I need help using a scanline overlay on a CRT

simillarian

When I hooked my raspberry pi to my CRT I couldn't help but notice there weren't any scanlines. All of the scanline config settings I have found are for 1080p and aren't working on my TV. Can someone help me get a scanline overlay working with 640x480 resolution?

Floob

I'm confused - if its a CRT wouldnt it have scanlines anyway?
https://en.wikipedia.org/wiki/Scan_line

What TV do you have?

This may also help:
https://www.google.co.uk/search?q=scanline&espv=2&biw=1920&bih=955&tbm=isch&source=lnt&tbs=isz:ex,iszw:640,iszh:480

simillarian

@Floob Thanks, I will try that 640x480 scanline image. I think my issue was that the default overlays in RetroPie were much larger resolution. I have a trinitron. I am wanting the scanlines that are generated at low console resolutions. At 480p it does have scanlines, it's just not the same as scanlines generated from a 256x240 input. I thought that the scanlines would be further apart when I set it to 240p but they are not.

Here are some examples:

NES through composite

480p RetroPie through composite

It looks the same just less sharp when I set RetroPie to 240p. Although emulation is quite different than original hardware, I am trying to mimic the experience as closely as possible.

EDIT: The resolution of the default overlay was giving me the trouble. The smaller resolution works, although not to the extent I was hoping. There is far too much of a rolling effect happening. The same thing was happening with shaders so I wanted to try an overlay. Ah well, thanks for the help!

starquake

The Retropie does not support 240p (yet). You are probably using 480i.

See here: http://scanlines.hazard-city.de/
and here https://github.com/raspberrypi/firmware/issues/683

edmaul69

@simillarian please read my post down below with my overlay and instructions

edmaul69

Also i forgot. You need to make overlay.cfg files to go with them. Just use one of the existing ones in the overlay folder but have them named and edited correctly. I dont have a way to post them here

Dochartaigh

I've been wondering about this - do the scanlines of the CRT-Pi shader for example, scale with the native source? Like will consoles with 240i native resolution have 240 scanlines using the CRT-Pi shader? And will 480i consoles have 480 scanlines with the same CRT-Pi shader? (I seriously haven't sat down and counted how many scanlines each emulator puts up on the screen ;)

edmaul69

@simillarian ok so i went with using the single line overlay posted above either single line image works. tested on an lcd but should work the same on a crt. so heres what i di. i used this image:

alt text

i renamed it "scanline1_640x480.png"

i placed it in:

/opt/retropie/emulators/retroarch/overlays/1080p_4-3/

then i made a .cfg file and pasted in the same folder. i named it "scanline1_640x480.cfg" inside that .cfg file i added this:

overlays = 1
overlay0_overlay = scanline1_640x480.png
overlay0_full_screen = true
overlay0_descs = 0

then i opened up /opt/retropie/configs/nes/retroarch.cfg and put a hashtag in front of all the lines for a shader to disable the shader . then i added this:

input_overlay = /opt/retropie/emulators/retroarch/overlays/edmaul69/scanline2_640x480.cfg
input_overlay_enable = "true"
input_overlay_opacity = 1.000000

then i saved the file and started the game

dankcushions

@Dochartaigh said in I need help using a scanline overlay on a CRT:

I've been wondering about this - do the scanlines of the CRT-Pi shader for example, scale with the native source? Like will consoles with 240i native resolution have 240 scanlines using the CRT-Pi shader? And will 480i consoles have 480 scanlines with the same CRT-Pi shader? (I seriously haven't sat down and counted how many scanlines each emulator puts up on the screen ;)

yes it will.

to OP - my understanding is that scanlines don't appear on CRT tvs unless you're running at the correct resolution, which will typically be 240P. still, this might help: https://www.reddit.com/r/retrogaming/comments/3nqijo/bigger_scanlines_on_a_trinitron_tutorial/

edmaul69

@dankcushions check out my last post i just uploaded. this should make the scanlines he needs with this overlay i created. here is how it looks on 640X480 on an lcd but should be the same on a crt.

alt text

dankcushions

@edmaul69 yeah that should work but IMO if you have a CRT you should have no need to fake it :)

starquake

If I understand it all correctly your scanline overlay is cutting your FPS in half. The advantage of the 240p is that the result is 60 full frames per second. When you use the interlaced mode (480i) 30 times per second the even lines are drawn and 30 times per second the odd lines are drawn. When the odd lines are covered by a black line this means you will only see 30 frames per second. Some NES game use blinking really fast to give the impression of something being half translucent. For example when your hit by an enemy in Mega Man. When you have your scanline overlay over it, this means you either see a fully opaque sprite, or it's entirely gone for awhile.

That's the exact reason why I created the issue on github.

(BTW. if you're using PAL instead of NTSC 480i becomes 576i and 50hz (=50/2 = 25FPS)

edmaul69

@starquake so how would it work based on the fact that none of my odd lines are black? Is it needing to alternate back and forth between odds and evens for flashing/translucent?

starquake

@edmaul69 I'm not sure I understand your question. Are you saying it works perfectly fine right now? Or are you asking how you should make it work?

edmaul69

@starquake if i am understanding right it alternates odds and even to create translucent. Or its flashing back and forth to give 60fps. If Which means a good overlay cant work on it correct? Taking the 1080p scanline overlay that is on the pi and making it 640x480 it still looks as crappy as it did before.

edmaul69

@starquake how would it look using the crt-pi shader?

starquake

No that's not what I meant. I'm sorry, I'm not sure how to explain it better than I already did. Maybe this helps:

simillarian

This post is deleted!

edmaul69

@starquake im half retarded today. 240p and 480i.. forgot the whole 480 interlacing bit and 240 being progressive. I never use a crt so i kinda spaced out about it. Thanks for the video to remind me

edmaul69

@simillarian noticed you deleted your post. What was the issue you are having?