[Octave-cvsupdate] SF.net SVN: octave:[10778] trunk/octave-forge/main/signal

[<mtm...@us...>]

Revision: 10778
          http://octave.svn.sourceforge.net/octave/?rev=10778&view=rev
Author:   mtmiller
Date:     2012-07-28 00:40:20 +0000 (Sat, 28 Jul 2012)
Log Message:
-----------
Fix rceps to work correctly on odd-length inputs

Reported by Sergei Steshenko on the mailing list.

Modified Paths:
--------------
    trunk/octave-forge/main/signal/NEWS
    trunk/octave-forge/main/signal/inst/rceps.m

Modified: trunk/octave-forge/main/signal/NEWS
===================================================================
--- trunk/octave-forge/main/signal/NEWS	2012-07-26 23:07:34 UTC (rev 10777)
+++ trunk/octave-forge/main/signal/NEWS	2012-07-28 00:40:20 UTC (rev 10778)
@@ -4,6 +4,8 @@
 signal-1.1.4   Release Date: 2012-XX-XX   Release Manager:
 ===============================================================================
 
+ ** The function `rceps' was fixed to work correctly with odd-length inputs.
+
  ** The following functions are new:
     movingrms  schtrig  clustersegment
 

Modified: trunk/octave-forge/main/signal/inst/rceps.m
===================================================================
--- trunk/octave-forge/main/signal/inst/rceps.m	2012-07-26 23:07:34 UTC (rev 10777)
+++ trunk/octave-forge/main/signal/inst/rceps.m	2012-07-28 00:40:20 UTC (rev 10778)
@@ -34,18 +34,22 @@
   if (nargin != 1)
     print_usage;
   end
-  y = real(ifft(log(abs(fft(x)))));
+  f = abs(fft(x));
+  if (any (f == 0))
+    error ("rceps: the spectrum of x contains zeros, unable to compute real cepstrum");
+  endif
+  y = real(ifft(log(f)));
   if nargout == 2
     n=length(x);
     if rows(x)==1
       if rem(n,2)==1
-        ym = [y(1), 2*y(2:n/2), zeros(1,n/2-1)];
+        ym = [y(1), 2*y(2:n/2+1), zeros(1,n/2)];
       else
         ym = [y(1), 2*y(2:n/2), y(n/2+1), zeros(1,n/2-1)];
       endif
     else
       if rem(n,2)==1
-        ym = [y(1,:); 2*y(2:n/2,:); zeros(n/2-1,columns(y))];
+        ym = [y(1,:); 2*y(2:n/2+1,:); zeros(n/2,columns(y))];
       else
         ym = [y(1,:); 2*y(2:n/2,:); y(n/2+1,:); zeros(n/2-1,columns(y))];
       endif
@@ -77,6 +81,13 @@
 %! assert(yt.', y, tol);
 %! assert(xmt.', xm, tol);
 
+%% Test that an odd-length input produces an odd-length output
+%!test
+%! x = randn(33, 4);
+%! [y, xm] = rceps(x);
+%! assert(size(y) == size(x));
+%! assert(size(xm) == size(x));
+
 %!demo
 %! f0=70; Fs=10000;           # 100 Hz fundamental, 10kHz sampling rate
 %! a=real(poly(0.985*exp(1i*pi*[0.1, -0.1, 0.3, -0.3]))); # two formants

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