README: Add section about time synchronization

Author: papr

README.md

@@ -23,4 +23,10 @@ The plugin opens a single outlet named `pupil_capture` that follows the [Gaze Me
 
 See our [pupil-helpers](https://github.com/pupil-labs/pupil-helpers/tree/master/LabStreamingLayer) for examples on how to record and visualize the published data.
 
-The published LSL data is simply a flattened version (see `extract_*()` functions in `pupil_lsl_relay.py`) of the original Pupil gaze data stream. The stream's channels will be filled with best effort, i.e. if there is a monocular gaze datum the values for the opposite eye will be set to `NaN`. The actual pairing of pupil data to binocular gaze data happens in [Capture](https://github.com/pupil-labs/pupil/blob/master/pupil_src/shared_modules/calibration_routines/gaze_mappers.py#L95-L140) and is not a LSL specific behaviour. Therefore, it is prossible to apply the same [flattening code](https://github.com/papr/App-PupilLabs/blob/master/pupil_lsl_relay.py#L226-L287) to offline calibrated gaze data and reproduce the stream published by the LSL outlet.
+The published LSL data is simply a flattened version (see `extract_*()` functions in `pupil_lsl_relay.py`) of the original Pupil gaze data stream. The stream's channels will be filled with best effort, i.e. if there is a monocular gaze datum the values for the opposite eye will be set to `NaN`. The actual pairing of pupil data to binocular gaze data happens in [Capture](https://github.com/pupil-labs/pupil/blob/master/pupil_src/shared_modules/calibration_routines/gaze_mappers.py#L95-L140) and is not a LSL specific behaviour. Therefore, it is prossible to apply the same [flattening code](https://github.com/papr/App-PupilLabs/blob/master/pupil_lsl_relay.py#L226-L287) to offline calibrated gaze data and reproduce the stream published by the LSL outlet.
+
+## LSL Clock Synchronization
+
+The `Pupil LSL Relay` plugin adjusts Capture's timebase to synchronize Capture's own clock with the `pylsl.local_clock()`. This allows the recording of native Capture timestamps and removes the necessity of manually synchronize timestamps after the effect.
+
+**Warning**: The time synchronization will potentially break if other time alternating actors (e.g. the `Time Sync` plugin or `hmd-eyes`) are active.