Trying to troubleshoot my beginner's setup

[JakeLane]

Hey all! I've recently started to livestream sports events, but it's a new field to me. I'm looking for advice on what I can cheaply do to make our setup more robust.

Our goal is to stream 1080p video to YouTube at 60fps.

Our cameras are:
2x GoPro Hero 10 Black with Media Mod
1x BMCC4k (by way of an Atmos monitor)

The cameras are cabled to cheap HDMI repeaters, which are connected via fiber optic HDMI cable to an ATEM Mini Pro ISO.

The ATEM switcher is connected to the streaming computer via USB C.

Separately, we have area mics on the court which are connected via XLR to a Focusrite Scarlett, which is also connected via USB C.

My computer is a MacBookPro (16" 2021) with an Apple M1 Max chip and 32 GB memory.
My current OBS settings are:
Audio Encoder = CoreAudio AAC
Video Encoder = x264
Rate Control = CBR
Bitrate = 6000 kbps
Keyframe Interval = 2s
CPU Usage Preset = veryfast

Base Resolution = 1920x1080
Output Resolution = 1280x720
Common FPS Values = 60

I'm using a replay buffer, and the estimated memory usage there is 6 MB.

The reason I need help is that, with the current setup, the stream will occasionally have minutes-long periods during which the video will freeze for a second or so at a time. The freezes happen most frequently when there's a lot of action filling the frame, which is making me think they may be somehow bitrate related?
OBS reports 0 dropped frames across the freezes.
After a few minutes of intermittent freezing, the freezes will trickle off, but the video will now be delayed by about half a second. I now have to change the delay of the Scarlett from 130ms to 630ms mid-stream.
Then, frustratingly, after a few minutes, the video will catch back up with the audio forcing me to change the delay back.

This cycle repeats every 15-20 minutes.

Settings on the "Atem Mini Pro" Video Capture Device:
Device = Blackmagic Design
Use Preset = Yes
Preset = High
Use Buffering = Yes

Does anyone have any ideas of what I can do to fix this issue? I'm having a hard time figuring out where to even start with troubleshooting!

 

[Lawrence_SoCal]

1. it would be a good idea to use System Monitor to make sure you aren't overloaded the M1 chip (or some other hardware resource component)
2. Re-scaling output is creating extra work. As I test I'd keep Base Resolution and Output canvas the same
3. Are those encoder settings the auto-config ones, or ??

Have you run the OBS Studio log thru the log analyzer?
don't ignore the pinned post in this forum about posting your OBS Studio log when asking for help

And basic computer 101 stuff
- you you do a full reboot before a live stream (like an hour or so before, or when you get there to set up?)
- are you making sure you don't have a bunch of unnecessary app/processes running? real-video video rendering is REALLY computationally intensive. don't make OBS compete for compute resources with random misc in the background that should be OFF/CLOSED

 

[JakeLane]

1. it would be a good idea to use System Monitor to make sure you aren't overloaded the M1 chip (or some other hardware resource component)
2. Re-scaling output is creating extra work. As I test I'd keep Base Resolution and Output canvas the same
3. Are those encoder settings the auto-config ones, or ??

Have you run the OBS Studio log thru the log analyzer?
don't ignore the pinned post in this forum about posting your OBS Studio log when asking for help

And basic computer 101 stuff
- you you do a full reboot before a live stream (like an hour or so before, or when you get there to set up?)
- are you making sure you don't have a bunch of unnecessary app/processes running? real-video video rendering is REALLY computationally intensive. don't make OBS compete for compute resources with random misc in the background that should be OFF/CLOSED

Thank you Lawrence!

Sorry, I missed that post. Here's my log from that session. Checking the log analyzer, the only notes it gives are to change the YUV color profile from "full" to "limited".

 

[Lawrence_SoCal]

Oh yea... Full isn't going to work on your computer (I don't think). that could easily be your entire issue.
Full typically is NOT a default YUV color profile setting. If you changed that on your own (equivalent of random button pressing), 2 lashes for you. ;^)
If you watched some YouTube video... mark that channel as idiots and ignore them from now on

 

[JakeLane]

Haha embarassingly, I think that very well may have been random button pressing. "Full" is better than "limited", right?? :p

Would that explain the stuttering I described? What would cause the picture to freeze for a moment and then jump in or out of sync with the audio?

 

[Lawrence_SoCal]

Full takes at least an order of magnitude more computation than limited YUV color space
hence my stating that could be your entire issue

 

[JakeLane]

Full takes at least an order of magnitude more computation than limited YUV color space
hence my stating that could be your entire issue

Gotcha! Thank you.

I guess what I'm asking is how to interpret the fact that the video and audio are going in and out of sync. My newbie intuition was that if I was overloading my computer, the whole stream, video and audio, would freeze and start together. Am I thinking about that the wrong way?

I'm also confused about why, when the video goes out of sync, it stays out of sync for minutes at a time before sudden correcting itself. Meanwhile, the audio continues to be pushed out in real time. It's almost as though there is some half-second buffer that is being intermittently applied to only the picture. I'm trying to understand what's happening there.

 

[Lawrence_SoCal]

Am I thinking about that the wrong way?

Yes. You are unaware or ignoring Operating System process priorities, and more technical details. Also, the video takes WAY more processing than audio, so impacts will be different

I'm also confused about why, when the video goes out of sync, it stays out of sync for minutes at a time before sudden correcting itself. Meanwhile, the audio continues to be pushed out in real time. It's almost as though there is some half-second buffer that is being intermittently applied to only the picture. I'm trying to understand what's happening there.

Audio is a couple of orders magnitude less demanding/less bitrate, etc... so MUCH easier for computer to keep it on track vs video
Understanding may well require getting WAY into the weeds on Operating System threads, processes, kernel operations, User vs System space and more. Or you could ask around, find out what you are describing is normal, and accept that an overloaded OBS Studio on your computer behaving as you've described sounds about right to others, and focus instead on not overloading computer (my recommendation)