Comment 7 for bug 1910537

Pretty good hint, interesting.

However, the ATEM is definitely able to take audio in on all four HDMI ports, since it has level indicators and buttons to turn it on and off (and AFV=Audio follows Video) and adjust the level on all four HDMI ports.

And I do have a camera with a builtin Mic (GoPro 4) on HDMI 2, which perfectly takes the Audio from the camera mic.

So there must be some difference in the HDMI signal coming from a camera (I had a Sony A6300, a Z-Cam e2c, and a GoPro 4 connected, all passing audio properly to the ATEM) and the HDMI signal coming from a Linux/Ubuntu notebook.

The cheap chinese LCD screen I used for testing doesn't care about the difference, it just plays the sound, while the ATEM obviously bothers about that difference, but, as Uldis figured out, only on Ports 2,3,4.