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Jianzhu Huai edited this page Oct 20, 2019 · 9 revisions

Overview

    

The MARS logger records RGB camera frames at 30Hz and IMU readings at 50+ Hz and the two data streams are synced to one clock.

Installation

Data Format

Record data

Android

Open the Mars Logger app, press the Record button to start logging, and then press the Stop button to finish logging.

By default upon start, auto exposure is on and auto focus is locked. Tap the screen to lock focus at a particular area and lock the exposure. Note it is observed that after locking focus at an area even the AF mode is not AF locked (i.e., CONTROL_AF_MODE_OFF), the recorded focus distance remains fixed.

iOS

Open the Mars Logger app, press the Record button to start logging, and press the Stop button to finish logging.

By default upon start, auto focus and auto exposure is on. Tap the screen to lock focus at a particular area in the camera view and fix the exposure duration. Long press the screen to unlock the focus and exposure duration.

Once finished, the Export button may be pressed to email the video frame metadata and inertial data to a user-specified mailbox. This is optional because you may also transfer the files by AirDrop from inside the iOS Files app or by connecting the device to a computer (see the below Transfer data section).

Transfer data

Clear data

Android

Use the File manager app, go into the Internal storage, then navigate to Android/data/edu.osu.pcv.marslogger/files/data, you may delete any folder at will.

If your computer has installed ADB(android-tools-adb), then you may open a prompt terminal, and run the following commands.

adb shell
cd /sdcard/Android/data/edu.osu.pcv.marslogger/files/data
ls
rm -rf FOLDER_TO_REMOVE

iOS

The recorded videos can be deleted by using the Camera app. The recorded csv files can be deleted by using the Files app for iOS 11+.

Convert to Rosbag

Use the bagcreator in python for creating a rosbag from the recorded visual inertial data. For instance, for one Android data session,

BAG_PYTHON=/vio_common/python/kalibr_bagcreater.py
ANDROID_DATA_DIR=/path/to/android/data/session
python $BAG_PYTHON --video $ANDROID_DATA_DIR/movie.mp4 \
--imu $ANDROID_DATA_DIR/gyro_accel.csv \
--video_time_file $ANDROID_DATA_DIR/frame_timestamps.txt \
--output_bag $ANDROID_DATA_DIR/movie.bag

For one iOS data session,

BAG_PYTHON=/vio_common/python/kalibr_bagcreater.py
IOS_DATA_DIR=/path/to/ios/data/session
python $BAG_PYTHON --video $IOS_DATA_DIR/IMG_4302.MP4 \
--imu $IOS_DATA_DIR/gyro_accel.csv \
--video_time_file $IOS_DATA_DIR/movie_metadata.csv \
--output_bag $IOS_DATA_DIR/movie.bag
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