Documentation of be_continuityBased

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Function Synopsis

[cmlC,cmlT,amlC,amlT] = be_continuityBased(anns,beats,params)

Help text

  function [cmlC,cmlT,amlC,amlT] = be_continuityBased(anns,beats,params)
   
  Description:
  Calculate the continuity based accuracy values as used in (Hainsworth, 2004) and (Klapuri et al, 2006)
   
  Inputs: 
  anns - sequence of ground truth beat annotations (in seconds)
  beats - sequence of estimated beat times (in seconds)
  params - structure of beat evaluation parameters
   
  Ouputs: 
  cmlC - beat tracking accuracy, continuity required at the correct metrical level 
  cmlT - beat tracking accuracy, continuity not required at the correct metrical level
  amlC - beat tracking accuracy, continuity required at allowed metrical levels 
  amlT - beat tracking accuracy, continuity not required at allowed metrical levels
   
  References:
  S. Hainsworth, "Techniques for the automated analysis of musical audio," Ph.D. dissertation, Department of Engineering, Cambridge University, 2004.
  A. P. Klapuri, A. Eronen, and J. Astola, "Analysis of the meter of acoustic musical signals," IEEE Transactions on Audio, Speech and Language Processing, vol. 14, no. 1, pp. 342–355, 2006.

  (c) 2009 Matthew Davies

Cross-Reference Information

Listing of function be_continuityBased

function [cmlC,cmlT,amlC,amlT] = be_continuityBased(anns,beats,params)


if nargin<3
  params = be_params;
end


% put the beats and annotations into column vectors
anns = anns(:);
beats = beats(:);

% remove beats and annotations that are within the first 5 seconds
anns(anns<params.minBeatTime) = [];
beats(beats<params.minBeatTime) = [];

% Check if there are any beats, if not then exit
if( or( (length(beats)<2), (length(anns)<2) ) ),
  disp('beat or annotation sequence is empty or too short, assigning zero to all outputs [cmlC,cmlT,amlC,amlT]');

  cmlC = 0;
  cmlT = 0;
  amlC = 0;
  amlT = 0;

  return;
end

% also check that the beat times are in seconds and not any other time units
if( or( (max(beats)>1000) , (max(anns)>1000) ) )
  error('either beats or annotations are not in seconds, please rectify.');
  return;
end
 

p = params.continuityBased.phaseThresh;
t = params.continuityBased.periodThresh;

doubleAnns = interp1([1:length(anns)],anns,[1:0.5:length(anns)]);

% make different variants of annotations
% normal annotations
testAnns{1} = anns;
% off-beats 
testAnns{2} = doubleAnns(2:2:end);
% double tempo
testAnns{3} = doubleAnns;
% half tempo odd-beats (i.e. 1,3,1,3)
testAnns{4} = anns(1:2:end);
% half tempo even-beat (i.e. 2,4,2,4)
testAnns{5} = anns(2:2:end);


% loop analysis over number of variants on annotations
for j=1:size(testAnns,2),

  [totAcc(j),contAcc(j)] = ContinuityEval(testAnns{j},beats,t,p);

end


% assign the accuracy scores
cmlC = contAcc(1);
cmlT = totAcc(1);
amlC = max(contAcc);
amlT = max(totAcc);

function [totAcc,contAcc] = ContinuityEval(anns,beats,t,p)
% sub-function for calculating continuity-based accuracy


checkanns = zeros(1,max(length(anns),length(beats)));
checkbeats = checkanns;

cond = 0;



for i=1:length(beats),

    cond = 0;
    [a,b] = min(abs(beats(i)-anns)); % look for nearest annotation to current beat

    if(checkanns(b)==1) % if we've already used this annotation..
        cond = 0;
    else
        
        if or(i==1,b==1), % either first beat or first annotation, look forward on both

            if (and((abs(a/(anns(b+1)-anns(b)))<p), ...
                    (abs(1-((beats(i+1)-beats(i))/(anns(b+1)-anns(b))))<t)));
                checkanns(b) = 1;
                cond = 1;
            end

        else % not first beat or first annotation, so can look backwards

            if (and((abs(a/(anns(b)-anns(b-1)))<p), ...
                    (abs(1-((beats(i)-beats(i-1))/(anns(b)-anns(b-1))))<t)));
                checkanns(b) = 1;
                cond = 1;
            end

        end

    end

    % for i^th beat what is the condition
    checkbeats(i) = double(cond);

end

checkbeats = [0 checkbeats(:)' 0];

[d1,d2,d3] = find(checkbeats==0);
checkbeats = checkbeats(2:end-1);

% in best case, d2 = 1 & length(checkbeats)
contAcc = 100*(max(diff(d2))-1)/length(checkbeats);
totAcc = 100*sum(checkbeats)/length(checkbeats);