function [PR,t,nn] = piano_roll(Notes,vel,ts) % % Inputs: % Notes: 從 midiInfo.m 返回的音符矩陣(N*8) % vel: (可選) 若vel==1, set value to note velocity instead of 1. (默認(rèn) 0) % ts: (可選) time step of one ’pixel’ 以秒為單位 (默認(rèn) 0.01) % % Outputs: % PR: PR(ni,ti): 在音符編號為ni，時刻編號為ti處（）的取值，只能取0/1 % 行數(shù)——音符數(shù)；列數(shù)——時刻標(biāo)記數(shù) % t: t(ti): 時刻編號為ti的時刻（以秒為單位） % nn: nn(ni): note number at note index ti % % (i.e. t and nn provide ’real-world units’ for PR) % % Copyright (c) 2009 Ken Schutte % more info at: http://www.kenschutte.com/midi if nargin < 2 vel = 0; end if nargin < 3 ts = 0.01; end Nnotes = size(Notes,1); n1 = round(Notes(:,5)/ts)+1; % start tics n2 = round(Notes(:,6)/ts)+1; % end tics if vel == 0 vals = ones(Nnotes,1); else vals = Notes(:,4); % velocity end Notes(:,3) = Notes(:,3) + (Notes(:,3)==0); % correct zeros in the tone PR = zeros(max(Notes(:,3)), max(n2)); for i=1:Nnotes PR(Notes(i,3), n1(i):n2(i)) = vals(i); end % create quantized time axis: t = linspace(0,max(Notes(:,6)),size(PR,2)); % note axis: nn = min(Notes(:,3)):max(Notes(:,3)); % truncate to notes used: PR = PR(nn,:);