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What is realtime-calib?

realtime-calib is a local, real-time, open-source multi-camera calibration application. It recovers both the intrinsics (focal length, distortion) and the extrinsics (6-DoF position and orientation) of a rig of USB cameras, with live feedback, and exports calibration files ready for Caliscope and the major 3D engines. The whole calibration is driven from a web app, so you can run it from any device on the same local network as the server the cameras are plugged into — the smartphone in your pocket, a tablet, or a laptop.

Why it exists​

realtime-calib grew out of using Caliscope to calibrate multi-camera USB rigs for computer-vision projects. Caliscope does the calibration math well, but three recurring points of friction got in the way:

  • Record-then-calibrate. Each session meant pre-recording every camera in OBS through a dedicated sync plugin — which was unstable, crashed, and sometimes silently lost frame sync, forcing manual video re-editing before calibration could even start.
  • No headless path. Some clients ran on headless Linux VMs, so calibrating meant standing up an extra VM with a desktop, passing the cameras through, and driving a GUI — just to run a calibration.
  • Export mismatch. The output convention didn't always match the target project's coordinate system, so results needed hand-conversion.

realtime-calib keeps what works about Caliscope — its calibration logic — and removes those three frictions.

What makes it different​

  • One-pass calibration. No separate video-recording step: capture, detection, quality feedback and computation happen live, in a single flow. What you see is what gets calibrated.
  • Runs headless, driven from any device. The service runs in Docker on the machine the cameras are plugged into — no desktop or GUI required on that host. The operator drives everything from a web app served over the local network, on any device: laptop, tablet or phone. This fits headless servers, robotics rigs, motion-capture setups and production lines.
  • Multi-format export. One calibration, exported to the convention your target actually uses — Caliscope-native TOML, or engine-ready JSON with the correct axis and handedness for three.js / OpenGL (Y-up, right-handed), Blender / ROS (Z-up, right-handed), Unity (Y-up, left-handed) and Unreal (Z-up, left-handed). The dangerous 3D math (axis remap, left-handed mirror) is done for you.
  • Local & private, CPU-only. Everything runs on your own hardware — no cloud, no GPU. Camera streams never leave the local network.
  • Caliscope-compatible. The TOML output keeps Caliscope's semantics, so existing Caliscope pipelines keep working.

The workflow​

An operator starts the stack (Docker), opens the web app (desktop, tablet or mobile), and follows a wizard:

  1. Target Config — define the board(s): ChArUco / ArUco.
  2. Camera Setup — discover and set up the USB cameras.
  3. Intrinsics — calibrate each camera, one by one.
  4. Extrinsics — solve the whole capture volume, with a 3D review of the reconstructed rig as its final sub-step.
  5. Export — Caliscope-compatible TOML and/or engine-ready JSON.

Everything happens in real time: camera streams are published over LiveKit, and detection/quality overlays are burned in server-side and streamed live.

Who is this for?​

  • Operators & users setting up a multi-camera rig for motion capture, volumetric capture, robotics or photogrammetry.
  • Researchers who need reproducible, inspectable calibration and a path to cite the method — see Research.

How it relates to Caliscope​

realtime-calib reimplements Caliscope's calibration logic (it is not a dependency) to make it real-time and single-pass, while staying output-compatible. Caliscope remains the conceptual reference for board definitions, calibrateCameraCharucoExtended, PnP/stereo extrinsic initialization and bundle adjustment.

Next step

Head to Installation, then run your first calibration.