From c8173aaf62679414cf120eed518a3c6c8e86d88e Mon Sep 17 00:00:00 2001 From: Themaister Date: Tue, 28 Feb 2012 00:29:45 +0100 Subject: [PATCH] Calculate imaginary part correctly. --- audio/test/snr.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/audio/test/snr.c b/audio/test/snr.c index 940dfefcce..4a9567b841 100644 --- a/audio/test/snr.c +++ b/audio/test/snr.c @@ -112,7 +112,7 @@ static void calculate_fft(const float *data, complex double *butterfly_buf, size // We only have real data. for (unsigned i = 1; i < samples / 2; i++) - butterfly_buf[i] += butterfly_buf[samples - i]; + butterfly_buf[i] += conj(butterfly_buf[samples - i]); // Normalize amplitudes. for (unsigned i = 0; i < samples / 2; i++) @@ -125,23 +125,29 @@ static void test_fft(void) float signal[32]; complex double butterfly_buf[16]; - const float freqs[] = { + const float cos_freqs[] = { 1.0, 4.0, 6.0, }; + const float sin_freqs[] = { + -2.0, 5.0, 7.0, + }; + for (unsigned i = 0; i < 16; i++) { signal[2 * i] = 0.0; - for (unsigned j = 0; j < sizeof(freqs) / sizeof(freqs[0]); j++) - signal[2 * i] += cos(2.0 * M_PI * i * freqs[j] / 16.0); + for (unsigned j = 0; j < sizeof(cos_freqs) / sizeof(cos_freqs[0]); j++) + signal[2 * i] += cos(2.0 * M_PI * i * cos_freqs[j] / 16.0); + for (unsigned j = 0; j < sizeof(sin_freqs) / sizeof(sin_freqs[0]); j++) + signal[2 * i] += sin(2.0 * M_PI * i * sin_freqs[j] / 16.0); } calculate_fft(signal, butterfly_buf, 16); printf("FFT: { "); for (unsigned i = 0; i < 7; i++) - printf("%4.2lf, ", cabs(butterfly_buf[i])); - printf("%4.2lf }\n", cabs(butterfly_buf[7])); + printf("(%4.2lf, %4.2lf), ", creal(butterfly_buf[i]), cimag(butterfly_buf[i])); + printf("(%4.2lf, %4.2lf) }\n", creal(butterfly_buf[7]), cimag(butterfly_buf[7])); } // This doesn't yet take account for slight phase distortions,