moved FFT-helper functions from Spectrum Analyzer plugin to core to make it also usable by other plugins

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@1407 0778d3d1-df1d-0410-868b-ea421aaaa00d

include/fft_helpers.h

@@ -0,0 +1,88 @@
+/*
+ * fft_helpers.h - some functions around FFT analysis
+ *
+ * Copyright (c) 2008 Tobias Doerffel <tobydox/at/users.sourceforge.net>
+ * 
+ * This file is part of Linux MultiMedia Studio - http://lmms.sourceforge.net
+ *
+ * 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 (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+
+#ifndef _FFT_HELPERS_H
+#define _FFT_HELPERS_H
+
+#include "lmmsconfig.h"
+
+#ifdef LMMS_HAVE_FFTW3F
+
+#include <fftw3.h>
+
+const int FFT_BUFFER_SIZE = 2048;
+
+enum WINDOWS
+{
+        KAISER=1,
+        RECTANGLE,
+        HANNING,
+        HAMMING
+};
+
+/* returns biggest value from abs_spectrum[spec_size] array
+ *
+ *    returns -1 on error
+ */
+float maximum( float * _abs_spectrum, unsigned int _spec_size );
+
+/* apply hanning or hamming window to channel
+ *
+ *    returns -1 on error
+ */
+int hanming( float * _timebuffer, int _length, WINDOWS _type );
+
+/* compute absolute values of complex_buffer, save to absspec_buffer
+ * take care that - compl_len is not bigger than complex_buffer!
+ *                - absspec buffer is big enough!
+ *
+ *    returns 0 on success, else -1
+ */
+int absspec( fftwf_complex * _complex_buffer, float * _absspec_buffer,
+							int _compl_length );
+
+/* build fewer subbands from many absolute spectrum values
+ * take care that - compressedbands[] array num_new elements long
+ *                - num_old > num_new
+ *                       
+ *    returns 0 on success, else -1
+ */
+int compressbands( float * _absspec_buffer, float * _compressedband,
+			int _num_old, int _num_new, int _bottom, int _top );
+
+
+int calc13octaveband31( float * _absspec_buffer, float * _subbands,
+				int _num_spec, float _max_frequency );
+
+/* compute power of finite time sequence
+ * take care num_values is length of timesignal[]
+ *
+ *    returns power on success, else -1
+ */
+float signalpower(float *timesignal, int num_values);
+
+#endif
+
+#endif