view aim-mat/modules/pcp/map/OutMidCrctFilt.m @ 4:537f939baef0 tip

various bug fixes and changed copyright message

%
%	Produce compensation filter to simulate outer/middle ear
%	IRINO Toshio
%	29 Aug. 1996 (check on 14 May  1997 )
%	8 Jan. 2002  (Multiply Win for avoid sprious)
%	19 Nov. 2002 (remez : even integer)
%
%	It is a linear phase filter for the ELC/MAF/MAP correction.
%	see OutMidCrct.m 
%
%	function [FIRCoef] = OutMidCrctFilt(StrCrct,SR);
%	INPUT	StrCrct: String for Correction ELC/MAF/MAP
%		SR: 	 Sampling Rate
%		SwPlot:  SwPlot
%	OUTPUT  FIRCoef: FIR filter coefficients 
%
function [FIRCoef] = OutMidCrctFilt(StrCrct,SR,SwPlot);

if nargin < 2, help OutMidCrctFilt; end;
if nargin < 3, SwPlot = 1; end;

if length(StrCrct)~=3, 
	error('Specifiy correction in 3 characters: ELC / MAF / MAP.'); 
end;
if ~(strcmp(upper(StrCrct(1:3)), 'ELC') | ...
	 strcmp(upper(StrCrct(1:3)),'MAF') ...
	| strcmp(upper(StrCrct(1:3)),'MAP')),
	error('Specifiy correction: ELC / MAF / MAP.'); 
end;

Nint = 1024;
% Nint = 0; % No spline interpolation:  NG no convergence at remez
[crctPwr freq] = OutMidCrct(StrCrct,Nint,SR,0);
crct = sqrt(crctPwr);

%% FIRCoef = remez(50/16000*SR,freq/SR*2,crct); % NG 
%% FIRCoef = remez(300/16000*SR,freq/SR*2,crct); % Original
% FIRCoef = remez(LenCoef/16000*SR,freq/SR*2,crct); % when odd num : warning
%% modified on 8 Jan 2002, 19 Nov 2002
LenCoef = 200; %  ( -45 dB) <- 300 (-55 dB)
FIRCoef = remez(fix(LenCoef/16000*SR/2)*2,freq/SR*2,crct);  % even number only
Win     = TaperWindow(length(FIRCoef),'han',LenCoef/10); 
	    % Necessary to avoid sprious
FIRCoef = Win.*FIRCoef;

if SwPlot==1
	[frsp freq2] = freqz(FIRCoef,1,Nint,SR);
	subplot(2,1,1)
	plot(FIRCoef);
	subplot(2,1,2)
	plot(freq2,abs(frsp),freq,crct,'--')
	%	plot(freq2,20*log10(abs(frsp)),freq,20*log10(crct))
	
	ELCError = mean((abs(frsp) - crct).^2)/mean(crct.^2);
	ELCErrordB = 10*log10(ELCError)          % corrected 
	if ELCErrordB > -30,
	    disp(['Warning: Error in ELC correction = ' ...
		    num2str(ELCErrordB) ' dB > -30 dB'])
	end;
end;

return;