highascg

USB / V4L2 video input

Capture UVC webcams and USB switchers (e.g. ATEM Mini Pro ISO) on a dedicated Caspar host channel. By default Caspar opens the device directly via PLAY … v4l2:///dev/videoN LOOP (ffmpeg producer). An optional FFmpeg UDP bridge (v4l2_capture_bridge: true) remains for legacy setups.

Requirements

• v4l-utils on the playout host (v4l2-ctl --list-devices). Included in scripts/setup/05-caspar-deps.sh and live ISO prep.
• Device must expose a capture node (not metadata-only). Loopback outputs such as CasparCG Out (/dev/video10) are excluded automatically.

Quick setup (ATEM Mini Pro ISO)

1. Settings → USB video — set count = 1, pick /dev/video0 (not /dev/video1).
2. Format mjpeg, 1920×1080, 50 fps if auto fails.
3. Optional audio: use a separate live-audio slot on the same ALSA card (V4L2 direct capture is video-only).
4. Save → Apply Caspar config + restart (required when count increases).
5. Apply PLAY (Settings tab or Sources → Live tile).
6. Drag route://hostCh-N from Sources → Live onto PGM or multiview.

Or: Sources → Live → + → USB Video (V4L2) — adds a slot and starts capture when channels exist.

Architecture

Piece	Role
Direct (default)	Caspar ffmpeg producer → v4l2:///dev/videoN
Optional bridge	v4l2-input-bridge.js → UDP 52400 + slot when v4l2_capture_bridge is true
Caspar channel	One dedicated host channel per slot (kind: v4l2)
On-air	route:// only — do not PLAY V4L2 directly on program layers

API

Method	Path
GET	/api/system/v4l2-devices?refresh=1
GET	/api/v4l2-inputs
POST	/api/v4l2-inputs/config
POST	/api/v4l2-inputs/apply

Status is also exposed as v4l2InputsStatus in GET /api/state.

Troubleshooting

Symptom	Check
Empty device list	v4l2-ctl --list-devices; install v4l-utils
ATEM missing	USB cable; ls -l /dev/video*
Black picture after route	Apply PLAY; AMCP connected; INFO hostCh-1 shows v4l2:// and advancing time
non-existing PPS in Caspar log	Disable UDP bridge — use direct v4l2:// (default)
Duplicate device warning	Only one slot per /dev/videoN
ALSA conflict warning	Same hw:C,D cannot be live-audio and V4L2 mux simultaneously

Related

• Work order: work/work-orders/121_WO_USB_WEBCAM_V4L2_INPUT.md
• Virtual camera output (loopback): virtual-camera-output.md — do not use /dev/video10 as input

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