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208 lines
6.4 KiB
C
208 lines
6.4 KiB
C
/* GStreamer
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* Copyright (C) <2007> Sebastian Dröge <slomo@circular-chaos.org>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#include <glib.h>
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#include <math.h>
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#include "_kiss_fft_guts_f32.h"
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#include "kiss_fftr_f32.h"
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#include "gstfft.h"
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#include "gstfftf32.h"
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/**
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* SECTION:gstfftf32
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* @short_description: FFT functions for 32 bit float samples
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*
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* #GstFFTF32 provides a FFT implementation and related functions for
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* 32 bit float samples. To use this call gst_fft_f32_new() for
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* allocating a #GstFFTF32 instance with the appropiate parameters and
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* then call gst_fft_f32_fft() or gst_fft_f32_inverse_fft() to perform the
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* FFT or inverse FFT on a buffer of samples.
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*
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* After use free the #GstFFTF32 instance with gst_fft_f32_free().
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*
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* For the best performance use gst_fft_next_fast_length() to get a
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* number that is entirely a product of 2, 3 and 5 and use this as the
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* @len parameter for gst_fft_f32_new().
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*
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* The @len parameter specifies the number of samples in the time domain that
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* will be processed or generated. The number of samples in the frequency domain
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* is @len/2 + 1. To get n samples in the frequency domain use 2*n - 2 as @len.
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*
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* Before performing the FFT on time domain data it usually makes sense
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* to apply a window function to it. For this gst_fft_f32_window() can comfortably
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* be used.
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*
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* Be aware, that you can't simply run gst_fft_f32_inverse_fft() on the
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* resulting frequency data of gst_fft_f32_fft() to get the original data back.
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* The relation between them is iFFT (FFT (x)) = x * nfft where nfft is the
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* length of the FFT. This also has to be taken into account when calculation
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* the magnitude of the frequency data.
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*
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*/
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/**
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* gst_fft_f32_new:
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* @len: Length of the FFT in the time domain
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* @inverse: %TRUE if the #GstFFTF32 instance should be used for the inverse FFT
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*
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* This returns a new #GstFFTF32 instance with the given parameters. It makes
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* sense to keep one instance for several calls for speed reasons.
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*
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* @len must be even and to get the best performance a product of
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* 2, 3 and 5. To get the next number with this characteristics use
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* gst_fft_next_fast_length().
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*
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* Returns: a new #GstFFTF32 instance.
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*/
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GstFFTF32 *
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gst_fft_f32_new (gint len, gboolean inverse)
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{
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GstFFTF32 *self;
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gsize subsize = 0, memneeded;
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g_return_val_if_fail (len > 0, NULL);
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g_return_val_if_fail (len % 2 == 0, NULL);
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kiss_fftr_f32_alloc (len, (inverse) ? 1 : 0, NULL, &subsize);
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memneeded = ALIGN_STRUCT (sizeof (GstFFTF32)) + subsize;
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self = (GstFFTF32 *) g_malloc0 (memneeded);
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self->cfg = (((guint8 *) self) + ALIGN_STRUCT (sizeof (GstFFTF32)));
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self->cfg = kiss_fftr_f32_alloc (len, (inverse) ? 1 : 0, self->cfg, &subsize);
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g_assert (self->cfg);
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self->inverse = inverse;
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self->len = len;
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return self;
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}
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/**
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* gst_fft_f32_fft:
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* @self: #GstFFTF32 instance for this call
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* @timedata: Buffer of the samples in the time domain
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* @freqdata: Target buffer for the samples in the frequency domain
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*
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* This performs the FFT on @timedata and puts the result in @freqdata.
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*
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* @timedata must have as many samples as specified with the @len parameter while
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* allocating the #GstFFTF32 instance with gst_fft_f32_new().
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*
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* @freqdata must be large enough to hold @len/2 + 1 #GstFFTF32Complex frequency
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* domain samples.
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*
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*/
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void
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gst_fft_f32_fft (GstFFTF32 * self, const gfloat * timedata,
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GstFFTF32Complex * freqdata)
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{
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g_return_if_fail (self);
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g_return_if_fail (!self->inverse);
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g_return_if_fail (timedata);
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g_return_if_fail (freqdata);
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kiss_fftr_f32 (self->cfg, timedata, (kiss_fft_f32_cpx *) freqdata);
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}
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/**
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* gst_fft_f32_inverse_fft:
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* @self: #GstFFTF32 instance for this call
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* @freqdata: Buffer of the samples in the frequency domain
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* @timedata: Target buffer for the samples in the time domain
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*
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* This performs the inverse FFT on @freqdata and puts the result in @timedata.
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*
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* @freqdata must have @len/2 + 1 samples, where @len is the parameter specified
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* while allocating the #GstFFTF32 instance with gst_fft_f32_new().
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*
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* @timedata must be large enough to hold @len time domain samples.
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*
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*/
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void
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gst_fft_f32_inverse_fft (GstFFTF32 * self, const GstFFTF32Complex * freqdata,
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gfloat * timedata)
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{
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g_return_if_fail (self);
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g_return_if_fail (self->inverse);
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g_return_if_fail (timedata);
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g_return_if_fail (freqdata);
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kiss_fftri_f32 (self->cfg, (kiss_fft_f32_cpx *) freqdata, timedata);
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}
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/**
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* gst_fft_f32_free:
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* @self: #GstFFTF32 instance for this call
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*
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* This frees the memory allocated for @self.
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*
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*/
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void
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gst_fft_f32_free (GstFFTF32 * self)
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{
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g_free (self);
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}
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/**
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* gst_fft_f32_window:
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* @self: #GstFFTF32 instance for this call
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* @timedata: Time domain samples
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* @window: Window function to apply
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*
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* This calls the window function @window on the @timedata sample buffer.
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*
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*/
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void
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gst_fft_f32_window (GstFFTF32 * self, gfloat * timedata, GstFFTWindow window)
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{
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gint i, len;
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g_return_if_fail (self);
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g_return_if_fail (timedata);
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len = self->len;
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switch (window) {
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case GST_FFT_WINDOW_RECTANGULAR:
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/* do nothing */
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break;
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case GST_FFT_WINDOW_HAMMING:
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for (i = 0; i < len; i++)
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timedata[i] *= (0.53836 - 0.46164 * cos (2.0 * G_PI * i / len));
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break;
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case GST_FFT_WINDOW_HANN:
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for (i = 0; i < len; i++)
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timedata[i] *= (0.5 - 0.5 * cos (2.0 * G_PI * i / len));
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break;
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case GST_FFT_WINDOW_BARTLETT:
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for (i = 0; i < len; i++)
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timedata[i] *= (1.0 - fabs ((2.0 * i - len) / len));
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break;
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case GST_FFT_WINDOW_BLACKMAN:
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for (i = 0; i < len; i++)
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timedata[i] *= (0.42 - 0.5 * cos ((2.0 * i) / len) +
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0.08 * cos ((4.0 * i) / len));
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break;
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default:
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g_assert_not_reached ();
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break;
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}
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}
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