stops/restarts ? (I think I'll end with a black video cue always running in the background but it isn't very convenient).

Regards,

Jérémie

[Chad Sellers]

Hello,

To your first question, I'm afraid not at this time.

As to continuous NDI flow, a stage will have "Keep rendering between cues" turned on by default, so your NDI feed should keep going when no cue is running. However, if you panic the workspace to stop everything, the NDI output will stop as well. We found lots of users were struggling with this and wished NDI outputs (as well as Syphon outputs) would continue running beyond panic. So, in 5.3, NDI and Syphon outputs now continue running when a workspace panics. So, if you try your test again with the 5.3 beta, you should find your NDI output won't stop once started. And apologies for leaving this out of the list of changes in the post before.

Also, I'd recommend setting your NDI output to Y'CbCr 4:2:2 pixel format. QLab's NDI outputs are BGRA by default, but we've found that Birddog devices like to default to Y'CbCr every time they have no signal and take some time to switch over to BGRA. You can edit this under the Output Devices tab in video settings.

I hope that helps.

Chad Sellers

Figure 53

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[jeremie.g...@free.fr]

Thanks for your precise answers, it will help a lot !

I try this as soon as I have access to the setup again.

Regards,

Jérémie

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De: "Chad Sellers" <ch...@figure53.com>
À: ql...@googlegroups.com
Envoyé: Jeudi 19 Octobre 2023 20:51:51
Objet: Re: [QLab] NDI questions

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[jeremie.g...@free.fr]

Hi !

Just a follow up to my previous posts for people having questions about NDI out in QLab.

I can confirm that 5.3 version helps with "keep rendering between cues" and audio outputs.

But I have a big problem with QLab becoming unresponsive after some times when I edit timeline Cues including video with NDI outputs (tested with 5.3.2).

After some edits, it starts to lag and when I trigger the cue, the video is out of sync with other events.

Even panicking the workspace let me see the spinning wheel (although my M1 Max MacBook Pro totally responsive with other apps) for several minutes and preloading the cues doesn't change anything.

In my workspace, each timeline include one video cue (with 2 NDI outputs) that is the support for a lot of synchronized network cues triggering Millumin for pixel mapping and EOS for lighting.

The only way I found to fix the problem is to replace NDI outputs by Syphon ones and use NDISyphon to send video streams to my Birddog Play devices on stage : with that workaround, everything runs fine (even without preloading the cues).

I'm in touch with QLab support team but if anyone has the same type of problem (and maybe a solution to fix it), it would be nice to know.

Regards,

Jérémie

[Kinetic Screen]

I think I might have also encountered this, though because it only happened during the show (!) I haven't been able to recreate or, so I've held off on reporting it.

I'll describe what I encountered and see if it matches up with your experience. 

I had 3 video screens, one of which was using an NDI Birddog receiver, the other 2 were direct HDMI connections. There were group cues I fired off, which had content on all 3 screens. When firing off this cue, it would lock up momentarily, and then when it finally fired, some of the videos were out of sync. This was clearly obvious, because I had a video package playing to 2 screens, and then a ProRes 4444 video with just subtitles overlayed on one of them. I remember the subtitles had essentially started correctly whereas the video / audio was delayed. I manually resynced the subtles by pausing and playing the cue directly in the live cue list.

The complicating factor to this was that the video screens involved in this cue were actually not the NDI output. My gut feeling was that it was something to do with the NDI, but I didn't have enough evidence or repeated experience to recreate it.

More recently, using Qlab as the video playback for a livestream (outputting via NDI) I had a similar 'lockup' happen when firing off a simple ProRes video file...

Again I don't really have enough data to make sense of it - and it also happened while on-air.

The only time I've had this same feeling of Qlab locking up, is sometimes when panicking a complicated series of runningn cues. It's always been a thing that just happens sometimes, but Qlab always ends up behaving itself after a few seconds of unresponsive, and continuing to play all the cues... This has always been a thing since at least v4

[Chris Ashworth]

All of these reports are very helpful to know, thanks everyone for sharing!

When it comes to NDI there is a large and ever-present possibility of bugs simply within NDI — the only option we have is to plunk their library into QLab and hope it works as advertised (and update it when they fix bugs), so it’s worth noting we have real limits to our ability to fix NDI related bugs that might exist. Any bugs in their library become our bugs, but not ones we can fix.

That said, there are still plenty of bugs possible with how we integrate with it, so these reports are also valuable to help us make sure we don’t have lingering issues there.

Best,

C