Introduction

One of the most frequently asked question in different forums regarding EDF files is its conversion from/to ASCII files. The creation of a general tool to face this problem is somewhat difficult. ASCII files are very appropriate to show channels sampled at the same rate but they have some difficulties to display signals whose sample rate is different.

Several approaches could be used to overcome this difficulty. edfAsc uses a very simple approach. In its present version it was designed to do the following processes

• Exporting the content of an EDF signal to a two-column (time and value) ASCII file. The program detects if the file is a discontinuous EDF+ file and sets the time signal properly
• Exporting the content of an EDF signal to a binary file containing little-endian 4 byte floats. Since floats can be easily read by most programs or languages, this is a very fast and easy procedure to share the content of EDF files with other tools
• Creating an EDF file from an ASCII file containing a matrix of values where each column correspond to a signal. This is a very common representation of signals. Sampling and duration of the data record are defined previously to the conversion

edfAsc was designed to be used together with edfAnn and edfEdit.

As an example the creation of an EDF+ file from two files containing the signals and the annotations would be

• Creation of a plain EDF file using edfAsc
• Modification of the header, setting the startdate, starttime and other relevant information using edfEdit
• Incorporation of annotations using edfAnn

The final result would be an EDF+ file containing the signals and the annotations.