480p scanlines overlay

[segaages]

Hi all, and thank you for the great work on Retropie!

Right now in order to use the crt-pi overlay and see scanlines properly retropie must be set to 1080p, causing a dip in performance on some systems, especially on RPi2 (which I am using).

I used to have my Retropie on RPi2 set on 480p resolution (even on a FullHD screen) in order to mantain optimal performance and because no system emulated actually needed a higher resolution but this way the crt-pi overlay doesn't show scanlines properly.

So I'm asking: why not add a 480p crti-pi overlay so that both scanlines and performance can be kept?

Right now I guess my problem could be solved like stated here (except for the crt part):
https://retropie.org.uk/forum/topic/3156/i-need-help-using-a-scanline-overlay-on-a-crt
but it's a quite complicated process, isn't there a way to simply copy and paste a overlay in the right folder and select it in the menu?

Sorry, this is both an idea and a support request but I thought it would fit better here.
Thank you!

[caver01]

@segaages There will probably be other responses to this, but a few thoughts off the top of my head are:

First, when folks reference CRT-PI they are usually referring to the RetroArch shader developed by DaveJ. This is not an overlay, although you might actually be talking about an overlay with that name. The difference may not seem like much when looking at the screen, but the affect can be significant. An overlay uses an image (typically with some transparency and/or color) which gets combined with the video image. Combined, the overlay can fill-in unused space with artwork or create lighter and darker areas using transparency to simlulate scanlines and shadow mask effects.

The CRT-PI shader is different in that it uses mathematics to affect the rendering of the video itself. This allows for a lot of flexibility, as it affects how each pixel of video gets displayed and can work at multiple resolutions. I am not sure where you heard that the CRT-PI requires 1080p, but if it is indeed the shader we are talking about, it works just fine on my system at 1024, and maybe even lower. It was designed to remain optimized up to 1080, but it works at lower resolutions too.

Now, as soon as you get into the 1:1 range of source pixels to rendered video, you really don't have any room for scanlines. Think about this: If your source game is 480p, and you are running your video at 480p, where are you going to draw black lines to simulate the effect? You would theoretically need to double the resolution of your video before you can take advantage of scanlines every other line of actual pixels. The higher resolution you go, the more "accurate" or believable the simulated scanlines can get. With anti-aliasing, or blurring effects, glow, bloom--there are all kinds of details that can fill the surrounding pixels of video making for some very realistic effects.

Others can chime in here who have experience with tiny displays, as there may be some fancy rendering tricks that allow scanlines to work at lower resolution, but to me, you just don't get much clarity at 480p to make faking a CRT worthwhile.

[Darksavior]

@segaages I'm on a pi2 oc'd to 1ghz. I've yet to encounter a game that ran full speed in 480p and then get slowdowns once I went to 1080p and added the crtpi shader. The only noticeable speed differences I got was from choosing another emulator to run a game faster.

[edmaul69]

@segaages crt-pi shader works fine in 4:3 for me. No slowdown on my pi 3. No graphic problems with it either.

[segaages]

@caver01 Sorry for the late response, been away for some days.

Indeed I was refering to the CRTI-PI shader, I misused the term overlay.
Also, I was refering to the fact that CRTI-PI shader is optimized for 1080p and up, with scanlines not scaled correctly using inferior resolutions (such as 480p).

I understand what you explain about 480p 1:1 source but I have this problem also with 240 source emulators like megadrive or snes.
Anyway I might need to tinker a little with configs in order to tune the shader when outputting in 480p.

What I was seeking is simply an immediate way to obtain a proper scanline visualization mantaining 480p output (without tinkering).

Thank you, time to read some .cfg files!

[segaages]

@Darksavior I'm on RPi2 w/o overlocking. SNES dips big time on some games in 1080p.

[caver01]

@segaages Yeah, you have the right idea. . . It seems to me that with 240p source, the best you will be able to get is a black (or dim) line every other pixel row, and maybe something similar every other column. Double-res is not much to work with, but it seems like a shader could do something.

[dankcushions]

i believe packaged with retroarch is a Wii scanlines overlay that can be activated. the Wii was 640x480 (or at least, that overlay is) so that should work well. i can't really demonstrate/remember how you load overlays but maybe that's enough to get you going :)

[caver01]

@segaages , as @dankcushions said above 480p scanlines overlay:

i believe packaged with retroarch is a Wii scanlines overlay that can be activated. the Wii was 640x480 (or at least, that overlay is) so that should work well. i can't really demonstrate/remember how you load overlays but maybe that's enough to get you going :)

This might be a low-overhead solution for you. There are other threads that have examples of the lines you could include in a retroarch.cfg (either per ROM or per Emulator) to setup an overlay as opposed to the shader. If you can find the file dankcushions is remembering, load it on the Pi and reference it as an overlay, (and assuming you like the look of it) it might be a simple way to achieve the effect without the need to learn OpenGL.