HDMI Output Issues

Good afternoon all,

I am a new Pi4b owner with RiscOS running nicely.

I have an issue with HDMI outputs.
- On the left HDMI socket (next to power) I get audio in the OS, but fullscreen RiscOS apps & games simply load to a black screen.
- If I reboot using the right HDMI socket, I am able to launch full-screen apps and games, but there is no OS or app audio (which is intentional by design as I understand, sound not supported on this output)

Anybody know what’s happening here? How do I get the apps to show when using the left socket?

Apps are run using ADFFS.

I am owning RPi 3B+, RPi 2B and RPi B. I think it is worth to look why the right HDMI socket doesn’t provide any sound.
I think you can configure the RPi (indepently of RISC OS) to use HDMI ports either as HDMI including sound or as DVI. I am still using an old but still excellent Monitor which can’t cope with HDMI sound signal. So I am using my RPis connected to it by a KVM-Switch in DVI mode.

This is configured somewhere inside !Boot.Loader.CONFIG/TXT file.

Have a look onto RPIs homepage for settings inside CONFIG.TXT and be careful! Setting something in a wrong way is easy.

I am using my RPi 2B in conjunction with a small HDMI monitor and I can acknowledge: RISC OS is definitely able to deliver sound over HDMI.

If full screen apps are giving a black screen it might be worth setting disable_mode_changes in cmdline.txt – more details here

Apps are run using ADFFS.

The installation instructions for ADFFS state that cmdline.txt should contain:

disable_mode_changes

whereas for the Pi 4 cmdline.txt should contain

disable_gamma disable_mode_changes

If you have the two parameters the other way round it doesn’t matter, but they must both be on the first line of the file.

This probably isn’t what has gone wrong, but it might prevent problems further down the line.

I will try these config entries asap and report back with results!

Thanks!

disable_mode_changes worked.
It was actually already in there, but didn’t realise the cmdline.txt file had to have all of its contents on one line.
No carriage returns, just spaces… worked!

Thanks all for helping me analyse where this was going wrong.