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SLAMCam

SLAMCam is a secondary development based on OpenCamera, designed to support synchronized recording of IMU, GPS, and video streams. All sensor data are aligned on a unified timeline, making it suitable for SLAM and Visual-Inertial Odometry (VIO) research. The software also supports a Chinese (Simplified) user interface.

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Features

• Synchronized IMU, GPS, and video recording
• Real-time timestamping for sensor data
• Remote control and multi-device synchronization (RecSync)
• Chinese (Simplified) UI support

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Requirements

• Android device with full Camera2 API support
• Optional: Wi-Fi connection for remote recording or multi-device sync

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Usage

1. IMU Recording

Note: Synchronized timestamps for camera and IMU are not supported on all devices. Check support in preferences.

Steps:

1. Open Preferences → enable Camera2 API → enable "Sync video IMU recording" in IMU settings.

2. (Optional) Disable video stabilization to minimize preprocessing effects.

3. (Optional) Enable save frames to verify recorded data.

4. (Optional) Enable flash strobe and set frequency in additional sensor settings.

5. Switch to video mode, adjust ISO and exposure as needed.

6. Record video.

7. Retrieve recorded data from DCIM/SLAMCam/{VIDEO_DATE}/:

   • {VIDEO_NAME}_gyro.csv – X, Y, Z, timestamp (ns)
   • {VIDEO_NAME}_accel.csv – X, Y, Z, timestamp (ns)
   • {VIDEO_NAME}_magnetic.csv – X, Y, Z, timestamp (ns)
   • {VIDEO_NAME}_timestamps.csv – timestamp (ns)
   • {VIDEO_NAME}_flash.csv – timestamp (ns) (flash firing timestamps)

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2. Remote Recording

Steps:

1. Connect your smartphone and PC to the same network.

2. Use scripts in ./api_client/ to send requests to SLAMCam.

   • The phase returned by start_recording can be used for synchronization with external devices.

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3. Multi-Device Synchronized Recording (RecSync)

Important: Devices must support real-time timestamping. Check "Timestamp source" in RecSync preview (should display "realtime"). Leader device manages timing; client devices follow the leader.

Leader Device Setup

1. Start a Wi-Fi hotspot.
2. Open SLAMCam → Preferences → RecSync settings → enable "Use RecSync".
3. (Optional) Enable phase alignment for higher synchronization precision (< half frame).
4. (Optional) Configure camera settings broadcast in "Sync settings".
5. Switch to video mode, adjust camera settings, and press settings synchronization.
6. Wait for clients to connect.
7. (If phase alignment enabled) Press phase alignment button; wait until "Phase error" turns green.
8. Start recording.

Client Device Setup

1. Connect to the leader's Wi-Fi hotspot.
2. Open SLAMCam → Preferences → RecSync settings → enable "Use RecSync".
3. Adjust camera settings not broadcasted by leader.
4. Wait for leader to start recording.

Phase alignment must be performed before every recording session.

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Best Practices

• Audio recording is disabled to avoid extra frames caused by MediaRecorder audio-sync issues.
• Disable video stabilization and OIS to reduce preprocessing and improve data consistency.

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