Audio-matlab-algorithm.zip_audio compression_音效 EQ_音效 matlab_音频压

function [b, a] = shelving(G, fc, fs, Q, type) % % Derive coefficients for a shelving filter with a given amplitude and % cutoff frequency. All coefficients are calculated as described in % Zolzer's DAFX book (p. 50 -55). % % Usage: [B,A] = shelving(G, Fc, Fs, Q, type); % % G is the logrithmic gain (in dB) % FC is the center frequency % Fs is the sampling rate % Q adjusts the slope be replacing the sqrt(2) term % type is a character string defining filter type % Choices are: 'Base_Shelf' or 'Treble_Shelf' % % Author: Jeff Tackett 08/22/05 % %Error Check if((strcmp(type,'Base_Shelf') ~= 1) && (strcmp(type,'Treble_Shelf') ~= 1)) error(['Unsupported Filter Type: ' type]); end K = tan((pi * fc)/fs); V0 = 10^(G/20); root2 = 1/Q; %sqrt(2) %Invert gain if a cut if(V0 < 1) V0 = 1/V0; end %%%%%%%%%%%%%%%%%%%% % BASE BOOST %%%%%%%%%%%%%%%%%%%% if(( G > 0 ) & (strcmp(type,'Base_Shelf'))) b0 = (1 + sqrt(V0)*root2*K + V0*K^2) / (1 + root2*K + K^2); b1 = (2 * (V0*K^2 - 1) ) / (1 + root2*K + K^2); b2 = (1 - sqrt(V0)*root2*K + V0*K^2) / (1 + root2*K + K^2); a1 = (2 * (K^2 - 1) ) / (1 + root2*K + K^2); a2 = (1 - root2*K + K^2) / (1 + root2*K + K^2); %%%%%%%%%%%%%%%%%%%% % BASE CUT %%%%%%%%%%%%%%%%%%%% elseif (( G < 0 ) & (strcmp(type,'Base_Shelf'))) b0 = (1 + root2*K + K^2) / (1 + root2*sqrt(V0)*K + V0*K^2); b1 = (2 * (K^2 - 1) ) / (1 + root2*sqrt(V0)*K + V0*K^2); b2 = (1 - root2*K + K^2) / (1 + root2*sqrt(V0)*K + V0*K^2); a1 = (2 * (V0*K^2 - 1) ) / (1 + root2*sqrt(V0)*K + V0*K^2); a2 = (1 - root2*sqrt(V0)*K + V0*K^2) / (1 + root2*sqrt(V0)*K + V0*K^2); %%%%%%%%%%%%%%%%%%%% % TREBLE BOOST %%%%%%%%%%%%%%%%%%%% elseif (( G > 0 ) & (strcmp(type,'Treble_Shelf'))) b0 = (V0 + root2*sqrt(V0)*K + K^2) / (1 + root2*K + K^2); b1 = (2 * (K^2 - V0) ) / (1 + root2*K + K^2); b2 = (V0 - root2*sqrt(V0)*K + K^2) / (1 + root2*K + K^2); a1 = (2 * (K^2 - 1) ) / (1 + root2*K + K^2); a2 = (1 - root2*K + K^2) / (1 + root2*K + K^2); %%%%%%%%%%%%%%%%%%%% % TREBLE CUT %%%%%%%%%%%%%%%%%%%% elseif (( G < 0 ) & (strcmp(type,'Treble_Shelf'))) b0 = (1 + root2*K + K^2) / (V0 + root2*sqrt(V0)*K + K^2); b1 = (2 * (K^2 - 1) ) / (V0 + root2*sqrt(V0)*K + K^2); b2 = (1 - root2*K + K^2) / (V0 + root2*sqrt(V0)*K + K^2); a1 = (2 * ((K^2)/V0 - 1) ) / (1 + root2/sqrt(V0)*K + (K^2)/V0); a2 = (1 - root2/sqrt(V0)*K + (K^2)/V0) / (1 + root2/sqrt(V0)*K + (K^2)/V0); %%%%%%%%%%%%%%%%%%%% % All-Pass %%%%%%%%%%%%%%%%%%%% else b0 = V0; b1 = 0; b2 = 0; a1 = 0; a2 = 0; end %return values a = [ 1, a1, a2]; b = [ b0, b1, b2];