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1 function varargout = mirzerocross(orig,varargin)
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2 % mirzeroscross(x) computes the sign-changes rate along the signal x,
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3 % i.e., how many time the waveform crosses the X-axis. When applied on
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4 % an audio waveform, gives a notion of noise.
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5 % Optional argument:
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6 % mirzerocross(...,'Per',p) precises the temporal reference for the
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7 % rate computation.
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8 % Possible values:
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9 % p = 'Second': number of sign-changes per second (Default).
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10 % p = 'Sample': number of sign-changes divided by the total
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11 % number of samples.
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12 % The 'Second' option returns a result equal to the one returned
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13 % by the 'Sample' option multiplied by the sampling rate.
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14 % mirzerocross(...,'Dir',d) precises the definition of sign change.
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15 % Possible values:
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16 % d = 'One': number of sign-changes from negative to positive
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17 % only (or, equivalently, from positive to negative only).
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18 % (Default)
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19 % d = 'Both': number of sign-changes in both ways.
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20 % The 'Both' option returns a result equal to twice the one
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21 % returned by the 'One' option.
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22
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23
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24 per.key = 'Per';
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25 per.type = 'String';
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26 per.choice = {'Second','Sample'};
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27 per.default = 'Second';
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28 option.per = per;
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29
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30 dir.key = 'Dir';
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31 dir.type = 'String';
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32 dir.choice = {'One','Both'};
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33 dir.default = 'One';
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34 option.dir = dir;
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35
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36 specif.option = option;
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37
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38 varargout = mirfunction(@mirzerocross,orig,varargin,nargout,specif,@init,@main);
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39
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40
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41 function [x type] = init(x,option)
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42 if not(isamir(x,'mirdata'))
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43 x = miraudio(x);
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44 end
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45 type = 'mirscalar';
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46
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47
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48 function z = main(a,option,postoption)
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49 if iscell(a)
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50 a = a{1};
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51 end
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52 d = get(a,'Data');
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53 f = get(a,'Sampling');
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54 v = cell(1,length(d));
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55 for h = 1:length(d)
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56 v{h} = cell(1,length(d{h}));
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57 for i = 1:length(d{h})
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58 di = d{h}{i};
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59 nc = size(di,2);
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60 nf = size(di,3);
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61 nl = size(di,1);
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62 zc = sum( di(2:end,:,:).*di(1:(end-1),:,:) < 0 ) /nl;
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63 if strcmp(option.per,'Second')
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64 zc = zc*f{h};
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65 end
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66 if strcmp(option.dir,'One')
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67 zc = zc/2;
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68 end
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69 v{h}{i} = zc;
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70 end
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71 end
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72 z = mirscalar(a,'Data',v,'Title','Zero-crossing rate'); |
