If the target display is low resolution...

[GhostToast]

If the target display is low resolution, can a lesser pi do the job? I am wanting to add this to an older Sony 8" CRT to give it even more of a retro feel. So 4k output isn't anywhere close to what I'd be targeting. Obviously I'll have to convert the signal to S-Video or something, but before I spend money on a new RPi5, I'm wondering if some of the hardware requirements could, theoretically, be ignored. How much of the 5 is needed just for processing the algorithms, vs pushing to a hi-def signal? And are there any settings in the config that would allow for such a downsampling to save on heat output? Rather than just degrading through the signal.

[kholbrook1303]

If the target display is low resolution, can a lesser pi do the job? I am wanting to add this to an older Sony 8" CRT to give it even more of a retro feel. So 4k output isn't anywhere close to what I'd be targeting. Obviously I'll have to convert the signal to S-Video or something, but before I spend money on a new RPi5, I'm wondering if some of the hardware requirements could, theoretically, be ignored. How much of the 5 is needed just for processing the algorithms, vs pushing to a hi-def signal? And are there any settings in the config that would allow for such a downsampling to save on heat output? Rather than just degrading through the signal.

I like the idea of this however I am not positive. I ordered a cable (3.5 to audio/composite) that should be in today. I also have a pi 3b+ lying around that supports the cable.

Let me do some testing and I will get back to you on this. If all goes well, I'll send you instructions then see what the best solution is for either adding this functionality or at minimum spin up a new repo.

[kholbrook1303]

If the target display is low resolution, can a lesser pi do the job? I am wanting to add this to an older Sony 8" CRT to give it even more of a retro feel. So 4k output isn't anywhere close to what I'd be targeting. Obviously I'll have to convert the signal to S-Video or something, but before I spend money on a new RPi5, I'm wondering if some of the hardware requirements could, theoretically, be ignored. How much of the 5 is needed just for processing the algorithms, vs pushing to a hi-def signal? And are there any settings in the config that would allow for such a downsampling to save on heat output? Rather than just degrading through the signal.

@GhostToast I have performed some testing and here is what we are looking at:

• The Raspberry Pi 3 (B/B+) is not capable of running the minimum requirements for OpenGL. I was able to get it installed with some tweaks but it will not run.
• The Raspberry Pi 4 does work but with some changes required to the configuration. By reducing the visualization presets to 30fps with a resolution of 320x240 you are able to get pretty decent performance from the presets. See below for additional steps and deviations from the manual installation instructions in the README.

RPI 4 running projectMAR over composite video:

Requirements:

• Raspberry Pi 4 with SD Card/Power Adapter
• 3.5mm composite video and audio cable similar to 'Adafruit A/V and RCA (Composite Video, Audio) Cable for Raspberry Pi
• Raspberry Pi OS Lite (64-bit) **This has not been tested on Desktop. It should work but expect lesser performance and would require the projectMAR.conf to have the resolution adjusted for display enforcement.

Setup Instructions:

Note: This assumes you are working off of a fresh image that has been already been updated.

• Run 'sudo raspi-config' then goto 'Display Options' -> 'Composite' -> Enable
• Run 'sudo nano /boot/firmware/config.txt' and change the following (Your changing kms to fkms):
  • Change 'dtoverlay=vc4-kms-v3d,composite' to 'dtoverlay=vc4-fkms-v3d,composite'
  • add 'enable_tvout=1' to the end of the file then 'ctrl+x' to close and 'y' to confirm
• Run 'sudo nano /boot/firmware/cmdline.txt' and add the following to the end of the single line (You may have to play with the margins to align with your screen):
  • Add 'video=Composite-1:margin_left=28,margin_right=32,margin_top=22,margin_bottom=24' then 'ctrl+x' to close and 'y' to confirm
• Run the installation steps from the README except you have to change one part. For libprojectM installation remove the '--parallel' option from the cmake command as running parallelism will cause a crash.
• Once completed you just have to modify your /opt/ProjectMSDL/projectMSDL.properties file to adjust for resolution and fps. Ensure the following variables are set:
  • window.width = 320
  • window.height = 240
  • projectM.fps = 30

I need some time to put this together into an independent repository but I have this on my todo list.

