Thanks, I'm sure that override will be helpful. If ARC uses CEC as part of the negotiation, then am I right in extrapolating that it's entirely up to the TV manufacturer to implement how they 'see' the device when it negotiates?hdmi_ignore_cec=1and hdmi_ignore_cec_init=1 both relate to the firmware based display stack only.
CEC is optional within the vc4 driver, so adding an override to disable it should be relatively straightforward - I'll add it to the to-do list.
ARC uses CEC as part of the negotiation, so if there is some upset then it is likely to fail. I am slightly curious as to what is upsetting the LG or Sonos, but CEC is not a trivial one to debug.
To make things more curious for you, when I was troubleshooting before the downgrade, I connected an HP laptop that has an HDMI 2.1 port to the same HDMI port + cable that the Pi was connected to. The LG C3 is HDMI 2.1 as well. In this situation, ARC passthrough worked perfectly.
The only difference between the HP and the Pi 3b is the fact that 3b is HDMI 1.3, which had limited CEC support. Don't know if this somehow caused things to break. Would have tested with a Pi4 as well to confirm this theory because the 4 is HDMI 2,0, but they're all on active duty.
Statistics: Posted by arbitraryentity — Fri Aug 01, 2025 2:02 pm