Recording Edf Files; Recording From The Eyelink Portable Duo Host Pc; Recording From The Eyelink Api Or Sr Research Experiment Builder; The Eyelink On-Line Parser - SR Research EyeLink Portable Duo User Manual

sent from applications running on the Display PC. These can be used to record
the time of a change in the display, or an experimental condition.

4.2 Recording EDF Files

EDF files are created by the EyeLink Portable Duo tracker, recording eye-
position data, events from the on-line parser, and button and input events.
These are recorded only when the tracker is in output (recording) mode.
Messages sent from applications on the Display PC through the Ethernet link
may be recorded at any time. Recording EDF files involves opening a data file,
recording data from one or more sessions in output mode, and closing the file.
These operations can be performed manually using the EyeLink Host
application on the Host PC, or remotely from the Display PC through the
Ethernet. For both applications, it is important that the screen settings are set
up properly for accurate recording of data resolution and velocity calculation.

4.2.1 Recording from the EyeLink Portable Duo Host PC

In some eye-tracking situations, it may be convenient to initiate the recording of
eye movement data directly. For example, displays may be generated by
manually-operated equipment, or by non-EyeLink applications. Special
provisions must be made to display the calibration pattern in these situations.
By using the EyeLink Portable Duo tracker's Output Screen, files may be
opened and closed, and recording sessions may be started and stopped. Refer to
Chapter 2 of this manual "EyeLink Portable Duo Host Software" for information.

4.2.2 Recording from the EyeLink API or SR Research Experiment Builder

Most eye-movement research involves running many participants through a
sequence of experimental trials, with tens or hundreds of recording blocks per
file. This is best done by remote control over the link from an experimental
application. The connection from the Display PC to the EyeLink eye tracker is
implemented by an Ethernet link. Refer to the EyeLink Programmer's Guide or
SR Research Experiment Builder User Manual for details on how to use the
Display PC software to set up and record EDF files.

4.3 The EyeLink On-Line Parser

As with all EyeLink systems, the Portable Duo Host Software incorporates a
unique on-line parsing system which analyzes eye position data into meaningful
events and states (saccades, fixations, and blinks).

4.3.1 Parser Operation

The parser uses velocity and acceleration-based saccade detection methods.
Because of the EyeLink tracker's exceptionally low noise levels and high spatial
resolution, very little data filtering is needed and thus delay is kept at a
minimum. For each data sample, the parser computes instantaneous velocity
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