Let me know if you have any questions about the procedure and I'll help as best I can. Please also provide any feedback post setup as I would love to hear how this went and make any changes necessary for future audiences.

[GhostToast]

Thanks so much for doing this research! At this point, I have an older 3, so that won't work. I'm wondering if, then, I should focus on finding a 4 or just go for the 5? In terms of cost they're probably similar if I'm starting from nothing. Just wondering if there's any connectivity options that the 4 offers which is optimal for this vs using HDMI and converting to RCA.

[kholbrook1303]

As far as the RPI4 is concerned it already comes with a 3.5mm 4-pole stereo audio and video output, but then you will need the cable for it.

The RPI5 does not have out-of-box support for composite, but you have the option to solder to the J7 composite video header to add it. That would solve the video problem but then you would need audio which would require a DAC. As you stated you could alternatively use an HDMI to RCA converter (I dont have much experience with these).

[GhostToast]

I got a chance to set this up and it's almost working great! So I did end up going with a R5 and mini-HDMI out to composite. I can get picture. I did not follow any of the steps to do composite out since those seemed relevant only to if I were to hardwire to the pinouts on this board. It works if I do nothing different, but while the desktop appears to conform to the size of the monitor, the visualization is not full screen and seems to be too large / off-center on startup. As I'd ideally not have a mouse/keyboard attached to this, I think I need to fiddle with some settings. I did try putting in the window.height, width and projectM.fps params, but the visualizer doesn't launch (crashes?) on startup.

attached image shows what i see on startup with those lines commented out. note that the left/right center seems good but the "center" appears to be in the bottom 3rd of the screen
also, what is the command to invoke the visualizer again if i were to quit it? i'll keep fiddling and report back if i find a winning combination. thanks so much for your help!

[GhostToast]

i ended up setting the window.fullscreen.width and height to the correct values, and enabling exclusive fullscreen. as well, i changed the conf file in the projectMAR folder to have the same resolution. i think this is good now! next up will be to maybe wire a couple buttons to use as next/prev visualizations. but not sure if/when i'll get to that. i'll keep you posted if i encounter any other issues. thanks again!

[kholbrook1303]

Thanks for the update! I have an HDMI to composite adapter coming in tomorrow to test with so if anything has changed I can add it to the README/installer.

To run this on-demand you can run:

/opt/ProjectMAR/env/bin/python3 /opt/ProjectMAR/projectMAR.py

You can also create a desktop shortcut using:

echo -e "/opt/ProjectMAR/env/bin/python3 /opt/ProjectMAR/projectMAR.py" > !/Desktop/projectMAR.sh
sudo chmod +x "~/Desktop/projectMAR.sh"

Regarding screen overflow, you may want to tinker with setting overscan in the cmdline.txt. Here is an example if using HDMI 1 with 1920x1080 resolution at a 60hz refresh rate. You can see your current settings by running either 'wlr-randr' (Wayland/LabWC) or 'xrandr' (X11).

The following would go at the end of cmdline.txt then require a reboot for changes to take effect.

 video=HDMI-A-1:1920x1080@60,margin_left=28,margin_right=32,margin_top=22,margin_bottom=24

[GhostToast]

Thanks, I might look into that. Fwiw this is going from HDMI to RCA via the ~$35 RCA adapter (doesn't require power) that's pretty readily available online. Just using the video cable (yellow) because I am capturing audio via a USB gooseneck mic on the RPi. I actually think the resolution is ideal but may tinker more with your suggestions. Here's a video of the installation working. Minidisc for music. DVD for movie, and second screen doing the visualizations. Everything but the pi is Sony (a strange little shrine/museum)

https://photos.app.goo.gl/oPwVF8K98qY1bQnp7

Thanks again for putting this all together!

[kholbrook1303]

Nice job, I really like the setup! Convertion cable comes in today but I likely wont get to testing it until this weekend as I have to rebuild my home PC. As soon as it is back up I'll start testing.