Dawn@4: function [HNR] = calculate_HNR( y, fs, noOfFrames, silenceFrames, pitch )
Dawn@4: 
Dawn@4:     %find the maximum lag M
Dawn@4:     DEBUG=0;
Dawn@4: 
Dawn@4:     maxPeriod = ceil(fs/getVariables('getMinFreq')); %get the default minimum fundatmental frequency
Dawn@4:     minPeriod = floor(fs/getVariables('getMaxFreq')); %get the default maximum fundamental frequency
Dawn@4: 
Dawn@4:     for i = 1:(noOfFrames - 1)
Dawn@4:         if( silenceFrames(i) == 1 )
Dawn@4:             
Dawn@4:             % frame is not silent
Dawn@4:            NA = xcorr(y(:,i), y(:,i), 'coeff');
Dawn@4:            NA = NA( ceil(length(NA)/2) : end );
Dawn@4:             
Dawn@4:            if(DEBUG)
Dawn@4:                 subplot(211); plot(y(:,i)); title(i);
Dawn@4:                 subplot(212); plot(NA); hold on;
Dawn@4:            end
Dawn@4:            
Dawn@4:             % find the maximum nearset to the predicted pitch
Dawn@4:            f0 = pitch(i);
Dawn@4:            if( (f0 < minPeriod) || (isnan(f0)) )
Dawn@4:                f0 = minPeriod;
Dawn@4:            end
Dawn@4:            % perform a search outwards from that point
Dawn@4:            startSearch = floor(f0-(f0*0.1));
Dawn@4:            endSearch = ceil(f0+(f0*0.1));
Dawn@4:            if( startSearch > length(NA) )
Dawn@4:                startSearch = length(NA) - 20;
Dawn@4:            end
Dawn@4:            if( endSearch > length(NA) )
Dawn@4:                endSearch = length(NA);
Dawn@4:            end
Dawn@4:            [max_value max_position] = max( NA( startSearch : endSearch ));
Dawn@4:            
Dawn@4:            if(DEBUG)
Dawn@4:                plot( max_position + startSearch - 1, max_value, 'gx' );
Dawn@4:                plot( startSearch : endSearch, NA(startSearch : endSearch), 'r');
Dawn@4:                hold off;
Dawn@4:            end
Dawn@4: 
Dawn@4:            HR(i) = max_value;
Dawn@4: 
Dawn@4:            if( HR(i) < 0)
Dawn@4:                % if the sample is negative it probably means the frame is
Dawn@4:                % silent so just set to  'most noisy so far'
Dawn@4: %                if(i>1)
Dawn@4: %                     HNR(i) = min( HNR );
Dawn@4: %                else
Dawn@4:                    HNR(i) = NaN;
Dawn@4: %                end
Dawn@4:            else
Dawn@4:                 HNR(i)= 10*log10(HR(i)/(1-HR(i)));
Dawn@4:            end
Dawn@4:            if(DEBUG) title(HNR(i)); end
Dawn@4:         else
Dawn@4:             HNR(i) = NaN;
Dawn@4:         end
Dawn@4:        
Dawn@4:     end
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