view functions/fe_funcs/mel_matrix.m @ 0:2fadb31a9d55 tip

Import code by Vuegen et al

function [M,fCen,Mfull]=mel_matrix(fs,NbCh,Nfft,warp,fhigh,flow)
% [M,fCen,Mfull]=mel_matrix(fs,NbCh,Nfft,warp,fhigh)
% returns Nfft/2+1 - by - NbCh matrix of triangular weights
% NbCh filterbanks linearly spaced on a MEL scale till fhigh
% warp: default 1.0
% fhigh: default=fs/2
% Mfull: matrix without truncation to Nfft/2+1 points

if nargin<4,
    warp=1;
end
if nargin<5,
    fhigh=fs/2;
end

LowMel=2595 * log10(1+flow/700);
NyqMel=2595 * log10(1+fhigh/700);

StartMel=LowMel + (0:NbCh-1)/(NbCh+1)*(NyqMel-LowMel);
fCen=warp*700*(10.^(StartMel/2595)-1);
StartBin=round(Nfft/fs*fCen)+1;

EndMel=LowMel + (2:NbCh+1)/(NbCh+1)*(NyqMel-LowMel);
EndBin=round(warp*Nfft/fs*700*(10.^(EndMel/2595)-1))+1;

TotLen=EndBin-StartBin+1;

LowLen=[StartBin(2:NbCh) EndBin(NbCh-1)]-StartBin+1;
HiLen=TotLen-LowLen+1;

M=sparse([],[],[],ceil(warp*Nfft/2+1),NbCh,sum(TotLen));
for k=1:NbCh,
    M(StartBin(k):StartBin(k)+LowLen(k)-1,k)=(1:LowLen(k))'/LowLen(k);
    M(EndBin(k)-HiLen(k)+1:EndBin(k),k)=(HiLen(k):-1:1)'/HiLen(k);
end
%TotWeight=sum(M,1);
Mfull=M;
M=M(1:Nfft/2+1,:);
%WeightSum=full([sum(M,1);TotWeight]);