diff aux/stripzeros.m @ 2:5e72201496c8

Bug fixes, added stripzeros function, added new loudness function, moved general documentation to top level, MATLAB_R2014b compatibility

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/aux/stripzeros.m	Mon Nov 17 19:43:43 2014 +0000
@@ -0,0 +1,57 @@
+function stripzeros(foldername)
+% STRIPZEROS strips off an array of samples that equal zero at the 
+% beginning and end of an audio file. 
+%
+% by Brecht De Man at Centre for Digital Music on 17 November 2014
+
+    tic;                                % start measuring time
+    list = dir([foldername '/*.wav']);  % get names of files
+
+    % remove hidden files from list
+    % see http://www.mathworks.co.uk/matlabcentral/newsreader/view_thread/258220
+    for k = length(list):-1:1
+        fname = list(k).name;
+        if fname(1) == '.'
+            list(k) = [ ];
+        end
+    end
+
+    for i = 1:length(list) % go over each file in the folder
+        [audio, fs] = audioread([foldername '/' list(i).name]);
+
+        numSamples  = size(audio,1);
+        numChannels = size(audio,2);
+        bitDepth    = 24; % not automated here
+        startIndex  = zeros(numChannels, 1);
+        stopIndex   = zeros(numChannels, 1);
+
+        % first and last non-zero elements (for all channels)
+        for channel = 1:numChannels
+            % ? more efficient way to find first and last non-zero sample?
+            indexOfNonZeroSamples = find(audio(:,channel)); % returns indices non-zero elements
+            startIndex(channel) = min(indexOfNonZeroSamples);
+            stopIndex(channel)  = max(indexOfNonZeroSamples);
+        end
+
+        start = max(startIndex);
+        stop  = min(stopIndex);
+
+        % if startIndex and stopIndex are both equal to first and last sample: 
+        % do nothing.
+        % else: 
+        if start>1 || stop<numSamples
+            audiowrite([foldername '/' list(i).name], audio([start:stop], :), ...
+                fs, 'BitsPerSample', bitDepth);
+        end
+
+        % debugging/monitoring: 
+        startCrop = (start-1)/fs; %
+        stopCrop  = (size(audio,1)-stop)/fs;
+        disp([num2str(startCrop) 's (start) / ' num2str(stopCrop) 's (end) stripped off ' list(i).name]);
+    end
+
+    elapsedTime = toc;  % stop measuring time
+    disp(['stripzeros took ' num2str(elapsedTime) ' seconds to strip zeros off the files in folder ' ...
+    foldername]);
+
+end
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