Output 720x480i from Pi3 (hdmi > vga > bnc)

pxel · April 24, 2023 at 6:50 PM

Hello,

My english is bad and I'm very tired, sorry in advance.

I'm trying to display LibreELEC on my CRT.
My Pi3 is linked to the TV like this : HDMI -> VGA -> BNC -> CRT

I successfully displayed 480i and even sometimes 240p with other OS like RaspberryPi OS (config.txt), but I can't with LibreELEC. I tried to edit the config.txt, one time I succeeded to display the splash logo in 480i but the OS doesn't go further, it was when I removed "vc4-kms-v3d" from "dtoverlay" in the file distroconfig.txt but I think the OS doesn't want to boot if this value is missing.

I also tried to go to the kodi display setting via hdmi on modern tv to see if I can manually choose "720x480i" and then reboot, but this resolution is missing (I can see this resolution in Kodi on raspbian for example, or Recalbox).

Now LibreELEC boot, but my crt doesn't support this resolution, and my screen is like cut in half.

Thank for your help

**chewitt** · April 25, 2023 at 10:16 AM

Create a clean LE11 image (to remove previous configuration attempts). Now edit "config.txt" and change "include distroconfig.txt" to "include distroconfig-composite.txt" and then boot the board. Working?

NB: Kodi only supports progressive output.

pxel · April 26, 2023 at 10:17 AM

Hi, it's not working but nevermind, I'm trying something else now with my Pi 4, maybe you can help me.
I plug my Pi 4 with this extension : https://www.recalbox.com/fr/recalbox-rgb-dual/

So I can output true RGB with this extension > scart cable > scart bnc.

Do you think it's possible to display LibreELEC from this extension ?

Thank you

VLouis · April 26, 2023 at 2:05 PM

Quote from pxel

Hi, it's not working but nevermind, I'm trying something else now with my Pi 4, maybe you can help me.
I plug my Pi 4 with this extension : https://www.recalbox.com/fr/recalbox-rgb-dual/
So I can output true RGB with this extension > scart cable > scart bnc.

Do you think it's possible to display LibreELEC from this extension ?

Thank you

Hi,

Sorry but I think you should let it go that very old CRT monitor with only BNC-RGB input.

The system (LE in this case) needs to know the supported picture modes from display, for that is used the EDID data, but that is missing in case of BNC-RGB connection. Also if that old CRT accept only interlaced picture when the Kodi only support the progressive mode... maybe can't be solved at all. For the both case, no matter what type of adapter-over-adapter connection you will use. The system want something what the display don't have it (EDID data) and the display want something what the Kodi can't provide (interlaced picture).

You should upgrade the display to something less old, which have digital input (HDMI or DVI) and less power hungry...

**Da Flex** · April 26, 2023 at 3:46 PM

CRT should work without additional hardware, just by using the headphone jack.

There is a known CRT bug since LE 10.0.2, and I don't know whether it's fixed now. So please test with LE 10.0.1.

Here are the settings: Click!

VLouis · April 26, 2023 at 5:43 PM

Quote from Da Flex

CRT should work without additional hardware, just by using the headphone jack.
There is a known CRT bug since LE 10.0.2, and I don't know whether it's fixed now. So please test with LE 10.0.1.
Here are the settings: Click!

Hi, it's not about a "classic" CRT TV display with composite video input. I repaired things like this 15-20 years ago, know them well, but even in that era, that type of connetion was very rare compared with VGA. It's a CRT monitor for PC with RGB input, three BNC connector for Red, Green and Blue analogue signals, usually with synchro signal mixed on Green or another two BNC input (for V-sync and H-sync signal). Same as the VGA connector signals, but without EDID connection. The RPi's composite video from jack connector can't be used for this and probably harder to transcode to analogue RGB than the HDMI output.

The cable (used after a HDMI-VGA adapter) probably is like this:

**Da Flex** · April 26, 2023 at 10:06 PM

VLouis Thanks for the explanation. I only remember RGB input as SCART. This one is exotic.

"Recalbox RGB Dual" doesn't use DSI port, just GPIO: Recalbox RGB Dual Manual

I would still suggest to try LE 10.0.1. Maybe the composite bug affects GPIO somehow.