GUI: try using FFTW for per-chan osc wave center

not reliable yet

extern/fftw/api/plan-guru-split-dft.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2003, 2007-14 Matteo Frigo
+ * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#include "api/api.h"
+#include "dft/dft.h"
+
+X(plan) XGURU(split_dft)(int rank, const IODIM *dims,
+			       int howmany_rank, const IODIM *howmany_dims,
+			       R *ri, R *ii, R *ro, R *io, unsigned flags)
+{
+     if (!GURU_KOSHERP(rank, dims, howmany_rank, howmany_dims)) return 0;
+
+     return X(mkapiplan)(
+	  ii - ri == 1 && io - ro == 1 ? FFT_SIGN : -FFT_SIGN, flags,
+	  X(mkproblem_dft_d)(MKTENSOR_IODIMS(rank, dims, 1, 1),
+			     MKTENSOR_IODIMS(howmany_rank, howmany_dims,
+						1, 1),
+			     TAINT_UNALIGNED(ri, flags),
+			     TAINT_UNALIGNED(ii, flags), 
+			     TAINT_UNALIGNED(ro, flags),
+			     TAINT_UNALIGNED(io, flags)));
+}