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High monitor resolutions on Raspberry Pi

Solution

Right now (TMS <= 8.1.x, TLXOS <= 4.7.x) we still use fixed resolution lists that limit the maximum resolution we offically support on the Raspberry Pi to 1920x1080, which is the highest resolution supported by the Pi's H.264 hardware decoder (without which, historically, your performance would have been very poor, although in practice use of the Pi's H.264 hardware decoder has become increasingly irrelevant for various reasons).  Our next releases will use dynamic lists of resolutions that your hardware is actually capable of, which allow selection of 4K resolution modes on the Pi 4.

It's possible to make the Pi run at higher resolutions, but other than leaving the resolution set to "Auto" in the Pi 4 case, you currently can't do this using ThinLinX UIs (TMS, or the local configuration tool (Tlxconfig)).

You can edit /boot/config.txt manually to enter the necessary hdmi_cvt or hdmi_timings commands (see any number of forum posts such as https://www.raspberrypi.org/forums/viewtopic.php?t=203100), but our scripting will keep resetting hdmi_mode to whatever resolution you specified in TMS or Tlxconfig, which will interfere with what you are trying to achieve, so you'll have to SSH to your device as root (see the separate knowledgebase article on this) and edit /etc/init.d/tlxinit also.

Unless you have NOOBS (which has a built-in config.txt editor), to edit /boot/config.txt you will have to SSH to the device as root (see the separate knowledgebase article on SSH access) and then run "mount -ro remount,rw /boot" followed by "nano /boot/config.txt" or similar.

The easiest thing to do is to arbitrarily pick one of the resolutions in TMS' list and change the mode number assignment in the lookup_rpi_modenum() function in /etc/init.d/tlxinit such that it corresponds to mode number 87 instead. Selecting that resolution in TMS will then give you your custom resolution (2560x1080 or whatever) instead. Reboot the device after making this change to ensure that it gets saved to flash.

In a future release we will modify TMS and Tlxconfig to present a dynamic list or resolutions obtained using "tvservice -m DMT" and "tvservice -m CEA", rather than a fixed list. This will remove the need for the /etc/init.d./tlxinit hack and allow you to just select mode 87 (assuming that you have already manually added the necessary hdmi_cvt or hdmi_timings information to /boot/config.txt).

Please note that the Pi's hardware cursor implementation (which is essential for Citrix HDX when using H.264 hardware acceleration) is likewise subject to the 1920x1080 hardware decoding overlay maximum resolution limit, and will cause problems if you attempt to operate your Pi display at higher resolutions.  If you are using a high resolution in HDX or Web mode, you must set the HDX submode option to something other than "H.264" to stop TLXOS from trying to turn the hardware cursor on.  If using Horizon mode, you must deselect the H.264 option in the Horizon Client GUI (or, in recent TMS/Tlxconfig releases, use the "BLAST (No H.264)" submode).

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Article details
Article ID: 12
Category: Knowledgebase
Date added: 2019-05-29 00:59:48
Views: 252

 
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