int main(void)
{
int i = 0;
fractional *p_real = &sigCmpx[0].real ;
fractcomplex *p_cmpx = &sigCmpx[0] ;
#ifndef FFTTWIDCOEFFS_IN_PROGMEM /* Generate TwiddleFactor Coefficients */
TwidFactorInit (LOG2_BLOCK_LENGTH, &twiddleFactors[0], 0); /* We need to do this only once at start-up */
#endif
for ( i = 0; i < FFT_BLOCK_LENGTH; i++ )/* The FFT function requires input data */
{ /* to be in the fractional fixed-point range [-0.5, +0.5]*/
*p_real = *p_real >>1 ; /* So, we shift all data samples by 1 bit to the right. */
*p_real++; /* Should you desire to optimize this process, perform */
} /* data scaling when first obtaining the time samples */
/* Or within the BitReverseComplex function source code */
p_real = &sigCmpx[(FFT_BLOCK_LENGTH/2)-1].real ; /* Set up pointers to convert real array */
p_cmpx = &sigCmpx[FFT_BLOCK_LENGTH-1] ; /* to a complex array. The input array initially has all */
/* the real input samples followed by a series of zeros */
for ( i = FFT_BLOCK_LENGTH; i > 0; i-- ) /* Convert the Real input sample array */
{ /* to a Complex input sample array */
(*p_cmpx).real = (*p_real--); /* We will simpy zero out the imaginary */
(*p_cmpx--).imag = 0x0000; /* part of each data sample */
}
/* Perform FFT operation */
#ifndef FFTTWIDCOEFFS_IN_PROGMEM
FFTComplexIP (LOG2_BLOCK_LENGTH, &sigCmpx[0], &twiddleFactors[0], COEFFS_IN_DATA);
#else
FFTComplexIP (LOG2_BLOCK_LENGTH, &sigCmpx[0], (fractcomplex *) __builtin_psvoffset(&twiddleFactors[0]), (int) __builtin_psvpage(&twiddleFactors[0]));
#endif
/* Store output samples in bit-reversed order of their addresses */
BitReverseComplex (LOG2_BLOCK_LENGTH, &sigCmpx[0]);
/* Compute the square magnitude of the complex FFT output array so we have a Real output vetor */
SquareMagnitudeCplx(FFT_BLOCK_LENGTH, &sigCmpx[0], &sigCmpx[0].real);
/* Find the frequency Bin ( = index into the SigCmpx[] array) that has the largest energy*/
/* i.e., the largest spectral component */
VectorMax(FFT_BLOCK_LENGTH/2, &sigCmpx[0].real, &peakFrequencyBin);
/* Compute the frequency (in Hz) of the largest spectral component */
peakFrequency = peakFrequencyBin*(SAMPLING_RATE/FFT_BLOCK_LENGTH);
while (1); /* Place a breakpoint here and observe the watch window variables */
}
void AudioProcAnalyzePitch(int16_t * samples,
uint8_t gain,
int16_t ** raw_buckets,
int16_t ** full_buckets,
int16_t ** octave_buckets) {
// Apply a window.
VectorWindow(ANALOG_BUFFER_LEN, samples, samples, window);
// Apply gain and convert to complex.
for (unsigned i = 0; i < ANALOG_BUFFER_LEN; ++i) {
complex_buf[i].real = samples[i] * gain;
complex_buf[i].imag = 0;
}
// In-place FFT.
FFTComplexIP(ANALOG_LOG2_BUFFER_LEN, complex_buf, twiddle, COEFFS_IN_DATA);
BitReverseComplex(ANALOG_LOG2_BUFFER_LEN, complex_buf);
// Compute magnitude (first half of the buffer).
SquareMagnitudeCplx(ANALOG_BUFFER_LEN / 2, complex_buf, samples);
// Harmonic suppression.
for (int i = ANALOG_BUFFER_LEN / 2 - 1; i >= 0; --i) {
samples[i] -= samples[i / 2] / 2;
if (samples[i] < 0) samples[i] = 0;
}
// Apply bucketing.
*raw_buckets = samples + ANALOG_BUFFER_LEN / 2;
*full_buckets = *raw_buckets + PITCH_COUNT;
*octave_buckets = *full_buckets + BUCKET_COUNT;
Bucket(samples, *raw_buckets, *full_buckets, *octave_buckets);
}
