annotate computeCQT.m @ 1:3ea8ed09af0f tip

additional clarifications

function [intCQT] = computeCQT(y)
% Settings for computing CQT for music signals (by E. Benetos)

% COMPUTING A CQT WITH 40ms STEP AND BASIC NOISE REDUCTION: 
%[intCQT] = computeCQT(filename);
%X = intCQT(:,round(1:7.1128:size(intCQT,2)))';
%noiseLevel1 = medfilt1(X',40);
%noiseLevel2 = medfilt1(min(X',noiseLevel1),40);
%X = max(X-noiseLevel2',0);
%Y = X(1:4:size(X,1),:);  % 40ms step


% Load .wav file
%[x fs bits] = wavread(filename);
%if (size(x,2) == 2) y = mean(x')'; clear('x'); else y=x; clear('x'); end;
%if (fs ~= 44100) y = resample(y,44100,fs); end;
%y = 0.5*y/max(y);
fs = 44100;


% Compute CQT
Xcqt = cqt(y,27.5,fs/3,60,fs,'q',0.80,'atomHopFactor',0.3,'thresh',0.0005,'win','hann');
%Xcqt = cqt(y,27.5,fs/3,120,fs,'q',0.35,'atomHopFactor',0.3,'thresh',0.0005,'win','hann'); % old resolution
absCQT = getCQT(Xcqt,'all','all');

% Crop CQT to useful time regions
emptyHops = Xcqt.intParams.firstcenter/Xcqt.intParams.atomHOP;
maxDrop = emptyHops*2^(Xcqt.octaveNr-1)-emptyHops;
droppedSamples = (maxDrop-1)*Xcqt.intParams.atomHOP + Xcqt.intParams.firstcenter;
outputTimeVec = (1:size(absCQT,2))*Xcqt.intParams.atomHOP-Xcqt.intParams.preZeros+droppedSamples;

lowerLim = find(outputTimeVec>0,1);
upperLim = find(outputTimeVec>length(y),1)-1;

%intCQT = absCQT(112:1200,lowerLim:upperLim); % old resolution
intCQT = absCQT(56:600,lowerLim:upperLim);


%figure; imagesc(imrotate(abs(intCQT),90));