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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Wed Feb 24, 2021 5:01 pm 


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setiawan wrote:
I've been able to pass through the equivalent resolution with pixel doubling, but it comes out weird. Like there are gaps between each doubled pixel. Not sure what's up with that. It's otherwise a stable image:


At this point, it's just guessing, but what that looks like to me is that the pixel clock is too slow and/or the H and V blanking periods are too short. When you send the pixel-doubled modline, you are literally sending the pixels twice, but they should be sent so fast that you can't see both of them; you could think of it like the pixels are only half-width and the two pixels are taking up the space of one pixel. (that's not quite accurate, but it might help you to visualize what's going on).


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Mon Mar 01, 2021 4:11 pm 



Joined: 14 Jan 2021
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vol.2 wrote:
setiawan wrote:
I've been able to pass through the equivalent resolution with pixel doubling, but it comes out weird. Like there are gaps between each doubled pixel. Not sure what's up with that. It's otherwise a stable image:


At this point, it's just guessing, but what that looks like to me is that the pixel clock is too slow and/or the H and V blanking periods are too short. When you send the pixel-doubled modline, you are literally sending the pixels twice, but they should be sent so fast that you can't see both of them; you could think of it like the pixels are only half-width and the two pixels are taking up the space of one pixel. (that's not quite accurate, but it might help you to visualize what's going on).



Have tried a variety of hdmi_timings now, and nothing seems to fix the issue. I'll try it out on a LCD display at some point, without any converters, to see if that same issue is there. If so I'll raise it in the Raspberry Pi forums.

As for not being able to pass through 320x240p without pixel doubling, I'm starting to think it's down to the Portta converter. I tried passing HDMI signals from my PC (Nvidia GTX1060) using Nvidia's custom resolutions through the Portta, and peculiarly I can pass more or less the same resolutions that I can pass with the pi (e.g. the weird 640x480i resolution I'd been using, 640x240p works too), but 320x240p also doesn't work. Similarly with both pi and PC, whenever I try to pass 320x240p through the Portta, it doesn't 'sound' like the CRT is trying to display anything. I.e. the frequency of the CRT whine when trying to display 320x240p is the same as the frequency when it's trying to display an unconnected source.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Tue Mar 02, 2021 12:37 am 


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For those who just rock 640x480 on a PC CRT, what are your favorite shaders? I use a mini-SLG when I go that particular route

https://www.instagram.com/p/CK77T8fFg3r ... 2l4f10ksg0

https://paradisearcadeshop.com/products ... 64c1&_ss=r

Very good option for laziness imho ;)
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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Tue Mar 02, 2021 1:00 pm 


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Quote:
I use a mini-SLG when I go that particular route

won't replace using a shader though, if you want to completely eliminate any shimmering.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Tue Mar 02, 2021 7:23 pm 


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Fudoh wrote:
Quote:
I use a mini-SLG when I go that particular route

won't replace using a shader though, if you want to completely eliminate any shimmering.


Ooh, that’s interesting! I really gotta study up on shaders beyond the “stock” ones that come with RetroArch / official Pi 3 images... I don’t even know where to find ‘em / which are the most highly-regarded! Most of the people in the Discords/forums I hang out in primarily use PC RetroArch or Wii. Looks like I have an afternoon project lined up for myself now :)
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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Tue Mar 02, 2021 7:41 pm 



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kitty666cats wrote:
Ooh, that’s interesting! I really gotta study up on shaders beyond the “stock” ones that come with RetroArch / official Pi 3 images... I don’t even know where to find ‘em / which are the most highly-regarded! Most of the people in the Discords/forums I hang out in primarily use PC RetroArch or Wii. Looks like I have an afternoon project lined up for myself now


Before you spend too much time on this, keep in mind that the more "advanced" shaders won't work on a Pi. Well, I don't have experience with a Pi4 so that may be a bit different.

