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Fix magnitude calculation for the first and the last frequency band

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This commit is contained in:
Alexander Kojevnikov 2012-10-13 16:27:12 -07:00
parent a6540309ac
commit 85b8a79cf0
1 changed files with 5 additions and 4 deletions

9
lib/spek-fft.c

@ -43,14 +43,15 @@ void spek_fft_execute(struct spek_fft_plan *p)
// Calculate magnitudes.
int n = p->n;
p->output[0] = p->input[0] * p->input[0] / (n * n);
p->output[n / 2] = p->input[1] * p->input[1] / (n * n);
float n2 = n * n;
p->output[0] = 10.0f * log10f(p->input[0] * p->input[0] / n2);
p->output[n / 2] = 10.0f * log10f(p->input[1] * p->input[1] / n2);
for (int i = 1; i < n / 2; i++) {
float val =
p->input[i * 2] * p->input[i * 2] +
p->input[i * 2 + 1] * p->input[i * 2 + 1];
val /= n * n;
p->output[i] = 10.0 * log10f (val);
val /= n2;
p->output[i] = 10.0f * log10f(val);
}
}