How to ensure time consistency between the IMU and image data?

[lida2003]

A: IMU data is re-calbrated or keep consistent with the time of companion computer by mavlink_msg_timesync. Fair enough!

B: I didn't know if below calculation can keep video time consistent with the companion computer?

-- code from https://github.com/chobitsfan/libcamera-apps/blob/ros_img/apps/libcamera_hello.cpp

1. systime - boot time?????

    uint64_t boot_epoch_offset = epoch_ts.tv_sec * 1000000000 + epoch_ts.tv_nsec - (boot_ts.tv_sec * 1000000000 + boot_ts.tv_nsec);

2. what's this sensor_ts ? sensor has a timestamp?

        auto sensor_ts = completed_request->metadata.get(controls::SensorTimestamp);
        uint64_t sensor_ts_epoch = *sensor_ts + boot_epoch_offset;
        ros::Time sensor_ros_ts(sensor_ts_epoch / 1000000000, sensor_ts_epoch % 1000000000);

Really confused here. Please help.