Cannot run 9 RTSP feeds on RPi4 4GB and 4K monitor

[shark92651]

I recently purchased a RPi4 4GB and a 4K TV for use as a wall mounted security camera monitor for our office wall. I understand that others have been able to display up to at least 14 different RTSP feeds on a RPi3 using the displaycameras package, which is a front-end to running multiple instances of omxplayer to display a split-screen camera matrix. I am pretty new to to the RPi and Linux in general, so please bear with me, but I have done quite a bit of testing and I am not sure if the issues I am having are related to the RPi4's support for 4K displays, issues with gpu_mem, or perhaps issues with omxplayer's support for the same. I will describe the steps I have taken and the results I am getting below in hopes of finding a solution.

I installed the latest release of Raspbian Buster Lite and installed all updates.

Using a 3x3 matrix of 9 H264 feeds at 704x480, 15fps, and display mode of 4k30hz:

gpu_mem set to 512 or less:
The pi will display all 9 feeds but I get severe flashing between all 9 feeds, as if the system cannot display more than 1 at a time.

gpu_mem set to 944 or greater:
The flashing issue is corrected, however a max of only 8 feeds is displayed.

set the display mode to 4k60hz:
The number of feeds displayed is reduced to 6

So as you can see the flashing issue is resolved if I go above the recommended max of 512 for gpu_mem. Additionally, the number of feeds displayed is affected by switching from a 30hz to a 60hz 4k display mode. Does anybody have any idea what is going on here and how I should proceed to try to resolve this? I am a bit of a noob so I need a lot of help. My first though is to check if the omxplayer is logging any errors. Where would I look for a log file and/or how to configure it?

Thanks,
David

[ddmunhoz]

4 years later. Same issue, I'll try and see what I can find and how to fix it. We are below the walls here, since omxplayer is eol now.