EDID Video/Sound Problem

I have a selection of Raspberry Pi computers (v2, v3B+, v4B) using RISC OS 5.29 (22 Dec 2020) which all work fine with a selection of different HD 1920×1080 monitors with their sound working through HDMI and no analogue sound – All great so far. The Configuration Screen setting is set to Auto. If I connect any of these Raspberry Pi computers to an Atem Mini video/audio mixer, I have no display on the HD monitor connected to it. If I manually set the RISC OS Configuration Screen to a real monitor with 1920×1080, 16 million and 60Hz, the display works fine on the HD monitor plugged into the Atem Mini. The problem is the sound from the Raspberry Pi isn’t coming through the HDMI cable to the Atem Mini. On testing the Raspberry Pi analogue output, sound is coming out of that instead, even though Config/txt is set to use HDMI sound.

I have tried several tweaks to the Config/txt file but nothing has got the HDMI sound working yet. I have tried:
hdmi_force_edid_audio=1
audio_pwm_mode=2
hdmi_force_hotplug=1
in addition to the normal hdmi_drive=2 command but none enable HDMI sound in this situation.
Any ideas on how to get the sound and/or EDID working please?

For reference, a Windows 10 PC plugged into the Atem Mini has video and sound both working fine. Atem Mini Support say it just needs an EDID compatible device.

I presume the HDMI protocol contains some scheme to determine the capabilities of the connected hardware. Maybe there is some bug there.

Have you tried an another OS on the PI to see if Atem works on it? If it works the problem would be an the RISC OS side.

I would suggest taking advantage of RISC OS’ lack of hotplug detection to try to fool it by starting the PI on another monitor then move the cable to the Atem.

I have only ever used RISC OS on a Pi. Never used Linux on any hardware. I will try your other suggestion.

I have tried: hdmi_force_edid_sound=1,

Should be,

hdmi_force_edid_audio=1

As the video resolution had to be set manually, and the sound didn’t go over HDMI, it suggests that the EDID process failed. I don’t know whether RISC OS records anything about the results, but I have a vague recollection of reading about a file to look at.

“Should be, hdmi_force_edid_audio=1”

Thank you Chris Gransden, a typo by me on this page.
I had it right in config/txt

“I would suggest taking advantage of RISC OS’ lack of hotplug detection to try to fool it by starting the PI on another monitor then move the cable to the Atem.”

Thank you André – Just tried this but sound still didn’t work on Atem Mini.

“As the video resolution had to be set manually, and the sound didn’t go over HDMI, it suggests that the EDID process failed. I don’t know whether RISC OS records anything about the results, but I have a vague recollection of reading about a file to look at.”

Thanks Alan Adams for that. I have found the file at:
Resources:$.Resources.ScreenMode.Monitors.EDID0
You can download it from here: EDID.zip
It correctly shows the name of the Atem Mini – ‘BMD HDMI’
The rest is all gibberish to me.

I still can’t get the HDMI sound to work from a Raspberry Pi with RISC OS 5.29 (2 Feb 2021) to an Atem Mini HDMI input (as per my original posting of this topic). Hoping someone can come up with a fix to enable this please.
The EDID0 file is still available to download.