NDI 5 lag in OBS, not in NDI Studio Monitor

[benoitvm]

I am recording/streaming a presentation where the presenter's laptop running the Powerpoint slideshow is connected to the OBS computer through ND5 over a LAN.
A very annoying thing is that while there is absolutely no lag when I check the slideshow on the OBS machine with NDI Studio Monitor, OBS exhibits often serious lag, or even seems to miss slide advance (a problem since there is then mismatch between the speech and the slide displayed in OBS). When that happens, I haven't found a way to "nudge" the NDI image inside the OBS monitor.
I have no clue what the problem might be, as the OBS computer has no bottleneck (e.g. a connected camera works just fine and Task Manager reports very low CPU & GPU utilization), and the LAN connection between the presenter's laptop and the OBS computer is working flawlessly (witnessed by the NDI Studio Monitor image). The problem is independent of recording/streaming state inside OBS.
Hints ?
This is rather urgent, I'm going live tonight...

 

[dichterDichter]

what i sometimes see is that the obs preview sometimes looks like it was lagging but the streamed or recorded video is fine. Have you recorded something and you see the same lags? Also i would check for same NDI Tools/runtime versions on the computers. The next thing is checking latency mode and source timing. What dows the cpu % while recording? Also check the graphics card (check what you are using to encode)

 

[JohnPee]

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obsproject.com

 

[benoitvm]

what i sometimes see is that the obs preview sometimes looks like it was lagging but the streamed or recorded video is fine. Have you recorded something and you see the same lags? Also i would check for same NDI Tools/runtime versions on the computers. The next thing is checking latency mode and source timing. What dows the cpu % while recording? Also check the graphics card (check what you are using to encode)

OK, the show went quite good, but here is what I noticed: because the speaker was quite fast this time, the slide succession was fast too and the refresh of the slides on the NDI source was ok; only near the end, after the closing slide was shown for several minutes (I have to check on the recording how long that was), the speaker went back to an earlier slide to answer a question from the andience and there, the NDI image in OBS did NOT update (I has to quickly switch to another scene, where only live camera video was recorded). It looks like the NDI source (OBS-NDI 4.13) somehow goes into sleep/freeze mode after a while :-P
both the streamed video and the local recording show the problem
NDI Tools 5.6.0.0 on both ends
OBS 30.0.2
OBS-NDI 4.13
other specs later on

 

[subnoize]

Hello, we see this all the time. Every slide in your PowerPoint needs a transition. Preferably a slow one (dissolve at 0.75 seconds is reliable).

The issue is how NDI prioritizes optimization for encoding. If you sit for a long period (20 seconds+) on a static slide and then do a cut to a new slide the NDI optimization engine will miss it for a few seconds or even a few minutes.

When I am given a presentation to display I will select all slides and just blindly apply the 0.75 second dissolve before I begin unless somebody promises me they have already done it themselves.

Hope that helps.

PS. If the PowerPoint presentation isn't in the preview or program even with the transitions NDI can miss a slide. So it must be visible at all times in OBS. You can just use a NDI Monitor to keep it active as well outside of OBS.

 

[benoitvm]

Hello, we see this all the time. Every slide in your PowerPoint needs a transition. Preferably a slow one (dissolve at 0.75 seconds is reliable).

The issue is how NDI prioritizes optimization for encoding. If you sit for a long period (20 seconds+) on a static slide and then do a cut to a new slide the NDI optimization engine will miss it for a few seconds or even a few minutes.

When I am given a presentation to display I will select all slides and just blindly apply the 0.75 second dissolve before I begin unless somebody promises me they have already done it themselves.

Hope that helps.

PS. If the PowerPoint presentation isn't in the preview or program even with the transitions NDI can miss a slide. So it must be visible at all times in OBS. You can just use a NDI Monitor to keep it active as well outside of OBS.

This makes sense, I think it is exactly what I need as info (and workaround !) - Thx
According to you, is this a NDI or a OBS-NDI issue ? Is the optimization engine you mention a part of NDI ? Nothing to tune there when using Powerpoint ?
I see NDI 6 is out, have you been able if this issue is still present ?

 

[subnoize]

Hello!

I have installed NDI v6 Tools and rebooted all machines and I no longer see the issue. I am using PP on a different machine than OBS with HX3 Screen Capture (including audio) . Hardware acceleration is enabled (this isn't related to the issue with VLC NDI as a media server, so keep hardware acceleration DISABLED for VLC over NDI if you get the green screen). Our PP machine is also our VLC NDI Media server and it works flawlessly for the moment.