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102 Data Files

-e or -ns outputs event data only

-nse blocks output of start events

-nmsg blocks message event output

-neye outputs only non-eye events (for sample-only

files)

-miss <string> replaces missing data in ASC file with <string>

-setres <xr>

<yr>

uses a fixed <xr>,<yr> resolution always

-defres <xr>

<yr>

uses a default <xr>,<yr> resolution if none in

file

4.9 The ASC File Format

The ASC file format is defined by the type of data lines that appear in it, the

format of these lines, and the order in which these lines occur. Data lines

consist of several types:

• Blank or comment lines, which are ignored. The first non-blank

character on a comment line is one of "#", "/" or ";".

• File preamble or file-description lines. These begin with "**". Usually

these lines are ignored when processing the ASC file.

• Sample data lines. Each line begins with a number, representing the

time of the sample.

• Event and data-description lines. Each line begins with a keyword,

identifying the type of data in the rest of the line.

4.9.1 ASC File Structure

For sample-only ASC files, file structure is very simple. These files are produced

using the "-s" or "-ne" options of EDF2ASC, and only sample data lines are

present. There is no data on what type of eye-position data or which eye

produced the data. Recording blocks are separated by samples lines consisting

of missing-value data (dots or the string specified with the "-miss" option). Gaps

in the sequence of sample timestamps may also be used to determine sample

block divisions.

For ASC files containing events (and optionally samples), the order of lines is

carefully structured. The order of items in an ASC file is similar to that of a

sorted EDF file. The file begins with a copy of the EDF file's preamble, with each

line preceded by "**". The preamble reports the file version, date created, and

any description from the application. Usually the preamble is ignored during

analysis.

The sequence of events and samples in the ASC file follows strict rules. These

are: