fps into the canvas window decreases

[richalt2]

I'm streaming outdoors, with an ambient temp of about 75F, using MacAir. After a few minutes at 30FPS, streaming to youtube just fine, suddenly the FPS as viewed in the canvas window, as uploaded to youtube, drops to about 3 fps. There are no dropped frames.
Why this downshift, what causes it?
I am using the Apple VT H264 Hardware Encoder, with a bitrate of 2500kbs.
The video source is a camcorder into a USB port of the Mac.
I do hear the cooling fan going quite loud. Is this some overheat downshift? Is there some indicator of the reason for downshift?

You can see the transition in my youtube video at about 13min:10 seconds in, https://www.youtube.com/watch?v=5pZktd7rV3Q
Once the FPS goes to about 3, it never recovers for the rest of the hour.

During setup, I saw this same reduction occur, and I exited OBS and restarted it, and it was fine until this livestream hit.
When I Stop Streaming, the canvas window continues to show the reduced FPS. The camcorder was recording and playing that back shows normal framerate of course! The camcorder is sending 1920x1080 60fps, and the canvas is set to 1280x720 30fps, and the video outstream is also 1280x720 30fps.

Thanks for any advice! I need the 30 FPS!
Help!
Rich

 

[richalt2]

Log file attached.
I believe this event is where the FPS dropped:
10:03:48.826: Video Capture Device 3: Device with unique ID '0x11430001bcf2c99' disconnected
10:03:48.827: Video Capture Device: Device with unique ID '0x8020000005ac8514' disconnected
10:03:49.063: Video Capture Device 3: Device with unique ID '0x11430001bcf2c99' connected, resuming capture
10:03:49.063: Video Capture Device 3: Selected device 'FHD Capture'
10:03:49.063: Video Capture Device 3: Using preset 1280x720
10:03:49.152: Video Capture Device: Device with unique ID '0x8020000005ac8514' connected, resuming capture
10:03:49.152: Video Capture Device: Selected device 'FaceTime HD Camera'
10:03:49.152: Video Capture Device: Using preset 1280x720

 

[richalt2]

OK, I think I have solved this one. I happened to touch the HDMI "video capture to USB" box today and it was hot!
I rested the device, an "HD Sun" model, on an ice pack to cool it, and the video FPS slowdown did not happen! So I will continue to notice, but I think this is a reasonable guess.

Does anyone have hot outdoor experience to offer?
Next my laptop started to complain constantly "Encoding Overloaded" from OBS. I'm thinking this is also a thermal issue. Will get another icepack and report back.

Why is no one talking about over heating?

 

[richalt2]

And finally I placed my laptop on top of an ice pack and despite the outdoor ambient being about 80, the CPU stayed cooler and no encoding problems for a 1.5 hr livestream!
So keeping the gear cool outdoors is very important! Why is this not in the FAQ info? The Encoding overload warning should specifically call out noticing any thermal clock reduction which is occurring!