Even old Pi's support the "interlace" shader. I think you have to dig around for it in the shader subfolders though (it's not a standalone preset in the CRT folder, but rather a shader used by other standalone presets), and then you can save it as a custom preset for easier use. I highlight this one because it is very simple and does exactly what a SLG is supposed to do via software.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Tue Mar 02, 2021 10:03 pm 


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fernan1234 wrote:
kitty666cats wrote:
Ooh, that’s interesting! I really gotta study up on shaders beyond the “stock” ones that come with RetroArch / official Pi 3 images... I don’t even know where to find ‘em / which are the most highly-regarded! Most of the people in the Discords/forums I hang out in primarily use PC RetroArch or Wii. Looks like I have an afternoon project lined up for myself now


Before you spend too much time on this, keep in mind that the more "advanced" shaders won't work on a Pi. Well, I don't have experience with a Pi4 so that may be a bit different.

Even old Pi's support the "interlace" shader. I think you have to dig around for it in the shader subfolders though (it's not a standalone preset in the CRT folder, but rather a shader used by other standalone presets), and then you can save it as a custom preset for easier use. I highlight this one because it is very simple and does exactly what a SLG is supposed to do via software.


Thanks for the heads-up, I will give that one a try!
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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Fri Mar 05, 2021 6:32 am 


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vol.2 wrote:
kitty666cats wrote:
I wish I had picture perfect integer scaling fully worked out, but as you can see in the images it’s not quite there - I’m not too bothered as things look pretty good and there’s no scrolling distortion, but the OCD never fails to get me... :(



I swear that this whole mess is 1000% easier if you just use RetroArch instead of messing with Retropie. RA let's you lock integer scaling from the video settings menu and all of your settings are controlled in one place. (outside of the config.txt)

It's really not that big of a deal to compile. I'll try to make separate post giving a blow-by-blow here at some point.


Would love to be “shown the ropes” on how to do this if you find the time soon - I know my way around RetroArch quite well now, but I am not at all familiar with Linux / reconfiguring my whole entire Pi and starting back at square one :o
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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Fri Mar 05, 2021 8:01 pm 


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kitty666cats wrote:
Would love to be “shown the ropes” on how to do this if you find the time soon - I know my way around RetroArch quite well now, but I am not at all familiar with Linux / reconfiguring my whole entire Pi and starting back at square one :o


Ok. I will refer you first to the guides that make sense. Although the one caveat is that none of them are written with 15kHz CRTs in mind, so there are going to be some changes.

This is the best guide so far: https://gist.github.com/AlexMax/32e5d03 ... ea75736805

To get it running for a CRT, follow the advice of Alphanu1 in the middle of the comments. Some of this is a little out of date, especially the Core, I think probably there should be a configure line that includes one or more of the following added: -march=armv8-a+crc+simd -mcpu=cortex-a72 -mtune=cortex-a72. I believe that "march" overrides "mcpu," but I can't remember exactly.

Quote:
There are many libraries missing in Buster. These need to be installed. The following is pretty much everything RA needs.

sudo apt install build-essential libxkbcommon-dev zlib1g-dev libfreetype6-dev libegl1-mesa-dev libgles2-mesa-dev libgbm-dev libavcodec-dev libsdl2-dev libsdl-image1.2-dev libxml2-dev yasm libavformat-dev libavdevice-dev libswresample-dev libavresample-dev libswscale-dev libv4l-dev libgl*-mesa-dev


Configure as follows.

CFLAGS="-mfpu=neon" ./configure --enable-alsa --enable-udev --enable-neon --disable-videocore --disable-opengl1 --disable-x11

Them make.

This method requires fkms-v3d to be enabled in the boot config.txt



This guy says he got everything square with GLES3, which is better because there are more cores compiled with ES support than there are for GL1 or GL2. Notably, I haven't found a compiled Mupen core for GL on Armhf. I'm sure it would work if you just compiled it (the mupen core) yourself for GL, but I haven't gotten around to it yet. There seems to be an available armhf for GLES binary available in one of the repository sites.

https://www.reddit.com/r/RetroArch/comm ... pberry_pi/

So I was going to next try that guy's guide because he claims amazing performance and stuff. Seems legit, but I just haven't had time recently.

IAC, I would also recommend you get a fresh SD card and hold onto your old one to fall back on if it things don't work out for you.

If you want to give this a shot, great, please share you results. If you want to wait for me to get caught up with it and fill you in, it may be a few weeks before I have the time.


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