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  1. PO
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    <p>You need to find the bug(s) in your code. My test code appears to work just fine.</p> <p>Complex-valued forward FFT with floats:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;math.h&gt; #include "kiss_fft.h" #ifndef M_PI #define M_PI 3.14159265358979324 #endif #define N 16 void TestFft(const char* title, const kiss_fft_cpx in[N], kiss_fft_cpx out[N]) { kiss_fft_cfg cfg; printf("%s\n", title); if ((cfg = kiss_fft_alloc(N, 0/*is_inverse_fft*/, NULL, NULL)) != NULL) { size_t i; kiss_fft(cfg, in, out); free(cfg); for (i = 0; i &lt; N; i++) printf(" in[%2zu] = %+f , %+f " "out[%2zu] = %+f , %+f\n", i, in[i].r, in[i].i, i, out[i].r, out[i].i); } else { printf("not enough memory?\n"); exit(-1); } } int main(void) { kiss_fft_cpx in[N], out[N]; size_t i; for (i = 0; i &lt; N; i++) in[i].r = in[i].i = 0; TestFft("Zeroes (complex)", in, out); for (i = 0; i &lt; N; i++) in[i].r = 1, in[i].i = 0; TestFft("Ones (complex)", in, out); for (i = 0; i &lt; N; i++) in[i].r = sin(2 * M_PI * 4 * i / N), in[i].i = 0; TestFft("SineWave (complex)", in, out); return 0; } </code></pre> <p>Output:</p> <pre><code>Zeroes (complex) in[ 0] = +0.000000 , +0.000000 out[ 0] = +0.000000 , +0.000000 in[ 1] = +0.000000 , +0.000000 out[ 1] = +0.000000 , +0.000000 in[ 2] = +0.000000 , +0.000000 out[ 2] = +0.000000 , +0.000000 in[ 3] = +0.000000 , +0.000000 out[ 3] = +0.000000 , +0.000000 in[ 4] = +0.000000 , +0.000000 out[ 4] = +0.000000 , +0.000000 in[ 5] = +0.000000 , +0.000000 out[ 5] = +0.000000 , +0.000000 in[ 6] = +0.000000 , +0.000000 out[ 6] = +0.000000 , +0.000000 in[ 7] = +0.000000 , +0.000000 out[ 7] = +0.000000 , +0.000000 in[ 8] = +0.000000 , +0.000000 out[ 8] = +0.000000 , +0.000000 in[ 9] = +0.000000 , +0.000000 out[ 9] = +0.000000 , +0.000000 in[10] = +0.000000 , +0.000000 out[10] = +0.000000 , +0.000000 in[11] = +0.000000 , +0.000000 out[11] = +0.000000 , +0.000000 in[12] = +0.000000 , +0.000000 out[12] = +0.000000 , +0.000000 in[13] = +0.000000 , +0.000000 out[13] = +0.000000 , +0.000000 in[14] = +0.000000 , +0.000000 out[14] = +0.000000 , +0.000000 in[15] = +0.000000 , +0.000000 out[15] = +0.000000 , +0.000000 Ones (complex) in[ 0] = +1.000000 , +0.000000 out[ 0] = +16.000000 , +0.000000 in[ 1] = +1.000000 , +0.000000 out[ 1] = +0.000000 , +0.000000 in[ 2] = +1.000000 , +0.000000 out[ 2] = +0.000000 , +0.000000 in[ 3] = +1.000000 , +0.000000 out[ 3] = +0.000000 , +0.000000 in[ 4] = +1.000000 , +0.000000 out[ 4] = +0.000000 , +0.000000 in[ 5] = +1.000000 , +0.000000 out[ 5] = +0.000000 , +0.000000 in[ 6] = +1.000000 , +0.000000 out[ 6] = +0.000000 , +0.000000 in[ 7] = +1.000000 , +0.000000 out[ 7] = +0.000000 , +0.000000 in[ 8] = +1.000000 , +0.000000 out[ 8] = +0.000000 , +0.000000 in[ 9] = +1.000000 , +0.000000 out[ 9] = +0.000000 , +0.000000 in[10] = +1.000000 , +0.000000 out[10] = +0.000000 , +0.000000 in[11] = +1.000000 , +0.000000 