gusucode.com > 声音的处理有:LPC,FFT,共振峰,频谱源码程序 > siganlandsystemusingMatlab/SSUM/sws/lpcfit2.m
function [a,e] = lpcfit(x,p,w,h) % [a,e] = lpcfit(x,p,w,h) Fit LPC to short-time segments % x is a stretch of signal. Using w point windows every % h points, fit order p LPC models. Return the successive % all-pole coefficients as rows of a, and the residual excitation % in e. % 2001-02-25 dpwe@ee.columbia.edu if nargin < 2 p = 12; end if nargin < 3 w = 256; end if nargin < 4 h = w/2; end npts = length(x); nhops = 1 + floor((npts-w)/h); a = zeros(nhops, p+1); e = zeros(1, npts); % Pre-emphasis pre = [1 -0.9]; x = filter(pre,1,x); for hop = 1:nhops % Extract segment of signal xx = x((hop - 1)*h + [1:w]); if max(xx)==0 & min(xx) == 0 xx(1) = 0.1; end % Apply hanning window wxx = xx .* hanning(w); % Form autocorrelation (calculates *way* too many points) rxx = xcorr(wxx,wxx); % extract just the points we need (middle p+1 points) rxx = rxx(w+[0:p]); % Setup the normal equations R = toeplitz(rxx(1:p)); % Solve for a (horribly inefficient to use full inv()) an = inv(R)*rxx(2:(p+1)); % Calculate residual by filtering xx (after windowing?) % rs = filter([1 -an'],1,xx); rs = filter([1 -an'],1,wxx); G = sqrt(mean(rs.^2)); % Save them; first column is residual MSE (gain) a(hop,:) = [G -an']; e((hop - 1)*h + [(1+h/2):(w-h/2)]) = rs([(1+h/2):(w-h/2)])/G; end