Question / Help Magewell Framerate stutter when stream/recording 60fps

[mystakin]

I've been using a Magewell XI100DUSB to stream from an older PC for about a year now with a lot of success. I've always been more of a mac guy so I picked up a 27" iMac recently, which has been going great except the capture card doesn't seem to work as well with it.

Log is included below of a test recording. My C922 webcam manages 55-60fps without much trouble but the Magewell struggles to stay above 40 most of the time. It doesn't seem like it's a power issue since there's 0 encoding lag and rendering lag is minimal if not 0. I thought turning off the canvas preview would help but that didn't do much, either.

The card still records a smooth 60fps on my old machine, but I'm at a loss for how to up the frame rate on the newer one.

Here's a video link to get an idea of the stutter. It's been slowed down to half speed to make it more obvious: https://youtu.be/_LxBtsgwYsk

 

[Narcogen]

Does it still do this if you don't downscale from 720p to 480p? Just curious, from the log there doesn't seem to be a problem in rendering or encoding.

 

[mystakin]

Still experience the problem without downscaling. Thought it may be a weird USB bottleneck, so I used a USB 3.0 to USB-C converter that seemed to fix the problem for, about an hour? Now it's back to capturing well below 60fps even through the converter. I'm out of ideas.

For now I'm using NDI to capture on my PC and send it to my Mac but it would be nice to be able to work off one machine. UPDATE: I think this solution has the same issue though less pronounced. I'm really baffled.

 

[mystakin]

Minor update in case this helps narrow the problem at all. I've updated the card to its most recent firmware and now it runs at a smooth 720p60fps in Quicktime but still stutters in OBS.

Here's a video comparison. OBS recording first, Quicktime recording second. The recordings were taken at the same time. https://youtu.be/zGoAYrWW9Ig

 

[Narcogen]

The log shows that some frames were dropped, but does not say why.

19:28:30.274: Output 'simple_file_output': stopping
19:28:30.274: Output 'simple_file_output': Total frames output: 1385
19:28:30.274: Output 'simple_file_output': Total drawn frames: 1444

If you increase the CPU preset, do these go away, or do they always happen?

 

[mystakin]

They always happen. Also, they don't match up with the visible frame drops. So in this log file, for example, it says it dropped 8 frames over 17 seconds or so but I can count 8 dropped frames in just the first 2 seconds of the video.

What's weird is I can't replicate it at all in Quicktime, that just works, and sometimes I'll try something and it'll work fine in OBS but when I come back the next day it starts dropping. Last night I thought I had it fixed cause I changed the card, capture, and stream to 59.94 instead of 60fps and it worked great... but this morning it was back to stuttering.

 

[mystakin]

I've done more testing and i feel like it's safe to say it's something going on with OBS and may be two different issues? A direct capture of the Magewell is almost always stuttery in OBS but if I open the card in Quicktime and display capture it, the result is fairly smooth. Since OBS doesn't have a way to hotkey filters (to my knowledge), I normally use scene sources to let me switch between having a filter on and off. It seems like the scene source also causes stuttering, but only sometimes.

Here's a link to a video of when it stutters and when it's working. This was using a scene source of the display capture and edited together from the stream that's logged below. https://www.youtube.com/watch?v=mVeLVI--_DQ