Pair sound with its screen

This guide plays a video on one monitor with its sound on that same monitor’s speakers: one claim, one pod, one screen. You need this operator and the display operator installed on your liken cluster, and a monitor with speakers on HDMI or DisplayPort.

How the pairing works

The two operators are separate Dynamic Resource Allocation (DRA) drivers, and each publishes its own reading of the same monitor. The display operator reads the EDID (Extended Display Identification Data) through the graphics card, and this operator reads the ELD (EDID-Like Data), the block the graphics driver writes into the audio driver. Both derive one attribute the same way, byte for byte: monitor.liken.sh/id, the pairing identity.

A single ResourceClaim holds one request against each driver, and a matchAttribute constraint requires one value of monitor.liken.sh/id across the two. The scheduler then allocates a screen and speakers that belong to one monitor, whichever connector it is on.

1. Write the claim

apiVersion: resource.k8s.io/v1
kind: ResourceClaim
metadata:
  name: kitchen-screen
  namespace: media
spec:
  devices:
    requests:
      - name: screen
        exactly:
          deviceClassName: display-output
          tolerations:
            - key: display.liken.sh/disconnected
              operator: Exists
              effect: NoExecute
              tolerationSeconds: 30
      - name: speakers
        exactly:
          deviceClassName: audio-output
          tolerations:
            - key: audio.liken.sh/disconnected
              operator: Exists
              effect: NoExecute
              tolerationSeconds: 30
    constraints:
      - requests: [screen, speakers]
        matchAttribute: monitor.liken.sh/id

matchAttribute takes the attribute’s full name. Only a CEL selector splits the name on its domain, as Play sound to an output shows.

As written, the claim takes any monitor that offers both a screen and speakers. To name one monitor, add a CEL selector to the screen request, on the display operator’s model or serial attributes. The constraint brings the matching speakers with it.

2. Reference the claim from a Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: kitchen-player
  namespace: media
spec:
  replicas: 1
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: kitchen-player
  template:
    metadata:
      labels:
        app: kitchen-player
    spec:
      resourceClaims:
        - name: monitor
          resourceClaimName: kitchen-screen
      containers:
        - name: player
          image: <your mpv image>
          args:
            - --fullscreen
            - --wayland-app-id=$(DISPLAY_APP_ID)
            - --ao=pipewire
            - https://media.example.com/movie.mkv
          resources:
            claims:
              - name: monitor

resources.claims names the claim once, so the container receives both allocations: the display operator’s delivery for the screen, and this operator’s for the speakers. Two of mpv’s flags route the two halves: --wayland-app-id=$(DISPLAY_APP_ID) puts the window on the allocated screen, and --ao=pipewire plays through PipeWire, which reads the delivered PIPEWIRE_REMOTE and PIPEWIRE_NODE itself.

3. What the container receives

Each driver applies its own edits, and they do not collide:

The display operator points XDG_RUNTIME_DIR at its own directory, and that does not misroute the audio: a PIPEWIRE_REMOTE that starts with a slash is used as an absolute socket path, and the runtime directory is not consulted.

The grain of the pairing

The pairing identity names a monitor’s model, not a unit. The ELD has no serial number, so two monitors of one model publish one value, and the constraint is satisfied by either pairing. Devices gives the derivation. On a machine with two identical monitors, the screen and the speakers the scheduler picks can come from different units, and no selector can prevent that. A serial selector on the screen request pins the screen to one unit, but this operator publishes no serial for the constraint to hold the speakers to. The ELD offers nothing finer.