Recording Multiple Subjects

If you're capturing several subjects in a row without moving the cameras, you don't need to repeat camera calibration for each one. Creating a new session from a previous, calibrated session carries over its camera calibration — only the new subject needs to be calibrated before you can start recording.

Full working example

See examples/scripts — the activity_recording script for each language loops through subjects this way, offering to start a new session with the same camera setup after each subject's activities are recorded.

When to Use This

• Cameras must stay in the same physical position as the source session. If you need to reposition any camera, recalibrate instead and start from a fresh session.
• The source session must have already completed camera calibration — that's what gets carried over.

Creating a New Session

Swift

let newSession = try await client.newSession(from: previousSession)

TypeScript

const newSession = await client.newSessionFromSession(previousSession);

Python

new_session = client.new_session_from_session(previous_session)

This returns a brand new, independent Session — the previous session is untouched and remains usable.

What Carries Over

	Carried over?
Camera calibration	Yes
Session configuration (framerate, OpenSim model, etc.)	Yes
Camera connection — no QR scan needed	Yes
Subject calibration	No — calibrate the new subject before recording

Since cameras are already paired and calibrated, skip straight to Subject Calibration for the new subject — there's no need to reconnect cameras or repeat checkerboard calibration.

Looping Over Subjects

Swift

repeat {
    let subject = pickOrCreateSubject()
    try await client.calibrateSubject(subject, in: session, statusUpdate: callback)

    // record one or more activities for this subject...

    guard confirm("Record another subject with the same camera setup?") else {
        break
    }
    session = try await client.newSession(from: session)
} while true

TypeScript

for (;;) {
  const subject = pickOrCreateSubject();
  await client.calibrateSubject(subject, session, callback);

  // record one or more activities for this subject...

  if (!(await confirm("Record another subject with the same camera setup?"))) {
    break;
  }
  session = await client.newSessionFromSession(session);
}

Python

while True:
    subject = pick_or_create_subject()
    client.calibrate_subject(subject, session, callback)

    # record one or more activities for this subject...

    if not confirm("Record another subject with the same camera setup?"):
        break
    session = client.new_session_from_session(session)

Troubleshooting

Request fails or session not found:

• Confirm the source session has completed camera calibration — sessions that haven't been calibrated yet can't be used as the source for this call
• Check network connectivity, as with any other session operation

Next Steps

With the new session created, proceed to Subject Calibration for the next subject.