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Functions
GstFFTS16 * | gst_fft_s16_new () |
void | gst_fft_s16_fft () |
void | gst_fft_s16_inverse_fft () |
void | gst_fft_s16_window () |
void | gst_fft_s16_free () |
Description
GstFFTS16 provides a FFT implementation and related functions for
signed 16 bit integer samples. To use this call gst_fft_s16_new()
for
allocating a GstFFTS16 instance with the appropriate parameters and
then call gst_fft_s16_fft()
or gst_fft_s16_inverse_fft()
to perform the
FFT or inverse FFT on a buffer of samples.
After use free the GstFFTS16 instance with gst_fft_s16_free()
.
For the best performance use gst_fft_next_fast_length()
to get a
number that is entirely a product of 2, 3 and 5 and use this as the
len
parameter for gst_fft_s16_new()
.
The len
parameter specifies the number of samples in the time domain that
will be processed or generated. The number of samples in the frequency domain
is len
/2 + 1. To get n samples in the frequency domain use 2*n - 2 as len
.
Before performing the FFT on time domain data it usually makes sense
to apply a window function to it. For this gst_fft_s16_window()
can comfortably
be used.
Be aware, that you can't simply run gst_fft_s16_inverse_fft()
on the
resulting frequency data of gst_fft_s16_fft()
to get the original data back.
The relation between them is iFFT (FFT (x)) = x / nfft where nfft is the
length of the FFT. This also has to be taken into account when calculation
the magnitude of the frequency data.
Functions
gst_fft_s16_new ()
GstFFTS16 * gst_fft_s16_new (gint len
,gboolean inverse
);
This returns a new GstFFTS16 instance with the given parameters. It makes sense to keep one instance for several calls for speed reasons.
len
must be even and to get the best performance a product of
2, 3 and 5. To get the next number with this characteristics use
gst_fft_next_fast_length()
.
[skip]
gst_fft_s16_fft ()
void gst_fft_s16_fft (GstFFTS16 *self
,const gint16 *timedata
,GstFFTS16Complex *freqdata
);
This performs the FFT on timedata
and puts the result in freqdata
.
timedata
must have as many samples as specified with the len
parameter while
allocating the GstFFTS16 instance with gst_fft_s16_new()
.
freqdata
must be large enough to hold len
/2 + 1 GstFFTS16Complex frequency
domain samples.
Parameters
self |
GstFFTS16 instance for this call |
|
timedata |
Buffer of the samples in the time domain |
|
freqdata |
Target buffer for the samples in the frequency domain |
gst_fft_s16_inverse_fft ()
void gst_fft_s16_inverse_fft (GstFFTS16 *self
,const GstFFTS16Complex *freqdata
,gint16 *timedata
);
This performs the inverse FFT on freqdata
and puts the result in timedata
.
freqdata
must have len
/2 + 1 samples, where len
is the parameter specified
while allocating the GstFFTS16 instance with gst_fft_s16_new()
.
timedata
must be large enough to hold len
time domain samples.
Parameters
self |
GstFFTS16 instance for this call |
|
freqdata |
Buffer of the samples in the frequency domain |
|
timedata |
Target buffer for the samples in the time domain |
gst_fft_s16_window ()
void gst_fft_s16_window (GstFFTS16 *self
,gint16 *timedata
,GstFFTWindow window
);
This calls the window function window
on the timedata
sample buffer.
Parameters
self |
GstFFTS16 instance for this call |
|
timedata |
Time domain samples |
|
window |
Window function to apply |