Sudden change of resolution Pi4

Stuffu

Hi

A strange this just happened, suddenly my pi4 changed to 4K resolution on hdmi0. Config is set up as suggested, checked that it’s still the case:

hdmi_group=1
hdmi_mode=16

Hdmi1 works fine and I don’t notice anything wrong, audio is fine etc.

Using pi4 in a nespi 4 case, ssd, nothing else attached, version 4.71 of rp.

I don’t mind using hdmi1 if there aren’t any drawbacks just running 1080p, but I still feel it’s strange that the resolution changed, a few days ago it was 1080p. Can you force it to 1080p somehow in some other way?

edit:

output of tvservice -s:

state 0xa [HDMI CUSTOM RGB lim 16:9], 3840x2160 @ 30.00Hz, progressive

mitu

@stuffu said in Sudden change of resolution Pi4:

Can you force it to 1080p somehow in some other way?

You can use the cmdline.txt configuration file and add at the end of the line:

  video=HDMI-A-1:1920x1080M@60

However, the config.txt should work - can you try changing the options to

hdmi_group:0=1
hdmi_mode:0=16

and see if the 1st display starts in 1080p ?

Stuffu

@mitu said in

However, the config.txt should work - can you try changing the options to
hdmi_group:0=1
hdmi_mode:0=16
and see if the 1st display starts in 1080p ?

I tried it and it is still 4k. I haven't done any changes to the system when the change occurred. Could there have been any OS updates that changed the behaviour? They are up to date as per yesterday.

mitu

@stuffu said in Sudden change of resolution Pi4:

Could there have been any OS updates that changed the behaviour? They are up to date as per yesterday.

Possibly, but I haven't seen any similar reports in the forums. Can you post your entire config.txt ?

EDIT: what version of the Linux kernel do you have installed (uname -a) ?

Stuffu

@mitu Not sure how many actually updates os...?

Anyway, uname output:

Linux retropie 5.4.72-v7l+ #1356 SMP Thu Oct 22 13:57:51 BST 2020 armv7l GNU/Linux

config.txt:
https://pastebin.com/TGxExYxa

Let me know if I should look into something more.

mitu

The config.txt file looks fine, there's no issue with it. Can you run

tvservice -m CEA

and see if 1080p is listed there ?

Stuffu

@mitu It is, but I noticed something odd, this line:

  (prefer) mode 95: 3840x2160 @ 30Hz 16:9, clock:297MHz progressive

Where do you "prefer" a resolution?! :)

mitu

@stuffu said in Sudden change of resolution Pi4:

Where do you "prefer" a resolution?! :)

You set it from the configuration file or is read from the EDID sent by your display (TV).

Stuffu

@mitu Hmm... since I didn't change anything manually it's strange the change occurred at all.

Is there anyway to revert it? From the TV I can't do any changes to preferred resolution and the config is set to 1080p... Am I missing something obvious? :)

edit: during boot the pi4 switches resolution three times. First from a really low resolution, like vga, the characters are really big, then it changes to 1080p, then again changes to 3840x2160.

edit 2: I added video=HDMI-A-1:1920x1080M@60 to cmdline.txt and it works. Problem solved I guess!

Thanks for pointing out the solution, just curious how it happened...

mitu

Just tested it myself and the config.txt configurations are taken into account, so nothing changed here. Are you booting into the desktop environment by any chance ?

Stuffu

@mitu nope, I’m using the official retropie image, nothing else added. If it doesn’t cause any problems elsewhere I’m fine using the current solution. But if you want me to investigate it further I’m happy to do so.

mitu

We can try debugging the bootloader. Add start_debug=1 at the end of the config.txt file, then re-boot (removing the cmdline.txt resolution setup, but leaving the config.txt settings for 1080p as they were initially).
After the boot, run

sudo vcdbg log msg

and post the output on pastebin.com. It should show the bootloader debug messages.

Stuffu

@mitu Here's the output https://pastebin.com/V2GygV9G

mitu

Add

gpu_mem=256

to config.txt and retry.

Stuffu

@mitu Sorry, retry with logging or try to run it as "default"?

mitu

Logging doesn't really matter - you can leave it on, just add the extra line and see if the PI starts in 1080p.

Stuffu

@mitu It still 4k with gpu_mem=256

If we can't find a reason for this happening, is there a reason not the use the cmdline alternative? Or even using the hdmi1?

mitu

If it works via HDMI1 - with the same settings as before - then that's ok. The 1st HDMI port is the only one able to do 4k@60Hz, other than that they're identical.

Stuffu

@mitu I haven't noticed anything strange with hdmi1 so I'll stick with that. Thanks for the effort :)