b@3: function autoalign(foldername)
b@3: % AUTOALIGN aligns audio in folder with selected file by inserting zeros
b@3: %  at the start of the files. 
b@2: %
b@2: % by Brecht De Man at Centre for Digital Music on 17 November 2014
b@2: 
b@3:     % error('Work in progress, function not finished'); % while unfinished
b@2:     
b@2:     tic;                                % start measuring time
b@3:     list = dir([foldername '/*.wav']);  % get names of files
b@2:     
b@2:     % remove hidden files from list
b@2:     % see http://www.mathworks.co.uk/matlabcentral/newsreader/view_thread/258220
b@2:     for k = length(list):-1:1
b@2:         fname = list(k).name;
b@2:         if fname(1) == '.'
b@2:             list(k) = [ ];
b@2:         end
b@2:     end
b@3:     
b@3:     shiftvec = zeros(length(list), 1); 
b@3:     
b@3:     % first file: 
b@12:     % TO DO: to save computation: take shortest file? 
b@3:     masterAudioChannels = audioread([foldername '/' list(1).name]); % read file
b@2:     masterAudio         = sum(masterAudioChannels, 2); % sum to mono
b@2:     
b@2:     % for each other file:
b@8:     for i = 2:length(list)
b@2:         slaveAudioChannels = audioread([foldername '/' list(i).name]); % read file
b@2:         slaveAudio         = sum(slaveAudioChannels, 2); % sum to mono
b@2:         
b@3:         % check sampling rate is the same (or: express in terms of seconds)
b@2:         % ... 
b@3:         
b@2:         % crosscorrelation function
b@3:         [xc, timeaxis] = xcorr(masterAudio, slaveAudio);
b@3:         [value, lag] = max(abs(xc));
b@3:         shiftvec(i) = timeaxis(lag);
b@2:         
b@3:         % debugging plots
b@3: %         figure;
b@3: %         title(['Crosscorrelation file 1 vs ' num2str(i)]);
b@3: %         subplot(2,1,1);
b@3: %         plot(timeaxis, xc);
b@3: %         xlabel('Samples');
b@3: %         ylabel('Crosscorrelation');
b@3: %         subplot(2,1,2);
b@3: %         plot(timeaxis, abs(xc));
b@3: %         xlabel('Samples');
b@3: %         ylabel('Absolute value of crosscorrelation');
b@2:         
b@2:         % monitoring/debugging
b@2:         
b@2:     end
b@3:     
b@3:     % add absolute of largest negative lag worth of zeros to all; 
b@3:     % then add 'shiftvec' value to that
b@3:     maxlag = min(shiftvec); 
b@3:     for i = 1:length(list)
b@3:         [audio, fs] = audioread([foldername '/' list(i).name]);
b@6:         audiowrite([foldername '/' list(i).name], ...
b@3:             [zeros(-maxlag + shiftvec(i), size(audio, 2)) ; audio], ...
b@3:             fs, 'BitsPerSample', 24);
b@3:     end
b@2: 
b@2:     elapsedTime = toc;  % stop measuring time
b@3:     disp(['autoalign took ' num2str(elapsedTime) ...
b@3:         ' seconds to align the files in folder ' foldername]);
b@2: 
b@2: end