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AudioGreg  
#1 Posted : Sunday, November 21, 2021 6:22:57 AM(UTC)
AudioGreg

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OK, I know this will be a big can of worms, but doing it anyway. :-) Please reference this screen shot, and understand this is a representation of an issue we've spent several weeks testing. Let's put aside any judgements of my setup or networking skills and assume for a sec that I know what I'm doing.

NDI stats

Here's the issue. NDI Screen Capture drops a lot of frames and I would like know why, or at least have NewTek say something about this as I believe it's a problem with their product. As you can see, I have several NDI sources for comparison. This shot shows about 5 minutes of elapsed time, and the number of frames each source dropped.

Birddog P100 camera - 0
BirdDog FlexIn - 2
Pana AW-HE40 (HX) - 8
NUC7i5BNK - Intel HD GPU running NDI Screen Capture 4.6 - 4109
vMix5 i9-11990K/Quadro GPU running NDI Screen Capture 5.0.10 (latest i think) - 4313

The switch is a Cisco SG350X-24PD, with an optimized vLAN for NDI traffic. My vMix computers live on 10G legs, the NUC on a 2.5G leg, and the rest of the contribution devices all have a gigabit leg to themselves. Before you ask, I've also tried the same switch with a factory reset config with nearly same results. I've tried several other multi-gigabit switches (Cisco, Netgear AV, TP-Link) with same results, incl. a generic gigabit dumb switch. BTW the NIC load coming into vMix4 never goes over 550Mb. We've tried different NIC drivers on the computers, different versions of vMix as the host, changed out cables and even tried different NICs in all 3 computers. We keep coming back to NDI Tools Screen Capture as the only thing we see these amounts of dropped frames on, no matter which computer we run it on.

Now all of that said, most techs here don't see a problem in the Screen Capture video feed (i see the occasional frame freeze-just 1 frame), although the drop rate is running several hundred frames per minute. Not horrendous I guess, but it reminds me of a joke where the punchline is "how many drops of urine can i put in your coffee before you notice?". We can load vMix Desktop capture utility on the same contribution computers and see a very small number (less than 10) of dropped frames in the same 5min window.


So here's the request to the forum, and anyone at vMix or NewTek that cares to follow up with this. What are your dropped frame stats in vMix using NDI Screen Capture?? Are you seeing the same thing that we are? Is there another tool besides vMix I can use to check for dropped frames?
Hypohamish  
#2 Posted : Thursday, November 25, 2021 5:47:03 AM(UTC)
Hypohamish

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Yes - it 'drops frames' when the NDI source stops moving, it's perfectly normal/expected behaviour.

So if you're screen capturing, let's say a PPT, once the slide has transitioned, the NDI feed effectively pauses until it detects a change/movement again, because presumably this is more efficient/it'd be a waste of bandwith to do anything otherwise.

You can test this yourself. Watch the stats live when you're screen capturing a desktop, move the mouse around and stuff and you'll notice it stops dropping frames. The second you stop moving/updating the screen, it'll drop hundreds of frames a minute!
thanks 1 user thanked Hypohamish for this useful post.
SportsNetUSA.net on 11/25/2021(UTC)
AudioGreg  
#3 Posted : Friday, November 26, 2021 9:40:29 AM(UTC)
AudioGreg

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in this case, the screen capture computers were running a full screen video playback with constant motion. we have also seen this behavior when using screen capture with zoom/teams/skype video call content. if it was just powerpoint slides i wouldn't care.
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