Raspberry composite output

Quote from Anard

Hi.

I've installed LibreElec on a RasPi3B+ to use it as media center.

My screen is a big plasma TV with 1024x768 resolution, but without HDMI inputs. So I use composite input with the Raspberry's mini-jack output.

First problem is that I can't see borders of the screen. It misses about 30px on each edge (see photo below). I tried to edit the screen settings without success.

The second is that there are interferences in audio output. It could be due to my cable but I tried just before the same configuration with Raspbian installed and it was OK.

Is there a way to prevent it by software ?

Thanks for your answers.

Display More

The 30px missing all around your image are because your plasma is 'over scanning' (or more accurately simulating it).

There is an option in config.txt to allow you to scale the Pi's output, reducing it in size, to counteract overscan in your display. This may only work with HDMI not composite though.

You can also calibrate within Kodi.

If your TV has component inputs - then an HDMI to component adaptor may also be worth a look to improve picture quality.

Quote from Anard

Thanks. I tried to edit the config.txt file but it can't in ssh as if I wasn't root. The only way is to remove the SD card and edit... Is it normal ?

It's not a problem if it wouldn't work for composite but I like to understand...

Finally, sure I'll use a HDMI to Scart or composite converter, video quality will be much better, but waiting for the converter, I'll continue to use it with my jack connection.

Code

LibreELEC:~ # cd /flash/
LibreELEC:/flash # ls -l | grep config
-rwxr-xr-x    1 root     root          3261 Jan 10 17:43 config.txt
-rwxr-xr-x    1 root     root           979 Apr 13  2018 distroconfig.txt
-rwxr-xr-x    1 root     root           321 Jan  1  1980 os_config.json
LibreELEC:/flash # nano config.txt
GNU nano 2.5.3              File: config.txt


################################################################################
#      This file is part of LibreELEC - http://www.libreelec.tv
#      Copyright (C) 2016 Team LibreELEC
#
#  LibreELEC is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 2 of the License, or
#  (at your option) any later version.
#
#  LibreELEC is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or xFITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with LibreELEC.  If not, see <http://www.gnu.org/licenses/>.
################################################################################
# Bootloader configuration - config.txt
################################################################################
[ Read 76 lines (Warning: No write permission) ]

Display More

You probably need to mount /flash as RW. I think it's RO by default in LibreElec - like most of the LE filesystem?

Details here in the wiki : Raspberry Pi Config.txt [LibreELEC.wiki]

If you add overscan settings in config.txt you also have to set overscan_scale=1, otherwise the settings don't apply to kodi (they only affect the framebuffer that's shown during boot). While that removes the borders you'll still get a stretched display on 16:9 screens in anamorphic mode which you'll need to compensate for in kodi screen calibration.

So, it's better to use only kodi's screen calibration to set both the corners and the aspect ratio, that's easier to do and also avoids having 2 scaling steps (one from kodi and one from the firmware).

so long,

Hias

I'm not 100% about the audio issues. Analog audio out of the RPi isn't great so almost no one uses it. Some time ago audio quality was improved via a firmware update (see this thread here Analogue audio testing - Raspberry Pi Forums) but this seems to have caused higher GPU load and people reported issues with HEVC playback or deinterlacing.

Going the HDMI route isn't easy, if you use HDMI then the analog video output will be disabled.

Probably the easiest and cheapest method will be to use one of the plenty RPi soundcards. Hifiberry, Iqaudio, Justboom, Pimoroni pHAT DAC and several others work out of the box (some need a dtoverlay line added to config.txt) or if you want it cheap get some RPi soundcard with a PCM5122 or PCM5102 from Asia - they should work fine as well and provide a lot better audio quality than the on-board output.

so long,

Hias

Hi,

I'm trying to get a Raspberry Pi 2b to run on my cars monitor. I have to use a rca cable though everything I get is some noise on the screen.

When using a hdmi cable on my TV it works fine.

How do I set it to use RCA for output video data?

Thanks

Without a HDMI cable connected the RPi defaults to analog/composite video and the only thing you need to configure is PAL/NTSC mode via the sdtv_mode option in config.txt.

If you get some noise make sure you use the correct cable (there are several different standards for TRRS-to-RCA cables so double-check you got one that's compatible with the RPi) and that the TRRS plug is fully plugged in on the RPi.

so long,

Hias

Thanks Anard,

Cable was the problem, didn't know there were 3 types so I had to swap ground and video.

Just a quick update for using under LE 10.X:

add "composite=1" to the kms dtoverlay in distroconfig.txt

dtoverlay=vc4-kms-v3d,composite=1

set your desired mode in cmdline.txt (on the same line after "quiet"). eg for PAL:

Code

video=Composite-1:720x576@50ie

or for NTSC:

Code

video=Composite-1:720x480@60ie

set your tv as composite and audio in config.txt

enable_tvout=1
dtparam=audio=on
audio_pwm_mode=1

So little work to do but at the end it is working like a charm on Raspberry Pi3 over composite cable