Knowledge Base

Synchronization

Collecting eye tracker data in The Observer XT allows you to combine it with other data modalities such as facial expressions and physiological data. It is crucial that all data are in sync. Use the procedure below to synchronize your data.

Procedure

1. In your coding scheme, define a Point event labeled, for example, sync.
2. Start an observation as usual in The Observer XT and start recording with the Tobii Glasses.
3. Use a light signal or another visual marker and ask the participant to look at it so that it is visible in the gaze overlay video. Alternatively, you can use an audio marker.
4. The very moment the marker is visible or audible, score the sync event.
5. Import the gaze overlay video made by the Tobii Pro software into The Observer XT, and check when the marker is visible or audible in the video. You can then calculate the difference in timing between that time (the Tobii video and data) and the time that you scored sync (the event log in The Observer XT). Note that this method relies on the coder's reaction time.

To Synchronize the Tobii Video and Data with the Event Log

1. Take note of the time difference value measured with the method above.
2. Open the observation and click the Offset button.
3. Click Numerical Offset.
4. Next to the name of the event log containing the eye tracking video and data, enter the time difference. For example, if the difference was 0.5 seconds, enter 00:00.500.

For more information, see External Data > Import External Data > Manual Synchronization in The Observer XT Help.

Source: The Observer XT 17 - Tobii Glasses Technical Note, Noldus Information Technology