Q Light Controller+

Posted: **Mon Dec 09, 2024 7:43 am**

Hey,

I have spent some time this WE to fix some bugs that occurs on my PI4 with Rasberry image. (qlcplus_raspios_bookworm_20241101.7z)

1- Random issue when a screen is connected to the PI at boot

When a screen is connected via HDMI to the raspi 4 the dri card device can be either /dev/dri/card0 or /dev/dri/card1 (for me it is random after each reboot)... the original script don't update $HOME/.qlcplus/eglfs.json if the file already exist so I have modified the file /usr/sbin/qlcplus-start.sh:

from:

Code: Select all

# detect DRI card
if [ ! -f $HOME/.qlcplus/eglfs.json ]; then
    mkdir -p $HOME/.qlcplus
    for i in {1..5}
    do
        GPUDEV=`find /dev/dri/by-path -name *gpu-card*`
        if [ ! -z "$GPUDEV" ]; then
            GPUDEV=`readlink -f $GPUDEV`
            echo '{ "device": "'$GPUDEV'" }' > $HOME/.qlcplus/eglfs.json
            break
        else
            sleep 2
        fi
    done
fi

to:

Code: Select all

# qlc folder check
if [ ! -d $HOME/.qlcplus ]; then
    mkdir -p $HOME/.qlcplus
fi

# detect DRI card
for i in {1..5}
do
    GPUDEV=`find /dev/dri/by-path -name *gpu-card*`
    if [ ! -z "$GPUDEV" ]; then
        GPUDEV=`readlink -f $GPUDEV`
        echo '{ "device": "'$GPUDEV'" }' > $HOME/.qlcplus/eglfs.json
        break
    else
        sleep 2
    fi
done

2- Working Audio triggers

This part was a little more tricky as the main "issue" is related to QT and the way it interract with Alsa + systemctl rights + user env linked to the previous comment

I am using a simple mic usb seen by the system as :
"alsa_card.usb-C-Media_Electronics_Inc._USB_PnP_Sound_Device-00"

The "easy" way that works for me using a fresh install of the image :

install pulse audio:

Code: Select all

sudo apt-get install pipwire pipwire-audio pipwire-alsa 
sudo apt-get install pulseaudio-utils (optional, for pactl tool that also works with pipewire)
sudo gpasswd -a pi pipewire

Do a little change in the systemctl qlcplus.service

Here I just add the XDG_RUNTIME_DIR env for systemctl (/usr/lib/systemd/system/qlcplus.service file)

Code: Select all

[Unit]
Description=Q Light Controller Plus
Documentation=man:qlcplus(1)
After=basic.target

[Service]
Environment="XDG_RUNTIME_DIR=/run/user/1000"
Type=simple
User=pi
Restart=on-failure
RestartSec=3
ExecStart=/usr/sbin/qlcplus-start.sh

[Install]
WantedBy=multi-user.target

Activate autologin

Connect with ssh to your raspi and activate the autologin , mandatory to have full env of the user needed by QT app.

Code: Select all

sudo raspi-config
Choose option: 1 System Options
Choose option: S5 Boot / Auto Login
Choose option: B2 Console Autologin
Select Finish, and reboot the Raspberry Pi.

Choose pipewire as audio input/output in your qlc project

Some usefull command in my notes:
alsamixer to set system volume of the mic device
pactl list sinks to list all devices & have a lot of info (if pulseaudio-utils is installed)
pw-record /tmp/audio.wav to test an audio record outside QLC
arecord -l to list record device

Very important : it only works with a screen attached meaning with "-platform eglfs" QLC start option, so if no screen is attached and qlc start in "-platform offscreen" the audio trigger doesn't work. I dont know why and I have tested vnc , linuxfb and so on and only eglfs works. (maybe QLC+ bug or another QT behavior ? ). Today as a workaround I will receive a simple HDMI dummy device to emulate a screen .

Hope that help

Posted: **Mon Dec 09, 2024 8:14 am**

Thanks for sharing your findings.
In theory, the -platform parameter specifies just a rendering backend that has nothing to do with audio. Go figure

Q Light Controller+

qlcplus 20241101 img: sharing change I have done (fix a random crash issue with screen connected& working Audio Trigger)

qlcplus 20241101 img: sharing change I have done (fix a random crash issue with screen connected& working Audio Trigger)

Re: qlcplus 20241101 img: sharing change I have done (fix a random crash issue with screen connected& working Audio Trig