|
Configuring the EDF2ASC GUI Converter
|
An EDF file may contain eye movement data in many types of data, especially if the default EyeLink recording parameters are used. For example, both left and right eye data may be present, with only one eye's data used in analysis. Eye position may be recorded in both gaze and HREF (angular) formats. Both samples and events may be recorded, with only events needed for analysis and samples for graphical viewing only. By default, EDF2ASC translates all samples and events, using gaze-position data only. Using the preference settings listed below allows the data present in the ASC file to be controlled.
By default, the converted ASC file(s) is saved in the directory from which the EDF files are loaded
("Preferences -> Save ASC File(s) to Original EDF Directory" enabled). By unslecting the default setting and clicking on
"Preferences -> ASC Output Directorty", a dialog will be presented and the use can specify the destination directory for file saving.
Use UTF8 Encoding: By default (unchecked), the saved output file will be a plain text file in ANSI encoding. If checked, the saved text file will be in UTF-8 encoding to better support non-ASCII characters.
The size and readability of the translated ASC file is controlled by selecting the types of events or samples present.
The presence of samples increases file size by a factor of 10 or 20, compared to events alone. Eliminating all samples and
eye-movement events makes the basic structure of the data file apparent, aiding design of analysis software.
By default, both samples and events are translated into the output ASC file. Samples may be eliminated with the
"Preferences -> Samples / Events -> Output Events Only". All events may be eliminated with the
"Preferences -> Samples / Events -> Output Samples Only" setting. This results in a file containing only sample data lines,
with no events, comments, or file structure lines.
Eye Selection for a Binocular Recording
To select one eye's data (both samples and events) from a binocular data file, specify left or right eye data with
"Preferences -> Binocular Recording -> Output Left Eye Only" or "Preferences -> Binocular Recording -> Output Left Eye Only"
respectively. These are ignored for monocular data files. By default, both eyes' data are extracted for a binocular recording.
Resolution and instantaneous velocity data may be included for sample data lines, as well as events. Resolution data is included if the "Preferences -> Output Resolution Data" setting is selected. Resolution data reported will match the type of eye-position data in the file. Gaze position resolution (in units of pixels per visual degree) is computed by the EyeLink II tracker, and must be recorded in the EDF file as it cannot be computed. No resolution data is available for raw pupil position data. Resolution for HREF data is determined by the position itself, and is computed by the EDF2ASC translator.
Velocity data in saccade and fixation events is reported directly if the "Preferences -> Output Velocity Data" setting is specified. For samples, the velocity is computed from the position and resolution data using the same processing used in the EyeLink II tracker. Velocity for gaze-position data cannot be computed unless gaze-resolution data is also present.
If data is recorded from external device (e.g., parallel port of the host computer or the digital input port of the EyeLink Analog Card), this data can be shown in the sample line by enabling the "Preferences -> Output Input Values" option.
By default, the tracker will report the time stamp of the events and sample as an integer number. Enabling the "Preferences -> Output Float Number" option allows to output EDF file time stamp as a float number; this is most useful for a 2000 hz recording collected from an EyeLink 1000/2k eye tracker.
Samples may contain several types of eye position data. Only one of these types may be output in the ASC file.
The desired data type is specified by clicking on "Preferences -> Eye Position Data -> Gaze" for gaze position data (the default),
"Preferences -> Eye Position Data -> HREF" for HREF data, and "Preferences -> Eye Position Data -> RAW" for raw pupil position data.
If the desired data type is not present in the file, a warning message will be logged and another data type will be used.
The type of position data reported for eye-movement events (saccades and fixations) is determined by the type of eye-position data
that was used in parsing the data in the EyeLink II tracker. This is set with the "recording_parse_type" command in the experiment
program.
If enabled, the EDF Coverter will import Experiment Builder generated log messages for inclusion in message output (if the log file exists in the same folder as the EDF file).
Unlike EyeLink I, II, 1000, 1000 Plus, or Portable Duo eye trackers, EyeLink 3 additionally records the head-in-space and eye-in-head data in screen pixel coordinates, and prvides 6DOF head tracking data (head position and head rotation). Options in the EyeLink 3 group allows users to disable the output of head tracking data and the extended eye/head position data. Users can also enable the output of pupil ellipse data, head-in-space/eye-in-head resolution data, and messages with !GEOM, !IMU, and !MIPI.
Recordings done with EyeLink II SceneLink software can convert the recordings into the Scene camera DV coordinate (720 * 480 resolution). This can be done by enabling the "Gaze Map" option. The "Insert Frame Numbers" option can be used to insert scene camera frame number messages in the ASC file. The latter option requires you to leave the EDF file in the folder containing all of the lookup table (*.ett) files.
Selective event filtering is possible. Only summary events (end of fixations, saccades, or blinks) are reported if "Preferences -> Block Start Event Output" is selected. This will halves the number of eye-movement events and may be acceptable for hand analysis or simple cognitive experiments. All eye-movement events may be removed with the "Preferences -> Block Eye Event Output" option, resulting in a listing of file messages and data blocks. This is useful as a summary of file structure when designing analysis software for experiments. Message events recorded in the file can be removed by selecting "Preferences -> Block Message Event Output". The "Preferences -> Block Viewer Commands" option may be selected if the user want to specifically remove the Data Viewer integration message.
Data collected with pupil-CR mode of EyeLink II and EyeLink 1000 eye trackers will have will have extra 3 (monocular) or 5 (binocular) character fields in the sample line to represent warning messages for that sample relating to the corneal reflection processing. These warning messages can be disabled by enabling "Preferences -> Block Flags Output". If the data file being processed was recorded using EyeLink Remote, sixteen extra columns will be recorded to the sample lines to encode the target distance, position, and eye/target status information. The head target information can be removed by enabling the "Preferences -> Block Target Data" option.
If "Preferences -> Use Tab Only as Delimiters" is selected, the fields in an event line will be separated with tabs.
In rare cases, the collected EDF files may be corrupted (e.g., due to a problem in file transfer).The user may run the "failsafe" mode to recover as much data as possible. This can be done by enabling the "Preferences -> Run in Fail Safe Mode" option.
To revert any changes made to the preference settings, users can select the Reset to Factory Defaults item in Preferences.
To make any changed preference settings persist for future sessions, users can select the Save Properties as Defaults item at the bottom of the Preferences section.
