Question / Help Newbie question about iMac 27"

[gwphoto]

Is this graphics card suitable to run OBS? I was shooting 1080p@ 30fps and had tons of
problems with lag/pixelating etc. CPU usage was 25% or so and FPS ran between 15-25.
Video and audio was horrid while wifi livestreaming via YouTube from this 27" iMac. 24MB ram

AMD Radeon R9 M395:

Chipset Model: AMD Radeon R9 M395
Type: GPU
Bus: PCIe
PCIe Lane Width: x16
VRAM (Dynamic, Max): 2048 MB
Vendor: AMD (0x1002)
Device ID: 0x6920
Revision ID: 0x0001
ROM Revision: 113-C905AA-799
VBIOS Version: 113-C905A1-007
EFI Driver Version: 01.00.799
Metal: Supported, feature set macOS GPUFamily1 v3
Displays:
iMac:
Display Type: Built-In Retina LCD
Resolution: 5120 x 2880 Retina
Framebuffer Depth: 30-Bit Color (ARGB2101010)
Main Display: Yes
Mirror: Off
Online: Yes
Automatically Adjust Brightness: No

 

[gwphoto]

Ok, so here is the Log file for my session that sucked. Any thoughts?

 

[Narcogen]

16:39:04.659: YUV mode: 709/Full

Change that to 709/Partial.

https://obsproject.com/forum/resour...t-color-range-settings-guide-test-charts.442/

17:53:50.951: Output 'adv_stream': Number of lagged frames due to rendering lag/stalls: 911 (17.1%)

GPU overload.

https://obsproject.com/wiki/GPU-overload-issues

Suggest either reducing GPU load produced by other apps, or lowering your canvas resolution. Changing to 709/Partial may reduce some of this, but possibly not all of it.

17:53:50.951: Video stopped, number of skipped frames due to encoding lag: 22/5298 (0.4%)

If you can't use the Apple VT Hardware encoder in the options, then CPU x264 encoding is your only option. You're getting a tiny bit of lag there, but it may not be enough to worry about. The issues you are seeing are almost certainly from the GPU overload (rendering lag) above.

 

[gwphoto]

Many thanks. I will try those solutions. I had no other apps running so I guess lowering canvas is the next effort. What about just rescaling down to 720p?

 

[Narcogen]

Downscaling won't reduce the rendering lag. The canvas resolution controls the size of the frame that's rendered. Then it's downscaled, then encoded.

Having them both the same, and the same as the native resolution of your display, is optimal. If you can't do that, then you can downscale output to reduce encoding lag and the load on your clients watching. If you can't do that, then you can make the canvas and output resolutions the same to avoid any scaling (but the scaling load itself is minimal).