Force display output to DP with audio on HDMI

    I have a Optiplex 3050 which has both a DisplayPort 1.2 (capable of 4k) and HDMI 1.4 (capable of 1080p only).

    I'm using LibreElec 11 stable (although tried 12 nightly too) and I cannot get HD audio to work on the DP using a Benfei DP->HDMI adapter (reading around, seems to be a common problem with NUC's as well). DD/DTS work fine.

    I can, however, get HD audio working over the HDMI 1.4 connection.

    So I want to utilize both connections simultaneously but, despite trying for a few days, whenever I connect the HDMI 1.4 cable, Kodi always output's it's display on that port rather than the DP:

    Kodi log shows:

    Code
    2024-01-15 11:34:25.035 T:876      info <general>: CDRMUtils::FindConnector - using connector: HDMI-A-1


    I tried adding the following to syslinux.cfg, but nothing changed:

    Code
    APPEND boot=UUID=1101-5649 disk=UUID=d8c7d193-fa09-4fcd-b27b-41b739035d2d portable quiet initrd=/edid.cpio drm.edid_firmware=edid/edid.bin video=DP-1:D


    If I remove the HDMI-A-1 in syslinux:

    Code
    APPEND boot=UUID=1101-5649 disk=UUID=d8c7d193-fa09-4fcd-b27b-41b739035d2d portable quiet initrd=/edid.cpio drm.edid_firmware=edid/edid.bin video=HDMI-A-1:d video=DP-1:D

    then Kodi starts on the DisplayPort, but the HDMI-A-1 is disabled and so does not output any audio (it also shows as disconnected under /sys/class/drm/card0-HDMI-A-1/status

    Is there any way to force Kodi to use the DP connection, whilst still allowing the HDMI for audio?

    I'm not sure if adding "video=DP-1:1920x1080M@60" will result in DRM (and thus Kodi) preferring DP-1 output over HDMI-A-1 or will simply force that output to 1080p and not change anything. It's a cheap trick to try though.

    Thanks for the suggestion, but same thing:

    Code
    APPEND boot=UUID=1101-5649 disk=UUID=d8c7d193-fa09-4fcd-b27b-41b739035d2d portable quiet initrd=/edid.cpio drm.edid_firmware=edid/edid.bin video=DP-1:1920x1080M@60
    Code
    2024-01-15 13:14:47.180 T:877      info <general>: CDRMUtils::FindConnector - using connector: HDMI-A-1
    Code
    <advancedsettings>
	<videoscreen>
		<monitor>Generic PnP Monitor #1</monitor>
	</videoscreen>
</advancedsettings>

    ^ that content goes in /storage/.kodi/userdata/advancedsettings.xml (from https://forum.kodi.tv/showthread.php?tid=363060) but I have no idea what to replace "Generic PnP Monitor #1" with. Perhaps "HDMI-A-1" or have a look in kodi.log for the m_deviceName and m_displayName values logged for audio cards as I have a hunch it'll be based on EDID data.

    Code
    <advancedsettings>
        <videoscreen>
                <monitor>DP-1</monitor>
        </videoscreen>
</advancedsettings>

    Thanks! That definitely forced it to use DP.

    However, it then it fails to load the GUI with this error:


    I tried ensuring the resolution I'm using is supported by both outputs (i.e. providing the following flags in syslinux.cfg):

    Code
    APPEND boot=UUID=10B4-4A77 disk=UUID=93786be3-5652-47ab-b200-e2f498d33733  quiet video=DP-1:1920x1080M@60 video=HDMI-A-1:1920x1080M@60

    Probably an (LS)PCON chip issue:

    Post

    RE: Time to upgrade my NUC. What's hot today?

    […]

    forum.libreelec.tv/core/attachment/10003/

    As you can see on this block diagram, NUC11PAxxx does not have a native HDMI port. It is using a DP->HDMI protocol converter (PCON) chip. It is more than likely the source of your audio passthrough issues. So this is not a gen11 issue but an issue specific to that NUC model. There is nothing to fix from LE/Kodi side.
    smp
    January 15, 2024 at 2:36 AM

    PS: Guys, please do me favor, and stop those double posts:

    Thread

    HD Audio from DisplayPort - no sound (HDMI works)

    Related thread: Force display output to DP with audio on HDMI where I am trying to use the HDMI for sound and DP for video.

    I wanted to dig deeper into why the DP 1.2 on my Optiplex 3050 is not able to play HD audio. I've made some progress (I think!) but I'm stuck on where to go from here. If it is a limitation of the DP itself, I'd like to understand why.

    Here's my findings:

    HD Audio (TrueHD and DTS HD MA) from HDMI 1.4 works - log here:

    (Code, 79 lines)



    HD Audio (TrueHD and DTS HD MA) from DP 1.2…
    fezster
    January 16, 2024 at 11:37 AM

    I suspected as much. Just seemed odd that 7.1 LPCM works fine (but not HD audio bitstreams).

    FYI - the other post was more focused on trying to fix the HD Audio, whereas this one was on utilizing 2 x display outputs. That's why I started a new thread.