LSL Tracker Element

Summary ¶

	LSL Tracker
Info
Category:	Eye trackers		AddIn:	LSL
Creator:	OkazoLab		Scope:	Experiment
Owns Snippets:	None		Usage:	Snippets

Synchronized actions ¶

Epoch	Actions
On Experiment Start	Starts processing tracker samples
On Experiment Start	Stops processing tracker samples

Properties ¶

Name	Description	Constraints	Type	On runtime change
LSL Settings
Stream Type	Defines the LSL stream that delivers signal data	Design Time..	String
LSL Stream	Defines which LSL stream will be connected at runtime. You must have the LSL stream running, when you change this property for the first time. Note that the channel configuration of the element is updated each time as you change this property	Design Time..	String
X Channel	Defines the LSL channel for X coordinates	Normal..	Int32
Y Channel	Defines the LSL channel for Y coordinates	Normal..	Int32
Chink Size	Defines the chuck size (in ms) in signal acquisition	Normal..	clTime
GLM Calibration
Run GLM Calibration	Runs the GLM calibration procedure, which calculates two pairs of linear coefficients for mapping of the tracker input into the screen coordinates. The calculated coefficients are automatically applied at runtime.	Design Time..	Boolean
Gain X	Defines the gain coefficient for the X axis in the GLM calibration model: X='GainX'*x+OffsetX	Normal..	Double
Gain Y	Defines the gain coefficient for the Y axis in the GLM calibration model: Y='GainY'*y+OffsetY	Normal..	Double
Offset X	Defines the offset coefficient for the X axis in the GLM calibration model: X=GainX*x+'OffsetX'	Normal..	Double
Offset Y	Defines the offset coefficient for the Y axis in the GLM calibration model: Y=GainY*y+'OffsetY'	Normal..	Double
Affine Mode	Defines the affine transformation (scale, translation and rotation) is used for calibration instead on the simpler GLM transformation (scale and translation)	Normal..	Boolean
Affine Rotation	Defines the rotation angle (deg) for the affine calibration	Normal..	Double
Save Calibration Now	Provides a runtime command that saves the current GLM calibration into a XML file. To run the command at runtime, assign a file name to this property.	Runtime Command..	String
Load Calibration Now	Provides a runtime command that loads the GLM calibration values from a XML file. To run the command at runtime, assign a file name to this property.	Runtime Command..	String
Drift Correction
Recalibrate Now	Runtime command that helps to correct drifts in tracking data.Correction is done by recalibration of the latest tracker position into a custom screen point defined by the 'Recalibration Point' property.nAs result, the offsets of the GLM calibration get adjusted (but not gains) to compensate a drift in further data.	Runtime Command..	Boolean
Recalibration Point	Defines the screen point to which the tracker position will be recalibrated on calling 'Recalibrate Now' action. The default auto value always denotes the screen center.	Normal..	clPoint
Filters
Smoothing Ratio	Defines a ratio for the fast FIR smoothing filter, which is applied to the gaze tracking within EventIDE. The filter convolves every new tracking position with the previous ones. The property value defines a tap weight for the previous data, such that the convolution looks like: X=(Xn*(1-Ratio)+Xn-1*Ratio)/2. The value has to be positive and less than 1 (0 means no filtering).	Normal..	Double
Logging
Log Folder	Opens the dialog for selecting a local folder that will hold all tracking logs	Runtime Command..	String
Open Log Designer	Opens a designer window where the log format can be defined.	Design Time..	Boolean
Is Logging	Defines whether logging is turn on/off.The value can be changed at any moment at runtime allowing selective logging during the relevant periods only.	Normal..	Boolean
User Field	Defines the custom user data that is added to every line in the log file. The property can be used for recording varying status information (e.g. trial number) together with the tracker data. The string value may contains multiple fields separated by delimiter.	Normal..	String
Runtime
Radar Point	Returns the newest calibrated tracking position provided by the tracker at runtime	Normal..	clPoint
Perspective Correction
Perspective Correction	Defines...	Normal..	Boolean
Configure Perspective		Design Time..	Boolean
Viewer Position	Defines...	Normal..	Point3D
Tracker Position	Defines...	Normal..	Point3D
Focal Length	Defines...	Normal..	Double
Control
Is Enabled	If set to false the element is completely omitted when the experiment is run	Design Time..	Boolean
Title	Title of the element	Design Time..	String

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Description ¶

Practical Use ¶

Configuring the element (once) ¶

1. Add the LSL tracker element and go to its properties
2. Make sure that a target LSL stream is running and visible in a network. You may need to start an application that generates the stream
3. Define Stream Type property, if it is know. If not, leave the property blank
4. Expand an editor for the LSL stream property. If the target stream is detected, it will be available for selection. If not, check the stream and reselect the element in the EventIDE GUI
5. If the stream is selected, set the X channel and Y channel properties of the element to the corresponding channels in the LSL stream.
6. Use the Open Log Designer property to define as structure of the tracker data file 
   

Usign the element for eye-tracking analysis withing EventIDE ¶

1. Similar to other tracker elements, the LSL Tracker Element can be used for an online eye-tracking analysis in EventIDE
   

Notes ¶

• The tracker LSL stream should be active, before you run your experiment