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<title>GstFFTF32: GStreamer Base Plugins 1.0 Library Reference Manual</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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Description
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GstFFTF32
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GstFFTF32 — FFT functions for 32 bit float samples
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Functions
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GstFFTF32 *
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gst_fft_f32_new ()
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void
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gst_fft_f32_fft ()
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void
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gst_fft_f32_inverse_fft ()
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void
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gst_fft_f32_window ()
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void
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gst_fft_f32_free ()
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Types and Values
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GstFFTF32
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struct
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GstFFTF32Complex
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Includes
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#include <gst/fft/fft.h>
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Description
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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 appropriate 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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After use free the GstFFTF32 instance with gst_fft_f32_free().
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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
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parameter for gst_fft_f32_new().
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The len
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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
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/2 + 1. To get n samples in the frequency domain use 2*n - 2 as len
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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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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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Functions
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gst_fft_f32_new ()
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GstFFTF32 *
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gst_fft_f32_new (gint len,
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gboolean inverse);
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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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len
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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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[skip]
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Parameters
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len
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Length of the FFT in the time domain
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inverse
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TRUE if the GstFFTF32 instance should be used for the inverse FFT
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Returns
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a new GstFFTF32 instance.
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gst_fft_f32_fft ()
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void
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gst_fft_f32_fft (GstFFTF32 *self,
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const gfloat *timedata,
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GstFFTF32Complex *freqdata);
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This performs the FFT on timedata
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and puts the result in freqdata
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timedata
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must have as many samples as specified with the len
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parameter while
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allocating the GstFFTF32 instance with gst_fft_f32_new().
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freqdata
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must be large enough to hold len
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/2 + 1 GstFFTF32Complex frequency
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domain samples.
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Parameters
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self
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GstFFTF32 instance for this call
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timedata
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Buffer of the samples in the time domain
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freqdata
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Target buffer for the samples in the frequency domain
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gst_fft_f32_inverse_fft ()
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void
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gst_fft_f32_inverse_fft (GstFFTF32 *self,
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const GstFFTF32Complex *freqdata,
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gfloat *timedata);
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This performs the inverse FFT on freqdata
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and puts the result in timedata
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freqdata
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must have len
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/2 + 1 samples, where len
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is the parameter specified
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while allocating the GstFFTF32 instance with gst_fft_f32_new().
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timedata
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must be large enough to hold len
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time domain samples.
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Parameters
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self
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GstFFTF32 instance for this call
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freqdata
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Buffer of the samples in the frequency domain
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timedata
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Target buffer for the samples in the time domain
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gst_fft_f32_window ()
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void
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gst_fft_f32_window (GstFFTF32 *self,
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gfloat *timedata,
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GstFFTWindow window);
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This calls the window function window
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on the timedata
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sample buffer.
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Parameters
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self
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GstFFTF32 instance for this call
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timedata
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Time domain samples
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window
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Window function to apply
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gst_fft_f32_free ()
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void
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gst_fft_f32_free (GstFFTF32 *self);
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This frees the memory allocated for self
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Parameters
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self
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GstFFTF32
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typedef struct _GstFFTF32 GstFFTF32;
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struct GstFFTF32Complex
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struct GstFFTF32Complex {
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gfloat r;
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gfloat i;
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};
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Data type for complex numbers composed of
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32 bit float.
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Members
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gfloat r;
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Real part
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