[RPi4] Bluetooth and "Now Playing"

    Hi all,

    now I've a mobile media center with 1 Rpi4, 2 SSD (and another nerd option.. :) ).

    RPI actual is connected to my car entertainment system by Bluetooth...

    I'm looking a way to see "now playing" information on car display (like a connection with my android phone)

    there is a solution with LE (or another tricks?)

    TNKs in advance...

    Ciao

    Alex

    Is LE or the head-unit the playback device? (where is media read, what is controlling playback) .. What's the OS/capabilities of the (factory, aftermarket?) head unit in the car?

    Quote from chewitt

    Is LE or the head-unit the playback device? (where is media read, what is controlling playback) .. What's the OS/capabilities of the (factory, aftermarket?) head unit in the car?

    Hi,

    The situation is:

    First: usb SSD --> LE rpi4 usb --> Bluetooth dongle ---> (only audio) --->car entrainment

    Second: internet --> android phone --> Bluetooth --> car entrainment

    in both situation car entrainment is like a Bluetooth speaker.

    but.. if I use a android phone on the car display I can se: Title, artist, cover, remaining time, etc... (now playng information)

    I like to see all information even with LE.

    TNKS

    Below is the "production-grade" procedure from scratch, which radically eliminates the ordering cycle error on LibreELEC.
    The principle is simple: kodi-avrcp must never be directly linked to kodi.service, kodi.target, or graphical.target.
    In production, it is started via a systemd post-boot timer.

    Production Installation (LibreELEC) – anti-ordering-cycle version

    1) Prerequisites on LibreELEC

    Enable SSH (if needed): LibreELEC Settings → Services → SSH ON
    Enable Kodi JSON-RPC via HTTP: Kodi Settings → Services → Control
    Allow remote control via HTTP: ON
    Port: 8080

    Quick verification (from LibreELEC):

    curl -s -u kodi:kodi -X POST -H 'Content-Type: application/json' \
    --data '{"jsonrpc":"2.0","method":"JSONRPC.Ping","id":1}' \
    http://127.0.0.1:8080/jsonrpc
    Expected: pong.

    2) Compile on PC (Ubuntu) for the correct architecture

    On LibreELEC:

    uname -m


    If it is armv7l:

    CGO_ENABLED=0 GOOS=linux GOARCH=arm GOARM=7 \
    go build -trimpath -ldflags="-s -w" -o kodi-avrcp


    If it is aarch64:

    CGO_ENABLED=0 GOOS=linux GOARCH=arm64 \
    go build -trimpath -ldflags="-s -w" -o kodi-avrcp


    Check:

    file ./kodi-avrcp

    2.2) Copy to LibreELEC
    scp ./kodi-avrcp root@IPLIBREELEC:/storage/.config/kodi-avrcp


    On LibreELEC:

    chmod +x /storage/.config/kodi-avrcp
    ls -l /storage/.config/kodi-avrcp

    3) "Root" cleanup (removes links that generate cycles)

    On LibreELEC:

    # Stop/disable any old versions
    systemctl disable --now kodi-avrcp.service 2>/dev/null || true
    systemctl disable --now kodi-avrcp.timer 2>/dev/null || true
    systemctl reset-failed kodi-avrcp.service 2>/dev/null || true

    # (Optional but recommended) if kodi-autostart creates cycles, disable it
    systemctl disable --now kodi-autostart.service 2>/dev/null || true
    systemctl reset-failed kodi-autostart.service 2>/dev/null ||
    [cite_start]true [cite: 8]

    # Remove any old units in /storage/.config/system.d
    rm -f /storage/.config/system.d/kodi-avrcp.service
    rm -f /storage/.config/system.d/kodi-avrcp.timer


    If you created drop-ins for kodi in the past (rare but possible), check:

    ls -l /storage/.config/system.d/kodi.service.d 2>/dev/null || true


    If files exist there that mention kodi-avrcp/kodi-autostart, delete them.

    4) Create the kodi-avrcp.service (without Kodi/graphical.target)

    On LibreELEC:

    mkdir -p /storage/.config/system.d

    cat > /storage/.config/system.d/kodi-avrcp.service <<'EOF'
    [Unit]
    Description=Kodi AVRCP metadata bridge (Kodi JSON-RPC -> BlueZ RegisterPlayer)
    After=bluetooth.service
    Wants=bluetooth.service

    [Service]
    Type=simple
    # Delay to allow time for BT and Kodi to be ready, without direct dependencies
    ExecStartPre=/bin/sh -c 'sleep 12'
    ExecStart=/storage/.config/kodi-avrcp
    Restart=always
    RestartSec=2

    Environment=KODI_URL=http://127.0.0.1:8080/jsonrpc
    Environment=KODI_USER=kodi
    Environment=KODI_PASS=kodi
    Environment=BLUEZ_ADAPTER=hci0
    # (optional) Environment=POLL_MS=900

    EOF


    Note: the [Install] WantedBy=... section is intentionally missing here.


    5) Create and enable the timer (post-boot start)
    This is the point that eliminates the cycle.

    cat > /storage/.config/system.d/kodi-avrcp.timer <<'EOF'
    [Unit]
    Description=Start kodi-avrcp after boot (avoid ordering cycles)

    [Timer]
    OnBootSec=25
    Unit=kodi-avrcp.service

    [Install]
    WantedBy=timers.target
    EOF


    Activate:

    systemctl daemon-reload
    systemctl enable --now kodi-avrcp.timer
    systemctl status kodi-avrcp.timer -l --no-pager

    6) Immediate test (without rebooting)

    Manual start:

    systemctl start kodi-avrcp.service
    systemctl status kodi-avrcp.service -l --no-pager
    journalctl -u kodi-avrcp.service -n 60 --no-pager


    Expected: a line like “Registered MPRIS player …”.