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ft_realtime_asynchronous.m
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ft_realtime_asynchronous.m
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function cmd = ft_realtime_asynchronous(cfg)
% FT_REALTIME_ASYNCHRONOUS is an example realtime application for
% asynchronous brain-computer interfaces
%
% Use as
%
% cmd = ft_realtime_asynchronous(cfg)
%
% where cmd is the last processed command and cfg has the following configuration options
% cfg.bcifun = the BCI function that is called
% cfg.blocksize = number, size of the blocks/chuncks that are processed in seconds (default = 1)
% cfg.overlap = overlap between blocks in seconds (default = 0)
% cfg.channel = cell-array, see FT_CHANNELSELECTION (default = 'all')
% cfg.bufferdata = whether to start on the 'first or 'last' data that is
% available when the function _starts_ (default = 'last')
% cfg.jumptoeof = whether to start on the 'first or 'last' data that is
% available when the function _starts_ (default = 'last')
%
% The source of the data is configured as
% cfg.dataset = string
% or alternatively to obtain more low-level control as
% cfg.datafile = string
% cfg.headerfile = string
% cfg.eventfile = string
% cfg.dataformat = string, default is determined automatic
% cfg.headerformat = string, default is determined automatic
% cfg.eventformat = string, default is determined automatic
%
% cfg.ostream = the output stream that is used to send a command via
% write_event (default = []
%
% The bcifun must be of the form
%
% cmd = bcifun(cfg,data)
%
% where cfg is the configuration passed by this function and data is the
% new data segment. Cmd is the command which is generated by the bcifun.
% This command will be send to an external device via cfg.ostream. Check
% bcifun_latidx for an example.
%
% Some notes about skipping data and catching up with the data stream:
%
% cfg.jumptoeof='yes' causes the realtime function to jump to the end
% when the function _starts_. It causes all data acquired prior to
% starting the RT function to be skipped.
%
% cfg.bufferdata=last causes the realtime function to jump to the last
% available data while _running_. If the RT loop is not fast enough,
% it causes some data to be dropped.
%
% If you want to skip all data that was acquired before you start the
% RT function, but don't want to miss any data that was acquired while
% the realtime function is started, then you should use jumptoeof=yes and
% bufferdata=first. If you want to analyze data from a file, then you
% should use jumptoeof=no and bufferdata=first.
%
% To stop the realtime function, you have to press Ctrl-C
% Copyright (C) 2010, Marcel van Gerven, Robert Oostenveld
%
% This file is part of FieldTrip, see http://www.fieldtriptoolbox.org
% for the documentation and details.
%
% FieldTrip is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% FieldTrip is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with FieldTrip. If not, see <http://www.gnu.org/licenses/>.
%
% $Id$
% set the default configuration options
if ~isfield(cfg, 'bcifun'), cfg.bcifun = @bcifun_latidx; end % example function computes lateralization index
if ~isfield(cfg, 'nsamples'), cfg.nsamples = inf; end % number of samples to process
if ~isfield(cfg, 'blocksize'), cfg.blocksize = 1; end % in seconds
if ~isfield(cfg, 'overlap'), cfg.overlap = 0; end % in seconds
if ~isfield(cfg, 'channel'), cfg.channel = 'all'; end % processed channels
if ~isfield(cfg, 'bufferdata'), cfg.bufferdata = 'last'; end % first or last
if ~isfield(cfg, 'jumptoeof'), cfg.jumptoeof = 'yes'; end % jump to end of file at initialization
if ~isfield(cfg, 'dataformat'), cfg.dataformat = []; end % default is detected automatically
if ~isfield(cfg, 'headerformat'), cfg.headerformat = []; end % default is detected automatically
if ~isfield(cfg, 'eventformat'), cfg.eventformat = []; end % default is detected automatically
if ~isfield(cfg, 'dataset') && ~isfield(cfg, 'header') && ~isfield(cfg, 'datafile')
cfg.dataset = 'buffer://localhost:1972';
end
if ~isfield(cfg, 'ostream'), cfg.ostream = []; end % no output by default
% translate dataset into datafile+headerfile
cfg = ft_checkconfig(cfg, 'dataset2files', 'yes');
cfg = ft_checkconfig(cfg, 'required', {'datafile' 'headerfile'});
% ensure that the persistent variables related to caching are cleared
clear ft_read_header
% start by reading the header from the realtime buffer
hdr = ft_read_header(cfg.headerfile, 'headerformat', cfg.headerformat, 'cache', true, 'retry', true);
% define a subset of channels for reading
cfg.channel = ft_channelselection(cfg.channel, hdr.label);
chanindx = match_str(hdr.label, cfg.channel);
nchan = length(chanindx);
if nchan==0, ft_error('no channels were selected'); end
% determine the size of blocks to process
blocksize = round(cfg.blocksize * hdr.Fs);
overlap = round(cfg.overlap*hdr.Fs);
if strcmp(cfg.jumptoeof, 'yes')
prevSample = hdr.nSamples * hdr.nTrials;
else
prevSample = 0;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% this is the general BCI loop where realtime incoming data is handled
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
cfg.count = 0; % current segment; can be used in bcifun
while cfg.count < cfg.nsamples
% determine number of samples available in buffer
hdr = ft_read_header(cfg.headerfile, 'headerformat', cfg.headerformat, 'cache', true);
% see whether new samples are available
newsamples = (hdr.nSamples*hdr.nTrials-prevSample);
if newsamples>=blocksize
% determine the samples to process
if strcmp(cfg.bufferdata, 'last')
begsample = hdr.nSamples*hdr.nTrials - blocksize + 1;
endsample = hdr.nSamples*hdr.nTrials;
elseif strcmp(cfg.bufferdata, 'first')
begsample = prevSample+1;
endsample = prevSample+blocksize;
else
ft_error('unsupported value for cfg.bufferdata');
end
% this allows overlapping data segments
if overlap && (begsample>overlap)
begsample = begsample - overlap;
endsample = endsample - overlap;
end
% remember up to where the data was read
prevSample = endsample;
cfg.count = cfg.count + 1;
fprintf('processing segment %d from sample %d to %d\n', cfg.count, begsample, endsample);
% read data segment from buffer
dat = double(ft_read_data(cfg.datafile, 'header', hdr, 'dataformat', cfg.dataformat, 'begsample', begsample,...
'endsample', endsample, 'chanindx', chanindx, 'checkboundary', false));
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% from here onward it is specific to the display of the data
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% put the data in a fieldtrip-like raw structure
data.trial{1} = dat;
data.time{1} = offset2time(0, hdr.Fs, endsample-begsample+1);
data.label = hdr.label(chanindx);
data.hdr = hdr;
data.fsample = hdr.Fs;
data.grad = [];
% apply BCI function
cmd = cfg.bcifun(cfg,data);
if ~isempty(cfg.ostream)
fprintf('writing command %s to %s\n',num2str(cmd),cfg.ostream);
% send command
evt.type = 'uint';
evt.offset = [];
evt.duration = [];
evt.sample = abs(data.time{1}(1)*data.fsample);
evt.timestamp = data.time{1}(1);
evt.value = cmd;
ft_write_event(cfg.ostream,evt);
else
fprintf('generated command %s\n',num2str(cmd));
end
cfg.count = cfg.count + 1;
end % if enough new samples
end % while true