67 lines
1.9 KiB
C
67 lines
1.9 KiB
C
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#include "pffft.h"
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#include <stdio.h>
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#include <stdlib.h>
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void c_forward_real_float(const int transformLen)
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{
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printf("running %s()\n", __FUNCTION__);
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/* first check - might be skipped */
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if (transformLen < pffft_min_fft_size(PFFFT_REAL))
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{
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fprintf(stderr, "Error: minimum FFT transformation length is %d\n", pffft_min_fft_size(PFFFT_REAL));
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return;
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}
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/* instantiate FFT and prepare transformation for length N */
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PFFFT_Setup *ffts = pffft_new_setup(transformLen, PFFFT_REAL);
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/* one more check */
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if (!ffts)
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{
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fprintf(stderr,
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"Error: transformation length %d is not decomposable into small prime factors. "
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"Next valid transform size is: %d ; next power of 2 is: %d\n",
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transformLen,
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pffft_nearest_transform_size(transformLen, PFFFT_REAL, 1),
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pffft_next_power_of_two(transformLen) );
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return;
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}
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/* allocate aligned vectors for input X and output Y */
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float *X = (float*)pffft_aligned_malloc(transformLen * sizeof(float));
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float *Y = (float*)pffft_aligned_malloc(transformLen * sizeof(float)); /* complex: re/im interleaved */
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float *W = (float*)pffft_aligned_malloc(transformLen * sizeof(float));
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/* prepare some input data */
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for (int k = 0; k < transformLen; k += 2)
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{
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X[k] = k;
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X[k+1] = -1-k;
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}
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/* do the forward transform; write complex spectrum result into Y */
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pffft_transform_ordered(ffts, X, Y, W, PFFFT_FORWARD);
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/* print spectral output */
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printf("output should be complex spectrum with %d complex bins\n", transformLen /2);
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for (int k = 0; k < transformLen; k += 2)
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printf("Y[%d] = %f + i * %f\n", k/2, Y[k], Y[k+1]);
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pffft_aligned_free(W);
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pffft_aligned_free(Y);
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pffft_aligned_free(X);
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pffft_destroy_setup(ffts);
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}
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int main(int argc, char *argv[])
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{
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int N = (1 < argc) ? atoi(argv[1]) : 32;
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c_forward_real_float(N);
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return 0;
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}
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