Local Display on HDMI0 and sound on HDMI1 on RPI4 ?

[Dubbs777]

Hi!

I'm new to moode and It seems quite promising! I installed it on a RPI4 recently and I managed to turn on local display through HDMI0 (quite easy btw) to a 7" touch screen.

I managed to use HDMI0 as audio output as well on my Amp but obviously, without the local display.

What I need is a way to send local display on HDMI0 and sound on HDMI1 to connect the screen and the amp to the RPI.

I had a look to the forum and did not find relevant posts about such setting.

My amp supports SPDIF and I have several USB soundcards (M-Audio, Steinberg) but I’d rather avoid extra hardware and/or HAT and rely on Amp DAC if it is possible.

[Tim Curtis]

It's prolly doable but I don't have any mini-HDMI to HDMI cables so it will be up to someone else with the cables, a monitor, an audio device with HDMI input, and some Linux experience to work out the configuration so it can be coded into moOde.

My Pi-4 only lists a single HDMI port...

Code:

pi@rp2:~ $ cat  /proc/asound/cards
0 [b1             ]: bcm2835_hdmi - bcm2835 HDMI 1
                     bcm2835 HDMI 1
1 [Headphones     ]: bcm2835_headphonbcm2835 Headphones - bcm2835 Headphones
                     bcm2835 Headphones

[TheOldPresbyope]

A year ago, there was an intriguing post to the Raspberry Pi Forum: "The development kernel does allow you to have HDMI audio on both ports at the same time. You'll have to wait for it to be pushed to general release via an apt update."

That ALSA still reports only one HDMI audio port suggests this push hasn't occurred yet but I haven't been following the issue and in any case I don't have any HDMI-based audio gear with which to test.

Even if only one HDMI port supports audio it would seem the other port could be used for display since folks have been running dual monitors on RPi4Bs since last year.

Regards,
Kent

[Tim Curtis]

The trick might be to figure out how to get moOde's LocalUI feature to output to the second HDMI port instead of the first.

The xserver startup script is /home/pi/.xinitrc

IIRC the xset commands default to HDMI 0 but also check for an exported var named DISPLAY.

export DISPLAY=:0
export DISPLAY=:1

The two other commands in the script, fbset and chromium-browser, may also use the value of DISPLAY var if it exists ??

Something like that.