out[11] = +0.000000 , +0.000000 in[12] = +1.000000 , +0.000000 out[12] = +0.000000 , +0.000000 in[13] = +1.000000 , +0.000000 out[13] = +0.000000 , +0.000000 in[14] = +1.000000 , +0.000000 out[14] = +0.000000 , +0.000000 in[15] = +1.000000 , +0.000000 out[15] = +0.000000 , +0.000000 SineWave (complex) in[ 0] = +0.000000 , +0.000000 out[ 0] = +0.000000 , +0.000000 in[ 1] = +1.000000 , +0.000000 out[ 1] = +0.000000 , +0.000000 in[ 2] = +0.000000 , +0.000000 out[ 2] = +0.000000 , +0.000000 in[ 3] = -1.000000 , +0.000000 out[ 3] = +0.000000 , +0.000000 in[ 4] = +0.000000 , +0.000000 out[ 4] = +0.000000 , -8.000000 in[ 5] = +1.000000 , +0.000000 out[ 5] = +0.000000 , +0.000000 in[ 6] = +0.000000 , +0.000000 out[ 6] = +0.000000 , +0.000000 in[ 7] = -1.000000 , +0.000000 out[ 7] = +0.000000 , +0.000000 in[ 8] = +0.000000 , +0.000000 out[ 8] = +0.000000 , +0.000000 in[ 9] = +1.000000 , +0.000000 out[ 9] = +0.000000 , +0.000000 in[10] = +0.000000 , +0.000000 out[10] = +0.000000 , +0.000000 in[11] = -1.000000 , +0.000000 out[11] = +0.000000 , +0.000000 in[12] = +0.000000 , +0.000000 out[12] = +0.000000 , +8.000000 in[13] = +1.000000 , +0.000000 out[13] = +0.000000 , +0.000000 in[14] = +0.000000 , +0.000000 out[14] = +0.000000 , +0.000000 in[15] = -1.000000 , +0.000000 out[15] = +0.000000 , +0.000000 </code></pre> <p>Real-valued forward FFT with floats:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;math.h&gt; #include "kiss_fftr.h" #ifndef M_PI #define M_PI 3.14159265358979324 #endif #define N 16 void TestFftReal(const char* title, const kiss_fft_scalar in[N], kiss_fft_cpx out[N / 2 + 1]) { kiss_fftr_cfg cfg; printf("%s\n", title); if ((cfg = kiss_fftr_alloc(N, 0/*is_inverse_fft*/, NULL, NULL)) != NULL) { size_t i; kiss_fftr(cfg, in, out); free(cfg); for (i = 0; i &lt; N; i++) { printf(" in[%2zu] = %+f ", i, in[i]); if (i &lt; N / 2 + 1) printf("out[%2zu] = %+f , %+f", i, out[i].r, out[i].i); printf("\n"); } } else { printf("not enough memory?\n"); exit(-1); } } int main(void) { kiss_fft_scalar in[N]; kiss_fft_cpx out[N / 2 + 1]; size_t i; for (i = 0; i &lt; N; i++) in[i] = 0; TestFftReal("Zeroes (real)", in, out); for (i = 0; i &lt; N; i++) in[i] = 1; TestFftReal("Ones (real)", in, out); for (i = 0; i &lt; N; i++) in[i] = sin(2 * M_PI * 4 * i / N); TestFftReal("SineWave (real)", in, out); return 0; } </code></pre> <p>Output:</p> <pre><code>Zeroes (real) in[ 0] = +0.000000 out[ 0] = +0.000000 , +0.000000 in[ 1] = +0.000000 out[ 1] = +0.000000 , +0.000000 in[ 2] = +0.000000 out[ 2] = +0.000000 , +0.000000 in[ 3] = +0.000000 out[ 3] = +0.000000 , +0.000000 in[ 4] = +0.000000 out[ 4] = +0.000000 , +0.000000 in[ 5] = +0.000000 out[ 5] = +0.000000 , +0.000000 in[ 6] = +0.000000 out[ 6] = +0.000000 , +0.000000 in[ 7] = +0.000000 out[ 7] = +0.000000 , +0.000000 in[ 8] = +0.000000 out[ 8] = +0.000000 , +0.000000 in[ 9] = +0.000000 in[10] = +0.000000 in[11] = +0.000000 in[12] = +0.000000 in[13] = +0.000000 in[14] = +0.000000 in[15] = +0.000000 Ones (real) in[ 0] = +1.000000 out[ 0] = +16.000000 , +0.000000 in[ 1] = +1.000000 out[ 1] = +0.000000 , +0.000000 in[ 2] = +1.000000 out[ 2] = +0.000000 , +0.000000 in[ 3] = +1.000000 out[ 3] = +0.000000 , +0.000000 in[ 4] = +1.000000 out[ 4] = +0.000000 , +0.000000 in[ 5] = +1.000000 out[ 5] = +0.000000 , +0.000000 in[ 6] = +1.000000 out[ 6] = +0.000000 , +0.000000 in[ 7] = +1.000000 out[ 7] = +0.000000 , +0.000000 in[ 8] = +1.000000 out[ 8] = +0.000000 , +0.000000 in[ 9] = +1.000000 in[10] = +1.000000 in[11] = +1.000000 in[12] = +1.000000 in[13] = +1.000000 in[14] = +1.000000 in[15] = +1.000000 SineWave (real) in[ 0] = +0.000000 out[ 0] = +0.000000 , +0.000000 in[ 1] = +1.000000 out[ 1] = +0.000000 , +0.000000 in[ 2] = +0.000000 out[ 2] = +0.000000 , +0.000000 in[ 3] = -1.000000 out[ 3] = +0.000000 , +0.000000 in[ 4] = +0.000000 out[ 4] = +0.000000 , -8.000000 in[ 5] = +1.000000 out[ 5] = +0.000000 , +0.000000 in[ 6] = +0.000000 out[ 6] = +0.000000 , +0.000000 in[ 7] = -1.000000 out[ 7] = +0.000000 , +0.000000 in[ 8] = +0.000000 out[ 8] = +0.000000 , +0.000000 in[ 9] = +1.000000 in[10] = +0.000000 in[11] = -1.000000 in[12] = +0.000000 in[13] = +1.000000 in[14] = +0.000000 in[15] = -1.000000 </code></pre>
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    1. POApplying Kiss FFT on audio samples and getting NaN output?
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      1. PTQuestion
    1. PTAnswer
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    1. USAlexey Frunze
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    1. POApplying Kiss FFT on audio samples and getting NaN output?
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    1. VO
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      1. VTAcceptedByOriginator
    2. VO
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      1. VTUpMod
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      1. VTUpMod
    1. COHello i m struglling with the same problem.. I have tested with the all zeros and ones it gives perfect o/p. bt when i try live audio it gives me wrong o/p...
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      1. USSunny Shah
    2. CO@Sunnyshah Either you're feeding it the wrong data or you're expecting the wrong result from it. As long as InverseFFT(FFT(signal))=signal, the problem is definitely in your code and not in the FFT. If, OTOH, InverseFFT(FFT(signal))≠signal, it's still very likely that you're not using the (I)FFT routines properly. I'm afraid, you'll have to debug your code.
      singulars
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      1. USAlexey Frunze
    3. COThanks i got my problem i was feeding wrong data.. but now i m strulling with another problem please look at that my code [Peak Problem](http://stackoverflow.com/questions/16934097/how-can-i-calculate-the-peak-using-kissfft)
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      1. USSunny Shah
 

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