int WebRtcSpl_RealForwardFFT(struct RealFFT* self,
const int16_t* real_data_in,
int16_t* complex_data_out) {
int i = 0;
int j = 0;
int result = 0;
int n = 1 << self->order;
// The complex-value FFT implementation needs a buffer to hold 2^order
// 16-bit COMPLEX numbers, for both time and frequency data.
int16_t complex_buffer[2 << kMaxFFTOrder];
// Insert zeros to the imaginary parts for complex forward FFT input.
for (i = 0, j = 0; i < n; i += 1, j += 2) {
complex_buffer[j] = real_data_in[i];
complex_buffer[j + 1] = 0;
};
WebRtcSpl_ComplexBitReverse(complex_buffer, self->order);
result = WebRtcSpl_ComplexFFT(complex_buffer, self->order, 1);
// For real FFT output, use only the first N + 2 elements from
// complex forward FFT.
memcpy(complex_data_out, complex_buffer, sizeof(int16_t) * (n + 2));
return result;
}
int WebRtcSpl_RealForwardFFTC(struct RealFFT* self,
const int16_t* data_in,
int16_t* data_out) {
memcpy(data_out, data_in, sizeof(int16_t) * (1 << (self->order + 1)));
WebRtcSpl_ComplexBitReverse(data_out, self->order);
return WebRtcSpl_ComplexFFT(data_out, self->order, 1);
}
