Posts by smp

    I have the same motherboard with the same Realtek chip. No issues here:

    Try to test with another cable. At Gigabit speed Realtek NICs are very picky with ethernet cables. I've seen some short cat5e cables that work fine at 100M but fail at 1000M.

    I'm using Cat6 7.5m cable.

    I think LibreELEC-Generic.x86_64-9.80-devel-20200201013402-e776789.img.gz contain a limit to use 8-bit output and if I remember correctly using 4:2:0 50/60hz 8-bit works

    Nope, 8-bit does not work too. I actually have to use only 8-bit because of the above mentioned issues with Samsung TVs.

    I need to get hold of version 8.2.5 for Le Potato.

    There is no 8.2.5 for Le Potato.

    And yes, 9.0.2 is buggy and unusable on Le Potato - live TV issues and also file transfer issues due to this buggy patch.

    I figured out how to force YCbCr 4:4:4 instead of RGB:

    Unfortunately this did not fix the Samsung issue. 4K YCbCr 4:4:4 8-bit works fine but "no signal" with 12-bit.

    Since GLK does not support 10bit modes, does that mean the signal being sent was 12bit?

    No, the signal was 8-bit. Despite the popular opinion HDR does not really require 10/12 bit and the TV will switch to HDR/ST.2084 mode when HDR metadata is present.

    I wasnt sure how to get more info from the j4105 about what display mode is being used.

    Enable DRM debug logging in syslinux.cfg:

    1. drm.debug=0x1e log_buf_len=5M


    journalctl -f | grep -E 'color|bpc'

    From memory, to get it working I booted the j4105 with the TV in UHD mode, got the available UHD modelines via SSH, and then added them via a boot script and xrandr.

    That will not give you the 12-bit Deep color modes in 4K (10-bit is not supported by GLK hardware). There is no difference how you force it to output the desired modes.

    I also tried to mess around with editing the EDIDs dumped with both HDMI UHD Color On and Off to narrow down the issue.

    Any 4K mode that requite the HDMI pixel clock higher than 297 Mhz give "no signal".

    Intel driver does not support YCbCr 4:2:2 output. When the EDID report the max.pixel clock of 297 Mhz (UHD Color Off) - Intel driver is using those modes for 4K and they work fine:

    4K 24/25/30Hz RGB 8-bit

    4K 50/60Hz YCbCr 4:2:0 8-bit

    When the EDID report the "high speed" pixel clock mode (594 Mhz) is available - Intel driver is using those modes (and they give no signal):

    4K 24/25/30Hz RGB 12-bit

    4K 50/60Hz RGB 8-bit

    IMO the issue has something to do with Samsung having limited support for 4K RGB modes. It probably expects YCbCr 4:2:2 which Intel does not support.

    I know still are some incompatibility example with Samsung HDR TV, which is actually issue of intel driver/

    I tried to figure out what is causing that "no signal" issue on Samsung TV when "HDMI UHD color" is enabled.

    At first I thought that Samsung does not support 4K RGB modes with Deep Color. But the odd thing is that when trying 4K 50/60 modes - Intel driver is switching to RGB 8-bit and it doesn't work as well.

    So, the only 4K HDMI modes that work with GLK+Samsung TV are:

    4K 24/25/30Hz RGB 8-bit

    4K 50/60Hz YCbCr 4:2:0 8-bit