A weird symptom with incorrect HDMI black level

    This is about a weird symptom i m having with black level which becomes washed gray even though everything is properly configured and black should be black.

    My setup at the moment is X86 mini PC running LE > HDMI cable to Yamaha AVR input > Yamaha AVR output HDMI cable to Samsung TV input. The black level setting option in LE is NOT checked to "limited range", so the black produced by LE should be deep black. And we can see it really IS black, when the PC is connected DIRECTLY to the TV via HDMI.

    But, when i run the signal through the Yamaha AVR, the black displayed on the TV bacomes gray. Of course the setting in LE is not changed, i mean when i do check that box in settings for limited range, the black on the TV becomes even more ...whiter gray :) So, there is no cure via LE setup (?) There is also no cure via AVR menu (there is no related setting for video signal treatment there)

    Leaving for last the Samsung TV, where there IS a setting about HDMI black level, which is set to AUTO by default. A setting that works fine when the PC is directly plugged in the TV. No changed needed, auto detect works. In my setup (via AVR) manually changing the setting to LOW on the TV menu, "fixes" the problem, BUT everytime the TV restarts, i guess it "reads" info from the HDMI cable, and is switching back to gray-looking black!!!.

    You could say its the Yamaha AVR, which "adds" a property to the HDMI signal that is interpreted by the TV as a different black level (?) or, NOT passing-through the correct signal properties, that would allow the TV to set the correct black level (?) Whatever the case may be, at this point it looks like its tha AVR's malfunction. Afterall, the levels are FINE when the LE PC is connected DIRECTLY to the TV.

    BUT... There is a BUT, hence this post here at the LE forum, and not at some Yamaha forum :) You see, the levels are FINE when an Amlogic S905X5 cheapo device running CoreElec is used at the same setup, connected via the same cables! Rulling out (?) the malfunction of AVR or TV.

    So, i m thinking, its a mystery.

    Anyone else had this weird problem before? Any ideas where to look?

    The upstream Linux kernel that LE consumes pursues technical standards and this sometimes results in compatibility issues when other hardware vendors implement things poorly. Problems are often resolved, but the changes often take time because Yamaha or the TV vendor will need to accept that it has a bug and then push corrections via firmware changes. It's also possible that the upstream kernel has bugs too of course, though crowdsourced testing via general purpose distros generally spots things.

    The downstream Amlogic vendor kernel that CE uses contains hacks to bend 'standards' around the shoddy implementations of other vendors. Some will claim this is a benefit because it's more likely to result in a working result for users, but the hacking can be invasive and the long-term maintainability of the codebase becomes poor. So it's all great until it doesn't work, when it becomes impossible to fix the issue for one vendor/device without breaking support for another vendor/device.

    It will be hard for you to pinpoint the problem without an intermediary device (HDFury or similar) to report exactly what is being sent to the TV with and without the AVR inline.

    chewitt I really appreciate the reply mate! Understand... And -after all this explanation- i think you are in the correct path. Thank you.

    I will update the Yamaha firmware to the latest, see if this changes something

    I noticed this behavior as well, also on x86 hardware, and also with a Yamaha receiver (it has no firmware upgrade possibility's)

    LE 10 was fine, it started with 11 so i think this has something to do with kernel change or the change to gbm?

    I settled for now due to lower the light intensity on my tv

    duck7000 (and for anyone else who may land in this page having a similar issue...)

    I have found a (silly) way to avoid this problem of TV black level getting washed grey every time the X86 Libreelec device starting/rebooting. There is a menu in Samsung TV's, where you can enable/disable "HDMI UHD Color"

    Uncheck (disable) UHD and the problem is fixed. Now, this seems stupid, i mean having payed all this money for 4K UHD HDR, but, no worries! When 4K HDR video playback starts, the TV still recognizes the change in hdmi signal, and picture settings are automatically switched to the correct for color space, calibration and everything else.