Using HDMI audio output on RPi 5 when TV not running on startup

Hello everyone!

i’ve installed the official “Home Assistant Operating System” image on a RPi5 and want to use it as spotify sink (with the “Spotify Connect” addon). audio output via HDMI works fine if the receiver and tv is running, when the raspberry boots up.

i can see a device when executing “ha audio info”

alsa_output.platform-107c706400.hdmi.hdmi-stereo

but usually receiver and tv are off, when doing an HA update (and therefor when the system reboots). then only a “Dummy Output” is shown when executing “ha audio info”. on my old installation on my RPi4 i solved that by setting

dtparam=audio=on
hdmi_drive=2
hdmi_safe=1

in /mnt/boot/config.txt. but this doesn’t work on my RPi5. i’ve read that several settings in “/mnt/boot/config.txt” will be ignored on RPi5, which seems to be true, because none of the settings above make any difference.

i also tried to set

video=HDMI-A-1:D

in /mnt/boot/cmdline.txt without success (HDMI video is working when i turn on receiver and tv after PRi bootup, but not audio). someone on
https://forums.raspberrypi.com/viewtopic.php?t=358917&start=50
suggests that setting the EDID via file using

drm.edid_firmware=edid.bin

should mitigate that problem, but i was unable to do that. the reason seems, i dont know where to put that file, so i can be read on bootup. /lib/firmware is a readonly squashfs on /, and put it in /mnt/boot/edid.bin doesn’t work either, because i dont know which path to set. i tried:

drm.edid_firmware=edid.bin
drm.edid_firmware=/edid.bin
drm.edid_firmware=/mnt/boot/edid.bin
drm.edid_firmware=/boot/edid.bin
drm.edid_firmware=/dev/nvme0n1p1/edid.bin

someone in the forum thread suggests to put it in the initramfs, but because there is no update-initramfs binary (and maybe also because the ramfs is located on the squashfs), this is also not possible.

i already have ordered an EDID emulator on Amazon (not arrived yet), and i think this will solve my problems, but a clean software/configuration solution would be appreciated.

thanks in advance
Thomas

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update: my EDID emulator dongle arrived today and fixed the problem. i hope, one day there is a software solution for this.