Random resolution after TV upgrade

1st Official Post

    I upgraded TV to 4K recently (LG OLED55C9PLA) running latest LE on Zotac ZBOX CI640.

    Never had any problem with starting up LE on old Samsung HDTV.

    I am getting random resolution after KODI is booted ranging from :

    - blank screen - no signal, very often

    - 1024x768 - most of the times, even video playback is broken

    - 1920x1080 - oversized, must reduce size by 4%, audio fails from time to time

    - 3840x2160 - audio does not work most (if not all) of the times

    TV says no signal between UEFI screen and sudden random resolution KODI screen (no signal instead of kodi logo)

    This works only if UEFI boot type is set to Win7 on Zotac. UEFI and Legacy options do not display anything (TV shows no signal).

    I need to get 3-20 restarts to get my both video and audio working correctly.

    Setting default resolution to 1920 in advancedsettings.xml not helping/working.

    Any suggestion welcome.

    • Official Post

    It's possible that your new TV transmits available HDMI modes at higher speed, and your box is unable to receive the modes correctly. If you are lucky, you just have to replace your HDMI cable (use "HDMI high speed" standard).

    Thank you Da Flex, considering cables as potential cause as well but got HDMI 1.4 (=high speed standard) gold cable. Tried 2 different cables, same outcome (unsure if worth to buy 20EUR DisplayPort cable to try to eliminate the cable root cause).

    I have HDMI splitter device between HDMI and TV to split sound from video but even if I remove the device and have TV with Zotac connected directly the behavior remains random/same too.

    If I could fix the default resolution but obvious edit to advancedsettings.xml does not seem to be doing any difference.

    • Official Post

    This part is interesting:

    Quote from bobacisko

    This works only if UEFI boot type is set to Win7 on Zotac. UEFI and Legacy options do not display anything (TV shows no signal).

    So it could be a timing issue, and the box misses the transmission of HDMI modes coming from the TV. Maybe switching HDMI off / on (after booting and running LE invisible) will enforce a complete transmission of HDMI modes. You could script HDMI off / on by using LE's autostart.sh.

    Thank you DaFlex,

    sorry for late follow up, was away from the set to test.

    Cable off/on after bad boot makes no difference. If it boots in No signal, remains no signal. If boots in wrong resolution screen reappears in the same wrong resolution after HDMI reconnected. TV restart makes no difference.

    Seems you can do lot of magic with autostart.sh (like How to LG TV power off via KODI power off - Guides & How-tos - CoreELEC Forums)

    Any suggestion on file content to test the timing issue hypothesis?

    I am puzzled by this 'screen resolution randomness'. I guess it 'randoms' into unsupported resolution when no signal and if into supported resolution it shows up.

    But then the no sound in 4k points to cable. I tried one more brand new high end cable with no difference.

    Could DisplayPort cable make any difference? Should I buy & try?

    Try changing the video refresh rate in Kodi from 60 to 59 and answer NO to the change when asked. That refreshes the audio driver for me - maybe it will refresh the video driver for you. If it works, someone can make a script for you.

    Thank you gentlemen

    blueribb - changing refresh rate does not have aadditional yes/no prompt but immediately goes to 'no signal'. (Fortunately it restores into random behavior after restart.)

    Da Flex

    do not know how to apply RPi instructions you shared on Intel but found some other article so if I SSH this command:

    echo 1080p60hz > /storage/.kodi/userdata/disp_cap | systemctl restart kodi

    it restarts KODI (very fast) but it comes back exactly in the resolution it randomly started in (1024x768 or 3840x2160)

    File disp.cap is created with this content:

    1080p60hz.

    Unsure if what I am doing is right but I do not seem to be able to change the resolution via SSH.

    Another puzzling thing I found is if I SSH

    Code
    tail /sys/class/drm/*/status

    LibreELEC:~ # tail /sys/class/drm/*/status

    ==> /sys/class/drm/card0-DP-1/status <==

    connected

    ==> /sys/class/drm/card0-DP-2/status <==

    disconnected

    ==> /sys/class/drm/card0-HDMI-A-1/status <==

    disconnected

    ==> /sys/class/drm/card0-HDMI-A-2/status <==

    disconnected

    Do not understand why it says DP1 connected when I have HDMI cable, not DisplayPort connected.

    After changing the refresh rate from 60 to 59, if the screen goes black (no signal) - wait about 10 seconds and press ENTER. That will cancel the 59 and reset back to 60. You shouldn't have to restart the computer to get the screen back again.

    Quote from Da Flex

    You need an HDMI 2.0 or 2.1 cable to use 4K resolution.

    Will get myself new 2.1 soon but it does not seem to be the cause of the problem I have (random KODI resolution or no signal).

    I borrowed high end cable last week and no change to behavior. 4k videos work well on my cables anyway (maybe I have some audio channels missing for some videos).

    Can you please validate if this command correct/sufficient to enforce full HD?

    echo 1080p60hz > /storage/.kodi/userdata/disp_cap | systemctl restart kodi

    Do not understand how storing a file with a name disp_cap and restarting system would do anything. Do I need to add disp_cap as a file somewhere to load or something?

    Quote from smp

    Because your Zotac use a DP to HDMI 2.0 converter chip.

    So if I understand you right Zotac has DP as 'primary/native' which is the result of the command

    and for physical HDMI output it goes via DP to HDMI 2.0 converter.

    Would it make sense to buy DP 2 HDMI cable please?

    thank yuo

    • Official Post
    Quote from bobacisko

    Can you please validate if this command correct/sufficient to enforce full HD?

    echo 1080p60hz > /storage/.kodi/userdata/disp_cap | systemctl restart kodi

    I only have an RPi, so I don't have a disp_cap file. Maybe blueribb can do the test, because he is an Intel NUC owner.

    Maybe you have some special setting at your TV, and you can switch between HDMI and Display Port mode.

    Quote from Da Flex

    Maybe you have some special setting at your TV, and you can switch between HDMI and Display Port mode.

    TV has only HDMI inputs (no DisplayPort).

    I can change System settings in KODI for Display/Monitor from Default to DP1 (but afraid to as do not have DP cable).

    Also realized the random resolution is max and can be only changed down in the LE settings.

    So if it starts in 1920x1080 at 30Hz I can not set 60Hz anymore. Sometimes it starts in same resolution in 60Hz - this is the winning case.

    I'll be AFK for over a week as of tomorrow, so unable to test anything.

    Appreciate any help as I am completely struggling to take even direction in which the solution might be. Do not want to change TV or Zotac, took a while to select these and suddenly they refuse to work together.