highascg

Virtual camera output (v4l2loopback)

Feed Caspar program output to Zoom, OBS, or other apps as a V4L2 webcam plus an optional ALSA virtual mic. HighAsCG uses the same safe JPEG buffer pattern as compose preview — Caspar writes a single overwriting JPEG; an ffmpeg relay pushes frames to v4l2loopback.

Default: off until the operator starts from Device View or the API.

Requirements

• v4l2loopback kernel module (video device, typically /dev/video10)
• snd-aloop when audio is enabled (ALSA loopback card HighAsCG_VCam)
• FFmpeg on the playout host
• Caspar AMCP connected

No PulseAudio / PipeWire — audio uses ALSA loopback + PortAudio capture only.

Quick setup

1. Device View → rear panel → Virtual cam — open inspector.
2. Set channel, resolution, fps; enable Include audio if needed.
3. Save settings → Start virtual cam.
4. In Zoom/OBS:
   • Camera: CasparCG Out (or label from config)
   • Mic (optional): HighAsCG_VCam / loopback capture (hw:HighAsCG_VCam,1,0)

Or cable a destination (PGM) to the Virtual cam port on the rear panel, Apply Caspar config — that sets virtualCamera.channel from the cabled source.

Kernel modules

Modules load automatically on Start when passwordless sudo is configured:

sudo bash scripts/setup/12-passwordless-sudo.sh

This installs /usr/local/lib/highascg/highascg-vcam-modules-up.sh and a NOPASSWD rule. HighAsCG writes /run/highascg/vcam-modules.conf then runs the wrapper via sudo -n.

Manual one-time per boot (if sudo wrapper not installed):

sudo modprobe v4l2loopback devices=1 video_nr=10 card_label="CasparCG Out"
sudo modprobe snd-aloop enable=1 index=20 id=HighAsCG_VCam pcm=2

Architecture

Caspar chN ──consumer 710──► media/highascg_vcam/chN.jpg  (mjpeg -update 1)
                                    │
                                    ▼
                          ffmpeg relay (HighAsCG subprocess)
                                    │
                                    ▼
                               /dev/video10  ──► Zoom / OBS

Caspar chN ──consumer 711──► ALSA plughw:HighAsCG_VCam,0,0  (playback)
                                    │
                                    ▼
                          hw:HighAsCG_VCam,1,0  ──► Zoom mic

Piece	Role
Consumer 710	Caspar FILE consumer → overwriting JPEG
Consumer 711	Caspar ALSA consumer → loopback playback
ffmpeg relay	Reads JPEG → v4l2loopback device
virtualCamera.enabled	Runtime gate — default false

Config (general.json → virtualCamera)

Key	Default	Notes
enabled	false	Runtime; cleared on Stop
channel	1	Caspar source channel
device	/dev/video10	v4l2loopback node
width / height	1920 / 1080	Full program resolution
fps	50	Relay frame rate
audioEnabled	true	ALSA loopback mic
alsaLoopbackCardId	HighAsCG_VCam	Card id for snd-aloop
showInDeviceView	true	Rear panel connector

API

Method	Path	Purpose
GET	/api/virtual-camera	Config + runtime status
GET	/api/virtual-camera/status	Alias
POST	/api/virtual-camera/config	Persist settings
POST	/api/virtual-camera/start	Start bridge (loads modules if needed)
POST	/api/virtual-camera/stop	Stop bridge

Status also on GET /api/state → virtualCameraStatus and Device View live.virtualCamera.

curl -s http://127.0.0.1:4200/api/virtual-camera/status | python3 -m json.tool
curl -s -X POST http://127.0.0.1:4200/api/virtual-camera/start \
  -H 'Content-Type: application/json' -d '{"channel":1}' | python3 -m json.tool

HTTP errors: 503 if Caspar disconnected; 502 if relay fails after start.

Troubleshooting

Symptom	Check
/dev/video10 missing	Run sudo setup script; ls -l /dev/video10
Start returns module error	sudo -n /usr/local/lib/highascg/highascg-vcam-modules-up.sh after conf exists
Video black in Zoom	Bridge running? ffplay -f v4l2 -video_size 1920x1080 /dev/video10
No audio in Zoom	snd-aloop loaded? aplay -l \| grep HighAsCG_VCam; pick loopback capture in app
Wrong channel	Inspector channel vs cabled destination — Apply after cabling
Disk fill	Bridge is opt-in; no unix-socket sink

Related

• Work order: work/work-orders/137_WO_VIRTUAL_CAMERA_OUTPUT_DEVICE_VIEW.md
• USB input (exclude loopback): usb-v4l2-input.md
• Passwordless sudo: HIGHASCG_PASSWORDLESS_SUDO.md

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