Introduction

If you are reading this tutorial, you probably know that EDF(+) (European Data Format) is a digital format used to interchange and process records in Clinical Neurophysiology (sleep recordings, EEG, EMG, nerve conduction studies, evoked potentials...). In some other tutorials in our site (see Neurotraces) I suggested that one approach to learn EDF is to program a small application that writes a small EDF file. Once written, we have to debug the result and analyze the different fields.

In order to edit the file, we have a lot of tools available on Windows system but they are more scarcer on Linux systems. This document describes edfEdit, a tool that allows the edition of the header of EDF and EDF+ files.

As you probably know, an EDF(+) file is, basically, a set of a header and one or more data records containing little endian short integers. The header is a String of ASCII characters of different length depending on the number of signals. Inside the Header there are a lot of fields describing the recording.

This is a list of some additional reasons to edit the header

• Some programs apply different processing methods depending on the label of each signal. For instance, sometimes the ECG is processed in some specific way. The labels required by the program are not necessarily coincident with the names of the original EDF file (e.g., the ECG can be placed in a signal named at X1-X2) and then changing the names of the signals can be necessary to force some action.
• Some devices produce EDF files not completely well formed or the program in charge of further processing is too strict. Sometimes the Version is not established, sometimes Digital maximum or Digital Minimum are stored as float (e.g., 128.0) and the program used to process the file is not able to read the file. Of course, following strictly the EDF(+) specifications would eliminate these problems but our world is not perfect yet.
• Sometimes your device includes the name of the patient and you want to publish anonymous records on the Internet (a practice that I strongly recommend) and changing the Patient name is necessary.
• Finally, sometimes you want to know more about some EDF(+) file. You want to know what is the duration of the data record or how many data records are included in the file.

The target audience of this program is an intermediate user of EDF. If you do not know anything about EDF, you probably should go to the EDF site and read something about the specifications of the format. If you are an advanced user you could consider other alternatives (e.g., a small program in Perl that changes the fields of the header allowing batch programming and then simultaneously changing all the files in a directory).

To compile the program you will need to install Qt. In this version (version 1.0) some new options were included.