An input lag investigation

BuZz

It should reduce lag in theory, but instead of doing that, if your tv upscales from 720p well, you could just use a 720p video mode. It is possible that screens that have a delay due to post processing could be quicker at a lower res also.

dispmanx also scales with a filter by default, so it might look better with a 720p video mode with the tv doing the scaling vs dispmanx (I prefer it on my tv)

davej

@ScOULaris said in An input lag investigation:

Hm. So I understand how a shader can add more input delay (increasingly in correlation with the complexity of the shader). Would lowering the Retroarch rendering resolution to 720p instead of the default 1080p for SNES have any impact on input delay since it's half of the pixels that need to be processed by the shader?

Yes, but probably not as much as you'd think. You'll also have poorer image quality to deal with. crt-pi's scan lines work best when scaling up 4x or more. If you are going to use a lower resolution than that I'd suggest using integer scaling - and don't go below 3x.

Scaling in the display hardware is essentially free but you are probably better off setting your Pi to a 720p screen mode and letting your TV do the upscaling. Try both and see which works best. If the scan lines are hard to see with such as low resolution, try setting MASK_TYPE to 0.

BuZz

Just to detail my tv/kodi setup downstairs:

/boot/config.txt contains

hdmi_group=1
hdmi_mode=4

which is 720 @ 60hz

/opt/retropie/configs/all/autostart.sh contains

sudo mount -t cifs -o username=blah,password=blah //mynas/retropie /home/pi/RetroPie
kodi #auto
emulationstation #auto

kodi is configured to display and output at 1080p (it can change video mode itself)

then I exit kodi, and I'm ready to game (in 720p)

the only other thing I have to do is switch the tv to game mode and back.

scrappbrapp

how do you change the display driver to Dispmanx? i assume mine is running stock, i never knew how to change.. Ive also yet to learn about shaders, so I'm not too worried about losing that ability.

BuZz

you can do it via the configuration editor (in advanced mode)

https://github.com/retropie/retropie-setup/wiki/Configuration-Editor

scrappbrapp

thank you, i found it.
Unfortunately, i think I noticed WORSE play on dispmanx.... I can tell that the video quality is worse... but mashing jump in mario world created a worse experience than before with GL. Also trying to do a "speed run" caused me to not have some jumps registered, thus plowing right into enemies...

scrappbrapp

This post is deleted!

silentq

I updated from binary and source and changed over to dismanx, I thought the video smoothing was supposed to be gone? I even tried to turn it off in retroarch.cfg for lr-fceumm by make video_smoothing="false" and its still there? Am I missing something?

BuZz

@silentq need to build latest retroarch from source. It only recently got support for switching scaling mode

BuZz

At least as I remember

silentq

Not sure if this is a bug, its not really major but I noticed using the dismanx driver that the retroarch status notifications at the bottom of the screen don't show anymore. Status messages like when you save or load state or a input remapping status don't show. Just thought I would mention it its not major but figured I would add that.

Rion

Sorry to reply to and old thread but this is the updated link to the same Thread at the libretro forums. I think this one is more up to date.

@Brunnis
An input lag investigation

pattaboy

I have noticed some input lag on psx games. especially when playing my childhood game bust a groove. Where you need timing to play the game. I couldn't even do one dancemove when pressing the button. Has this ever been noticed that the PSX emulator has input lag?

Rion

@pattaboy Every emulator, if it's on Windows, Linux or Mac has some form of input lag.

Just read this thread and the one on Libretro to try different things that might help.

Just to name a few

Game Mode on you TV
Runcommand set to Performance
Render Resolution