Frequently asked questions
Does realtime-calib run headless, without a GUI?
Yes. The service runs in Docker on the machine the cameras are plugged into — no desktop environment or GUI is needed on that host. You drive the whole calibration from a web app on any device on the same local network. See Installation.
Can I run a calibration from a phone or a tablet?
Yes. The operator interface is a responsive web app served over your LAN; desktop, tablet and phone all work. The heavy computation stays on the server.
Do I need a GPU for camera calibration?
No. Everything — board detection, live overlays, intrinsic and extrinsic solves, bundle adjustment — runs on CPU. No cloud either: camera streams never leave your local network. See the architecture overview.
Which calibration board should I use?
It depends on the step.
For intrinsic calibration, use a ChArUco board. Its ArUco markers make detection robust to occlusion and partial views, while its interpolated chessboard corners give subpixel accuracy — a good fit when the board fills a fair part of the frame, one camera at a time.
For extrinsic calibration in a large volume (a room, a hall, a wide capture space), a plain ArUco marker is often the better choice. Seen from across a large volume, the squares of a ChArUco board become too small in the image to detect reliably; the alternative — printing a very large ChArUco board — is bulky and expensive. A single ArUco marker stays detectable at a distance, so a small, cheap board is enough to link the cameras.
Whichever you use, measure it with calipers after printing and enter the real size — that measurement sets the metric scale. See Define a calibration board and the best practices.
Can I export the calibration to Unity, Unreal, Blender, three.js or ROS?
Yes. Export writes one file per selected target with the axis remap and handedness already applied: three.js / OpenGL (Y-up, right-handed), Blender / ROS (Z-up, right-handed), Unity (Y-up, left-handed), Unreal (Z-up, left-handed) — plus a Caliscope-compatible TOML. See Export.
Is realtime-calib compatible with Caliscope?
Yes. The TOML export keeps Caliscope's native field semantics
(project-specific fields are strictly additive), so pipelines built on
Caliscope's camera_array.toml keep working unchanged. For a full comparison,
see realtime-calib vs Caliscope.
Do my cameras need hardware synchronization (genlock)?
No hardware sync is required. Frames are timestamped and grouped into synchronized instants, and you control the maximum sync spread (in milliseconds) tolerated within a group when preparing the extrinsic solve.
Why does the live preview look lower-quality than the resolution I selected?
That is expected, and it does not affect your calibration. To keep the CPU encoder and the network light, the live preview streamed to your browser is downscaled to at most 960 px wide (e.g. 960×540 from a 1080p camera) and capped at 30 fps. It is a display stream only.
Detection, recording and the calibration itself run at the full calibration resolution you selected — not at the preview size. You can confirm it by checking the resolution of the recorded videos in the session folder: they are written at the capture resolution, not at 960 px. See Configure cameras for how the calibration resolution is chosen.
What operating system does the camera server need?
A Linux host: cameras are read via V4L2 and the stack runs with Docker Compose. The operator device only needs a modern browser — any OS. See Installation.
Can I use RTSP or IP cameras, or only USB?
Right now, only USB cameras are supported — they are read via V4L2 on the Linux host. RTSP streams and IP cameras are not supported yet.
It is a natural extension, though. If you need it, open an issue or a feature request on GitHub — demand is what drives the roadmap, and RTSP / IP-camera support could land in a future version.
How accurate is the calibration?
realtime-calib follows the same calibration lineage as Caliscope and OpenCV: ChArUco intrinsics with the 8-coefficient rational model, stereo-initialized extrinsics refined by bundle adjustment (methodology and sources). In practice, accuracy depends mostly on your capture — board quality, tilt, frame coverage: see the best practices. Public benchmarks are being assembled.
Is realtime-calib free?
Yes — free and open source under AGPL-3.0. If you need to embed it in a proprietary product or offer it as a closed service, a commercial license and custom development are available.