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1 function [x,CF,CM] = chromsynth(F,bp,sr)
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2 % [x,CF,CM] = chromsynth(F,bp,sr)
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3 % Resynthesize a chroma feature vector to audio
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4 % F is 12 rows x some number of columns, one per beat
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5 % bp is the period of one beat in sec (or a vector of beat times)
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6 % sr is the sampling rate of the output waveform
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7 % x is returned as a 12 semitone-spaced sines modulated by F
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8 % CF,CM return actual sinusoid matrices passed to synthtrax
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9 % Actual Shepard tones now implemented! 2007-04-19
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10 % 2006-07-14 dpwe@ee.columbia.edu
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11
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12 if nargin < 2; bp = 0.5; end % 120 bpm
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13 if nargin < 3; sr = 22050; end
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14
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15 [nchr,nbts] = size(F);
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16
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17 % resynth
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18 if length(bp) == 1
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19 bups = 8; % upsampling factor
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20 framerate = bups/bp;
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21 ncols = nbts*bups;
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22 CMbu = zeros(nchr, ncols);
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23 for i = 1:bups
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24 CMbu = CMbu + upsample(F', bups, i-1)';
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25 end
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26 else
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27 % vector of beat times - quantize
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28 framerate = 50; % frames per sec
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29 nbeats = length(bp);
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30 lastbeat = bp(nbeats) + (bp(nbeats) - bp(nbeats-1));
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31 ncols = round(lastbeat * framerate);
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32 CMbu = zeros(nchr, ncols);
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33 xF = [zeros(12,1),F];
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34 for i = 1:ncols
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35 CMbu(:,i) = xF(:,max(find(i/framerate >= [0,bp])));
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36 end
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37 end
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38
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39 %CFbu = repmat(440*2.^([0:(nchr-1)]'/nchr),1,ncols);
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40 %x = synthtrax(CFbu,CMbu,sr,round(sr/framerate));
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41 octs = 7;
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42 basefrq = 27.5; % A1; +6 octaves = 3520
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43 CFbu = repmat(basefrq*2.^([0:(nchr-1)]'/nchr),1,ncols);
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44 CF = [];
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45 CM = [];
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46 % what bin is the center freq?
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47 f_ctr = 440;
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48 f_sd = 0.5;
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49 f_bins = basefrq*2.^([0:(nchr*octs - 1)]/nchr);
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50 f_dist = log(f_bins/f_ctr)/log(2)/f_sd;
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51 % actually just = ([0:(nchr*octs - 1)]/nchr-log2(f_ctr/basefrq))/f_sd
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52 % Gaussian weighting centered of f_ctr, with f_sd
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53 f_wts = exp(-0.5*f_dist.^2);
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54 for oct = 1:octs
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55 CF = [CF;(2^oct)*CFbu];
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56 % pick out particular weights
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57 CM = [CM;diag(f_wts((oct-1)*nchr+[1:nchr]))*CMbu];
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58 end
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59 % Remove sines above nyquist
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60 CFok = (CF(:,1) < sr/2);
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61 CF = CF(CFok,:);
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62 CM = CM(CFok,:);
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63 % Synth the sines
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64 x = synthtrax(CF,CM,sr,round(sr/framerate));
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65
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66 % Playing synth along with audio:
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67 %>> rdc = chromsynth(Dy.F(:,160+[1:300]),Dy.bts(160+[1:300]) - Dy.bts(160),sr);
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68 %>> Dy.bts(161)*sr
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69 %ans =
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70 % 279104
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71 %>> size(rdc)
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72 %ans =
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73 % 1 498401
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74 %>> ddd = db(279104+[1:498401]);
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75 %>> soundsc([ddd,rdc'/40],sr)
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