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HDMI Force RGB Option
Issue Brief
With some TV monitors, there is a bug in their HDMI implementation that sometimes trigger the selection of the wrong colorspace in a magenta/green display.
It looks TV reports that is capable of YUV422 or YUV444 but it's not indeed.
To avoid this situation, you can use forcergb option to set COLORSPACE_SPACE_RGB444 forcely.
Here are the more investigations and discussions in ODROID Forum.
How to set boot.ini to activate forcergb
To activate it, add hdmitx=forcergb in bootargs.
setenv bootargs ${bootargs} hdmitx=forcergb
Here is the catch.
The env hdmitx has other parameters related to HDMI CEC Control.
If you use CEC options, the env format can be hdmitx=cecf,forcergb or hdmitx=cec0,forcergb.
The ODROID Forum user, wrxtasy already implemented a good guide for this case.
https://github.com/wrxtasy/LibreELEC.tv.7.0/blob/libreelec-7.1/projects/Odroid_C2/bootloader/boot.ini
# Enable | Disable HDMI CEC Control
setenv hdmi_cec "0" # Disabled
# setenv hdmi_cec "1" # Enabled
# setenv hdmi_cec "2" # Enabled but disable auto TV switching ON
# Force HDMI to use RGB colorspace regardless of TV request
# setenv hdmi_forcergb "0" # Disabled
setenv hdmi_forcergb "1" # Enabled
if test "${hdmi_cec}" = "0"; then setenv hdmitx "hdmitx=cec0"; fi
if test "${hdmi_cec}" = "1"; then setenv hdmitx "hdmitx=cecf"; fi
if test "${hdmi_cec}" = "2"; then setenv hdmitx "hdmitx=cec7"; fi
if test "${hdmi_forcergb}" = "1"; then setenv hdmitx "${hdmitx},forcergb"; fi
setenv bootargs "${rootopt} ${consoleopt} hdmimode=${hdmimode} ${hdmitx} vout=${vout_mode} ............"
