How to fix weird lag?

sonicmartin76

Hi all. Super new to all this. Just started my first set up (very addictive!) I am experiencing a weird lag in parts of some games. Most noticeably on backgrounds and some sprites. Thunderforce 3 on megadrive is really bad. I have connected my set up to smaller 24inch monitor and it is fine but on my 40inch 4k TV the lag is there. Any ideas?
Pi Model or other hardware: 4b with 4gb ram
Power Supply used: official pi psu
RetroPie Version Used: 4.8
Built From: straight imager download to sd card
USB Devices connected: 2 x super famicon retroflag (wired usb)

windg

I believe it is because of the 4k resolution. Try to change the video mode from runcommand menu, to 1080p resolution:
https://retropie.org.uk/docs/Runcommand/ . You have to do this for all emulators.

Another way is to change the resolution of the Pi from raspi-config command. This will affect all emulators and EmulationStation menu.

sleve_mcdichael

@sonicmartin76 https://retropie.org.uk/docs/Pi4/#issues-using-a-4k-tv

sonicmartin76

Thanks you two. Seems to have fixed the issue. Just very small screen now. Will have to look into that bezel project.

dankcushions

@sonicmartin76 can clarify what you mean by "very small screen"? it's normal to get vertical borders when playing a 4:3 aspect ratio game on a widescreen modern TV, but the picture should at least be the full height of the TV.

the bezel project can fill in the gaps to the left and right, but if you're seeing large borders on the top/bottom you may have a more fundamental issue.

sonicmartin76

Yeah the picture is a small box in the middle with black all round. A good 3 inches top and bottom. I can change the res to 1600x1050 and it fills the screen much more fully and still scrolls smoothly

windg

Black all around means that you have to configure the overscan settings. This happens because you choose a lower resolution from the default. You have to modify the config.txt file in the boot partition and especially this values :

#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16

First uncomment the lines (remove the #)
Give ~~positive~~ negative numbers untill you find the correct values that fill correctly the screen. You have to restart the system for the change to take effect(the annoying part).

dankcushions

i wouldn't like to use overscan to correct problems involving "3 inches" of border - that suggests a different problem. stretching it via overscan settings will probably produce scaling artefacts.

@sonicmartin76 what videomode are you using in config.txt that produces the borders? a 1080p mode should be handled correctly by your TV without significant borders.

ps i would suggest setting the resolution via raspi-config/the config.txt as per https://retropie.org.uk/docs/Pi4/#issues-using-a-4k-tv - remove any settings via runcommand if you have made them, as the fix needs to be global to the system, not just to a specific system/game.