wolffd@0: function varargout = mirzerocross(orig,varargin)
wolffd@0: %   mirzeroscross(x) computes the sign-changes rate along the signal x,
wolffd@0: %       i.e., how many time the waveform crosses the X-axis. When applied on
wolffd@0: %       an audio waveform, gives a notion of noise.
wolffd@0: %   Optional argument:
wolffd@0: %       mirzerocross(...,'Per',p) precises the temporal reference for the
wolffd@0: %           rate computation.
wolffd@0: %           Possible values:
wolffd@0: %               p = 'Second': number of sign-changes per second (Default).
wolffd@0: %               p = 'Sample': number of sign-changes divided by the total 
wolffd@0: %                   number of samples.
wolffd@0: %           The 'Second' option returns a result equal to the one returned
wolffd@0: %               by the 'Sample' option multiplied by the sampling rate.
wolffd@0: %       mirzerocross(...,'Dir',d) precises the definition of sign change.
wolffd@0: %           Possible values:
wolffd@0: %               d = 'One': number of sign-changes from negative to positive 
wolffd@0: %                   only (or, equivalently, from positive to negative only).
wolffd@0: %                       (Default)
wolffd@0: %               d = 'Both': number of sign-changes in both ways.
wolffd@0: %           The 'Both' option returns a result equal to twice the one
wolffd@0: %               returned by the 'One' option.
wolffd@0: 
wolffd@0: 
wolffd@0:         per.key = 'Per';
wolffd@0:         per.type = 'String';
wolffd@0:         per.choice = {'Second','Sample'};
wolffd@0:         per.default = 'Second';
wolffd@0:     option.per = per;
wolffd@0: 
wolffd@0:         dir.key = 'Dir';
wolffd@0:         dir.type = 'String';
wolffd@0:         dir.choice = {'One','Both'};
wolffd@0:         dir.default = 'One';
wolffd@0:     option.dir = dir;
wolffd@0:     
wolffd@0: specif.option = option;
wolffd@0:      
wolffd@0: varargout = mirfunction(@mirzerocross,orig,varargin,nargout,specif,@init,@main);
wolffd@0: 
wolffd@0: 
wolffd@0: function [x type] = init(x,option)
wolffd@0: if not(isamir(x,'mirdata'))
wolffd@0:     x = miraudio(x);
wolffd@0: end
wolffd@0: type = 'mirscalar';
wolffd@0: 
wolffd@0: 
wolffd@0: function z = main(a,option,postoption)
wolffd@0: if iscell(a)
wolffd@0:     a = a{1};
wolffd@0: end
wolffd@0: d = get(a,'Data');
wolffd@0: f = get(a,'Sampling');
wolffd@0: v = cell(1,length(d));
wolffd@0: for h = 1:length(d)
wolffd@0:     v{h} = cell(1,length(d{h}));
wolffd@0:     for i = 1:length(d{h})
wolffd@0:         di = d{h}{i};
wolffd@0:         nc = size(di,2);
wolffd@0:         nf = size(di,3);
wolffd@0:         nl = size(di,1);
wolffd@0:         zc = sum( di(2:end,:,:).*di(1:(end-1),:,:) < 0 ) /nl;
wolffd@0:         if strcmp(option.per,'Second')
wolffd@0:             zc = zc*f{h};
wolffd@0:         end
wolffd@0:         if strcmp(option.dir,'One')
wolffd@0:             zc = zc/2;
wolffd@0:         end
wolffd@0:         v{h}{i} = zc;
wolffd@0:     end
wolffd@0: end
wolffd@0: z = mirscalar(a,'Data',v,'Title','Zero-crossing rate');