Read EDF (European Data Format) files

edf.m

function [ header, records ] = edf ( filepath )

	% Parse EDF file information based on the EDF/EDF+ specs
	% @see http://www.edfplus.info/specs/index.html


	fid = fopen( filepath, 'rb' );
	data = fread(fid,256,'*char');

	% TODO regex to strip trailing whitespace

	header = struct();
	header.version = data(1:8);
	header.patient_id = data(9:88);
	header.rec_id = data(89:168);
	header.startdate = data(169:176);
	header.starttime = data(177:184);
	header.header_bytes = data(185:192);
	header.num_items = data(237:244);
	header.data_duration = data(245:252);
	header.num_signals = str2double(data(253:256));

	% advance to the second part of the header
	data = fread(fid, header.num_signals * 256,'*char');

	lengths = [ 16, 80, 8, 8, 8, 8, 8, 80, 8, 32 ];
	values = cell(length(lengths),header.num_signals);
	s = 0;

	for i=1:length(lengths)
		for j=0:header.num_signals-1
			values{i,j+1} = data(s + j*lengths(i) + 1 : s + j*lengths(i)+lengths(i));
		end
		s = s + j*lengths(i)+lengths(i);
	end

	headerkeys = { 
		'labels', 
		'transducer',
		'dimension',
		'phys_min',
		'phys_max',
		'dig_min',
		'dig_max',
		'prefiltering',
		'num_samples' 
	};

	for i=1:length(headerkeys)
		header.(headerkeys{i}) = { values{i,:} };
	end

	% the data record begins at 256 + ( num_signals * 256 ) bytes and is stored as n records of 2 * num_samples bytes
	% values are stored as 2 byte ascii in 2's complement
	s = 0;
	records = cell(header.num_signals,1);

	for i=1:header.num_signals
		data = fread(fid, str2double(header.num_samples{i}),'int16');
		records{i} = data;
	end


	% finally, close the file and return
	fclose(fid);
end