No HBR Audio with LSPCON - Trying to collect information

    Recently it seems quite a few people have had issue with no HBR Audio when an LSPCON is used. For NUCs this is often a case of update the LSPCon firmware but this is not always the solution / an option.

    For anyone reading this and wondering what an LSPCON is or does my setup use one; an LSPCON converts from Displayport to HDMI in this case. Older Intel 7000/8000/9000 CPU motherboards with an HDMI 2.0 port will be using an LSPCON. If you are using an "Active" Displayport to HDMI converter then your setup will also be using an LSPCON. HBR audio is DTS HD Master Audio or Dolby TruedHD with the bitstream option enabled in Kodi (You need to switch to Expert mode and make sure DTSHD and Dolby TrueHD are enabled too).

    My experience of this issue is PCM 7.1 and legacy SPDIF Dolby Digital and DTS work fine. I'm interested in hardware and other info from people who have had similar issues of no HBR audio with an LSPCon in the chain.

    Below are my findings. Before anyone mentions an immediate firmware update for the LSPCon some of these adapters are known to have firmware which work with HBR audio and they also work fine in Windows. Ultimately I would like to raise an appropriate bug but I need more results in order to spot any pattern (Other than using an LSPCON); I'm not sure if this issue is only when using Intel graphics.

    CPU: Intel I3-8300S
    Chipset: Intel C246
    Video Card: Integrated
    LSPCON: Paradetech PS175
    LSPCON Type: Integrated on motherboard
    LSPCON Firmware Version: 0x2C
    General Operation: OK
    HDR: OK
    HBR Audio: Broken (Silence)
    Notes: All OK in Windows

    CPU: Intel I3-8300S
    Chipset: Intel C246
    Video Card: Integrated
    LSPCON: Paradetech PS175
    LSPCON Type: Integrated on motherboard
    LSPCON Firmware Version: 0x40
    General Operation: Problematic - No 24/50Hz 4K support
    HDR: OK
    HBR Audio: Broken (Silence)
    Notes: HBR Audio ok in Windows but same 24/50Hz issues as Libreelec.

    CPU: Intel I3-8300S
    Chipset: Intel C246
    Video Card: Integrated
    LSPCON: VMM7100
    LSPCON Type: External Adapter (CAC-1087)
    LSPCON Firmware Version: 7.02.120
    General Operation: OK
    HDR: OK
    HBR Audio: Broken (Silence)
    Notes: All OK in Windows. Linux seems to uniquely offer 120hz support with this combination (Assume it is 4K/120/4:2:0 to 4:2:2 conversion).

    CPU: AMD 7600X
    Chipset: AMD X670E
    Video Card: Nvidia RTX3080
    LSPCON: VMM7100
    LSPCON Type: External Adapter (CAC-1087)
    LSPCON Firmware Version: 7.02.120
    General Operation: No display after splash screen
    Notes: Using required Generic Legacy image.

    CPU: AMD 7600X
    Chipset: AMD X670E
    Video Card: Integrated Graphics
    LSPCON: VMM7100
    LSPCON Type: External Adapter (CAC-1087) via USB-C passive cable
    LSPCON Firmware Version: 7.02.120
    General Operation: OK at 4K/60 but not at 4K/24
    HDR: Broken (Black screen)
    HBR Audio: Broken (Intermittent)
    Notes: PCM audio has slight interruptions. SPDIF/legacy bitstream has same interruptions as HBR audio.

    sky42 I saw you mentioned the same issue when you tried a Displayport to HDMI adapter; can you provide further info?

    Edited once, last by Krobar (April 1, 2024 at 3:56 PM).

    Just tested the same external Displayport to HDMI adapter with AMD integrated graphics. The results are different to Intel, HBR audio is intermittent instead of completely silent.

    If you start to poke around in the Gitlab issue log for the Intel DRM driver you'll see reports and triage that reveal the problem isn't simple like LSPCON vs. no-LSPCON; as there are different LSPCON chips (different chip vendors) with different properties, and even identical LSPCON chips can have rather different implementations (different electrical properties, resulting in different bandwidths available on internal connections) on different boards. In some cases firmware changes can tweak voltages and such that drive the LSPCON chip differently so achieve improvements. In other cases the LSPCON implementation is more fundamentally wrong and no tweaking can get the right result. Most of the issue reports are focused on graphics performance; but the underlying issue is related to bandwidth and thus HBR audio (needing more bandwidth) suffers similarly to higher resolution and refresh rate and colour depth graphics (needing more bandwidth). TL/DR; /shrug

    Quote from chewitt

    If you start to poke around in the Gitlab issue log for the Intel DRM driver you'll see reports and triage that reveal the problem isn't simple like LSPCON vs. no-LSPCON; as there are different LSPCON chips (different chip vendors) with different properties, and even identical LSPCON chips can have rather different implementations (different electrical properties, resulting in different bandwidths available on internal connections) on different boards. In some cases firmware changes can tweak voltages and such that drive the LSPCON chip differently so achieve improvements. In other cases the LSPCON implementation is more fundamentally wrong and no tweaking can get the right result. Most of the issue reports are focused on graphics performance; but the underlying issue is related to bandwidth and thus HBR audio (needing more bandwidth) suffers similarly to higher resolution and refresh rate and colour depth graphics (needing more bandwidth). TL/DR; /shrug

    Thanks for the tip. I understand your point but the same external adapter and internal LSPCon I list above work fine with Windows for HBR audio which means I know this is a Linux software issue. This is a recurring theme with a lot of these LSPCon issues too; works fine with Windows but broken in Linux. Whilst a sample of one does not mean much the fact the same external DP to HDMI adapter produces some HBR audio with AMD means this might actually be an Intel Graphics driver issue/quirk but I'm hoping for more feedback from others to help confirm or deny this theory.

    I realise that this is not a Libreelec specific issue and these problems likely lie in the kernel / firmware but I suspect a high proportion of those that are affected by LSPCON HBR audio issues are Libreelec users so I hope you don't mind me posting this topic here.