User manual

Data Files
© 2005-2008 SR Research Ltd.
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4.9.4 Data-Specification Lines
Immediately following a START line, several lines of data specifications may be
present. These lines contain more extensive data than the START line about
what data can be expected in the START...END block. These are most easily
processed by creating a set of flags for each possible data option (left-eye events,
right-eye samples, sample velocity, etc.), clearing these when the START line is
encountered, and setting the appropriate flags when keywords ("LEFT", "VEL",
etc.) are encountered in a data specification line.
• PRESCALER <prescaler>
If gaze-position data or gaze-position resolution is used for saccades and events
are used, they must be divided by this value. For EDF2ASC, the prescaler is
always 1. Programs that write integer data may use a larger prescaler (usually
10) to add precision to the data.
• VPRESCALER <prescaler>
If velocity data is present, it must be divided by this value. For EDF2ASC, the
prescaler is always 1. Programs that write integer data may use a larger
prescaler (usually 10) to add precision to the data.
• EVENTS <data type> <eye> <data options>
This specifies what types of data is present in event lines, as a sequence of
keywords. The <data type> is one of "GAZE", "HREF" or "PUPIL". The eye
recorded will be one word ("LEFT" or "RIGHT"). The <data option> keywords
currently supported are:
o "RES" for resolution data (both may be present).
o “RATE” for the sample rate (250.00, 500.00, 1000.0, or 2000.0)
o “TRACKING” for the tracking mode (P = Pupil, CR = Corneal
Reflection)
o “FILTER” for the filter level used (0=off, 1=standard, 2=extra)
• SAMPLES <data type> <eye> <data options>
This specifies what types of data is present in sample lines, as a sequence of
keywords. The <data type> is one of "GAZE", "HREF" or "PUPIL". The eye
recorded will be "LEFT" or "RIGHT". The <data option> keywords currently
supported are:
o "VEL" for instantaneous velocity data
o "RES" for resolution data (both may be present).
o “RATE” for the sample rate ((250.00, 500.00, 1000.0, or 2000.0)
o “TRACKING” for the tracking mode (P = Pupil, CR = Corneal
Reflection)
o “FILTER” for the filter level used (0=off, 1=standard, 2=extra)